Bioinspired Hierarchical Structure for an Ultrawide‐Range Multifunctional Flexible Sensor Using Porous Expandable Polyethylene/Loofah‐Like Polyurethane Sponge Material

Abstract

Capacitive sensors show promising applications for human–computer interface due to their potential capabilities of both pressure and proximity sensing. However, the sensitivity loss at large strain and the complicated process of fabrication technology limit related applications. Herein, inspired by gradient and hierarchical structures in biological systems and using porous materials with different stiffness, a capacitive flexible sensor with both proximity and pressure sensing abilities is proposed. Such hierarchical structures effectively reduce the attenuation of sensitivity as the pressure increases, realizing an ultrawide detection range with high sensitivity. A theoretical mathematical model is developed and the corresponding capacitive sensor is fabricated by using the high‐performance porous impregnated dust‐free paper as the electrode and expandable polyethylene (EPE)/loofah‐like polyurethane sponge (LPS) as double‐layer porous dielectric. This sensor has an ultrawide detection range up to 3000 kPa with a significantly low sensitivity loss of 0.0195% kPa−1 and the noncontact sensing mode reaches a sensing range up to 28 cm (0.122 cm−1). Notably, a strategy is provided to design the high sensitivity sensor over an ultrawide detection range from approaching to pressuring, and eventually its promising application is presented as human–computer interaction.