Imagine a robot with fingers so flexible they can grasp an object the same way a human hand does. That\u2019s the goal of soft robotics, but a major obstacle in advancing the field has been finding flexible materials that resemble human tissues and can be programmed to generate reversible shape changes.<\/p>\n
Two biophysicists at the University of Wisconsin-Milwaukee have introduced a method that could turn protein hydrogels into smart materials with shape-memory capabilities. Protein hydrogels are biomaterials made almost entirely from proteins, which are the molecules that carry out most of the functions inside our cells.<\/p>\n
Protein-based hydrogels have been more difficult to manipulate than their alternative, polymer hydrogels, in medical uses, such as tissue scaffolding and drug delivery. But they have more potential in these and other shape-changing applications because the proteins they contain naturally change their shapes in order to carry out biological functions \u2013 a process called \u201cprotein folding.\u201d<\/p>\n
A technique developed by Ionel Popa and Luai Khoury makes it easier to program protein hydrogels to take complex shapes by treating them with polyelectrolytes, which are polymers that become electrically conductive in water. The hydrogels then lose their 3D structures in the presence of certain chemical denaturants.<\/p>\n
The work, described in a paper published today in Nature Communications, could lead to much wider uses of protein hydrogels, both as conventional biomaterials and as new materials for fields such as soft robotics, said Popa, a 51ÁÔÆæ assistant professor of physics.<\/p>\n
In our bodies, proteins accomplish all the functions necessary to sustain life \u2013 from maintaining our bodies\u2019 temperature to orchestrating the complex process of turning food into energy. Proteins \u201cactivate\u201d by folding or unfolding into different 3D shapes, each of which corresponds to a specific function.<\/p>\n
\u201cThe point is that protein-folding can be reversed,\u201d said Popa. \u201cHere we take advantage of the inherent property that proteins have to undergo many unfolding and refolding cycles, resulting in macroscopic changes in the material shape. This folding\/unfolding is unique to proteins, and could have not been done using polymer hydrogels.\u201d<\/p>\n
Popa and Khoury, a postdoctoral researcher and the paper\u2019s first author, have been using a technique developed at UW-Milwaukee called force-clamp rheometry, which measures the elastic response of biomaterials containing proteins.<\/p>\n
Khoury found that incubating a protein hydrogel in a solution of polyelectrolyte forms a secondary network in addition to the primary protein network. This secondary network stiffens the hydrogels, which is necessary to program their shapes.<\/p>\n
By applying a denaturing solution, the programmed protein hydrogel will relax as its protein in the primary network pivot to their unfolded state. With the denaturing solution washed out, the hydrogel reverts to its original programmed shape.<\/p>\n
The researchers anticipate that, in the future, the reversible response also could be induced by other protein-folding triggers, such as salt, light, temperature or pH.<\/p>\n
\u00a0<\/strong>Khoury credits the custom instrumentation built by Popa with helping them in their discovery. \u201cThese proteins are hard to produce \u2013 and expensive,\u201d Khoury said. \u201cPopa\u2019s apparatus uses a very low amount of material and exposes the soft hydrogels to low forces, similar to those encountered in the human body.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":" 51ÁÔÆæ researchers Ionel Popa and Luai Khoury have developed a technique that may advance the field of soft robotics, which involves robots made of pliable materials like those found in living organisms. <\/p>\n","protected":false},"author":836,"featured_media":77571,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":"","uwm_wg_additional_authors":[]},"categories":[174],"tags":[],"section":[140,139],"display_categories":[115,116],"related-coverage":[282],"uwmnews-feed":[158,161],"class_list":["post-77570","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","section-science","section-science-technology","display_categories-top-story-secondary","display_categories-top-story-section","related-coverage-physics","uwmnews-feed-letters-science","uwmnews-feed-hard-science"],"yoast_head":"\n