Soybean Root-Inspired\nSWCNT/Ag@Au Composite Electrode\nfor Ionic Polymer–Metal Composite Actuators

Ionic polymer–metal composites (IPMCs), as innovative\nsoft\nsmart polymers, can effectively convert electrical energy into mechanical\nenergy through electrochemically induced ion migration, demonstrating\nsignificant potential in soft intelligent robotics. As the actuation\ncharacteristics of IPMC actuators are largely determined by the electrochemical\nkinetics within the electrodes, it is highly desired to fabricate\ntailored electrodes with excellent electrical conductivity and superior\nelectrochemical characteristics to develop high-performance IPMC actuators.\nTaking inspiration from the distinctive structure of soybean roots,\nwe propose the concept of developing a soybean root-style composite\nelectrode consisting of single-walled carbon nanotubes, silver nanoparticles,\nand gold nanoparticles for IPMCs using a combination of spray coating\nand electroplating technologies. The developed electrodes have a unique\nhierarchical structure, low surface resistance (2.80 Ω/sq),\nand greatly enhanced electrochemical characteristics because of the\nredox reactions of silver nanoparticles during the actuation process,\nwhich would facilitate the ion migration and storage in actuation.\nAccordingly, the resulting IPMC actuator outputs excellent electromechanical\nwork under 2 V voltage, including large peak-to-peak deformation (displacement\n14.91 mm, strain 0.94%), high deformation rate (1.07 mm/s), wide frequency\nresponse (0.01–10 Hz), and high generated stress (3.67 MPa).\nThe IPMC actuators can be used to construct flexible artificial fingers,\nenabling efficient grasping and transport of delicate flowers without\ncausing any damage to their surfaces. This study provides insight\ninto the design and optimization of composite electrode materials\nfor advanced IPMC actuators with improved functional capabilities\nin various applications.