A living organism is a bundle of dynamic, integrated adaptive processes: not only does it continuously respond to constant changes in temperature, sunlight, nutrients, and other features of its environment, but it does so by coordinating hierarchies of feedback among cells, tissues, organs, and networks all continuously adapting to each other. At the root of it all is one of the most fundamental adaptive processes: the constant tug of war between chemistry and mechanics that interweaves chemical signals with endless reconfigurations of macromolecules, fibers, meshworks, and membranes. In this tutorial we explore how such chemomechanical feedback – as an inherently dynamic, iterative process connecting size and time scales – can and has been similarly evoked in synthetic materials to produce a fascinating diversity of complex multiscale responsive behaviors. We discuss how chemical kinetics and architecture can be designed to generate stimulus-induced 3D spatiotemporal waves and topographic patterns within a single bulk material, and how feedback between interior dynamics and surface-wide instabilities can further generate higher order buckling and wrinkling patterns. Building on these phenomena, we show how yet higher levels of feedback and spatiotemporal complexity can be programmed into hybrid materials, and how these mechanisms allow hybrid materials to be further integrated into multicompartmental systems capable of hierarchical chemo-mechano-chemical feedback responses. These responses no doubt represent only a small sample of the chemomechanical feedback behaviors waiting to be discovered in synthetic materials, and enable us to envision nearly limitless possibilities for designing multiresponsive, multifunctional, self-adapting materials and systems.
This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences Tutorial Review Chem Soc Rev Downloaded by Harvard University on 26/04/2013 22:18:02. Published on 26 April 2013 on http://pubs.rsc.org | doi:10.1039/C3CS60045A View Article Online This journal is c The Royal Society of Chemistry 2013 Chem. Soc. Rev. and Engineering under award number DE-SC0005247 (design of adaptive materials); by the U.S. Air Force Office of Scientific Research Multidisciplinary University Research Initiative under award number FA9550-09-1-0669-DOD35CAP (dynamic optical structures); and by the U.S. National Science Foundation under award number CMMI-1124839 (chemo-mechanical feedback systems). We gratefully acknowledge Dr Michael DeVolder for providing the image of hydrogel-infiltrated carbon nanotubes.