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 scales1,2,3,4,5,6,7. In contrast, most synthetic materials are incapable of continuous self-monitoring and self-regulating behaviour owing to their limited single-directional chemomechanical7,8,9,10,11,12 or mechanochemical13,14 modes. Applying the concept of homeostasis to the design of autonomous materials15 would have substantial impacts in areas ranging from medical implants that help stabilize bodily functions to ‘smart’ materials that regulate energy usage2,16,17. Here we present a versatile strategy for creating self-regulating, self-powered, homeostatic materials capable of precisely tailored chemo-mechano-chemical feedback loops on the nano- or microscale. We design a bilayer system with hydrogel-supported, catalyst-bearing microstructures, which are separated from a reactant-containing ‘nutrient’ layer. Reconfiguration of the gel in response to a stimulus induces the reversible actuation of the microstructures into and out of the nutrient layer, and serves as a highly precise ‘on/off’ switch for chemical reactions. We apply this design to trigger organic, inorganic and biochemical reactions that undergo reversible, repeatable cycles synchronized with the motion of the microstructures and the driving external chemical stimulus. By exploiting a continuous feedback loop between various exothermic catalytic reactions in the nutrient layer and the mechanical action of the temperature-responsive gel, we then create exemplary autonomous, self-sustained homeostatic systems that maintain a user-defined parameter—temperature—in a narrow range. The experimental results are validated using computational modelling that qualitatively captures the essential features of the self-regulating behaviour and provides additional criteria for the optimization of the homeostatic function, subsequently confirmed experimentally. This design is highly customizable owing to the broad choice of chemistries, tunable mechanics and its physical simplicity, and may lead to a variety of applications in autonomous systems with chemo-mechano-chemical transduction at their core.
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Bao, G. et al. Molecular biomechanics: the molecular basis of how forces regulate cellular function. Cell. Mol. Bioeng. 3, 91–105 (2010)
Fratzl, P. & Barth, F. G. Biomaterial systems for mechanosensing and actuation. Nature 462, 442–448 (2009)
Guyton, A. C. & Hall, J. E. Human Physiology and Mechanisms of Disease 6th edn 3–8 (Saunders, 1997)
Prosser, B. L., Ward, C. W. & Lederer, W. J. X-ROS signaling: rapid mechano-chemo transduction in heart. Science 333, 1440–1445 (2011)
Sambongi, Y. et al. Mechanical rotation of the c subunit oligomer in ATP synthase (F0F1): direct observation. Science 286, 1722–1724 (1999)
Spaet, T. H. Analytical review: hemostatic homeostasis. Blood 28, 112–123 (1966)
Hess, H. Engineering applications of biomolecular motors. Annu. Rev. Biomed. Eng. 13, 429–450 (2011)
Fritz, J. et al. Translating biomolecular recognition into nanomechanics. Science 288, 316–318 (2000)
Lahann, J. & Langer, R. Smart materials with dynamically controllable surfaces. MRS Bull. 30, 185–188 (2005)
Li, D. B. et al. Molecular, supramolecular, and macromolecular motors and artificial muscles. MRS Bull. 34, 671–681 (2009)
Paxton, W. F., Sundararajan, S., Mallouk, T. E. & Sen, A. Chemical locomotion. Angew. Chem. Int. Ed. 45, 5420–5429 (2006)
Sidorenko, A., Krupenkin, T., Taylor, A., Fratzl, P. & Aizenberg, J. Reversible switching of hydrogel-actuated nanostructures into complex micropatterns. Science 315, 487–490 (2007)
Ariga, K., Mori, T. & Hill, J. P. Control of nano/molecular systems by application of macroscopic mechanical stimuli. Chem. Sci. 2, 195–203 (2011)
Todres, Z. V. Organic Mechanochemistry and its Practical Applications (CRC/Taylor & Francis, 2006)
Harris, T. J., Seppala, C. T. & Desborough, L. D. A review of performance monitoring and assessment techniques for univariate and multivariate control systems. J. Process Contr. 9, 1–17 (1999)
Stuart, M. A. C. et al. Emerging applications of stimuli-responsive polymer materials. Nature Mater. 9, 101–113 (2010)
Yerushalmi, R., Scherz, A., van der Boom, M. E. & Kraatz, H. B. Stimuli responsive materials: new avenues toward smart organic devices. J. Mater. Chem. 15, 4480–4487 (2005)
Das, M., Mardyani, S., Chan, W. C. W. & Kumacheva, E. Biofunctionalized pH-responsive microgels for cancer cell targeting: rational design. Adv. Mater. 18, 80–83 (2006)
Murthy, N. et al. A macromolecular delivery vehicle for protein-based vaccines: acid-degradable protein-loaded microgels. Proc. Natl Acad. Sci. USA 100, 4995–5000 (2003)
Nayak, S., Lee, H., Chmielewski, J. & Lyon, L. A. Folate-mediated cell targeting and cytotoxicity using thermoresponsive microgels. J. Am. Chem. Soc. 126, 10258–10259 (2004)
Siegel, R. A. in Chemomechanical Instabilities in Responsive Materials (eds Borckmans, P., Kepper, P. D. & Khokhlov, A. R. ) 139–173 (Springer, 2009)
Horváth, J., Szalai, I., Boissonade, J. & De Kepper, P. Oscillatory dynamics induced in a responsive gel by a non-oscillatory chemical reaction: experimental evidence. Soft Matter 7, 8462–8472 (2011)
Kovacs, K., Leda, M., Vanag, V. K. & Epstein, I. R. Small-amplitude and mixed-mode pH oscillations in the bromate-sulfite-ferrocyanide-aluminum(III) system. J. Phys. Chem. A 113, 146–156 (2009)
Maeda, S., Hara, Y., Sakai, T., Yoshida, R. & Hashimoto, S. Self-walking gel. Adv. Mater. 19, 3480–3484 (2007)
Vanag, V. K. & Epstein, I. R. Resonance-induced oscillons in a reaction-diffusion system. Phys. Rev. E 73, 016201 (2006)
Koga, S., Williams, D. S., Perriman, A. & Mann, S. Peptide-nucleotide microdroplets as a step towards a membrane-free protocell model. Nature Chem. 3, 720–724 (2011)
Richter, A. et al. Review on hydrogel-based pH sensors and microsensors. Sensors 8, 561–581 (2008)
Zarzar, L. D., Kim, P. & Aizenberg, J. Bio-inspired design of submerged hydrogel-actuated polymer microstructures operating in response to pH. Adv. Mater. 23, 1442–1446 (2011)
Schild, H. G. Poly(n-isopropylacrylamide)-experiment, theory and application. Prog. Polym. Sci. 17, 163–249 (1992)
Okano, T., Bae, Y. H., Jacobs, H. & Kim, S. W. Thermally on-off switching polymers for drug permeation and release. J. Control. Release 11, 255–265 (1990)
Kuksenok, O., Yashin, V. V. & Balazs, A. C. Three-dimensional model for chemoresponsive polymer gels undergoing the Belousov-Zhabotinsky reaction. Phys. Rev. E 78, 041406 (2008)
Yashin, V. V. & Balazs, A. C. Pattern formation and shape changes in self-oscillating polymer gels. Science 314, 798–801 (2006)
Yashin, V. V., Kuksenok, O. & Balazs, A. C. Modeling autonomously oscillating chemo-responsive gels. Prog. Polym. Sci. 35, 155–173 (2010)
We thank P. Kim for assistance with the gel formulation, M. Khan for microstructure fabrication, R. S. Friedlander for assistance with confocal imaging, M. Kolle and A. Ehrlicher for technical assistance, and A. Grinthal for help with manuscript preparation. The work was supported by the US DOE under award DE-SC0005247 (experiment) and by the US NSF under award CMMI-1124839 (computational modelling).
The authors declare no competing financial interests.
This file contains Supplementary Text and Data 1-5, Supplementary Figures 1-10 and additional references. (PDF 1813 kb)
This movie shows pulsed O2 gas generation controlled by the actuation of microfins within a microfluidic channel. Alternating flow of aqueous solution of pH 3 (yellow) and pH 6 (purple) was used to control the actuation of the microstructures out of and into the H2O2 layer and thus the cyclic bubble generation. The colour arises from bromophenol blue indicator. Movie played at a realtime speed. (MOV 8431 kb)
This movie shows a self-regulated chemo-mechanical feedback system showing self-contained autonomous oscillation and the corresponding temperature regulation during 6 h. The movie presents three cycles at the beginning, two cycles 3 h later, and two cycles 6 hours later. Movie played at 60x speed. (MOV 11769 kb)
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He, X., Aizenberg, M., Kuksenok, O. et al. Synthetic homeostatic materials with chemo-mechano-chemical self-regulation. Nature 487, 214–218 (2012). https://doi.org/10.1038/nature11223
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