A Venus flytrap closes its leaves to trap prey when it senses a stimulus. Taking inspiration from this plant, KAIST researchers have combined the roles of a skin that senses approaching objects and a muscle that grasps them in a single soft material. When an electrically charged object comes near, ions inside the material move and produce an electrical signal. When ultraviolet (UV) light is applied, the material bends and grasps the object. Because it holds its deformed shape for more than 10 minutes after the light is turned off, the material shows potential for soft robotic hands that require fewer components and less wiring.

KAIST (President Choongsik Bae) announced on September 30 that a research team led by Professor Hong Chul Moon from the Department of Chemical and Biomolecular Engineering has developed the ‘Ionograsper,’ an ionic soft robot that senses nearby objects and moves in response to light. An ionic material contains ions, small particles that carry a positive or negative electric charge, which allow the material to respond to electrical changes in its surroundings.

Humans notice objects with their eyes or skin and grasp them by moving their muscles. Robots likewise need sensors to detect their surroundings and actuators to generate movement. However, when these devices are attached separately to a soft robot, which bends flexibly, the number of components and the amount of wiring increase, and the structure becomes more complex.

The research team combined the roles of a robot’s skin and muscle in a single soft polymer material. Polymers are substances made of small molecules linked into long chains; plastics and rubber are common examples. The team combined azobenzene, a compound that changes shape when exposed to light, with a hygroscopic polymer that absorbs moisture from the air. This produced a network structure in which ions can move.

When a charged object approaches, its electric field causes the positive and negative ions inside the material to redistribute. As a result, changes occur inside the material even without direct contact. The researchers used the resulting electrical signal to detect the approach and movement of objects without applying a separate sensing voltage.
To make the material move, the researchers irradiate it with UV light. Azobenzene changes its molecular shape when it absorbs light, and moisture escapes from the irradiated side of the material. This causes the material to bend toward the light, which can be used to grasp an object.

When the light is turned off, moisture re-enters the material through nanoscale pores that formed on its surface during irradiation. The material then bends in the opposite direction and holds its deformed shape for more than 10 minutes, until the polymer structure slowly relaxes. This means the light does not need to stay on for the material to maintain its grasping position.

A defining feature of the study is that three functions, sensing an object, moving, and retaining a changed shape for a period of time, are realized in a single material. The researchers also analyzed how light-induced changes in the molecules and in moisture content lead to bidirectional bending and shape retention.

This material design approach could help reduce the components and wiring required when sensors and actuators are mounted separately on soft robots. The work, however, remains at the research stage: the material currently detects charged objects and is actuated by UV light. The team plans to increase the sensing distance, actuation speed, durability under repeated use, and load-bearing capacity, and to make the material responsive to visible or near-infrared light.

“Rather than attaching a robot’s skin and muscles separately, we created a single material that senses objects and moves when it receives light, and a key feature is that it maintains its deformed shape even after the light is turned off,” said Professor Hong Chul Moon. He added that the team plans to combine the material with AI control technologies and develop it into a sensing and actuation material for physical AI robots.

Professor Yong Min Kim of the School of Chemical Engineering at Jeonbuk National University served as the first author, and Professor Hong Chul Moon of KAIST’s Department of Chemical and Biomolecular Engineering served as the corresponding author. The study was published online in the international journal Advanced Materials on September 14, 2026, and was selected as the front cover article of Issue 62.

※ Paper title: A Multifunctional Ionograsper Enabling Ion-Redistribution Proximity Sensing and Structural-Reconfiguration-Driven Bidirectional Actuation, DOI: 10.1002/adma.74981
※ Authors: Yong Min Kim (Jeonbuk National University, first author); Jin Han Kwon, Hyeon Woo Yang, Sungryong Kim, and Gyeong Rok Lee (KAIST, co-authors); Hong Chul Moon (KAIST, corresponding author)
※ Related Video: https://advanced.onlinelibrary.wiley.com/doi/10.1002/adma.74981

This research was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (Ministry of Science and ICT, MSIT) (RS-2025-00554260) and by the Nano & Material Technology Development Program through the NRF, funded by the MSIT (RS-2025-02221332).