A research team led by Prof. WANG Long from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences has developed a highly stretchable and conductive foam sensor with an ultra-wide operational range using supercritical CO₂ (scCO₂) foaming.

This study was published in Materials Today Physics.

Piezoresistive strain sensors utilize conductive elastomeric composite foams to detect movement or touch. These sensors are lightweight, highly compressible, and exhibit stable responses, making them promising for applications in motion tracking, health monitoring, human-robot interaction, and robotics.

Porous conductive materials hold potential for flexible electronics; however, electrical failure or material damage during stretching limits their strain response range.

To overcome this challenge, the researchers introduced a porous structure in a segregated composite made of high aspect ratio carbon nanostructures (CNS) and flexible polyolefin elastomer (POE). By employing scCO₂ foaming, they were able to reconstruct the conductive network structure, resulting in porous conductive materials with an ultra-wide strain response range.

The developed POE/CNS foam exhibits remarkable stretchability (952.5% strain), elasticity (with a residual strain of 13.8%), and electrical conductivity (with a resistance of 50 kΩ). The segregated structure gives the POE/CNS foam sensor an exceptional strain response range from 0.5% to 762%, significantly outperforming randomly distributed structures.

In addition to high sensitivity, rapid response, and outstanding reproducibility, the POE/CNS foam sensor maintains stable performance over 4,000 tensile cycles, showcasing exceptional long-term durability.

This work presents a simple and eco-friendly method for producing high-performance polymer-based foam sensors, indicating strong potential for applications in wearable electronics and engineering equipment.

The POE/CNS foam sensor with segregated structure (Image by NIMTE)