Simultaneously Stretchable and Compressible Flexible Strain Sensors Based on Carbon Nanotube Composites for Motion Monitoring and Human–Computer Interactions

Simultaneously stretchable and compressible flexible strain sensors are highly desired in many advanced applications including the wearable field. However, the fabrication of such dual-function sensors with a wide sensing range is still challenging. In this work, a simultaneously stretchable and compressible foam strain sensor was fabricated by skillfully introducing oriented pores into the highly stretchable elastic composite based on carbon nanotubes and poly(styrene-b-ethylene–butylene-b-styrene) (SEBS) by a freeze-drying method, in which cyclohexane was employed as the freeze-drying solvent. The high stretchability of SEBS and the abundant compressible space imparted by the pores endowed the resultant flexible foam sensor with highly stretchable (250%) and compressive (−50%) characteristics simultaneously. Thanks to the outstanding flexible features, the foam sensor enabled simultaneous monitoring of multiple human movements, such as bidirectional wrist bending, knee bending, foot stepping, and so forth. The foam sensor could encrypt human gesture signals into electrical signals and transmit them to the machine to realize the human–computer interaction, which could greatly broaden the application prospect of flexible strain sensors in the field of intelligent sensing.