Untethered unidirectionally crawling gels driven by asymmetry in contact forces
Untethered unidirectionally crawling gels driven by asymmetry in contact forces
复制标题
DOI：
10.1126/scirobotics.add2903
复制
发表时间：
2022-12-14
期刊：
影响因子：
25
通讯作者：
Gracias, David H.
中科院分区：
文献类型：
--
作者：
Pantula, Aishwarya;Datta, Bibekananda;Gracias, David H.
可逆热响应水凝胶，在30度到60摄氏度的温度范围内膨胀和收缩（deswell），为在人类生理和环境条件下操作无系绳软机器人提供了一种有吸引力的材料。以前已经用热响应性水凝胶证明了爬行，但需要图案或约束凝胶或底物来打破单向运动的对称性。在这里，我们展示了一种单向爬行凝胶的运动机制，这种运动机制是由带有悬浮连接物的分段主动热响应性聚（n -异丙基丙烯酰胺）（pNIPAM）和被动聚丙烯酰胺（pAAM）双分子层在膨胀和膨胀过程中自发的不对称接触力驱动的。驱动研究表明，这些凝胶爬行器在平面、无图案的基底上进行多次热循环时，具有一致的单向运动。我们使用有限元模拟和不同的实验参数（如连接件刚度和双层段的数量）来解释这一机制。我们阐明了设计准则，并利用图像分析和有限元模型验证了实验。我们预计这种机制可以潜在地应用于其他形状变化的运动。
Reversible thermoresponsive hydrogels, which swell and shrink (deswell) in the temperature range of 30 degrees to 60 degrees C, provide an attractive material class for operating untethered soft robots in human physiological and ambient conditions. Crawling has been demonstrated previously with thermoresponsive hydrogels but required patterned or constrained gels or substrates to break symmetry for unidirectional motion. Here, we demonstrate a locomotion mechanism for unidirectionally crawling gels driven by spontaneous asymmetries in contact forces during swelling and deswelling of segmented active thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) and passive polyacrylamide (pAAM) bilayers with suspended linkers. Actuation studies demonstrate the consistent unidirectional movement of these gel crawlers across multiple thermal cycles on flat, unpatterned substrates. We explain the mechanism using finite element simulations and by varying experimental parameters such as the linker stiffness and the number of bilayer segments. We elucidate design criteria and validate ex-periments using image analysis and finite element models. We anticipate that this mechanism could potentially be applied to other shape-changing locomotors.