Mechanical Control of Periodic Precipitation in Stretchable Gels to Retrieve Information on Elastic Deformation and for the Complex Patterning of Matter

Abstract

Material design using nonequilibrium systems provides straightforward access to complexity levels that are possible through dynamic processes. Pattern formation through nonequilibrium processes and reaction–diffusion can be used to achieve this goal. Liesegang patterns (LPs) are a kind of periodic precipitation patterns formed through reaction–diffusion. So far, it has been shown that the periodic band structure of LPs and the geometry of the pattern can be controlled by experimental conditions and external fields (e.g., electrical or magnetic). However, there are no examples of these systems being used to retrieve information about the changes in the environment as they form, and there are no studies making use of these patterns for complex material preparation. This work shows the formation of LPs by a diffusion–precipitation reaction in a stretchable hydrogel and the control of the obtained patterns by the unprecedented and uncommon method of mechanical input. Additionally, how to use this protocol and how deviations from “LP behavior” of the patterns can be used to “write and store” information about the time, duration, extent, and direction of gel deformation are presented. Finally, an example of using complex patterning to deposit polypyrrole by using precipitation patterns is shown as a template.

Chemical Tracking of Temperature by Concurrent Periodic Precipitation Pattern Formation in Polyacrylamide Gels

“… 23 However, on the experimental side, there is no study on the temperature field change on such control or monitoring the environmental changes by “reading” a precipitation pattern system. In our previous study, 24 we illustrated how mechanical deformation could be tracked based on the evolution of the periodic precipitates. This technique was employed to understand the extent of deformation, and the time and duration of the deformation were revealed in the visual appearance of LPs.…”

The impact of reaction rate on the formation of flow-driven confined precipitate patterns

“…14 The stretching history of elastic materials can be retrieved via Liesegang-type precipitation reactions as well. 15 All the examples listed above highlight how diverse precipitation studies are in either applied or fundamental research areas. As a next step to improve the control over product properties, an appropriate coupling, i.e., time scale matching of the chemical reaction with the transport phenomenon, is essential.…”

Reversible switching of polymeric gel structure and property by solvent exchange

“…The distinctive attributes of the dynamic polymeric gels, such as configurable mechanical behavior [1-6], external stimuliresponsiveness [7-13] and self-healing ability [14-17], underlie their extensive applications in materials science, ranging from tissue-adaptive biomaterials [18][19][20] through high-efficient energy materials [21][22][23] to intelligent information materials [24][25][26]. For instance, stiffness-changing trait (e.g., rigid-to-soft transition) is especially desired in medical devices, since the rigid state allows for the easy insertion, while the soft state favors biocompatibility with surrounding tissues [19,27].…”