Improved dielectricity of anisotropic wood slices and bioinspired micropatterned film electrodes for highly sensitive flexible electronic sensors

Abstract

Taking inspiration and utilizing materials directly from nature, a simple and green strategy to fabricate biomass-based highly sensitive flexible tactile sensors was developed. Capacitive sensing devices were constructed by stacking a conductive micropatterned PDMS bottom electrode, an anisotropic wood slice/ionic liquid (IL@wood) dielectric layer and an unpatterned PDMS top electrode. After IL impregnation, the wood cross slice (CS) had an average weight gain rate (R_w) and an improved relative dielectric constant (ε_r) of 493.9% and 32.6, respectively, while those of the axial one were 82.1% and 6.6. The sensor made of an IL@wood cross (IL@CS) section and a lotus-leaf-like PDMS/silver nanowire (AgNWs@PDMS) film had a maximum capacitance value in the order of 10⁰ μF cm⁻² under 80 kPa compression, thereby exhibiting outstanding signal-to-noise ratio and responsive stability of the device. Its sensitivity reached 2.09 kPa⁻¹ without obvious attenuation after 500 cycles. Additionally, it could not only monitor multiple motions including speaking, chewing and wrist bending but also decode handwriting and detect temperature variations.