Synthetic homeostatic materials with chemo-mechano-chemical self-regulation

• Published in: Nature (London) 2012-07, Vol.487 (7406), p.214-218
• Main Authors: He, Ximin, Aizenberg, Michael, Kuksenok, Olga, Zarzar, Lauren D., Shastri, Ankita, Balazs, Anna C., Aizenberg, Joanna
• Format: Article
• Language: English
• Subjects: 639/301/54/990; 639/638/92/552; Autonomous; Biological and medical sciences; Chemical elements; Chemical Engineering; Chemical reactions; Click Chemistry; Computer Simulation; Control systems; Control theory; Design; Design engineering; Feedback; Feedback loops; Fundamental and applied biological sciences. Psychology; Homeostasis; Humanities and Social Sciences; Hydrogels; Hydrogen-Ion Concentration; letter; Manufactured Materials - standards; Metabolisms and neurohumoral controls; Methods; Microstructure; multidisciplinary; Nanostructure; Nutrients; Science; Science (multidisciplinary); Temperature; Temperature measurements; Time Factors; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Water and mineral metabolism. Osmoregulation. Acidobasic balance
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature11223

A bilayer material comprising catalyst-bearing microstructures embedded in a responsive gel and actuated into and out of a reactant-containing ‘nutrient’ layer continuously interconverts chemical, thermal and mechanical energy and thereby shows autonomous, self-sustained homeostatic behaviour, which regulates the temperature of the system in a narrow range. Flexible materials: get SMARTS Taking their cue from the ability of living organisms to maintain control over their local environment through homeostasis, Joanna Aizenberg and colleagues have developed a way to produce synthetic homeostatic materials that autonomously regulate a wide range of parameters at the micrometre scale through a series of chemo-mechanical feedback loops. They describe a bilayer of hydrogel-supported catalyst-bearing microstructures separated from a reactant-containing 'nutrient' layer. Reconfiguration of the gel in response to a stimulus induces reversible actuation of the microstructures in and out of the nutrient layer, and serves as an on/off switch for chemical reactions — a sort of artificial homeostasis. This design triggers organic, inorganic and biochemical reactions that undergo reversible, repeatable cycles that are synchronized with the motion of the microstructures and the driving external chemical stimulus. The authors suggest that SMARTS (self-regulated mechano-chemical adaptively reconfigurable tunable systems) could be tailored to modulate variables such as light, pH, glucose, pressure and oxygen. Applications might include robotics, biomedical engineering and building materials. Living organisms have unique homeostatic abilities, maintaining tight control of their local environment through interconversions of chemical and mechanical energy and self-regulating feedback loops organized hierarchically across many length scales 1 , 2 , 3 , 4 , 5 , 6 , 7 . In contrast, most synthetic materials are incapable of continuous self-monitoring and self-regulating behaviour owing to their limited single-directional chemomechanical 7 , 8 , 9 , 10 , 11 , 12 or mechanochemical 13 , 14 modes. Applying the concept of homeostasis to the design of autonomous materials 15 would have substantial impacts in areas ranging from medical implants that help stabilize bodily functions to ‘smart’ materials that regulate energy usage 2 , 16 , 17 . Here we present a versatile strategy for creating self-regulating, self-powered, homeostatic materials capable of precisely tailored chemo-mechano-