{"id":115414,"date":"2013-04-24T17:59:40","date_gmt":"2013-04-24T20:59:40","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=115414"},"modified":"2016-02-11T18:19:20","modified_gmt":"2016-02-11T20:19:20","slug":"imitation-of-nature","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/imitation-of-nature\/","title":{"rendered":"Imitation of nature"},"content":{"rendered":"

\"076-077_Compositos_205\"<\/a>A technique for joining rigid and elastic materials together, inspired by nature’s way of connecting muscle to bone in the human body, has been developed by a team of Brazilian, European and American researchers at the Complex Materials group of the Federal Institute of Technology (ETH) in Zurich, Switzerland.\u00a0 Using the new technique, the researchers produce bio-inspired composites that show great potential for application in biomedical implants, not to mention components for the automobile and aerospace industries. The method for joining polymers to ceramics was described in a paper published in December 2012 in the journal Nature Communications<\/i>.<\/p>\n

The group’s leader, Andr\u00e9 Studart, a Brazilian professor and engineer, says that attachments between rigid and flexible materials are very common in living beings. \u201cIn our own bodies, for example, highly elastic parts like tendons are connected to extremely rigid ones, like bones,\u201d he explains. \u201cUnlike what we see in artificial products, our bodies are able to sustain high mechanical loads at the point where these two materials are joined, without that connection point failing.\u201d Rafael Libanori, a Brazilian chemist, has also applied nature’s principles to produce high-performance artificial materials. The other members of the group include two Swiss researchers, one French, one Austrian, and one American.<\/p>\n

Transforming these natural characteristics into technology, creating an artificial mechanism that makes it possible to connect elastic materials to rigid ones, is not as easy as nature would make it seem. On the contrary, joining two products with different mechanical properties is currently a major challenge for many fields of engineering. This is why the work being done by Studart’s group is so important. \u201cWe developed a method for producing artificial heterogeneous materials that can be used to connect rigid structures to elastic ones efficiently, like in nature,\u201d he says.<\/p>\n

The group observed that nature solved the problem by gradually changing the mechanical properties of the coupling structure, known as a tendon-bone insertion. \u201cNear the tendon, the insertion is relatively elastic and is composed mainly of collagen fibers,\u201d Libanori explains. \u201cBut as it gets closer to the bone, the concentration of reinforcing mineral elements increases gradually, resulting in a heterogeneous composite that can distribute mechanical strain uniformly along the length of the insertion.\u201d This gradual transition of mechanical properties takes place both lengthwise and crosswise, minimizing the development of intense mechanical strain at the tendon-bone junction.<\/p>\n

Transition in teeth
\n<\/b>The mechanical properties of collagen are typical of elastic materials, whereas reinforcing mineral elements like hydroxyapatite exhibit the usual characteristics of rigid ceramics. Hydroxyapatite is made of calcium phosphate, the main component in bones.\u00a0 Teeth are another example of a biological material that gradually transitions between different types of mechanical properties. \u201cThe inner part of our teeth is made of dentin, which is more elastic, whereas the outer layer, the tooth enamel, is much more rigid and hard,\u201d Libanori explains. \u201cThis gradual transition occurs perpendicularly, from the inside of the tooth outward toward the enamel.\u201d<\/p>\n

The method created by the group, called \u201chierarchical reinforcement of polyurethane elastomers\u201d, was developed during Libanori’s doctoral studies at ETH, where Studart was his advisor. \u201cIn this case, the word \u2018hierarchical\u2019 is used because the polymer matrix is reinforced with increasingly rigid components at different size scales: molecular, nanometric, and micrometric,\u201d says Libanori. \u201cThis way, we can combine layers of materials with differing degrees of rigidity, using a procedure called solvent welding.\u201d In their Nature Communications<\/i> paper, the researchers describe a matrix of polyurethane \u2013 a polymer used in the manufacture of foams, shoe soles, textiles, and adhesives, among other things \u2013 reinforced with nanometric and micrometric ceramic particles (respectively, a synthetic clay called laponite and aluminum oxide). Nanometric sizes are equivalent to 1 millimeter divided by 1 million, and micrometric particles are thousandths of a millimeter in diameter.<\/p>\n

According to Studart, this method enables the creation of polymeric composites that were unimaginable until now. \u201cFor instance, we created a material whose rigidity at its upper surface is equivalent to that of our teeth and bones, whereas the elasticity of its bottom surface resembles that of our skin,\u201d the professor reveals. The researchers have also shown that rigid electronic devices integrated with a flexible substrate, as in the case of LED circuits, can be effectively protected from mechanical failure. This significantly increases the equipment’s useful lifetime.<\/p>\n

Flexible devices produced via this method can be stretched to as much as 4.5 times their initial size without compromising the response of their rigid electronic components. According to Libanori, the project is still in the academic research stage and the group is looking for companies interested in licensing the technology. \u201cAt this time, we are discussing the possibilities for collaboration with a major company in the electronics industry,\u201d he says.<\/p>\n

Professor Edson Roberto Leite, from the Chemistry Department at the Federal University of S\u00e3o Carlos (UFSCar), has been keeping track of Libanori and Studart’s work for several years. \u201cI was Rafael Libanori’s advisor during his undergraduate research and masters program, and I referred him to Studart,\u201d he says. \u201cTheir work is very important because they create composite material processing methods that make it possible to emulate nature’s hierarchical way of organizing materials. This is the group’s major breakthrough. Going beyond simply studying how nature works, they are artificially reproducing the way it builds materials, without using biochemistry or genetics.\u201d According to Leite, research in that field is still incipient in Brazil. \u201cSome groups are working on artificial photosynthesis, like ours here at UFSCar, and only a handful of others are working on bio-inspired composites,\u201d he says. \u201cElsewhere in the world, this subject is gaining prominence and large groups are performing cutting-edge research.\u201d<\/p>\n

Scientific article<\/em>
\nLIBANORI, R. et al.<\/i> Stretchable heterogeneous composites with extreme mechanical gradients<\/a>. Nature Communications,<\/b> v.3, article 1.65, 11 December 2012 (online).<\/p>\n","protected":false},"excerpt":{"rendered":"Brazilian researchers develop a way to connect plastic to ceramics","protected":false},"author":20,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[169],"tags":[243],"coauthors":[112],"class_list":["post-115414","post","type-post","status-publish","format-standard","hentry","category-technology","tag-innovation"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/115414","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/20"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=115414"}],"version-history":[{"count":0,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/115414\/revisions"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=115414"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=115414"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=115414"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=115414"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}