Zhang Bo, Jia Lianghao, Jiang Jinrui, Wu Shanshan, Xiang Tao, Zhou Shaobing
Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China.
ACS Appl Mater Interfaces. 2021 Aug 4;13(30):36574-36586. doi: 10.1021/acsami.1c10051. Epub 2021 Jul 24.
The design of hydrogels with switchable adhesion and stable antiswelling property in a wet environment has remained a challenge. Here, we report a biomimetic hydrogel that can adhere and detach on-demand on various material surfaces, which is realized by thermal-triggered switchable shape transformation on hexagonal micropillar patterned hydrogels. The hydrogels are cross-linked by two cross-linkers of poly(ethylene glycol) dimethacrylate and 2-ureidoethyl methacrylate, which guarantee the strong mechanical property and stable antiswelling property in a wet environment. The hydrogels can maintain stable water content in solutions with variable pH, temperature, and salt concentration, and the change in volume does not exceed 2%. In addition, due to the dynamical hydrogen bonds and dipole-dipole interaction in the hydrogels, the hydrogels exhibit a thermal-triggered shape-memory effect. The hydrogel can recover shape more than 80% in 15 s. Furthermore, inspired by the surface structure of tree-frog footpads, the hexagonal micropillar patterned hydrogels exhibit improved underwater adhesion strength. The underwater adhesion strength of hexagonal micropillar patterned hydrogels is seven times more than that of flat hydrogels. Based on the shape-memory effect of hydrogels, the adhesion strength can be altered by a thermal stimulus. The adhesion strength of the microstructures recovered from the hydrogel surface decreased to 15.4% of the initial adhesion strength. The switchable underwater adhesion of hydrogels can be applied in the fields of transfer printing, medical adhesives, mobile robots, etc.
设计出在潮湿环境中具有可切换粘附性和稳定抗溶胀性能的水凝胶一直是一项挑战。在此，我们报道了一种仿生水凝胶，它能够在各种材料表面按需粘附和分离，这是通过六方微柱图案化水凝胶上的热触发可切换形状转变实现的。这些水凝胶由聚乙二醇二甲基丙烯酸酯和甲基丙烯酸2-脲基乙酯两种交联剂交联而成，这保证了其在潮湿环境中的强机械性能和稳定的抗溶胀性能。该水凝胶在不同pH值、温度和盐浓度的溶液中能保持稳定的含水量，体积变化不超过2%。此外，由于水凝胶中存在动态氢键和偶极-偶极相互作用，水凝胶表现出热触发形状记忆效应。水凝胶能在15秒内恢复超过80%的形状。此外，受树蛙脚垫表面结构的启发，六方微柱图案化水凝胶展现出增强的水下粘附强度。六方微柱图案化水凝胶的水下粘附强度比平面水凝胶高七倍。基于水凝胶的形状记忆效应，粘附强度可通过热刺激改变。从水凝胶表面恢复后的微结构的粘附强度降至初始粘附强度的15.4%。水凝胶的可切换水下粘附性可应用于转印、医用粘合剂、移动机器人等领域。
