A light-response bilayer actuator for light-controlled capsule system

Microrobotics technology shows great potential in the field of minimally invasive medicine but still faces key challenges regarding motion control, safety, and cost. Hence, a near-infrared light-response bilayer actuator is designed in this work. The light-driving mechanism and its application in the light-controlled drug release capsule system is deeply explored by taking the double-layer polyvinyl alcohol (PVA)-carbon nanotube (CNT)/polyethylene (PE)-graphene oxide (GO) (PVA-CNT/PE-GO) composite films as the core actuating material. Due to the significant mismatch in thermal expansion coefficients between PVA and PE, the film achieves large bending deformation with a rapid response under NIR irradiation, demonstrating excellent actuation performance. Furthermore, the effects of CNT concentration gradients and PVA-CNT layer thickness on the performance of the flexible films are analyzed to ensure superior stability and fatigue resistance. Additionally, based on COMSOL finite element simulations, a "light-thermal-mechanical" energy conversion model is proposed to validate the thermal response and actuation mechanism of the composite films. Ultimately, based on the light-response bilayer actuator, a light-controlled capsule is designed to demonstrate the photothermal actuation and on-demand opening, providing a design strategy for light-response actuators with potential for further biomedical exploration.