A team of researchers from the Korea Advanced Institute of Science and Technology (KAIST) has taken inspiration from the Venus flytrap, which closes its leaves to capture prey when it senses a stimulus, to develop a material that enables a robotic hand to grasp objects.
The team calls the result the "Ionograsper." The material contains ions, small particles that carry a positive or negative electric charge, and those ions let it respond to electrical changes in its surroundings. That's what allows the Ionograsper to sense nearby objects. When ultraviolet (UV) light is applied, the soft material bends and grasps the object.
The material is being eyed specifically for robotic hands because it maintains its deformed shape for more than 10 minutes once the light is off.
To integrate sensing and muscle-like functions into a single material, the team combined azobenzene — a compound that changes shape when exposed to light — with a hygroscopic polymer that absorbs moisture from the air. Together, the materials form an interconnected network that allows ions to move throughout the structure.
The resulting material detects nearby charged objects without physical contact or an external sensing voltage. As a charged object approaches, its electric field drives the positive and negative ions within the material to rearrange. This movement generates an electrical signal that indicates the object’s presence and tracks its movement.
The material also functions as an actuator when exposed to UV light. The light changes the shape of the azobenzene molecules, forcing moisture out of the illuminated side and causing the material to bend toward the light. This bending motion allows the material to grasp objects.
The material can maintain its grip even after the UV light is turned off. Once irradiation stops, moisture gradually re-enters through nanoscale pores that form during exposure, but the material does not immediately return to its original shape, eliminating the need for continuous UV illumination.
The researchers said the technology could simplify soft robots by combining sensing and actuation in a single material, potentially reducing components and wiring. The technology remains in the research stage, however. Future work will focus on extending sensing range, increasing actuation speed, durability and load capacity, and enabling operation with visible or near-infrared light.
An article detailing the work, “A Multifunctional Ionograsper Enabling Ion-Redistribution Proximity Sensing and Structural-Reconfiguration-Driven Bidirectional Actuation,” appears in the journal Advanced Materials.
