Self-Wrinkling in Polyacrylamide Hydrogel Bilayers
Self-Wrinkling in Polyacrylamide Hydrogel Bilayers
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DOI：
10.1021/acs.langmuir.2c03264
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发表时间：
2023-03-08
期刊：
影响因子：
3.9
通讯作者：
Okumura, Dai
中科院分区：
文献类型：
--
作者：
Nagashima, So;Akamatsu, Naoki;Okumura, Dai
附着在软基底上的凝胶膜的溶胀可引起表面不稳定性，这导致形成高度有序的图案，如皱纹和褶皱。这种现象已被利用来制造功能设备和合理化形态。然而，在不将膜浸入溶剂中的情况下获得厘米级图案仍然具有挑战性。在这里，我们表明，皱纹的波长高达几厘米，可以自发地创建在露天制造的膜-基底双层聚丙烯酰胺（PAAm）水凝胶。当在PAAm水凝胶基底上制备的丙烯酰胺的预凝胶水溶液的膜经历露天凝胶化时，最初在表面上出现六边形堆积的凹坑，其后来演变成随机取向的皱纹。这种自组织图案的形成可以归因于在露天制造过程中双层系统中的自主水运输引起的表面不稳定性。图案的时间演变可归因于水凝胶膜中的过应力的增加，这是由于水的持续吸收。通过调节预凝胶水溶液的膜厚度，可以将皱纹波长控制在厘米级范围内。我们的自折叠方法提供了一种简单的机制，用于产生溶胀诱导的厘米级皱纹，而不需要外部溶剂，这是传统方法无法实现的。
Swelling of a gel film attached to a soft substrate can induce surface instability, which results in the formation of highly ordered patterns such as wrinkles and folds. This phenomenon has been exploited to fabricate functional devices and rationalize morphogenesis. However, obtaining centimeter-scale patterns without immersing the film in a solvent remains challenging. Here, we show that wrinkles with wavelengths of up to a few centimeters can be spontaneously created during the open-air fabrication of film-substrate bilayers of polyacrylamide (PAAm) hydrogels. When the film of an aqueous pregel solution of acrylamide prepared on the PAAm hydrogel substrate undergoes open-air gelation, hexagonally packed dimples initially emerge on the surface, which later evolve into randomly oriented wrinkles. The formation of such self-organized patterns can be attributed to the surface instability resulting from autonomous water transport in the bilayer system during open-air fabrication. The temporal evolution of the patterns can be ascribed to an increase in overstress in the hydrogel film due to continued water uptake. The wrinkle wavelength can be controlled in the centimeter-scale range by adjusting the film thickness of the aqueous pregel solution. Our self wrinkling method provides a simple mechanism for the generation of swelling-induced centimeter-scale wrinkles without requiring an external solvent, which is unachievable with conventional approaches.