Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

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

Abstract

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.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: General design of SMARTS.
Figure 2: Oscillations in exemplary chemical reactions triggered by pH changes.
Figure 3: Homeostasis in SMARTS via self-regulated chemo-thermo-mechanical feedback loops.
Figure 4: Computer simulations of the self-sustained thermal regulation.

References

  1. 1

    Bao, G. et al. Molecular biomechanics: the molecular basis of how forces regulate cellular function. Cell. Mol. Bioeng. 3, 91–105 (2010)

    Article  Google Scholar 

  2. 2

    Fratzl, P. & Barth, F. G. Biomaterial systems for mechanosensing and actuation. Nature 462, 442–448 (2009)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Guyton, A. C. & Hall, J. E. Human Physiology and Mechanisms of Disease 6th edn 3–8 (Saunders, 1997)

    Google Scholar 

  4. 4

    Prosser, B. L., Ward, C. W. & Lederer, W. J. X-ROS signaling: rapid mechano-chemo transduction in heart. Science 333, 1440–1445 (2011)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Sambongi, Y. et al. Mechanical rotation of the c subunit oligomer in ATP synthase (F0F1): direct observation. Science 286, 1722–1724 (1999)

    CAS  Article  Google Scholar 

  6. 6

    Spaet, T. H. Analytical review: hemostatic homeostasis. Blood 28, 112–123 (1966)

    CAS  PubMed  Google Scholar 

  7. 7

    Hess, H. Engineering applications of biomolecular motors. Annu. Rev. Biomed. Eng. 13, 429–450 (2011)

    CAS  Article  Google Scholar 

  8. 8

    Fritz, J. et al. Translating biomolecular recognition into nanomechanics. Science 288, 316–318 (2000)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Lahann, J. & Langer, R. Smart materials with dynamically controllable surfaces. MRS Bull. 30, 185–188 (2005)

    CAS  Article  Google Scholar 

  10. 10

    Li, D. B. et al. Molecular, supramolecular, and macromolecular motors and artificial muscles. MRS Bull. 34, 671–681 (2009)

    Article  Google Scholar 

  11. 11

    Paxton, W. F., Sundararajan, S., Mallouk, T. E. & Sen, A. Chemical locomotion. Angew. Chem. Int. Ed. 45, 5420–5429 (2006)

    CAS  Article  Google Scholar 

  12. 12

    Sidorenko, A., Krupenkin, T., Taylor, A., Fratzl, P. & Aizenberg, J. Reversible switching of hydrogel-actuated nanostructures into complex micropatterns. Science 315, 487–490 (2007)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Ariga, K., Mori, T. & Hill, J. P. Control of nano/molecular systems by application of macroscopic mechanical stimuli. Chem. Sci. 2, 195–203 (2011)

    CAS  Article  Google Scholar 

  14. 14

    Todres, Z. V. Organic Mechanochemistry and its Practical Applications (CRC/Taylor & Francis, 2006)

    Google Scholar 

  15. 15

    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)

    CAS  Article  Google Scholar 

  16. 16

    Stuart, M. A. C. et al. Emerging applications of stimuli-responsive polymer materials. Nature Mater. 9, 101–113 (2010)

    ADS  Article  Google Scholar 

  17. 17

    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)

    CAS  Article  Google Scholar 

  18. 18

    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)

    CAS  Article  Google Scholar 

  19. 19

    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)

    ADS  CAS  Article  Google Scholar 

  20. 20

    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)

    CAS  Article  Google Scholar 

  21. 21

    Siegel, R. A. in Chemomechanical Instabilities in Responsive Materials (eds Borckmans, P., Kepper, P. D. & Khokhlov, A. R. ) 139–173 (Springer, 2009)

    Google Scholar 

  22. 22

    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)

    ADS  Article  Google Scholar 

  23. 23

    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)

    CAS  Article  Google Scholar 

  24. 24

    Maeda, S., Hara, Y., Sakai, T., Yoshida, R. & Hashimoto, S. Self-walking gel. Adv. Mater. 19, 3480–3484 (2007)

    CAS  Article  Google Scholar 

  25. 25

    Vanag, V. K. & Epstein, I. R. Resonance-induced oscillons in a reaction-diffusion system. Phys. Rev. E 73, 016201 (2006)

    ADS  Article  Google Scholar 

  26. 26

    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)

    ADS  CAS  Article  Google Scholar 

  27. 27

    Richter, A. et al. Review on hydrogel-based pH sensors and microsensors. Sensors 8, 561–581 (2008)

    CAS  Article  Google Scholar 

  28. 28

    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)

    CAS  Article  Google Scholar 

  29. 29

    Schild, H. G. Poly(n-isopropylacrylamide)-experiment, theory and application. Prog. Polym. Sci. 17, 163–249 (1992)

    CAS  Article  Google Scholar 

  30. 30

    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)

    CAS  Article  Google Scholar 

  31. 31

    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)

    ADS  Article  Google Scholar 

  32. 32

    Yashin, V. V. & Balazs, A. C. Pattern formation and shape changes in self-oscillating polymer gels. Science 314, 798–801 (2006)

    ADS  MathSciNet  CAS  Article  Google Scholar 

  33. 33

    Yashin, V. V., Kuksenok, O. & Balazs, A. C. Modeling autonomously oscillating chemo-responsive gels. Prog. Polym. Sci. 35, 155–173 (2010)

    CAS  Article  Google Scholar 

Download references

Acknowledgements

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).

Author information

Affiliations

Authors

Contributions

M.A. and J.A. planned the project and supervised the research. X.H. and M.A. designed and conducted the experiments and data analysis. X.H., L.D.Z. and A.S. conducted the characterization. X.H. and L.D.Z. carried out microfluidic device design. A.S. carried out hydrogel deposition optimization. O.K. and A.C.B. developed the model and numerical code and carried out the computational simulations. All authors wrote the manuscript.

Corresponding author

Correspondence to Joanna Aizenberg.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Text and Data 1-5, Supplementary Figures 1-10 and additional references. (PDF 1813 kb)

Supplementary Movie 1

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)

Supplementary Movie 2

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)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

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

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing