Multi‐material and dual‐stimulus coupled actuation micro‐gears for shape–rotation control in intelligent micro‐electro‐mechanical systems

Abstract Multi‐stimulus responsive micro‐actuators are crucial for intelligent micro‐electro‐mechanical systems (MEMS) capable of adaptive operations in complex microenvironments. However, achieving reliable integration of multiple sensing and actuation mechanisms within a single microscale device remains highly challenging due to constraints in microscale fabrication, complex stimulus coupling, and the lack of scalable strategies for integrating autonomous sensing with remote actuation. In this work, a multi‐material and dual‐stimulus coupled actuation micro‐gear (MDCAMG) fabricated via femtosecond‐laser three‐dimensional printing combined with post‐processing magnetic nanoparticle absorption is proposed. The micro‐gear is integrated with two functional modules: a pH‐responsive hydrogel body and a magnetically driven surface layer. The hydrogel matrix enables autonomous swelling and shrinking under varying pH conditions, providing reversible size modulation and environmental sensing capabilities. The magnetic coating endows the structure with remotely controlled rotation behaviors, including speed regulation and directional switching. The two responding modules of the micro‐gear are fabricated independently, and can collaborate with each other to achieve the angular locking as the swelling of the micro‐gear in a slight alkaline environment (pH > 7) brings it into contact with a limiting structure located at a larger radius. This strategy is expected to be used to microfluidic chips, smart drug delivery and intelligent MEMS.