Localized Gradient Conductivity Enabled Ultrasensitive Flexible Tactile Sensors with Ultrawide Linearity Range

The high sensitivity and wide linearity are crucial for flexible tactile sensors in adapting to diverse application scenarios with high accuracy and reliability. However, conventional optimization strategies of constructing microstructures suffer from the mutual restriction between the high sensitivity and wide linearity. Herein, a novel design of localized gradient conductivity (LGC) with partly covered low-conductivity (low-σ) carbon/Polydimethylsiloxane layer on high-conductivity (high-σ) silver nanowires film upon the micro-dome structure is proposed. The LGC configuration enables a unique pressure-motivated series-parallel switching to allow the low-σ and high-σ components to separately take dominant effects in different pressure ranges. The ultrawide linearity can thus be realized by customizing the segmented linear current variation via the rationally associated coverage degree and conductivity gradient of the low-σ and high-σ components. Moreover, the ultrahigh sensitivity can be originally endowed by the conductivity difference between the low-σ and high-σ components without compromising linearity. The optimized sensor exhibits an ultrahigh sensitivity of 1546.35 kPa^-1 within an ultrabroad linear sensing range of 0-3000 kPa, which is first reported. With such an excellent sensing performance, the potential applications, e.g., reliable healthcare monitoring, convenient smart home control, and ground detection of intelligent vehicles, are successfully demonstrated.