MIT Engineers Develop Light-Responsive Soft Material

A team of engineers from MIT and collaborating institutions has developed a soft, flexible material that can change its electrical conductivity in response to light. The research was published in the open-access journal Nature Communications.

The material's conductivity can increase by approximately 400 times when exposed to light, transitioning from an insulating to a conductive state.

How the Material Works

The research centers on a class of materials known as photo-ion generators (PIGs). These materials can become about 1,000 times more conductive when exposed to light.

The MIT-led team developed a method to incorporate a PIG into a polyurethane rubber matrix. The process involved first dissolving the PIG powder in a solvent and then using a swelling method to integrate it into the rubber, creating a soft composite gel.

According to the researchers, this mechanism allows for the dynamic control of local ion population within the soft material.

The Field of Ionotronics

This work is situated within the field of ionotronics, which focuses on transferring data and signals using ions (charged molecules) rather than electrons.

A key motivation for ionotronics is its potential to create a bridge between conventional electronic devices and biological tissues, as living systems naturally use ions—such as potassium and sodium—for cellular communication.

The researchers noted that while previous ionotronic materials have achieved high conductivities, they have generally lacked easy methods for controlling or switching that conductivity.

Researcher Perspectives

Thomas J. Wallin, the John F. Elliott Career Development Professor in MIT’s Department of Materials Science and Engineering, who led the work, stated: "We've found a mechanism to dynamically control local ion population in a soft material. That could allow a system that is self-adaptive to environmental stimuli, in this case light."

Xu Liu, first author of the paper and a former MIT postdoc, added: "What we're doing is using light to switch a soft material from insulating to something that is 400 times more conductive."

Potential Future Applications

The researchers identified several potential future applications for light-responsive ionotronic materials, including:

• Human-machine interfaces
• Biocompatible devices
• Soft robotics
• Soft wearable technology
• Systems that automatically adapt to environmental stimuli
• Complex signal processing within soft materials