Wireless Passive Flexible Radio Frequency Tactile Sensor for Material Recognition

Developing intelligent tactile systems for perceiving the real world is significant for electronic skin and wearable devices. However, avoiding complex circuitry and achieving lightweight and wireless tactile devices remain challenging. This study presents a biomimetic, ultrasensitive, and multifunctional wireless radio frequency tactile sensor (WiRFTS), which comprises a porous polyaniline–polydimethylsiloxane (PANI–PDMS) sponge, pressure electrodes, and a communication coil. Benefiting from the synergistic effect of the porous microstructure and the high dielectric PANI particles, the WiRFTS exhibits an ultrahigh sensitivity of 1.394 MHz/kPa (<10 kPa), a linear sensitivity of 0.319 MHz/kPa (10–200 kPa), and a high resolution of 0.28%. Especially, the electromagnetic field at the surface of WiRFTS endows it with exceptional spatial perception. A noncontact intelligent material cognition system is established by combining WiRFTS with artificial intelligence algorithms, achieving 100% recognition accuracy for eight materials. Extensive study of RF-based dielectric properties ensures the system surpasses other technologies in material identification diversity.