4D Printing of thermoresponsive OEGMA-based hydrogels with tunable response [data]

Hydrogels, particularly those exhibiting responsive behaviors, have gained significant attention, especially with the advent of 4D printing. Among thermoresponsive hydrogels, poly(N-isopropylacrylamide) (PNIPAM)-based materials remain a benchmark for 4D microprinting featuring typical lower critical solution temperatures (LCSTs) ranging from 32 to 37 °C. However, precise tuning of the LCST to a broader temperature range is necessary to expand the application window. This study introduces thermoresponsive poly(oligo(ethylene glycol)methacrylate) (POEGMA)-based polymers as alternative printable materials for two-photon laser printing (2PLP). First, a library of prepolymers with LCSTs ranging from 33 to 66 °C is synthesized and characterized. By formulating these prepolymers with a suitable photoinitiator in water, inks compatible with 2PLP are created. The printing performance of each ink is evaluated by fabricating complex 4D microstructures, including various platonic solids exhibiting LCSTs ranging from 33 to 66 °C, surpassing the constraints of PNIPAM. The actuation performance of each material is evaluated quantitatively by monitoring volume changes at different temperatures. Finally, arrays of “twistable” tetrahedrons are fabricated in multi-material fashion, showcasing temperature selective actuation. Thus, we demonstrate that the careful design of the macromolecular architecture offers precise LCST adjustment in final printed microstructures, a feature highly beneficial for applications like soft microrobotics among others.水凝胶，尤其是具备响应性行为的水凝胶，随着4D打印技术的问世，已受到广泛关注。在温敏水凝胶领域，基于聚(N-异丙基丙烯酰胺)（poly(N-isopropylacrylamide, PNIPAM)）的材料仍是4D微打印的基准材料，其典型最低临界溶液温度（lower critical solution temperatures, LCSTs）区间为32至37 ℃。不过，为拓展应用场景，需将LCST精准调控至更宽的温度范围。本研究引入基于聚(寡聚乙二醇甲基丙烯酸酯)（poly(oligo(ethylene glycol)methacrylate, POEGMA)）的温敏聚合物，作为双光子激光打印（two-photon laser printing, 2PLP）的可打印替代材料。首先，研究团队合成并表征了一系列LCST区间为33至66 ℃的预聚物库。将这些预聚物与合适的光引发剂在水中复配，即可制备适配双光子激光打印的墨水。通过制备复杂4D微结构（包括各类LCST区间为33至66 ℃的柏拉图立体），评估了每一种墨水的打印性能，突破了PNIPAM材料的温度限制。通过监测不同温度下的体积变化，定量评估了每种材料的驱动性能。最后，以多材料方式制备了“可扭转”四面体阵列，展示了温度选择性驱动特性。综上，本研究证明，通过精心设计大分子结构，可精准调控最终打印微结构的LCST，这一特性在软体微机器人学等诸多应用领域具有重要价值。