Responsive soft actuator: harnessing multi-vapor, light, and magnetic field stimuli

Bioinspired soft actuators, capable of undergoing shape deformation in response to external triggers, hold great potential in fields such as soft robotics, artificial muscles, drug delivery, and smart switches. However, their widespread application is hindered by limitations in responsiveness, durability, and complex fabrication processes. In this study, we propose a new approach to tackle these challenges by developing a single-layer soft actuator that responds to multiple stimuli using a straightforward solution-casting method. This actuator comprises bio-polymer gelatin, bio-compatible PEDOT:PSS, and iron oxide (Fe₃O₄) nanoparticles. Our actuator exhibits responsiveness to a range of organic solvent vapors, including water vapor, light, and magnetic fields. Notably, it exhibits rapid and reversible bending in distinct directions in response to different vapors, bending upwards in the presence of water vapor and downwards in the presence of alcohol vapor. Moreover, exposure to infrared (IR) light induces a bending toward the light source. The incorporation of magnet-responsive Fe₃O₄ nanoparticles induces multi-functionality in the actuator. The actuation characteristics of the actuator are controlled by leveraging its responsiveness to dual stimuli, such as water vapor and magnetic fields, as well as light and magnetic fields. For the proof of concept, we showcase several potential applications of our multi-stimuli responsive soft actuator, including magnet-triggered electrical switches, cargo transportation, soft grippers, targeted drug delivery, energy harvesting, and bio-mimicry.