Self-fulfilling prophecy

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Self-fulfilling_prophecy

A self-fulfilling prophecy is a prediction that comes true at least in part as a result of a person's belief or expectation that the prediction would come true. In the phenomena, people tend to act the way they have been expected to in order to make the expectations come true. Self-fulfilling prophecies are an example of the more general phenomenon of positive feedback loops. A self-fulfilling prophecy can have either negative or positive outcomes. Merely applying a label to someone or something can affect the perception of the person/thing and create a self-fulfilling prophecy. Interpersonal communication plays a significant role in establishing these phenomena as well as impacting the labeling process.

American sociologists W. I. Thomas and Dorothy Swaine Thomas were the first Western scholars to investigate this phenomenon. In 1928, they developed the Thomas theorem (also known as the Thomas dictum): "If men define situations as real, they are real in their consequences." Another American sociologist, Robert K. Merton, continued the research, and is credited with coining the term "self-fulfilling prophecy" and popularizing the idea that "a belief or expectation, correct or incorrect, could bring about a desired or expected outcome." The works of philosophers Karl Popper and Alan Gewirth also contributed to the idea.

History

An early precursor of the concept appears in Edward Gibbon's Decline and Fall of the Roman Empire: "During many ages, the prediction, as it is usual, contributed to its own accomplishment".

The phrase "self-fulfilling prophecy" was coined by Robert K. Merton, a sociologist who also developed the ideas of anomie, social structure, and the modes of individual adaption. In his book Social Theory and Social Structure, he uses the example of a bank run to show how self-fulfilling thoughts can make unwanted situations happen. In his illustration, rumors spread about the town that the local bank is going to file for bankruptcy, causing many people to rush to the bank and close their accounts. Because banks do not keep their total assets in cash, the bank was unable to fulfill all its customers' withdrawals, which eventually caused the bank to go bankrupt. Merton concludes with the analysis, "The prophecy of collapse led to its own fulfillment".

While Merton's example focused on self-fulfilling prophecies within a community, self-fulfilling prophecies also apply to individuals, as individuals often conform to the expectations of others. This is also known as the Pygmalion effect, based on the experiments by Robert Resenthal and Lenore Jacobson, where teachers were told that a random selection of students were expected to perform exceptionally well; those students showed a significant increase in test scores at the end of the year.

Philosopher Karl Popper called the self-fulfilling prophecy the Oedipus effect:

One of the ideas I had discussed in The Poverty of Historicism was the influence of a prediction upon the event predicted. I had called this the "Oedipus effect", because the oracle played a most important role in the sequence of events which led to the fulfilment of its prophecy. [...] For a time I thought that the existence of the Oedipus effect distinguished the social from the natural sciences. But in biology, too—even in molecular biology—expectations often play a role in bringing about what has been expected.

The idea is similar to that discussed by the philosopher William James as "The Will to Believe." But James viewed it positively, as the self-validation of a belief.

Applications

Examples abound in studies of cognitive dissonance theory and the related self-perception theory; people will often change their attitudes to come into line with what they profess publicly.

In the United States, the concept was broadly and consistently applied in the field of public education reform, following the "war on poverty", as teacher expectations have been shown to influence student academic performance. Theodore Brameld noted: "In simplest terms, education already projects and thereby reinforces whatever habits of personal and cultural life are considered to be acceptable and dominant." The effects of teacher attitudes, beliefs, and values, affecting their expectations have been tested repeatedly, most notably in the Pygmalion in the Classroom study, where teachers were told arbitrarily that random students were likely to show significant intellectual growth. As a result, those random students actually ended the year with significantly greater improvement when given another IQ test. Though the changes may be subconscious, teachers who have higher expectations typically give "more time to answer questions, more specific feedback, and more approval". Likewise, students who have positive experiences with their teachers may study more. Academic self-fulfilling prophecies can be negative, however: one study indicated that female students may perform worse if they expect their male instructor to be sexist.

The phenomenon of the "inevitability of war" is a self-fulfilling prophecy that has received considerable study.

Fear of failure leads to deterioration of results, even if the person is objectively able to adequately cope with the problem. For example, fear of falling leads to more falls among older people.

Americans of Chinese and Japanese origin are more likely to die of a heart attack on the 4th of each month, due to the number four being considered unlucky and a portent of death.

Moore's law predicting that the number of transistors in an integrated circuit (IC) doubles about every two years is often considered as a self-fulfilling prophecy.

The belief that a bank is insolvent may help create the fact, but confidence in the bank's prospects may improve them. Similarly, stock-exchange panics and speculative bubbles can be both triggered by a widespread belief that the stock will go down (or up), thus starting the selling/buying mass move, etc.

People adapt to the judgments and assessments made by society, regardless of whether they were originally correct or not. There are certain prejudices against a socially marginalized group (e.g., homeless people, drug addicts or other minorities), and therefore, people in this marginalized group actually begin to behave in accordance with expectations.

Relationships

A leading study by Columbia University found that self-fulfilling prophecies have some part in relationships: the beliefs by people in relationships can impact the likelihood of a breakup or the overall health of the relationship. L. Alan Sroufe suggested that "rejection expectations can lead people to behave in ways that elicit rejection from others." The study looked at the inner workings behind the role of self-fulfilling prophecies in romantic relationships of people who were deemed high in rejection sensitivity, which was defined as "the disposition to anxiously expect, readily perceive, and overreact to rejection". The study found that women were more likely to experience rejection sensitivity in comparison to the negativity held by men about the future of their relationships, and that women sensitive to rejection "may be more likely to behave in ways that exacerbate conflicts," which could lead to behavior that would "erode their partners' relationship satisfaction and commitment."

Other specific examples discussed in psychology include:

• "Clever Hans" effect
• Observer-expectancy effect
• Hawthorne effect
• Placebo effect
• Nocebo effect
• Pygmalion effect
• Stereotype threat

International relations

Self-fulfilling prophecies have been apparent throughout history with the 'Thucydides trap': the occurrence of a rising power threatening a ruling or dominant power. Thucydides was an Athenian historian and general who recorded the Peloponnesian war between Sparta and Athens. He wrote, "It was the rise of Athens and the fear that this instilled in Sparta that made war inevitable."

Another example of self-fulfilling prophecies is the United States' invasion of Iraq in 2003. The invasion was based on the assumption that Iraq posed a terrorist threat to the United States, though evidence shows that no threat was actually posed. The invasion and subsequent overthrowing of the Ba'athist regime created the conditions for an insurgency that resulted in Iraq becoming a stronghold for the terrorist organization Al Qaeda, thus fulfilling the initial belief of a potential threat.

Stereotype

Self-fulfilling prophecies are one of the main contributions to racial prejudice and vice versa. According to the Dictionary of Race, Ethnicity & Culture, "Self-fulfilling prophecy makes it possible to highlight the tragic vicious circle which victimizes people twice: first, because the victim is stigmatized with an inherent negative quality; and secondly, because he or she is prevented from disproving this quality." An example is given where white workers expected that black people would be against the principles of trade unionism because they considered black workers to be "undisciplined in traditions of trade unionism and the art of collective bargain-ing." Due to this belief, black workers were not hired at white-owned businesses, which made black workers unable to learn the principles of trade unionism, and thus prevented them from unionizing.

Teachers can encourage stereotype-based courses and can interact with students in a manner that encourages self-fulfilling thoughts: for example, female students may seem to be bad at math if teachers never encouraged them to improve their mathematical abilities.

The term "self-fulfilling prophecy" made its first appearance in educational literature in the 1960s, when African-American psychologist Kenneth B. Clark studied the responses of black children to black and white dolls. The responses from Clark's study ranged from some children calling the black doll ugly to one girl bursting into tears when prompted to pick the doll she identified with. The black children internalized the inferiority they learned and acted accordingly. Clark, whose work pushed the Supreme Court to desegregate schools, noted the influence of teachers on the achievement levels between Black and White students. This prompted Clark to begin a study in ten inner-city schools where he assessed the attitudes and behaviors of teachers. The belief held by teachers was that minority students were unintelligent, and therefore the teachers put no effort into teaching them. This led to a feedback loop of those students not being educated, and thus being perceived as unintelligent.

Literature, media, and the arts

In literature, self-fulfilling prophecies are often used as plot devices. They have been used in stories for millennia, but are especially popular in science fiction and fantasy. They are often used for dramatic irony, with the prophesied events coming to pass due to the attempts to prevent the prophecy. They are also sometimes used as comic relief.

Classical

Many myths, legends, and fairy-tales make use of this motif as a central element of narratives that are designed to illustrate inexorable fate, fundamental to the Hellenic world-view. In a common motif, a child, whether newborn or not yet conceived, is prophesied to cause something that those in power do not want to happen, but the prophesied events come about as a result of the actions taken to prevent them.

Greek

The word "prophet" is derived from the Greek word prophete, meaning "one who speaks for another."

Oedipus in the arms of Phorbas

The best-known example from Greek legend is that of Oedipus. Warned that his child would one day kill him, Laius abandoned his newborn son Oedipus to die, but Oedipus was found and raised by others, and thus in ignorance of his true origins. When he grew up, Oedipus was warned that he would kill his father and marry his mother. He sought to avoid this, and, believing his foster parents to be his real parents, left his home and travelled to Greece, eventually reaching the city where his biological parents lived. There, he got into a fight with a stranger, killed him, and married his widow, only to discover that the stranger he had killed was his biological father, and his new wife was his biological mother.

Although the legend of Perseus opens with the prophecy that he will kill his grandfather Acrisius, the prophecy is only self-fulfilling in some variants. In some, he accidentally spears his grandfather at a competition—an act that could have happened regardless of Acrisius' response to the prophecy. In other variants, his presence at the games is due to his hearing of the prophecy. In still others, Acrisius is one of the wedding guests when Polydectes tries to force Danaë to marry him, and is accidentally killed when Perseus turns all the guests to stone with the Gorgon's head.

Greek historiography provides a famous variant: when the Lydian king Croesus asked the Delphic Oracle if he should invade Persia, the response came that if he did, he would destroy a great kingdom. Assuming this meant he would succeed, he attacked, only to fail—the kingdom he destroyed was his own.

When it was predicted that Cronos would be overthrown by his son, and usurp his throne as King of the Gods, Cronus ate his children, each shortly after they were born, enraging his wife, Rhea. To get revenge, when she bore Zeus, she gave Cronos a stone to eat instead, sending Zeus to be raised by Amalthea. Cronos' attempt to avoid the prophecy made Zeus his enemy, ultimately leading to its fulfilment.

Roman

Romulus and Remus nursed by a she-wolf

The story of Romulus and Remus is another example. According to legend, a man overthrew his brother, the king. He then ordered that his two nephews, Romulus and Remus, be drowned, fearing that they would someday kill him as he did to his brother. The boys were placed in a basket and thrown in the Tiber River. A wolf found the babies and she raised them. Later, a shepherd found the twins and named them Romulus and Remus. As teenagers, they discovered their heritage, and killed their uncle in revenge, fulfilling the prophecy.

Arabic

A variation of the self-fulfilling prophecy is the self-fulfilling dream, which dates back to medieval Arabic literature. Several tales in the One Thousand and One Nights, also known as the Arabian Nights, use this device to foreshadow what is going to happen, as a special form of literary prolepsis. A notable example is "The Ruined Man Who Became Rich Again Through a Dream", in which a man is told in his dream to leave his native city of Baghdad and travel to Cairo, where he will discover the whereabouts of some hidden treasure. The man travels there and experiences misfortune after losing belief in the prophecy, ending up in jail, where he tells his dream to a police officer. The officer mocks the idea of foreboding dreams and tells the protagonist that he himself had a dream about a house with a courtyard and fountain in Baghdad where treasure is buried under the fountain. The man recognizes the place as his own house and, after he is released from jail, he returns home and digs up the treasure. In other words, the foreboding dream not only predicted the future, but the dream was the cause of its prediction coming true. A variant of this story later appears in English folklore as the "Pedlar of Swaffham".

Another variation of the self-fulfilling prophecy can be seen in "The Tale of Attaf", where Harun al-Rashid consults his library (the House of Wisdom), reads a random book, "falls to laughing and weeping and dismisses the faithful vizier" Ja'far ibn Yahya from sight. Ja'far, "disturbed and upset flees Baghdad and plunges into a series of adventures in Damascus, involving Attaf and the woman whom Attaf eventually marries." After returning to Baghdad, Ja'far reads the same book that caused Harun to laugh and weep, and discovers that it describes his own adventures with Attaf. In other words, it was Harun's reading of the book that provoked the adventures described in the book to take place. This is an early example of reverse causality. In the 12th century, this tale was translated into Latin by Petrus Alphonsi and included in his Disciplina Clericalis. In the 14th century, a version of this tale also appears in the Gesta Romanorum and Giovanni Boccaccio's The Decameron.

Hinduism

Krishna playing his flute with Radha

Self-fulfilling prophecies appear in classical Sanskrit literature. In the story of Krishna in the Indian epic Mahabharata, the ruler of the Mathura kingdom, Kamsa, afraid of a prophecy that predicted his death at the hands of his sister Devaki's son, had her cast into prison where he planned to kill all of her children at birth. After killing the first six children, and Devaki's apparent miscarriage of the seventh, Krishna (the eighth son) was born. As his life was in danger he was smuggled out to be raised by his foster parents Yashoda and Nanda in the village of Gokula. Years later, Kamsan learned about the child's escape and kept sending various demons to put an end to him. The demons were defeated at the hands of Krishna and his brother Balarama. Krishna, as a young man returned to Mathura to overthrow his uncle, and Kamsa was eventually killed by his nephew Krishna. It was due to Kamsa's attempts to prevent the prophecy that it came true, thus fulfilling the prophecy.

Ruthenian

Oleg of Novgorod was a Varangian prince who ruled over the Rus people during the early tenth century. As old East Slavic chronicles say, it was prophesied by the pagan priests that Oleg's stallion would be the source of Oleg's death. To avoid this he sent the horse away. Many years later he asked where his horse was, and was told that it had died. He asked to see the remains and was taken to the place where the bones lay. When he touched the horse's skull with his boot a snake slithered from the skull and bit him. Oleg died, thus fulfilling the prophecy. In the Primary Chronicle, Oleg is known as the Prophet, ironically referring to the circumstances of his death. The story was romanticized by Alexander Pushkin in his celebrated ballad "The Song of the Wise Oleg". In Scandinavian traditions, this legend lived on in the saga of Orvar-Odd.

European fairy-tales

Many fairy-tales, such as The Devil With the Three Golden Hairs, The Fish and the Ring, The Story of Three Wonderful Beggars, or The King Who Would Be Stronger Than Fate, feature a prophecy that a poor boy will marry a rich girl (or, less frequently, a poor girl will marry a rich boy). This is story type 930 in the Aarne–Thompson classification scheme. The girl's father's efforts to prevent it are the reason why the boy ends up marrying her.

Another fairy-tale occurs with older children. In The Language of the Birds, a father forces his son to tell him what the birds say: that the father would be the son's servant. In The Ram, the father forces his daughter to tell him her dream: that her father would hold an ewer for her to wash her hands in. In both, the father takes the child's response as evidence of malice and drives the child off; this allows the child to change so that the father will not recognize his own offspring later and so offer to act as the child's servant.

In some variants of Sleeping Beauty, such as Sun, Moon, and Talia, the sleep is not brought about by a curse, but a prophecy that she will be endangered by flax (or hemp) results in the royal order to remove all the flax or hemp from the castle, resulting in her ignorance of the danger and her curiosity.

Shakespeare

Shakespeare's Macbeth is another classic example of a self-fulfilling prophecy. The three witches prophecy that Macbeth will eventually become king, but that the offspring of his best friend will rule instead of his own. Spurred by the prophecy, Macbeth kills the king and his own friend, something he arguably would not have done otherwise, leading to a revolution against him, and his death. The later prophecy by the first apparition of the witches that Macbeth should "Beware Macduff" is also a self-fulfilling prophecy. If Macbeth had not been told this, then he might not have regarded Macduff as a threat. Therefore, he would not have killed Macduff's family, and Macduff would not have sought revenge and killed Macbeth.

Modern

New age religion

The law of attraction is a typical example of self-fulfilling prophecy. It is the name given to the belief that "like attracts like" and that by focusing on positive or negative thoughts, one can bring about positive or negative results. According to this law, all things are created first by imagination, which leads to thoughts, then to words and actions. The thoughts, words and actions held in mind affect someone's intentions which makes the expected result happen. Although there are some cases where positive or negative attitudes can produce corresponding results (principally the placebo and nocebo effects), there is no scientific basis to the law of attraction.

Sports

Some researchers from 2008 found that in basketball, the head coaches gave more biased feedback while the assistant coaches gave more critical feedback. They predicted this was due to the external expectations from the coaches to the athletes which could have resulted in the Pygmalion effect with positive and negative results.

Researcher Helen Brown published findings of two experiments performed on athletes, investigating the effect that the media has on them, and concluded that the athlete's performance was impacted by and aligned with expectations of their performance. A follow-up experiment in London found that such expectations can impact their judgement and thought processes, and can even have a dangerous and destructive impact on some athletes.

Causal loop

See also: Causal loop and Newcomb's paradox

A self-fulfilling prophecy may be a form of causality loop. Predestination does not necessarily involve a supernatural power, and could be the result of other "infallible foreknowledge" mechanisms. Problems arising from infallibility and influencing the future are explored in Newcomb's paradox. A notable fictional example of a self-fulfilling prophecy occurs in classical play Oedipus Rex, in which Oedipus becomes the king of Thebes, whilst in the process unwittingly fulfills a prophecy that he would kill his father and marry his mother. The prophecy itself serves as the impetus for his actions, and thus it is self-fulfilling. The movie 12 Monkeys heavily deals with themes of predestination and the Cassandra complex, where the protagonist who travels back in time explains that he cannot change the past.

Unintended consequences

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Unintended_consequences

A gully erosion in Australia caused by rabbits, an unintended consequence of their introduction as game animals

In the social sciences, unintended consequences (sometimes unanticipated consequences or unforeseen consequences, more colloquially called knock-on effects) are outcomes of a purposeful action that are not intended or foreseen. The term was popularized in the 20th century by American sociologist Robert K. Merton.

Unintended consequences can be grouped into three types:

• Unexpected benefit: A positive unexpected benefit (also referred to as luck, serendipity, or a windfall).
• Unexpected drawback: An unexpected detriment occurring in addition to the desired effect of the policy (e.g., while irrigation schemes provide people with water for agriculture, they can increase waterborne diseases that have devastating health effects, such as schistosomiasis).
• Perverse result: A perverse effect contrary to what was originally intended (when an intended solution makes a problem worse).

History

John Locke

The idea of unintended consequences dates back at least to John Locke who discussed the unintended consequences of interest rate regulation in his letter to Sir John Somers, Member of Parliament.

Adam Smith

The idea was also discussed by Adam Smith, the Scottish Enlightenment, and consequentialism (judging by results).

The invisible hand theorem is an example of the unintended consequences of agents acting in their self-interest. As Andrew S. Skinner puts it:

"The individual undertaker (entrepreneur), seeking the most efficient allocation of resources, contributes to overall economic efficiency; the merchant's reaction to price signals helps to ensure that the allocation of resources accurately reflects the structure of consumer preferences; and the drive to better our condition contributes to economic growth."

Marx and Engels

Influenced by 19th century positivism and Charles Darwin's evolution, for both Friedrich Engels and Karl Marx, the idea of uncertainty and chance in social dynamics (and thus unintended consequences beyond results of perfectly defined laws) was only apparent, (if not rejected) since social actions were directed and produced by deliberate human intention.

While discerning between the forces that generate changes in nature and those that generate changes in history in his discussion of Ludwig Feuerbach, Friedrich Engels touched on the idea of (apparent) unintended consequences:

In nature [...] there are only blind, unconscious agencies acting upon one another, [...] In the history of society, on the contrary, the actors are all endowed with consciousness, are men acting with deliberation or passion, working towards definite goals; nothing happens without a conscious purpose, without an intended aim. [...] For here, also, on the whole, in spite of the consciously desired aims of all individuals, accident apparently reigns on the surface. That which is willed happens but rarely; in the majority of instances the numerous desired ends cross and conflict with one another, or these ends themselves are from the outset incapable of realization, or the means of attaining them are insufficient. Thus the conflicts of innumerable individual wills and individual actions in the domain of history produce a state of affairs entirely analogous to [...] the realm of unconscious nature. The ends of the actions are intended, but the results which actually follow from these actions are not intended; or when they do seem to correspond to the end intended, they ultimately have consequences quite other than those intended. Historical events thus appear on the whole to be likewise governed by chance. But where on the surface accident holds sway, there actually it is always governed by inner, hidden laws, and it is only a matter of discovering these laws.

— Ludwig Feuerbach and the End of Classical German Philosophy (Ludwig Feuerbach und der Ausgang der klassischen deutschen Philosophie), 1886.

For his part, for Karl Marx what can be understood as unintended consequences are actually consequences that should be expected but are obtained unconsciously. These consequences (that no one consciously sought) would be (in the same way as it is for Engels) product of conflicts that confront actions from countless individuals. The deviation between the original intended goal and the product derived from conflicts would be a marxist equivalent to «unintended consequences.

This social conflicts would happen as a result of a competitive society, and also lead society to sabotage itself and prevent historical progress. Thus, historical progress (in Marxist terms) should eliminate these conflicts and make unintended consequences predictable.

Austrian School

Unintended consequences are a common topic of study and commentary for the Austrian school of economics given its emphasis on methodological individualism. This is to such an extent that unexpected consequences can be considered as a distinctive part of Austrian tenets.

Carl Menger

In "Principles of Economics", Austrian school founder Carl Menger (1840 - 1921) noted that the relationships that occur in the economy are so intricate that a change in the condition of a single good can have ramifications beyond that good. Menger wrote:

If it is established that the existence of human needs capable of satisfaction is a prerequisite of goods-character [...] This principle is valid whether the goods can be placed in direct causal connection with the satisfaction of human needs, or derive their goods-character from a more or less indirect causal connection with the satisfaction of human needs. [...]
Thus quinine would cease to be a good if the diseases it serves to cure should disappear, since the only need with the satisfaction of which it is causally connected would no longer exist. But the disappearance of the usefulness of quinine would have the further consequence that a large part of the corresponding goods of higher order would also be deprived of their goods-character. The inhabitants of quinine-producing countries, who currently earn their livings by cutting and peeling cinchona trees, would suddenly find that not only their stocks of cinchona bark, but also, in consequence, their cinchona trees, the tools and appliances applicable only to the production of quinine, and above all the specialized labor services, by means of which they previously earned their livings, would at once lose their goods-character, since all these things would, under the changed circumstances, no longer have any causal relationship with the satisfaction of human needs.

— Principles of Economics (Grundsätze der Volkswirtschaftslehre), 1871.

Friedrich Hayek and Catallactics

Economist and philosopher Friedrich Hayek (1899 – 1992) is another key figure in the Austrian School of Economics who is notable for his comments on unintended consequences.

In "The Use of Knowledge in Society" (1945) Hayek argues that a centrally planned economy cannot reach the level of efficiency of the free market economy because the necessary (and pertinent) information for decision-making is not concentrated but dispersed among a vast number of agents. Then, for Hayek, the price system in the free market allows the members of a society to anonymously coordinate for the most efficient use of resources, for example, in a situation of scarcity of a raw material, the price increase would coordinate the actions of an uncountable amount of individuals "in the right direction".

The development of this system of interactions would allow the progress of society, and individuals would carry it out without knowing all its implications, given the dispersion (or lack of concentration) of information.

The implication of this is that the social order (which derives from social progress, which in turn derives from the economy), would be result of a spontaneous cooperation and also an unintended consequence, being born from a process of which no individual or group had all the information available or could know all possible outcomes.

In the Austrian school, this process of social adjustment that generates a social order in an unintendedly way is known as catallactics.

For Hayek and the Austrian School, the number of individuals involved in the process of creating a social order defines the type of unintended consequence:

1. If the process involves interactions and decision making of as many individuals (members of a society) as possible (thus gathering the greatest amount of knowledge dispersed among them), this process of "catallaxy" will lead to unexpected benefits (a social order and progress)
2. On the other hand, attempts by individuals or limited groups (who lack all the necessary information) to achieve a new or better order, will end in unexpected drawbacks.

Robert K. Merton

Sociologist Robert K. Merton popularised this concept in the twentieth century.

In "The Unanticipated Consequences of Purposive Social Action" (1936), Merton tried to apply a systematic analysis to the problem of unintended consequences of deliberate acts intended to cause social change. He emphasized that his term purposive action, "[was exclusively] concerned with 'conduct' as distinct from 'behavior.' That is, with action that involves motives and consequently a choice between various alternatives". Merton's usage included deviations from what Max Weber defined as rational social action: instrumentally rational and value rational. Merton also stated that "no blanket statement categorically affirming or denying the practical feasibility of all social planning is warranted."

Everyday usage

More recently, the law of unintended consequences has come to be used as an adage or idiomatic warning that an intervention in a complex system tends to create unanticipated and often undesirable outcomes.

Akin to Murphy's law, it is commonly used as a wry or humorous warning against the hubristic belief that humans can fully control the world around them, not to presuppose a belief in predestination or a lack or a disbelief in that of free will.

Causes

Possible causes of unintended consequences include the world's inherent complexity (parts of a system responding to changes in the environment), perverse incentives, human stupidity, self-deception, failure to account for human nature, or other cognitive or emotional biases. As a sub-component of complexity (in the scientific sense), the chaotic nature of the universe—and especially its quality of having small, apparently insignificant changes with far-reaching effects (e.g., the butterfly effect)—applies.

In 1936, Robert K. Merton listed five possible causes of unanticipated consequences:

• Ignorance, making it impossible to anticipate everything, thereby leading to incomplete analysis.
• Errors in analysis of the problem or following habits that worked in the past but may not apply to the current situation.
• Immediate interests overriding long-term interests.
• Basic values which may require or prohibit certain actions even if the long-term result might be unfavourable (these long-term consequences may eventually cause changes in basic values).
• Self-defeating prophecy, or, the fear of some consequence which drives people to find solutions before the problem occurs, thus the non-occurrence of the problem is not anticipated.

In addition to Merton's causes, psychologist Stuart Vyse has noted that groupthink, described by Irving Janis, has been blamed for some decisions that result in unintended consequences.

Types

Unexpected benefits

The creation of "no-man's lands" during the Cold War, in places such as the border between Eastern and Western Europe, and the Korean Demilitarized Zone, has led to large natural habitats.

Sea life on the wreck of the sunken USS Oriskany

The sinking of ships in shallow waters during wartime has created many artificial coral reefs, which can be scientifically valuable and have become an attraction for recreational divers. This led to the deliberate sinking of retired ships for the purpose of replacing coral reefs lost to global warming and other factors.

In medicine, most drugs have unintended consequences ('side effects') associated with their use. However, some are beneficial. For instance, aspirin, a pain reliever, is also an anticoagulant that can help prevent heart attacks and reduce the severity and damage from thrombotic strokes. Beneficial side effects have also lead to off-label use –prescription or use of a drug for an unlicensed purpose. Famously, the drug Viagra was developed to lower blood pressure, with its use for treating erectile dysfunction being discovered as a side effect in clinical trials.

In papal conclave journalism, Cardinal Fridolin Ambongo Besungu of Kinshasa in the Democratic Republic of Congo, the elected leader of all the bishops of Africa (including Madagascar), by early 2024 had come to be regarded as papabile for his adroit handling of the issue of blessing same sex unions, to which he is staunchly opposed.

Unexpected drawbacks

The implementation of a profanity filter by AOL in 1996 had the unintended consequence of blocking residents of Scunthorpe, North Lincolnshire, England, from creating accounts because of a false positive. The accidental censorship of innocent language, known as the Scunthorpe problem, has been repeated and widely documented.

In 1990, the Australian state of Victoria made safety helmets mandatory for all bicycle riders. While there was a reduction in the number of head injuries, there was also an unintended reduction in the number of juvenile cyclists—fewer cyclists obviously leads to fewer injuries, all else being equal. The risk of death and serious injury per cyclist seems to have increased, possibly because of risk compensation. Research by Vulcan et al. found that the reduction in juvenile cyclists was because the youths considered wearing a bicycle helmet unfashionable. A health-benefit model developed at Macquarie University in Sydney suggests that, while helmet use reduces "the risk of head or brain injury by approximately two-thirds or more", the decrease in exercise caused by reduced cycling as a result of helmet laws is counterproductive in terms of net health.

Prohibition in the 1920s United States, originally enacted to suppress the alcohol trade, drove many small-time alcohol suppliers out of business and consolidated the hold of large-scale organized crime over the illegal alcohol industry. Since alcohol was still popular, criminal organisations producing alcohol were well-funded and hence also increased their other activities. Similarly, the war on drugs, intended to suppress the illegal drug trade, instead increased the power and profitability of drug cartels who became the primary source of the products.

In CIA jargon, "blowback" describes the unintended, undesirable consequences of covert operations, such as the funding of the Afghan Mujahideen and the destabilization of Afghanistan contributing to the rise of the Taliban and Al-Qaeda.

The introduction of exotic animals and plants for food, for decorative purposes, or to control unwanted species often leads to more harm than good done by the introduced species.

• The introduction of rabbits in Australia and New Zealand for food was followed by an explosive growth in the rabbit population; rabbits have become a major feral pest in these countries.
• Cane toads, introduced into Australia to control canefield pests, were unsuccessful and have become a major pest in their own right.
• Kudzu, introduced to the US as an ornamental plant in 1876 and later used to prevent erosion in earthworks, has become a major problem in the Southeastern United States. Kudzu has displaced native plants and has effectively taken over significant portions of land.

The protection of the steel industry in the United States reduced production of steel in the United States, increased costs to users, and increased unemployment in associated industries.

Perverse results

See also: Perverse incentive and Perverse subsidies

The infamous photo of the Streisand Estate

In 2003, Barbra Streisand unsuccessfully sued Kenneth Adelman and Pictopia.com for posting a photograph of her home online. Before the lawsuit had been filed, only 6 people had downloaded the file, two of them Streisand's attorneys. The lawsuit drew attention to the image, resulting in 420,000 people visiting the site. The Streisand Effect was named after this incident, describing when an attempt to censor or remove a certain piece of information instead draws attention to the material being suppressed, resulting in the material instead becoming widely known, reported on, and distributed.

Passenger-side airbags in motorcars were intended as a safety feature, but led to an increase in child fatalities in the mid-1990s because small children were being hit by airbags that deployed automatically during collisions. The supposed solution to this problem, moving the child seat to the back of the vehicle, led to an increase in the number of children forgotten in unattended vehicles, some of whom died under extreme temperature conditions.

Risk compensation, or the Peltzman effect, occurs after implementation of safety measures intended to reduce injury or death (e.g. bike helmets, seatbelts, etc.). People may feel safer than they really are and take additional risks which they would not have taken without the safety measures in place. This may result in no change, or even an increase, in morbidity or mortality, rather than a decrease as intended.

According to an anecdote, the British government, concerned about the number of venomous cobra snakes in Delhi, offered a bounty for every dead cobra. This was a successful strategy as large numbers of snakes were killed for the reward. Eventually, enterprising people began breeding cobras for the income. When the government became aware of this, they scrapped the reward program, causing the cobra breeders to set the now-worthless snakes free. As a result, the wild cobra population further increased. The apparent solution for the problem made the situation even worse, becoming known as the Cobra effect.

Theobald Mathew's temperance campaign in 19th-century Ireland resulted in thousands of people vowing never to drink alcohol again. This led to the consumption of diethyl ether, a much more dangerous intoxicant—owing to its high flammability—by those seeking to become intoxicated without breaking the letter of their pledge.

It was thought that adding south-facing conservatories to British houses would reduce energy consumption by providing extra insulation and warmth from the sun. However, people tended to use the conservatories as living areas, installing heating and ultimately increasing overall energy consumption.

A reward for lost nets found along the Normandy coast was offered by the French government between 1980 and 1981. This resulted in people vandalizing nets to collect the reward.

Beginning in the 1940s and continuing into the 1960s, the Canadian federal government gave Quebec $2.75 per day per psychiatric patient for their cost of care, but only $1.25 a day per orphan. The perverse result is that the orphan children were diagnosed as mentally ill so Quebec could receive the larger amount of money. This psychiatric misdiagnosis affected up to 20,000 people, and the children are known as the Duplessis Orphans in reference to the Premier of Quebec who oversaw the scheme, Maurice Duplessis.

There have been attempts to curb the consumption of sugary beverages by imposing a tax on them. However, a study found that the reduced consumption was only temporary. Also, there was an increase in the consumption of beer among households.

The New Jersey Childproof Handgun Law, which was intended to protect children from accidental discharge of firearms by forcing all future firearms sold in New Jersey to contain "smart" safety features, has delayed, if not stopped entirely, the introduction of such firearms to New Jersey markets. The wording of the law caused significant public backlash, fuelled by gun rights lobbyists, and several shop owners offering such guns received death threats and stopped stocking them. In 2014, 12 years after the law was passed, it was suggested the law be repealed if gun rights lobbyists agree not to resist the introduction of "smart" firearms.

Drug prohibition can lead drug traffickers to prefer stronger, more dangerous substances, that can be more easily smuggled and distributed than other, less concentrated substances.

Televised drug prevention advertisements may lead to increased drug use.

Increasing usage of search engines, also including recent image search features, has contributed in the ease of which media is consumed. Some abnormalities in usage may have shifted preferences for pornographic film actors, as the producers began using common search queries or tags to label the actors in new roles.

The passage of the Stop Enabling Sex Traffickers Act has led to a reported increase in risky behaviors by sex workers as a result of quashing their ability to seek and screen clients online, forcing them back onto the streets or into the dark web. The ads posted were previously an avenue for advocates to reach out to those wanting to escape the trade.

The use of precision guided munitions meant to reduce the rate of civilian casualties encouraged armies to narrow their safety margins, and increase the use of deadly force in densely populated areas. This in turn increased the danger to uninvolved civilians, who in the past would have been out of the line of fire because of armies' aversion of using higher-risk weaponry in densely populated areas. The perceived ability to operate precision weaponry from afar (where in the past heavy munitions or troop deployment would have been needed) also led to the expansion of the list of potential targets. As put by Michael Walzer: "Drones not only make it possible for us to get at our enemies, they may also lead us to broaden the list of enemies, to include presumptively hostile individuals and militant organizations simply because we can get at them—even if they aren't actually involved in attacks against us." This idea is also echoed by Grégoire Chamayou: "In a situation of moral hazard, military action is very likely to be deemed 'necessary' simply because it is possible, and possible at a lower cost."

After Dobbs v. Jackson Women's Health Organization (2022) overturned Roe v. Wade (1973), the number of abortions in the United States increased and the number of births fell, due to the right to travel between states.

Other

According to Lynn White, the invention of the horse stirrup enabled new patterns of warfare that eventually led to the development of feudalism (see Stirrup Thesis).

Perverse consequences of environmental intervention

Almost all environmental problems, from chemical pollution to global warming, are the unexpected consequences of the application of modern technologies. Traffic congestion, deaths and injuries from car accidents, air pollution, and global warming are unintended consequences of the invention and large scale adoption of the automobile. Hospital infections are the unexpected side-effect of antibiotic resistance, and even human population growth leading to environmental degradation is the side effect of various technological (i.e., agricultural and industrial) revolutions.

Because of the complexity of ecosystems, deliberate changes to an ecosystem or other environmental interventions will often have (usually negative) unintended consequences. Sometimes, these effects cause permanent irreversible changes. Examples include:

Chinese poster encouraging children to attack sparrows

• During the Four Pests campaign, Maoist China ordered the killing of sparrows, as well as rats, flies, and mosquitoes. The campaign was successful in reducing the sparrow population; however, in their absence, locust populations previously kept in check by sparrow predation grew out of control and came to infest crops. Rice yields were substantially decreased; the campaign was one of the causes of the Great Chinese Famine.
• During the Great Plague of London a killing of dogs and cats was ordered. If left untouched, they would have made a significant reduction in the rat population that carried the fleas which transmitted the disease.
• The installation of smokestacks to decrease pollution in local areas, resulting in spread of pollution at a higher altitude, and acid rain on an international scale.
• After about 1900, public demand led the US government to fight forest fires in the American West, and set aside land as national forests and parks to protect them from fires. This policy led to fewer fires, but also led to growth conditions such that, when fires did occur, they were much larger and more damaging. Modern research suggests that this policy was misguided, and that a certain level of wildfires is a natural and important part of forest ecology.
• Side effects of climate engineering to counter global warming could involve even further warming as a consequence of reflectivity-reducing afforestation or crop yield reductions and rebound effects after solar dimming measures with even more accelerated warming.

Nanotechnology

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Nanotechnology

Fullerene nanogears

Nanotechnology is the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing properties of matter. This definition of nanotechnology includes all types of research and technologies that deal with these special properties. It is common to see the plural form "nanotechnologies" as well as "nanoscale technologies" to refer to research and applications whose common trait is scale. An earlier understanding of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabricating macroscale products, now referred to as molecular nanotechnology.

Nanotechnology defined by scale includes fields of science such as surface science, organic chemistry, molecular biology, semiconductor physics, energy storage, engineering, microfabrication, and molecular engineering. The associated research and applications range from extensions of conventional device physics to molecular self-assembly, from developing new materials with dimensions on the nanoscale to direct control of matter on the atomic scale.

Nanotechnology may be able to create new materials and devices with diverse applications, such as in nanomedicine, nanoelectronics, agricultural sectors, biomaterials energy production, and consumer products. However, nanotechnology raises issues, including concerns about the toxicity and environmental impact of nanomaterials, and their potential effects on global economics, as well as various doomsday scenarios. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.

Origins

Main article: History of nanotechnology

The concepts that seeded nanotechnology were first discussed in 1959 by physicist Richard Feynman in his talk There's Plenty of Room at the Bottom, in which he described the possibility of synthesis via direct manipulation of atoms.

Comparison of nanomaterials sizes

The term "nano-technology" was first used by Norio Taniguchi in 1974, though it was not widely known. Inspired by Feynman's concepts, K. Eric Drexler used the term "nanotechnology" in his 1986 book Engines of Creation: The Coming Era of Nanotechnology, which achieved popular success and helped thrust nanotechnology into the public sphere. In it he proposed the idea of a nanoscale "assembler" that would be able to build a copy of itself and of other items of arbitrary complexity with atom-level control. Also in 1986, Drexler co-founded The Foresight Institute to increase public awareness and understanding of nanotechnology concepts and implications.

The emergence of nanotechnology as a field in the 1980s occurred through the convergence of Drexler's theoretical and public work, which developed and popularized a conceptual framework, and experimental advances that drew additional attention to the prospects. In the 1980s, two breakthroughs helped to spark the growth of nanotechnology. First, the invention of the scanning tunneling microscope in 1981 enabled visualization of individual atoms and bonds, and was successfully used to manipulate individual atoms in 1989. The microscope's developers Gerd Binnig and Heinrich Rohrer at IBM Zurich Research Laboratory received a Nobel Prize in Physics in 1986. Binnig, Quate and Gerber also invented the analogous atomic force microscope that year.

Buckminsterfullerene C₆₀, also known as the buckyball, is a representative member of the carbon structures known as fullerenes. Members of the fullerene family are a major subject of research falling under the nanotechnology umbrella.

Harry Kroto (top) won the 1996 Nobel Prize in Chemistry along with Richard Smalley and Robert Curl for their 1985 discovery of buckminsterfullerene, while Sumio Iijima (middle) won the inaugural 2008 Kavli Prize in Nanoscience for his 1991 discovery of carbon nanotubes.

Second, fullerenes (buckyballs) were discovered in 1985 by Harry Kroto, Richard Smalley, and Robert Curl, who together won the 1996 Nobel Prize in Chemistry. C₆₀ was not initially described as nanotechnology; the term was used regarding subsequent work with related carbon nanotubes (sometimes called graphene tubes or Bucky tubes) which suggested potential applications for nanoscale electronics and devices. The discovery of carbon nanotubes is attributed to Sumio Iijima of NEC in 1991, for which Iijima won the inaugural 2008 Kavli Prize in Nanoscience.

In the early 2000s, the field garnered increased scientific, political, and commercial attention that led to both controversy and progress. Controversies emerged regarding the definitions and potential implications of nanotechnologies, exemplified by the Royal Society's report on nanotechnology. Challenges were raised regarding the feasibility of applications envisioned by advocates of molecular nanotechnology, which culminated in a public debate between Drexler and Smalley in 2001 and 2003.

Meanwhile, commercial products based on advancements in nanoscale technologies began emerging. These products were limited to bulk applications of nanomaterials and did not involve atomic control of matter. Some examples include the Silver Nano platform for using silver nanoparticles as an antibacterial agent, nanoparticle-based sunscreens, carbon fiber strengthening using silica nanoparticles, and carbon nanotubes for stain-resistant textiles.

Governments moved to promote and fund research into nanotechnology, such as American the National Nanotechnology Initiative, which formalized a size-based definition of nanotechnology and established research funding, and in Europe via the European Framework Programmes for Research and Technological Development.

By the mid-2000s scientific attention began to flourish. Nanotechnology roadmaps centered on atomically precise manipulation of matter and discussed existing and projected capabilities, goals, and applications.

Fundamental concepts

Nanotechnology is the science and engineering of functional systems at the molecular scale. In its original sense, nanotechnology refers to the projected ability to construct items from the bottom up making complete, high-performance products.

One nanometer (nm) is one billionth, or 10⁻⁹, of a meter. By comparison, typical carbon–carbon bond lengths, or the spacing between these atoms in a molecule, are in the range 0.12–0.15 nm, and DNA's diameter is around 2 nm. On the other hand, the smallest cellular life forms, the bacteria of the genus Mycoplasma, are around 200 nm in length. By convention, nanotechnology is taken as the scale range 1 to 100 nm, following the definition used by the American National Nanotechnology Initiative. The lower limit is set by the size of atoms (hydrogen has the smallest atoms, which have an approximately ,25 nm kinetic diameter). The upper limit is more or less arbitrary, but is around the size below which phenomena not observed in larger structures start to become apparent and can be made use of. These phenomena make nanotechnology distinct from devices that are merely miniaturized versions of an equivalent macroscopic device; such devices are on a larger scale and come under the description of microtechnology.

To put that scale in another context, the comparative size of a nanometer to a meter is the same as that of a marble to the size of the earth.

Two main approaches are used in nanotechnology. In the "bottom-up" approach, materials and devices are built from molecular components which assemble themselves chemically by principles of molecular recognition. In the "top-down" approach, nano-objects are constructed from larger entities without atomic-level control.

Areas of physics such as nanoelectronics, nanomechanics, nanophotonics and nanoionics have evolved to provide nanotechnology's scientific foundation.

Larger to smaller: a materials perspective

Image of reconstruction on a clean Gold(100) surface, as visualized using scanning tunneling microscopy. The positions of the individual atoms composing the surface are visible.

Main article: Nanomaterials

Several phenomena become pronounced as system size. These include statistical mechanical effects, as well as quantum mechanical effects, for example, the "quantum size effect" in which the electronic properties of solids alter along with reductions in particle size. Such effects do not apply at macro or micro dimensions. However, quantum effects can become significant when nanometer scales. Additionally, physical (mechanical, electrical, optical, etc.) properties change versus macroscopic systems. One example is the increase in surface area to volume ratio altering mechanical, thermal, and catalytic properties of materials. Diffusion and reactions can be different as well. Systems with fast ion transport are referred to as nanoionics. The mechanical properties of nanosystems are of interest in research.

Simple to complex: a molecular perspective

Main article: Molecular self-assembly

Modern synthetic chemistry can prepare small molecules of almost any structure. These methods are used to manufacture a wide variety of useful chemicals such as pharmaceuticals or commercial polymers. This ability raises the question of extending this kind of control to the next-larger level, seeking methods to assemble single molecules into supramolecular assemblies consisting of many molecules arranged in a well-defined manner.

These approaches utilize the concepts of molecular self-assembly and/or supramolecular chemistry to automatically arrange themselves into a useful conformation through a bottom-up approach. The concept of molecular recognition is important: molecules can be designed so that a specific configuration or arrangement is favored due to non-covalent intermolecular forces. The Watson–Crick basepairing rules are a direct result of this, as is the specificity of an enzyme targeting a single substrate, or the specific folding of a protein. Thus, components can be designed to be complementary and mutually attractive so that they make a more complex and useful whole.

Such bottom-up approaches should be capable of producing devices in parallel and be much cheaper than top-down methods, but could potentially be overwhelmed as the size and complexity of the desired assembly increases. Most useful structures require complex and thermodynamically unlikely arrangements of atoms. Nevertheless, many examples of self-assembly based on molecular recognition in exist in biology, most notably Watson–Crick basepairing and enzyme-substrate interactions.

Molecular nanotechnology: a long-term view

Main article: Molecular nanotechnology

Ribosome translating DNA is a biological machine functioning as a molecular assembler. Protein domain dynamics can now be seen by neutron spin echo spectroscopy

Molecular nanotechnology, sometimes called molecular manufacturing, concerns engineered nanosystems (nanoscale machines) operating on the molecular scale. Molecular nanotechnology is especially associated with molecular assemblers, machines that can produce a desired structure or device atom-by-atom using the principles of mechanosynthesis. Manufacturing in the context of productive nanosystems is not related to conventional technologies used to manufacture nanomaterials such as carbon nanotubes and nanoparticles.

When Drexler independently coined and popularized the term "nanotechnology", he envisioned manufacturing technology based on molecular machine systems. The premise was that molecular-scale biological analogies of traditional machine components demonstrated molecular machines were possible: biology was full of examples of sophisticated, stochastically optimized biological machines.

Drexler and other researchers have proposed that advanced nanotechnology ultimately could be based on mechanical engineering principles, namely, a manufacturing technology based on the mechanical functionality of these components (such as gears, bearings, motors, and structural members) that would enable programmable, positional assembly to atomic specification. The physics and engineering performance of exemplar designs were analyzed in Drexler's book Nanosystems: Molecular Machinery, Manufacturing, and Computation.

In general, assembling devices on the atomic scale requires positioning atoms on other atoms of comparable size and stickiness. Carlo Montemagno's view is that future nanosystems will be hybrids of silicon technology and biological molecular machines. Richard Smalley argued that mechanosynthesis was impossible due to difficulties in mechanically manipulating individual molecules.

This led to an exchange of letters in the American Chemical Society publication Chemical & Engineering News in 2003. Though biology clearly demonstrates that molecular machines are possible, non-biological molecular machines remained in their infancy. Alex Zettl and colleagues at Lawrence Berkeley Laboratories and UC Berkeley constructed at least three molecular devices whose motion is controlled via changing voltage: a nanotube nanomotor, a molecular actuator, and a nanoelectromechanical relaxation oscillator.

Ho and Lee at Cornell University in 1999 used a scanning tunneling microscope to move an individual carbon monoxide molecule (CO) to an individual iron atom (Fe) sitting on a flat silver crystal and chemically bound the CO to the Fe by applying a voltage.

Research

Graphical representation of a rotaxane, useful as a molecular switch

This DNA tetrahedron is an artificially designed nanostructure of the type made in the field of DNA nanotechnology. Each edge of the tetrahedron is a 20 base pair DNA double helix, and each vertex is a three-arm junction.

Rotating view of C₆₀, one kind of fullerene

This device transfers energy from nano-thin layers of quantum wells to nanocrystals above them, causing the nanocrystals to emit visible light.

Nanomaterials

Many areas of science develop or study materials having unique properties arising from their nanoscale dimensions.

• Interface and colloid science produced many materials that may be useful in nanotechnology, such as carbon nanotubes and other fullerenes, and various nanoparticles and nanorods. Nanomaterials with fast ion transport are related to nanoionics and nanoelectronics.
• Nanoscale materials can be used for bulk applications; most commercial applications of nanotechnology are of this flavor.
• Progress has been made in using these materials for medical applications, including tissue engineering, drug delivery, antibacterials and biosensors.
• Nanoscale materials such as nanopillars are used in solar cells.
• Applications incorporating semiconductor nanoparticles in products such as display technology, lighting, solar cells and biological imaging; see quantum dots.

Bottom-up approaches

The bottom-up approach seeks to arrange smaller components into more complex assemblies.

• DNA nanotechnology utilizes Watson–Crick basepairing to construct well-defined structures out of DNA and other nucleic acids.
• Approaches from the field of "classical" chemical synthesis (inorganic and organic synthesis) aim at designing molecules with well-defined shape (e.g. bis-peptides).
• More generally, molecular self-assembly seeks to use concepts of supramolecular chemistry, and molecular recognition in particular, to cause single-molecule components to automatically arrange themselves into some useful conformation.
• Atomic force microscope tips can be used as a nanoscale "write head" to deposit a chemical upon a surface in a desired pattern in a process called dip-pen nanolithography. This technique fits into the larger subfield of nanolithography.
• Molecular-beam epitaxy allows for bottom-up assemblies of materials, most notably semiconductor materials commonly used in chip and computing applications, stacks, gating, and nanowire lasers.

Top-down approaches

These seek to create smaller devices by using larger ones to direct their assembly.

• Many technologies that descended from conventional solid-state silicon methods for fabricating microprocessors are capable of creating features smaller than 100 nm. Giant magnetoresistance-based hard drives already on the market fit this description, as do atomic layer deposition (ALD) techniques. Peter Grünberg and Albert Fert received the Nobel Prize in Physics in 2007 for their discovery of giant magnetoresistance and contributions to the field of spintronics.
• Solid-state techniques can be used to create nanoelectromechanical systems or NEMS, which are related to microelectromechanical systems or MEMS.
• Focused ion beams can directly remove material, or even deposit material when suitable precursor gasses are applied at the same time. For example, this technique is used routinely to create sub-100 nm sections of material for analysis in transmission electron microscopy.
• Atomic force microscope tips can be used as a nanoscale "write head" to deposit a resist, which is then followed by an etching process to remove material in a top-down method.

Functional approaches

Functional approaches seek to develop useful components without regard to how they might be assembled.

• Magnetic assembly for the synthesis of anisotropic superparamagnetic materials such as magnetic nano chains.
• Molecular scale electronics seeks to develop molecules with useful electronic properties. These could be used as single-molecule components in a nanoelectronic device, such as rotaxane.
• Synthetic chemical methods can be used to create synthetic molecular motors, such as in a so-called nanocar.

Biomimetic approaches

• Bionics or biomimicry seeks to apply biological methods and systems found in nature to the study and design of engineering systems and modern technology. Biomineralization is one example of the systems studied.
• Bionanotechnology is the use of biomolecules for applications in nanotechnology, including the use of viruses and lipid assemblies. Nanocellulose, a nanopolymer often used for bulk-scale applications, has gained interest owing to its useful properties such as abundance, high aspect ratio, good mechanical properties, renewability, and biocompatibility.

Speculative

These subfields seek to anticipate what inventions nanotechnology might yield, or attempt to propose an agenda along which inquiry could progress. These often take a big-picture view, with more emphasis on societal implications than engineering details.

• Molecular nanotechnology is a proposed approach that involves manipulating single molecules in finely controlled, deterministic ways. This is more theoretical than the other subfields, and many of its proposed techniques are beyond current capabilities.
• Nanorobotics considers self-sufficient machines operating at the nanoscale. There are hopes for applying nanorobots in medicine. Nevertheless, progress on innovative materials and patented methodologies have been demonstrated.
• Productive nanosystems are "systems of nanosystems" could produce atomically precise parts for other nanosystems, not necessarily using novel nanoscale-emergent properties, but well-understood fundamentals of manufacturing. Because of the discrete (i.e. atomic) nature of matter and the possibility of exponential growth, this stage could form the basis of another industrial revolution. Mihail Roco proposed four states of nanotechnology that seem to parallel the technical progress of the Industrial Revolution, progressing from passive nanostructures to active nanodevices to complex nanomachines and ultimately to productive nanosystems.
• Programmable matter seeks to design materials whose properties can be easily, reversibly and externally controlled though a fusion of information science and materials science.
• Due to the popularity and media exposure of the term nanotechnology, the words picotechnology and femtotechnology have been coined in analogy to it, although these are used only informally.

Dimensionality in nanomaterials

Nanomaterials can be classified in 0D, 1D, 2D and 3D nanomaterials. Dimensionality plays a major role in determining the characteristic of nanomaterials including physical, chemical, and biological characteristics. With the decrease in dimensionality, an increase in surface-to-volume ratio is observed. This indicates that smaller dimensional nanomaterials have higher surface area compared to 3D nanomaterials. Two dimensional (2D) nanomaterials have been extensively investigated for electronic, biomedical, drug delivery and biosensor applications.

Tools and techniques

Typical AFM setup. A microfabricated cantilever with a sharp tip is deflected by features on a sample surface, much like in a phonograph but on a much smaller scale. A laser beam reflects off the backside of the cantilever into a set of photodetectors, allowing the deflection to be measured and assembled into an image of the surface.

Scanning microscopes

The atomic force microscope (AFM) and the scanning tunneling microscope (STM) are two versions of scanning probes that are used for nano-scale observation. Other types of scanning probe microscopy have much higher resolution, since they are not limited by the wavelengths of sound or light.

The tip of a scanning probe can also be used to manipulate nanostructures (positional assembly). Feature-oriented scanning may be a promising way to implement these nano-scale manipulations via an automatic algorithm. However, this is still a slow process because of low velocity of the microscope.

The top-down approach anticipates nanodevices that must be built piece by piece in stages, much as manufactured items are made. Scanning probe microscopy is an important technique both for characterization and synthesis. Atomic force microscopes and scanning tunneling microscopes can be used to look at surfaces and to move atoms around. By designing different tips for these microscopes, they can be used for carving out structures on surfaces and to help guide self-assembling structures. By using, for example, feature-oriented scanning approach, atoms or molecules can be moved around on a surface with scanning probe microscopy techniques.

Lithography

Various techniques of lithography, such as optical lithography, X-ray lithography, dip pen lithography, electron beam lithography or nanoimprint lithography offer top-down fabrication techniques where a bulk material is reduced to a nano-scale pattern.

Another group of nano-technological techniques include those used for fabrication of nanotubes and nanowires, those used in semiconductor fabrication such as deep ultraviolet lithography, electron beam lithography, focused ion beam machining, nanoimprint lithography, atomic layer deposition, and molecular vapor deposition, and further including molecular self-assembly techniques such as those employing di-block copolymers.

Bottom-up

In contrast, bottom-up techniques build or grow larger structures atom by atom or molecule by molecule. These techniques include chemical synthesis, self-assembly and positional assembly. Dual-polarization interferometry is one tool suitable for characterization of self-assembled thin films. Another variation of the bottom-up approach is molecular-beam epitaxy or MBE. Researchers at Bell Telephone Laboratories including John R. Arthur. Alfred Y. Cho, and Art C. Gossard developed and implemented MBE as a research tool in the late 1960s and 1970s. Samples made by MBE were key to the discovery of the fractional quantum Hall effect for which the 1998 Nobel Prize in Physics was awarded. MBE lays down atomically precise layers of atoms and, in the process, build up complex structures. Important for research on semiconductors, MBE is also widely used to make samples and devices for the newly emerging field of spintronics.

Therapeutic products based on responsive nanomaterials, such as the highly deformable, stress-sensitive transfersome vesicles, are approved for human use in some countries.

Applications

One of the major applications of nanotechnology is in the area of nanoelectronics with MOSFET's being made of small nanowires ≈10 nm in length.

Nanowire lasers for ultrafast transmission of information in light pulses

This section needs to be updated. Please help update this article to reflect recent events or newly available information. (May 2024)

Main article: List of nanotechnology applications

As of August 21, 2008, the Project on Emerging Nanotechnologies estimated that over 800 manufacturer-identified nanotech products were publicly available, with new ones hitting the market at a pace of 3–4 per week. Most applications are "first generation" passive nanomaterials that includes titanium dioxide in sunscreen, cosmetics, surface coatings, and some food products; Carbon allotropes used to produce gecko tape; silver in food packaging, clothing, disinfectants, and household appliances; zinc oxide in sunscreens and cosmetics, surface coatings, paints and outdoor furniture varnishes; and cerium oxide as a fuel catalyst.

In the electric car industry, single wall carbon nanotubes (SWCNTs) address key lithium-ion battery challenges, including energy density, charge rate, service life, and cost. SWCNTs connect electrode particles during charge/discharge process, preventing battery premature degradation. Their exceptional ability to wrap active material particles enhanced electrical conductivity and physical properties, setting them apart multi-walled carbon nanotubes and carbon black.

Further applications allow tennis balls to last longer, golf balls to fly straighter, and bowling balls to become more durable. Trousers and socks have been infused with nanotechnology to last longer and lower temperature in the summer. Bandages are infused with silver nanoparticles to heal cuts faster. Video game consoles and personal computers may become cheaper, faster, and contain more memory thanks to nanotechnology. Also, to build structures for on chip computing with light, for example on chip optical quantum information processing, and picosecond transmission of information.

Nanotechnology may have the ability to make existing medical applications cheaper and easier to use in places like the doctors' offices and at homes. Cars use nanomaterials in such ways that car parts require fewer metals during manufacturing and less fuel to operate in the future.

Nanoencapsulation involves the enclosure of active substances within carriers. Typically, these carriers offer advantages, such as enhanced bioavailability, controlled release, targeted delivery, and protection of the encapsulated substances. In the medical field, nanoencapsulation plays a significant role in drug delivery. It facilitates more efficient drug administration, reduces side effects, and increases treatment effectiveness. Nanoencapsulation is particularly useful for improving the bioavailability of poorly water-soluble drugs, enabling controlled and sustained drug release, and supporting the development of targeted therapies. These features collectively contribute to advancements in medical treatments and patient care.

Nanotechnology may play role in tissue engineering. When designing scaffolds, researchers attempt to mimic the nanoscale features of a cell's microenvironment to direct its differentiation down a suitable lineage. For example, when creating scaffolds to support bone growth, researchers may mimic osteoclast resorption pits.

Researchers used DNA origami-based nanobots capable of carrying out logic functions to target drug delivery in cockroaches.

A nano bible (a .5mm2 silicon chip) was created by the Technion in order to increase youth interest in nanotechnology.

Implications

Main article: Implications of nanotechnology

One concern is the effect that industrial-scale manufacturing and use of nanomaterials will have on human health and the environment, as suggested by nanotoxicology research. For these reasons, some groups advocate that nanotechnology be regulated. However, regulation might stifle scientific research and the development of beneficial innovations. Public health research agencies, such as the National Institute for Occupational Safety and Health research potential health effects stemming from exposures to nanoparticles.

Nanoparticle products may have unintended consequences. Researchers have discovered that bacteriostatic silver nanoparticles used in socks to reduce foot odor are released in the wash. These particles are then flushed into the wastewater stream and may destroy bacteria that are critical components of natural ecosystems, farms, and waste treatment processes.

Public deliberations on risk perception in the US and UK carried out by the Center for Nanotechnology in Society found that participants were more positive about nanotechnologies for energy applications than for health applications, with health applications raising moral and ethical dilemmas such as cost and availability.

Experts, including director of the Woodrow Wilson Center's Project on Emerging Nanotechnologies David Rejeski, testified that commercialization depends on adequate oversight, risk research strategy, and public engagement. As of 206 Berkeley, California was the only US city to regulate nanotechnology.

Health and environmental concerns

Main articles: Health and safety hazards of nanomaterials and Pollution from nanomaterials

Inhaling airborne nanoparticles and nanofibers may contribute to pulmonary diseases, e.g. fibrosis. Researchers found that when rats breathed in nanoparticles, the particles settled in the brain and lungs, which led to significant increases in biomarkers for inflammation and stress response and that nanoparticles induce skin aging through oxidative stress in hairless mice.

A two-year study at UCLA's School of Public Health found lab mice consuming nano-titanium dioxide showed DNA and chromosome damage to a degree "linked to all the big killers of man, namely cancer, heart disease, neurological disease and aging".

A Nature Nanotechnology study suggested that some forms of carbon nanotubes could be as harmful as asbestos if inhaled in sufficient quantities. Anthony Seaton of the Institute of Occupational Medicine in Edinburgh, Scotland, who contributed to the article on carbon nanotubes said "We know that some of them probably have the potential to cause mesothelioma. So those sorts of materials need to be handled very carefully." In the absence of specific regulation forthcoming from governments, Paull and Lyons (2008) have called for an exclusion of engineered nanoparticles in food. A newspaper article reports that workers in a paint factory developed serious lung disease and nanoparticles were found in their lungs.

Regulation

Main article: Regulation of nanotechnology

Calls for tighter regulation of nanotechnology have accompanied a debate related to human health and safety risks. Some regulatory agencies cover some nanotechnology products and processes – by "bolting on" nanotechnology to existing regulations – leaving clear gaps. Davies proposed a road map describing steps to deal with these shortcomings.

Andrew Maynard, chief science advisor to the Woodrow Wilson Center's Project on Emerging Nanotechnologies, reported insufficient funding for human health and safety research, and as a result inadequate understanding of human health and safety risks. Some academics called for stricter application of the precautionary principle, slowing marketing approval, enhanced labelling and additional safety data.

A Royal Society report identified a risk of nanoparticles or nanotubes being released during disposal, destruction and recycling, and recommended that "manufacturers of products that fall under extended producer responsibility regimes such as end-of-life regulations publish procedures outlining how these materials will be managed to minimize possible human and environmental exposure".