Reverse engineering

From Wikipedia, the free encyclopedia

Reverse engineering, also called back engineering, is the process by which a man-made object is deconstructed to reveal its designs, architecture, or to extract knowledge from the object; similar to scientific research, the only difference being that scientific research is about a natural phenomenon.


Reverse engineering is applicable in the fields of mechanical engineering, electronic engineering, software engineering, chemical engineering,^[2] and systems biology.^[3]

Overview

Reverse engineering has its origins in the analysis of hardware for commercial or military advantage.^[4]:13 However, the reverse engineering process in itself is not concerned with creating a copy or changing the artifact in some way; it is only an analysis in order to deduce design features from products with little or no additional knowledge about the procedures involved in their original production.^[4]:15 In some cases, the goal of the reverse engineering process can simply be a redocumentation of legacy systems.^[4]:15[5] Even when the product reverse engineered is that of a competitor, the goal may not be to copy them, but to perform competitor analysis.^[6] Reverse engineering may also be used to create interoperable products and despite some narrowly tailored United States and European Union legislation, the legality of using specific reverse engineering techniques for this purpose has been hotly contested in courts worldwide for more than two decades.^[7]

There are many reasons for performing reverse engineering in various fields. Reverse engineering software can help to improve the understanding of the underlying source code for the maintenance and improvement of the software, relevant information can be extracted in order to make a decision for software development and graphical representations of the code can provide alternate views regarding the source code, which can help to detect and fix a software bug or vulnerability.

Frequently, as some software develops, its design information and improvements are often lost over time, but this lost information can usually be recovered with reverse engineering. This process can also help to cut down the time required to understand the source code, reducing the overall cost of the software development.^[8] Reverse engineering can also help to detect and eliminate a malicious code written to the software with better code detectors. Reversing a source code can be used to find alternate uses of the source code, such as to detect unauthorized replication of the source code where it wasn't intended to be used, or to reveal how a competitors product was built.^[1] This process is commonly used for "cracking" software and media to remove their copy protection,^[1]:7 or to create a (possibly improved) copy or even a knockoff, which is usually the goal of a competitor or a hacker.^[1]:8 Malware developers often use reverse engineering techniques to find vulnerabilities in an operating system (OS), in order build a computer virus that can exploit the system vulnerabilities.^[1]:5 Reverse engineering is also being used in cryptanalysis in order to find vulnerabilities in substitution cipher, symmetric-key algorithm or public-key cryptography.^[1]:6

• Interfacing. Reverse engineering can be used when a system is required to interface to another system and how both systems would negotiate is to be established. Such requirements typically exist for interoperability.
• Military or commercial espionage. Learning about an enemy’s or competitor’s latest research by stealing or capturing a prototype and dismantling it, which may result in development of similar product, or a better countermeasure against it.
• Obsolescence. Integrated circuits are often designed on proprietary systems, and built on production lines which become obsolete in only a few years. When systems using these parts can no longer be maintained (since the parts are no longer made), the only way to incorporate the functionality into new technology is to reverse engineer the existing chip and then redesign it using newer tools, using the understanding gained as a guide. Another obsolescence originated problem which can be solved by reverse engineering is the need to support (maintenance and supply for continuous operation) existing, legacy devices which are no longer supported by their original equipment manufacturer (OEM). This problem is particularly critical in military operations.
• Product security analysis. To examine how a product works, what are specifications of its components, estimate costs and identify potential patent infringement. Acquiring sensitive data by disassembling and analysing the design of a system component.^[9] Another intent may be to remove copy protection, or circumvention of access restrictions.
• Competitive technical intelligence. Understand what one's competitor is actually doing, versus what they say they are doing.
• Saving money, when one finds out what a piece of electronics is capable of, it can spare a user from purchase of a separate product.
• Repurposing, when obsolete objects are reused in a different but useful manner.

Common situations

Reverse engineering of machines

As computer-aided design (CAD) has become more popular, reverse engineering has become a viable method to create a 3D virtual model of an existing physical part for use in 3D CAD, CAM, CAE or other software.^[10] The reverse-engineering process involves measuring an object and then reconstructing it as a 3D model. The physical object can be measured using 3D scanning technologies like CMMs, laser scanners, structured light digitizers, or Industrial CT Scanning (computed tomography). The measured data alone, usually represented as a point cloud, lacks topological information and is therefore often processed and modeled into a more usable format such as a triangular-faced mesh, a set of NURBS surfaces, or a CAD model.^[11]

Hybrid Modelling is commonly used term when NURBS and Parametric modelling are implemented together. Using a combination of geometric and freeform surfaces can provide a powerful method of 3D modelling. Areas of freeform data can be combined with exact geometric surfaces to create a hybrid model. A typical example of this would be the reverse engineering of a cylinder head, which includes freeform cast features, such as water jackets and high tolerance machined areas.^[12]

Reverse engineering is also used by businesses to bring existing physical geometry into digital product development environments, to make a digital 3D record of their own products, or to assess competitors' products. It is used to analyse, for instance, how a product works, what it does, and what components it consists of, estimate costs, and identify potential patent infringement, etc.

Value engineering is a related activity also used by businesses. It involves de-constructing and analysing products, but the objective is to find opportunities for cost cutting.

Reverse engineering of software

In 1990, Institute of Electrical and Electronics Engineers (IEEE) defined reverse engineering as "the process of analyzing a subject system to identify the system's components and their interrelationships and to create representations of the system in another form or at a higher level of abstraction", where the "subject system" is the end product of software development. Reverse engineering is a process of examination only: the software system under consideration is not modified (which would make it re-engineering or restructuring). Reverse engineering can be performed from any stage of the product cycle, not necessarily from the functional end product.

There are two components in reverse engineering: redocumentation and design recovery. Redocumentation is the creation of new representation of the computer code so that it is easier to understand. Meanwhile, design recovery is the using of deduction or reasoning from general knowledge or personal experience of the product in order to fully understand the product functionality.^[8] It can also be seen as "going backwards through the development cycle".^[13] In this model, the output of the implementation phase (in source code form) is reverse-engineered back to the analysis phase, in an inversion of the traditional waterfall model. Another term for this technique is program comprehension.^[5] Working Conference on Reverse Engineering (WCRE) has been held yearly to explore and expand the techniques of reverse engineering.^[1][14] Computer-aided software engineering (CASE) and automated code generation have contributed greatly in the field of reverse engineering.^[1]

Software anti-tamper technology like obfuscation is used to deter both reverse engineering and re-engineering of proprietary software and software-powered systems. In practice, two main types of reverse engineering emerge. In the first case, source code is already available for the software, but higher-level aspects of the program, perhaps poorly documented or documented but no longer valid, are discovered. In the second case, there is no source code available for the software, and any efforts towards discovering one possible source code for the software are regarded as reverse engineering. This second usage of the term is the one most people are familiar with. Reverse engineering of software can make use of the clean room design technique to avoid copyright infringement.

On a related note, black box testing in software engineering has a lot in common with reverse engineering. The tester usually has the API, but their goals are to find bugs and undocumented features by bashing the product from outside.^[15]

Other purposes of reverse engineering include security auditing, removal of copy protection ("cracking"), circumvention of access restrictions often present in consumer electronics, customization of embedded systems (such as engine management systems), in-house repairs or retrofits, enabling of additional features on low-cost "crippled" hardware (such as some graphics card chip-sets), or even mere satisfaction of curiosity.

Binary software

Binary reverse engineering is performed if source code for a software is unavailable.^[1] This process is sometimes termed Reverse Code Engineering, or RCE.^[16] As an example, decompilation of binaries for the Java platform can be accomplished using Jad. One famous case of reverse engineering was the first non-IBM implementation of the PC BIOS which launched the historic IBM PC compatible industry that has been the overwhelmingly dominant computer hardware platform for many years. Reverse engineering of software is protected in the U.S. by the fair use exception in copyright law.^[17] The Samba software, which allows systems that are not running Microsoft Windows systems to share files with systems that are, is a classic example of software reverse engineering,^[18] since the Samba project had to reverse-engineer unpublished information about how Windows file sharing worked, so that non-Windows computers could emulate it. The Wine project does the same thing for the Windows API, and OpenOffice.org is one party doing this for the Microsoft Office file formats. The ReactOS project is even more ambitious in its goals, as it strives to provide binary (ABI and API) compatibility with the current Windows OSes of the NT branch, allowing software and drivers written for Windows to run on a clean-room reverse-engineered Free Software (GPL) counterpart. WindowsSCOPE allows for reverse-engineering the full contents of a Windows system's live memory including a binary-level, graphical reverse engineering of all running processes.

Another classic, if not well-known example is that in 1987 Bell Laboratories reverse-engineered the Mac OS System 4.1, originally running on the Apple Macintosh SE, so they could run it on RISC machines of their own.^[19]

Binary software techniques

Reverse engineering of software can be accomplished by various methods. The three main groups of software reverse engineering are

1. Analysis through observation of information exchange, most prevalent in protocol reverse engineering, which involves using bus analyzers and packet sniffers, for example, for accessing a computer bus or computer network connection and revealing the traffic data thereon. Bus or network behavior can then be analyzed to produce a stand-alone implementation that mimics that behavior. This is especially useful for reverse engineering device drivers. Sometimes, reverse engineering on embedded systems is greatly assisted by tools deliberately introduced by the manufacturer, such as JTAG ports or other debugging means. In Microsoft Windows, low-level debuggers such as SoftICE are popular.
   
2. Disassembly using a disassembler, meaning the raw machine language of the program is read and understood in its own terms, only with the aid of machine-language mnemonics. This works on any computer program but can take quite some time, especially for someone not used to machine code. The Interactive Disassembler is a particularly popular tool.
   
3. Decompilation using a decompiler, a process that tries, with varying results, to recreate the source code in some high-level language for a program only available in machine code or bytecode.

Software classification

Software classification is the process of identifying similarities between different software binaries (for example, two different versions of the same binary) used to detect code relations between software samples. This task was traditionally done manually for several reasons (such as patch analysis for vulnerability detection and copyright infringement) but nowadays can be done somewhat automatically for large numbers of samples.

This method is being used mostly for long and thorough reverse engineering tasks (complete analysis of a complex algorithm or big piece of software). In general, statistical classification is considered to be a hard problem and this is also true for software classification, therefore there aren't many solutions/tools that handle this task well.

Source code

A number of UML tools refer to the process of importing and analysing source code to generate UML diagrams as "reverse engineering".

Although UML is one approach to providing "reverse engineering" more recent advances in international standards activities have resulted in the development of the Knowledge Discovery Metamodel (KDM). This standard delivers an ontology for the intermediate (or abstracted) representation of programming language constructs and their interrelationships. An Object Management Group standard (on its way to becoming an ISO standard as well), KDM has started to take hold in industry with the development of tools and analysis environments which can deliver the extraction and analysis of source, binary, and byte code. For source code analysis, KDM's granular standards' architecture enables the extraction of software system flows (data, control, & call maps), architectures, and business layer knowledge (rules, terms, process). The standard enables the use of a common data format (XMI) enabling the correlation of the various layers of system knowledge for either detailed analysis (e.g. root cause, impact) or derived analysis (e.g. business process extraction). Although efforts to represent language constructs can be never-ending given the number of languages, the continuous evolution of software languages and the development of new languages, the standard does allow for the use of extensions to support the broad language set as well as evolution. KDM is compatible with UML, BPMN, RDF and other standards enabling migration into other environments and thus leverage system knowledge for efforts such as software system transformation and enterprise business layer analysis.

Reverse engineering of protocols

Protocols are sets of rules that describe message formats and how messages are exchanged (i.e., the protocol state-machine). Accordingly, the problem of protocol reverse-engineering can be partitioned into two subproblems; message format and state-machine reverse-engineering.

The message formats have traditionally been reverse-engineered through a tedious manual process, which involved analysis of how protocol implementations process messages, but recent research proposed a number of automatic solutions.^[20][21][22] Typically, these automatic approaches either group observed messages into clusters using various clustering analyses, or emulate the protocol implementation tracing the message processing.

There has been less work on reverse-engineering of state-machines of protocols. In general, the protocol state-machines can be learned either through a process of offline learning, which passively observes communication and attempts to build the most general state-machine accepting all observed sequences of messages, and online learning, which allows interactive generation of probing sequences of messages and listening to responses to those probing sequences. In general, offline learning of small state-machines is known to be NP-complete,^[23] while online learning can be done in polynomial time.^[24] An automatic offline approach has been demonstrated by Comparetti et al.^[22] and an online approach by Cho et al.^[25]

Other components of typical protocols, like encryption and hash functions, can be reverse-engineered automatically as well. Typically, the automatic approaches trace the execution of protocol implementations and try to detect buffers in memory holding unencrypted packets.^[26]

Reverse engineering of integrated circuits/smart cards

Reverse engineering is an invasive and destructive form of analyzing a smart card. The attacker grinds away layer after layer of the smart card and takes pictures with an electron microscope. With this technique, it is possible to reveal the complete hardware and software part of the smart card. The major problem for the attacker is to bring everything into the right order to find out how everything works. The makers of the card try to hide keys and operations by mixing up memory positions, for example, bus scrambling.^[27][28] In some cases, it is even possible to attach a probe to measure voltages while the smart card is still operational. The makers of the card employ sensors to detect and prevent this attack.^[29] This attack is not very common because it requires a large investment in effort and special equipment that is generally only available to large chip manufacturers. Furthermore, the payoff from this attack is low since other security techniques are often employed such as shadow accounts. It is uncertain at this time whether attacks against CHIP/PIN cards to replicate encryption data and consequentially crack PINS would provide a cost effective attack on multifactor authentication.

Reverse engineering for military applications

Reverse engineering is often used by people in order to copy other nations' technologies, devices, or information that have been obtained by regular troops in the fields or by intelligence operations. It was often used during the Second World War and the Cold War. Well-known examples from WWII and later include:

• Jerry can: British and American forces noticed that the Germans had gasoline cans with an excellent design. They reverse-engineered copies of those cans. The cans were popularly known as "Jerry cans".
• Panzerschreck: The Germans captured an American Bazooka during World War II, and reverse engineered it to create the larger Panzerschreck.
• Tupolev Tu-4: In 1944, three American B-29 bombers on missions over Japan were forced to land in the USSR. The Soviets, who did not have a similar strategic bomber, decided to copy the B-29. Within three years, they had developed the Tu-4, a near-perfect copy.
• SCR-584 radar: copied by USSR after the Second World War. Known in the form a few modifications - СЦР-584, Бинокль-Д.
• V-2 rocket: Technical documents for the V2 and related technologies were captured by the Western Allies at the end of the war. The American side focused their reverse engineering efforts via operation Paperclip, which led to the development of the PGM-11 Redstone rocket.^[30] The Soviet side used captured German engineers to reproduce technical documents and plans, and work from captured hardware in order to make their clone of the rocket, the R-1. Thus began the postwar Soviet rocket program that led to the R-7 and the beginning of the space race.
• K-13/R-3S missile (NATO reporting name AA-2 Atoll), a Soviet reverse-engineered copy of the AIM-9 Sidewinder, was made possible after a Taiwanese AIM-9B hit a Chinese MiG-17 without exploding in September 1958.^[31] The missile became lodged within the airframe, and the pilot returned to base with what Russian scientists would describe as a university course in missile development.
• BGM-71 TOW Missile: In May 1975, negotiations between Iran and Hughes Missile Systems on co-production of the TOW and Maverick missiles stalled over disagreements in the pricing structure, the subsequent 1979 revolution ending all plans for such co-production. Iran was later successful in reverse-engineering the missile and are currently producing their own copy: the Toophan.
• China has reversed engineered many examples of Western and Russian hardware, from fighter aircraft to missiles and HMMWV cars.
• During the Second World War, Polish and British cryptographers studied captured German "Enigma" message encryption machines for weaknesses. Their operation was then simulated on electro-mechanical devices called "Bombes" that tried all the possible scrambler settings of the "Enigma" machines to help break the coded messages sent by the Germans.
• Also during the Second World War, British scientists analyzed and defeated a series of increasingly sophisticated radio navigation systems being used by the German Luftwaffe to perform guided bombing missions at night. The British countermeasures to this system were so effective that in some cases German aircraft were led by signals to land at RAF bases, believing they were back in German territory.

Overlap with patent law

Reverse engineering applies primarily to gaining understanding of a process or artifact, where the manner of its construction, use, or internal processes is not made clear by its creator.

Patented items do not of themselves have to be reverse-engineered to be studied, since the essence of a patent is that the inventor provides detailed public disclosure themselves, and in return receives legal protection of the invention involved. However, an item produced under one or more patents could also include other technology that is not patented and not disclosed. Indeed, one common motivation of reverse engineering is to determine whether a competitor's product contains patent infringements or copyright infringements.

Legality

United States

In the United States even if an artifact or process is protected by trade secrets, reverse-engineering the artifact or process is often lawful as long as it has been legitimately obtained.^[32]

Reverse engineering of computer software in the US often falls under both contract law as a breach of contract as well as any other relevant laws. This is because most EULAs (end user license agreement) specifically prohibit it, and U.S. courts have ruled that if such terms are present, they override the copyright law which expressly permits it (see Bowers v. Baystate Technologies^[33][34]). Sec. 103(f) of the DMCA (17 U.S.C. § 1201 (f)) says that a person who is in legal possession of a program, is permitted to reverse-engineer and circumvent its protection if this is necessary in order to achieve "interoperability" — a term broadly covering other devices and programs being able to interact with it, make use of it, and to use and transfer data to and from it, in useful ways. A limited exemption exists that allows the knowledge thus gained to be shared and used for interoperability purposes.^[35]

European Union

EU Directive 2009/24 — which superseded an earlier (1991) directive^[36] — on the legal protection of computer programs, governs reverse engineering in the European Union.^[37][38]

Biomimetics

From Wikipedia, the free encyclopedia

 

The tiny hooks on bur fruits ...

... inspired Velcro tape.

Biomimetics or biomimicry is the imitation of the models, systems, and elements of nature for the purpose of solving complex human problems.^[1] The terms "biomimetics" and "biomimicry" derive from Ancient Greek: βίος (bios), life, and μίμησις (mīmēsis), imitation, from μιμεῖσθαι (mīmeisthai), to imitate, from μῖμος (mimos), actor. A closely related field is bionics.

Living organisms have evolved well-adapted structures and materials over geological time through natural selection. Biomimetics has given rise to new technologies inspired by biological solutions at macro and nanoscales. Humans have looked at nature for answers to problems throughout our existence. Nature has solved engineering problems such as self-healing abilities, environmental exposure tolerance and resistance, hydrophobicity, self-assembly, and harnessing solar energy.

History

One of the early examples of would-be biomimicry was the study of birds to enable human flight. Although never successful in creating a "flying machine", Leonardo da Vinci (1452–1519) was a keen observer of the anatomy and flight of birds, and made numerous notes and sketches on his observations as well as sketches of "flying machines".^[3] The Wright Brothers, who succeeded in flying the first heavier-than-air aircraft in 1903, allegedly derived inspiration from observations of pigeons in flight.^[4]

During the 1950s the American biophysicist and polymath Otto Schmitt developed the concept of "biomimetics".^[5] During his doctoral research he developed the Schmitt trigger by studying the nerves in squid, attempting to engineer a device that replicated the biological system of nerve propagation.^{[6][need quotation to verify]} He continued to focus on devices that mimic natural systems and by 1957 he had perceived a converse to the standard view of biophysics at that time, a view he would come to call biomimetics.^[5]

Biophysics is not so much a subject matter as it is a point of view. It is an approach to problems of biological science utilizing the theory and technology of the physical sciences. Conversely, biophysics is also a biologist's approach to problems of physical science and engineering, although this aspect has largely been neglected.

— Otto Herbert Schmitt, In Appreciation, A Lifetime of Connections: Otto Herbert Schmitt, 1913 - 1998

In 1960 Jack E. Steele coined a similar term, bionics, at Wright-Patterson Air Force Base in Dayton, Ohio, where Otto Schmitt also worked. Steele defined bionics as "the science of systems which have some function copied from nature, or which represent characteristics of natural systems or their analogues".^[2][7] During a later meeting in 1963 Schmitt stated,

Let us consider what bionics has come to mean operationally and what it or some word like it (I prefer biomimetics) ought to mean in order to make good use of the technical skills of scientists specializing, or rather, I should say, despecializing into this area of research

— Otto Herbert Schmitt, In Appreciation, A Lifetime of Connections: Otto Herbert Schmitt, 1913 - 1998

In 1969 Schmitt used the term “biomimetic“ in the title one of his papers,^[8] and by 1974 it had found its way into Webster's Dictionary, bionics entered the same dictionary earlier in 1960 as "a science concerned with the application of data about the functioning of biological systems to the solution of engineering problems". Bionic took on a different connotation when Martin Caidin referenced Jack Steele and his work in the novel Cyborg which later resulted in the 1974 television series The Six Million Dollar Man and its spin-offs. The term bionic then became associated with "the use of electronically operated artificial body parts" and "having ordinary human powers increased by or as if by the aid of such devices".^[9] Because the term bionic took on the implication of supernatural strength, the scientific community in English speaking countries largely abandoned it.^[10]

The term biomimicry appeared as early as 1982.^[11] Biomimicry was popularized by scientist and author Janine Benyus in her 1997 book Biomimicry: Innovation Inspired by Nature. Biomimicry is defined in the book as a "new science that studies nature's models and then imitates or takes inspiration from these designs and processes to solve human problems". Benyus suggests looking to Nature as a "Model, Measure, and Mentor" and emphasizes sustainability as an objective of biomimicry.^[12]

Commercial applications

Fabrication

Scanning electron micrograph of rod shaped tobacco mosaic virus particles

Biomorphic mineralization is a technique that produces materials with morphologies and structures resembling those of natural living organisms by using bio-structures as templates for mineralization. Compared to other methods of material production, biomorphic mineralization is facile, environmentally benign and economic.^[13]

Display technology

Vibrant blue color of Morpho butterfly due to structural coloration

Morpho butterfly wings contain microstructures that create its coloring effect through structural coloration rather than pigmentation. Incident light waves are reflected at specific wavelengths to create vibrant colors due to multilayer interference, diffraction, thin film interference, and scattering properties.^[14] The scales of these butterflies consist of microstructures such as ridges, cross-ribs, ridge-lamellae, and microribs that have been shown to be responsible for coloration. The structural color has been simply explained as the interference due to alternating layers of cuticle and air using a model of multilayer interference. The same principles behind the coloration of soap bubbles apply to butterfly wings. The color of butterfly wings is due to multiple instances of constructive interference from structures such as this. The photonic microstructure of butterfly wings can be replicated through biomorphic mineralization to yield similar properties. The photonic microstructures can be replicated using metal oxides or metal alkoxides such as titanium sulfate (TiSO₄), zirconium oxide (ZrO₂), and aluminium oxide (Al₂O₃). An alternative method of vapor-phase oxidation of SiH4 on the template surface was found to preserve delicate structural features of the microstructure.^[15] A display technology ("Mirasol") based on the reflective properties of Morpho butterfly wings was commercialized by Qualcomm in 2007. The technology uses Interferometric Modulation to reflect light so only the desired color is visible in each individual pixel of the display.^[16]

Possible future applications

Leonardo da Vinci's design for a flying machine with wings based closely upon the structure of bat wings

Biomimetics could in principle be applied in many fields. Because of the complexity of biological systems, the number of features that might be imitated is large. Biomimetic applications are at various stages of development from technologies that might become commercially usable to prototypes.^[17]

Prototypes

Researchers studied the termite's ability to maintain virtually constant temperature and humidity in their termite mounds in Africa despite outside temperatures that vary from 1.5 °C to 40 °C (35 °F to 104 °F). Researchers initially scanned a termite mound and created 3-D images of the mound structure, which revealed construction that could influence human building design. The Eastgate Centre, a mid-rise office complex in Harare, Zimbabwe,^[18] stays cool without air conditioning and uses only 10% of the energy of a conventional building of the same size.

In structural engineering, the Swiss Federal Institute of Technology (EPFL) has incorporated biomimetic characteristics in an adaptive deployable "tensegrity" bridge. The bridge can carry out self-diagnosis and self-repair.^[19]

Technologies

Practical underwater adhesion is an engineering challenge since current technology is unable to stick surface strongly underwater because of barriers such as hydration layers and contaminants on surfaces. However, marine mussels can stick easily and efficiently to surfaces underwater under the harsh conditions of the ocean. They use strong filaments to adhere to rocks in the inter-tidal zones of wave-swept beaches, preventing them from being swept away in strong sea currents. Mussel foot proteins attach the filaments to rocks, boats and practically any surface in nature including other mussels. These proteins contain a mix of amino acid residues which has been adapted specifically for adhesive purposes. Researchers from the University of California Santa Barbara borrowed and simplified chemistries that the mussel foot uses to overcome this engineering challenge of wet adhesion to create copolyampholytes,^[20] and one-component adhesive systems^[21] with potential for employment in nanofabrication protocols.

Spider web silk is as strong as the Kevlar used in bulletproof vests. Engineers could in principle use such a material, if it could be reengineered to have a long enough life, for parachute lines, suspension bridge cables, artificial ligaments for medicine, and other purposes.^[12] Other research has proposed adhesive glue from mussels, solar cells made like leaves, fabric that emulates shark skin, harvesting water from fog like a beetle, and more.^[18] Murray's law, which in conventional form determined the optimum diameter of blood vessels, has been re-derived to provide simple equations for the pipe or tube diameter which gives a minimum mass engineering system.^[22] Aircraft wing design ^[3] and flight techniques^[23] are being inspired by birds and bats.

The BionicKangaroo reproduces the jumping locomotion of a kangaroo, bouncing to recover much of the energy of each jump.

Biorobots based on the physiology and methods of locomotion of animals include BionicKangaroo which moves like a kangaroo, saving energy from one jump and transferring it to its next jump,^[24] and climbing robots,^[25] boots and tape^[26] mimicking geckos feet and their ability for adhesive reversal. Kamigami Robots, a children's toy, mimic cockroach locomotion to run quickly and efficiently over indoor and outdoor surfaces.^[27] Nanotechnology surfaces that recreate properties of shark skin are intended to enable more efficient movement through water.^[28] Tire treads have been inspired by the toe pads of tree frogs.^[29] The self-sharpening teeth of many animals have been copied to make better cutting tools.^[30] Protein folding has been used to control material formation for self-assembled functional nanostructures.^[31] The structural coloration of butterfly wings has been adapted to provide improved interferometric modulator displays and everlasting colours.^[32] New ceramics copy the properties of seashells.^[33] Polar bear fur has inspired the design of thermal collectors and clothing.^[34] The arrangement of leaves on a plant has been adapted for better solar power collection.^[35] The light refractive properties of the moth's eye has been studied to reduce the reflectivity of solar panels.^[36] Self-healing materials, polymers and composite materials capable of mending cracks have been produced based on biological materials.^[37]

The Bombardier beetle's powerful repellent spray inspired a Swedish company to develop a "micro mist" spray technology, which is claimed to have a low carbon impact (compared to aerosol sprays). The beetle mixes chemicals and releases its spray via a steerable nozzle at the end of its abdomen, stinging and confusing the victim.^[38]

Most viruses have an outer capsule 20 to 300 nm in diameter. Virus capsules are remarkably robust and capable of withstanding temperatures as high as 60 °C; they are stable across the pH range 2-10.^[13] Viral capsules can be used to create nano device components such as nanowires, nanotubes, and quantum dots. Tubular virus particles such as the tobacco mosaic virus (TMV) can be used as templates to create nanofibers and nanotubes, since both the inner and outer layers of the virus are charged surfaces which can induce nucleation of crystal growth. This was demonstrated through the production of platinum and gold nanotubes using TMV as a template.^[39] Mineralized virus particles have been shown to withstand various pH values by mineralizing the viruses with different materials such as silicon, PbS, and CdS and could therefore serve as a useful carriers of material.^[40] A spherical plant virus called cowpea chlorotic mottle virus (CCMV) has interesting expanding properties when exposed to environments of pH higher than 6.5. Above this pH, 60 independent pores with diameters about 2 nm begin to exchange substance with the environment. The structural transition of the viral capsid can be utilized in Biomorphic mineralization for selective uptake and deposition of minerals by controlling the solution pH. Possible applications include using the viral cage to produce uniformly shaped and sized quantum dot semiconductor nanoparticles through a series of pH washes. This is an alternative to the apoferritin cage technique currently used to synthesize uniform CdSe nanoparticles.^[41] Such materials could also be used for targeted drug delivery since particles release contents upon exposure to specific pH levels.

Surface tension biomimetics are being researched for technologies such as hydrophobic or hydrophilic coatings and microactuators.^{[42][43][44][45][46]}

Biomimetic materials are gaining increasing attention in the field of optics and photonics. For example, the chiral self-assembly of cellulose inspired by the Pollia condensata berry has been exploited to make optically active films.^[47] Similarly, phase-separation has been used to fabricate ultra-white scattering membranes from polymethylmethacrylate, mimicking the extraordinary properties of the beetle Cyphochilus.

Artificial enzyme

From Wikipedia, the free encyclopedia

Schematic drawing of artificial phosphorylase

An artificial enzyme is a synthetic, organic molecule or ion that recreate some function of an enzyme. The area promises to deliver catalysis at rates and selectivity observed in many enzymes.

History

Enzyme catalysis of chemical reactions occur with high selectivity and rate. The substrate is activated in a small part of the enzyme's macromolecule called the active site. There, the binding of a substrate close to functional groups in the enzyme causes catalysis by so-called proximity effects. It is possible to create similar catalysts from small molecule by combining substrate-binding with catalytic functional groups. Classically artificial enzymes bind substrates using receptors such as cyclodextrin, crown ethers, and calixarene.^[1][2]

Artificial enzymes based on amino acids or peptides as characteristic molecular moieties have expanded the field of artificial enzymes or enzyme mimics. For instance, scaffolded histidine residues mimics certain metalloproteins and -enzymes such as hemocyanin, tyrosinase, and catechol oxidase).^[3]

Artificial enzymes have been designed from scratch via a computational strategy using Rosetta.^[4] In December 2014, it was announced that active enzymes had been produced that were made from artificial molecules which do not occur anywhere in nature.^[5] In 2017, a book chapter entitled "Artificial Enzymes: The Next Wave" was published.[1]

Nanozymes

Nanozymes are nanomaterials with enzyme-like characteristics.^[6] They have been widely explored for various applications, such as biosensing, bioimaging, tumor diagnosis and therapy, antibiofouling.

1990s

In 1996 and 1997, Dugan et al. discovered the superoxide dismutase (SOD) mimicking activities of fullerene derivatives.^[12][13]

2000s

In 2004, the term "nanozymes" was coined by Flavio Manea, Florence Bodar Houillon, Lucia Pasquato, and Paolo Scrimin.^[14] In 2006, nanoceria (i.e., CeO2 nanoparticles) was used for preventing retinal degeneration induced by intracellular peroxides.^[15][16] In 2007, Xiyun Yan and coworkers reported that ferromagnetic nanoparticles possessed intrinsic peroxidase-like activity.^[17][18] In 2008, Hui Wei and Erkang Wang developed an iron oxide nanozyme based sensing platform for bioactive molecules (such as hydrogen peroxide and glucose).^[19]

2010s

In 2012, recombinant human heavy-chain ferritin coated iron oxide nanoparticle with peroxidase-like activity was prepared and used for targeting and visualizing tumour tissues.^[20] In 2012, vanadium pentoxide nanoparticles with vanadium haloperoxidase mimicking activities were used for preventing marine biofouling.^[21] In 2014, it was demonstrated that carboxyfullerene could be used to treat neuroprotection postinjury in Parkinsonian nonhuman primates.^[22] In 2015, a supramolecular regulation strategy was proposed to modulate the activity of gold-based nanozymes for imaging and therapeutic applications.^[23][24] A nanozyme-strip for rapid local diagnosis of Ebola was developed.^[25][26] Nanoceria nanozymes were used for DNA sensing.^[27] An integrated nanozyme has been developed for real time monitoring the dynamic changes of cerebral glucose in living brains.^[28][29] Cu(OH)2 nanozymes with peroxidase-like activities were reported.^[30] Ionic FePt, Fe3O4, Pd, and CdSe NPs with peroxidase-like activities were reported.^[31] A book entitled "Nanozymes: Next Wave of Artificial Enzymes" was published.^[32] A book chapter entitled "Nanozymes" in the book of "Enzyme Engineering" was published (in Chinese).^[33] Oxidase-like nanoceria has been used for developing self-regulated bioassays.^[34] Multi-enzyme mimicking Prussian blue was developed for therapeutics.^[35] Histidine was used to modulate iron oxide nanoparticles' peroxidase mimicking activities.^[36] Gold nanoparticles' peroxidase mimicking activities were modulated via a supramolecular strategy for cascade reactions.^[37] A molecular imprinting strategy was developed to improve the selectivity of Fe3O4 nanozymes with peroxidase-like activity.^[38] A new strategy was developed to enhance the peroxidase mimicking activity of gold nanoparticles by using hot electrons.^[39] Researchers have designed gold nanoparticles (AuNPs) based integrative nanozymes with both SERS and peroxidase mimicking activities for measuring glucose and lactate in living tissues.^[40] Cytochrome c oxidase mimicking activity of Cu2O nanoparticles was modulated by receiving electrons from cytochrome c.^[41] Fe3O4 NPs were combined with glucose oxidase for tumor therapeutics.^[42] Manganese dioxide nanozymes have been used as cytoprotective shells.^[43] Mn3O4 Nanozyme for Parkinson's Disease (cellular model) was reported.^[44] Heparin elimination in live rats has been monitored with 2D MOF based peroxidase mimics and AG73 peptide.^[45] Glucose oxidase and iron oxide nanozymes were encapsulated within multi-compartmental hydrogels for incompatible tandem reactions.^[46] A cascade nanozyme biosensor was developed for detection of viable Enterobacter sakazakii.^[47] An integrated nanozyme of GOx@ZIF-8(NiPd) was developed for tandem catalysis.^[48] Charge-switchable nanozymes were developed.^[49] Site-selective RNA splicing nanozyme was developed.^[50] A nanozymes special issue in Progress in Biochemistry and Biophysics was published.^[51] Mn3O4 nanozymes with ROS scavenging activities have been developed for in vivo anti-inflammation.^[52] A concept entitled "A Step into the Future – Applications of Nanoparticle Enzyme Mimics" was proposed.^[53] Facet-dependent oxidase and peroxidase-like activities of Pd nanoparticles were reported.^[54] Au@Pt multibranched nanostructures as bifunctional nanozymes were developed.^[55] Ferritin coated carbon nanozymes were developed for tumor catalytic therapy.^[56] CuO nanozymes were developed to kill bacteria via a light-controlled manner.^[57] Enzymatic activity of oxygenated CNT was studied.^[58] Nanozymes were used to catalyze the oxidation of l-Tyrosine and l-Phenylalanine to dopachrome.^[59] Nanozyme as an emerging alternative to natural enzyme for biosensing and immunoassay was summarized.^[60]

Conferences

Several conferences have focused on nanozymes. In 2015, a nanozyme workshop for was held at the 9th Asian Biophysics Associatation (ABA) Symposium.^[61] In Pittcon 2016, a Networking entitled "Nanozymes in Analytical Chemistry and Beyond" was devoted to nanozymes.^[62] An Xiangshan Science Conference was devoted to nanozyme research.^[63][64] A scientific session was devoted to "Biomimetic Nanocatalysis" in 15th Chinese Biophysics Congress.^[65] The "Nanozymes for Bioanalysis (Oral)" section was included in the 256th ACS National Meeting (2018 Fall, Boston).^[66]

Carbon nanotubes too weak to get a space elevator off the ground

13 June 2016 By Jacob Aron

Original link:  https://www.newscientist.com/article/2093356-carbon-nanotubes-too-weak-to-get-a-space-elevator-off-the-ground/

Andrey Prokhorov/Getty

For want of an atom, the space elevator failed.

Carbon nanotubes (CNTs) are famed for being a future wonder material that will enable a swathe of super-strong but light applications from racing bikes to computer components.

But now it seems a single out-of-place atom is enough to cut their strength by more than half. That means one of the more outlandish applications for CNT fibres – a sci-fi space elevator – might never happen.

The tubes’ strength is a result of their atomic structure, with walls made from just a single layer of carbon atoms locked in a hexagonal grid. Theoretical studies suggest that a single CNT can have a tensile strength of 100 gigapascals (GPa), making it one of the strongest materials around, but efforts to spin multiple nanotubes into a practical large-scale fibre have only produced ropes with strengths of 1 GPa.

To find out why, Feng Ding of the Hong Kong Polytechnic University and his colleagues simulated CNTs with a single atom out of place, turning two of the hexagons into a pentagon and heptagon, and creating a kink in the tube. They found this simple change was enough to cut the ideal strength of a CNT to 40 GPa, with the effect being even more severe when they increased the number of misaligned atoms.

Fracture sequence

The team’s simulations show that the kink acts as a weak point in the tube, easily snapping the normally strong carbon-carbon bonds. Once this happens, the bonds in the adjacent hexagons also break, unzipping the entire tube. The effect on CNTs spun together into fibres is similar – once one CNT breaks, the strain on the others increases, fracturing them in sequence.

The results suggest just one misplaced atom is enough to weaken an entire CNT fibre, and since nanotube manufacturing processes are flawed at the moment, you will inevitably end up with a bad tube in your fibre.

“Only CNTs with extreme quality are able to retain their ideal strength,” says Ding. “Most mass-produced CNTs are highly defective, and high-quality CNTs are hard to produce in large quantity.”

That’s bad news for people who want to build a space elevator, a cable between the Earth and an orbiting satellite that would provide easy access to space.

Estimates suggest such a cable would need a tensile strength of 50 GPa, so CNTs were a promising solution, but Ding’s research suggests they won’t work. “Unless great breakthroughs on CNT synthesis can be achieved, using CNTs to build a space elevator would be extremely challenging,” he says.

Journal reference: ACS Nano DOI: 10.1021/acsnano.6b03231