4D Printed Soft Microactuator for Particle Manipulation via Surrounding Medium Variation

Soft actuators have assumed vital roles in a diverse number of research and application fields, driving innovation and transformative advancements. Using 3D molding of smart materials and combining these materials through structural design strategies, a single soft actuator can achieve multiple functions. However, it is still challenging to realize soft actuators that possess high environmental adaptability while capable of different tasks. Here, the response threshold of a soft actuator is modulated by precisely tuning the ratio of stimulus‐responsive groups in hydrogels. By combining a heterogeneous bilayer membrane structure and in situ multimaterial printing, the obtained soft actuator deformed in response to changes in the surrounding medium. The response medium is suitable for both biotic and abiotic environments, and the response rate is fast. By changing the surrounding medium, the precise capture, manipulation, and release of micron‐sized particles of different diameters in 3D are realized. In addition, static capture of a single red blood cell is realized using biologically responsive medium changes. Finally, the experimental results are well predicted using finite element analysis. It is believed that with further optimization of the structure size and autonomous navigation platform, the proposed soft microactuator has significant potential to function as an easy‐to‐manipulate multifunctional robot. Microactuators are engineered and prepared to respond simultaneously to temperature, pH, and ion concentration in the environment. Their response threshold and performance are optimized through a material configuration and a tailored heterogenous bilayer structure strategy. These devices achieve precise capture, manipulation, and securement of micrometer‐scale particles, as well as the static retention of erythrocytes within a biocompatible environment.