Tian Ye, Hou Li Xin, Zhang Xin Ning, Du Miao, Zheng Qiang, Wu Zi Liang
Ministry of Education Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310058, China.
College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou, 310023, China.
Small. 2024 Sep;20(37):e2308570. doi: 10.1002/smll.202308570. Epub 2024 May 8.
Soft-lithography is widely used to fabricate microstructured surfaces on plastics and elastomers for designable physical properties such as wetting and adhesions. However, it remains a big challenge to construct high-aspect-ratio microstructures on the surface of hydrogels due to the difficulty in demolding from the gel with low strength and stiffness. Demonstrated here is the engineering of tough hydrogels by soft-lithography to form well-defined micropillars. The mechanical properties of poly(acrylamide-co-methacrylic acid) hydrogels with dense hydrogen-bond associations severely depend on temperature, with Young's modulus increasing from 8.1 MPa at 15 °C to 821.8 MPa at -30 °C, enabling easy demolding at low temperatures. Arrays of micropillars are maintained on the surface of the gel, and can be used at room temperature when the gel restores soft and stretchable. The hydrogel also exhibits good shape-memory property, favoring tailoring the morphology with a switchable tilt angle of micropillars. Consequently, the hydrogel shows tunable wetting and adhesion properties, as manifested by varying contact angles and adhesion strengths. These surface properties can also be tuned by geometry and arrangement of micropillars. This facile strategy by harnessing tunable viscoelasticity of supramolecular hydrogels should be applicable to other soft materials, and broaden their applications in biomedical and engineering fields.
软光刻技术被广泛用于在塑料和弹性体上制造具有可设计物理特性（如润湿性和粘附性）的微结构表面。然而，由于难以从强度和刚度较低的水凝胶中脱模，在水凝胶表面构建高纵横比的微结构仍然是一个巨大的挑战。本文展示了通过软光刻技术对坚韧水凝胶进行工程设计以形成轮廓清晰的微柱。具有密集氢键缔合的聚（丙烯酰胺 - 共 - 甲基丙烯酸）水凝胶的机械性能严重依赖于温度，其杨氏模量从15°C时的8.1MPa增加到 - 30°C时的821.8MPa，使得在低温下易于脱模。凝胶表面保持有微柱阵列，并且当凝胶恢复柔软和可拉伸状态时可在室温下使用。该水凝胶还表现出良好的形状记忆性能，有利于通过微柱的可切换倾斜角度来定制形态。因此，该水凝胶表现出可调的润湿性和粘附性，表现为接触角和粘附强度的变化。这些表面性能也可以通过微柱的几何形状和排列来调节。这种利用超分子水凝胶可调粘弹性的简便策略应适用于其他软材料，并拓宽其在生物医学和工程领域的应用。
