Department of Mechanical Engineering, Seoul National University, Seoul 08826, Korea.
Department of Mechanical Engineering, Ajou University, Suwon 16499, Korea.
Proc Natl Acad Sci U S A. 2023 Jan 10;120(2):e2211416120. doi: 10.1073/pnas.2211416120. Epub 2023 Jan 3.
Soft systems that respond to external stimuli, such as heat, magnetic field, and light, find applications in a range of fields including soft robotics, energy harvesting, and biomedicine. However, most of the existing systems exhibit nondirectional, nastic movement as they can neither grow nor sense the direction of stimuli. In this regard, artificial systems are outperformed by organisms capable of directional growth in response to the sense of stimuli or tropic growth. Inspired by tropic growth schemes of plant cells and fungal hyphae, here we report an artificial multistimuli-responsive tropic tip-growing system based on nonsolvent-induced phase separation of polymer solution, where polymer precipitates as its solvent dissolves into surrounding nonsolvent. We provide a theoretical framework to predict the size and velocity of growing precipitates and demonstrate its capability of sensing the directions of gravity, mechanical contact, and light and adjusting its growing direction in response. Exploiting the embedded physical intelligence of sensing and responding to external stimuli, our soft material system achieves multiple tasks including printing 3D structures in a confined space, bypassing mechanical obstacles, and shielded transport of liquids within water.
对热、磁场和光等外部刺激做出响应的软系统在软机器人、能量收集和生物医学等多个领域都有应用。然而，大多数现有系统表现出非定向的、弹性运动，因为它们既不能生长，也不能感知刺激的方向。在这方面，人工系统不如能够根据对刺激的感知或向性生长来进行定向生长的生物体表现出色。受植物细胞和真菌菌丝的向性生长方案的启发，我们在这里报告了一种基于聚合物溶液中非溶剂诱导相分离的人工多刺激响应向性尖端生长系统，其中聚合物在其溶剂溶解到周围非溶剂中时沉淀出来。我们提供了一个理论框架来预测生长沉淀物的大小和速度，并展示了它感知重力、机械接触和光的方向以及响应调整生长方向的能力。利用对外部刺激进行感测和响应的嵌入式物理智能，我们的软材料系统实现了多项任务，包括在受限空间内打印 3D 结构、绕过机械障碍物以及在水中屏蔽液体运输。
