Multistimulus-Responsive Janus Flexible Actuators for Cross-Scale Multiphase Manipulation and Sensing Detection

Bionic actuators that respond to environmental stimuli and mimic movements of living organisms have potential applications in smart devices. We report a concept and fabrication method of making bilayer Janus flexible actuators consisting of 2D MXene layer and flexible stretchable magnetic Fe 3 O 4 @PDMS layer, which enables the large difference in thermal expansion in response to IR light and magnetic stimuli; therefore, the sensor is capable of detecting various chemicals as well as cross-scale multiphase manipulation of liquid droplets and solids. The Fe 3 O 4 @PDMS surface was laser-textured with microstructural arrays realizing the superhydrophobicity, whereas the MXene surface remains hydrophilic, making a Janus structure. A prestressed BMFA in a curled state changed into a flat state under IR light irradiation due to thermal expansion, and vice versa. The bending angle reached a maximum of 216°. A 4-leg magnetic manipulator was able to grab and transport solid materials of varying sizes. The change of relative electrical resistance (Δ R / R 0 ) under external stimuli enabled the BMFA to function as a sensor for detecting IR light intensity, type, and concentration of chemical reagents. Δ R / R 0 changed from 1.37 to 15.8 by exposing to acetone vapor with the quickest response time of 0.6 s and the maximum bending angle of 358°. The multistimulus BMFA exhibits both sensing and materials transportation functions, providing a potential solution for the design and fabrication of intelligent soft robotics and bionic smart devices.