Adjusting Sensitivity and Linearity of the Wearable Pressure Sensors by an Arbitrary Micro‐Protuberance Structure of Polyvinylidene Fluoride/Reduced Graphene Oxide Dielectric Films

Abstract

Flexible pressure sensors with high sensitivity over a broad linear range and fast response have extension applications in wearable electronics. Herein, we prepared a tunable capacitive pressure sensors based on arbitrary micro‐protuberances geometry films via low‐cost soft lithography, employing the polyvinylidene fluoride/reduced graphene oxide (PVDF/rGO) composite with a high dielectric constant of 172 and low loss tangent of 0.48. The hierarchical microstructures’ different sizes endow the sensors adjustable pressure response, achieving the regulation of sensitivity and linear detection range. The superior microstructured film‐based sensor exhibits a high sensitivity (1.19 kPa−1) over 20 times that of the bulk film, wide linearity (1.3 kPa), a rapid response (43 ms), a low limit of detection (10.6 Pa), and remarkable durability over 5000 compression/release cycles. In addition, based on the excellent sensing performance above‐mentioned, the device is successfully employed in the scenario of monitoring pressure interaction and human activities by mounting on different parts of the human body or object. This work provides a means to optimize the sensor's sensitivity and linearity by hierarchical structure and contributes to its wearable electronic applications.

Multi‐Hierarchical Microstructures Boosted Linearity of Flexible Capacitive Pressure Sensor

“…The hierarchical microstructure of PVDF/rGO dielectric film was prepared by low‐cost soft lithography, as reported in our work. [ 30 ] Specifically, the microstructured PDMS templates were fabricated by commercial sandpaper with various granularities (marked as 150 Cw, 400 Cw, 800 Cw, 1200 Cw, and 2000 Cw). Subsequently, the PVDF/rGO dielectric films with hierarchical microstructure were obtained using the as‐prepared PDMS templates, which is described as follows: First, graphene oxide (GO) powder (Chongqing Mohi Technology Co., Ltd., average particles size <45 μm; purity >99%) was dispersed in a 10 mL of dimethylformamide (Guoyao Group Chem.…”

“…Moreover, the permittivity performance of PVDF/reduced graphene oxide (PVDF/rGO) composite films has been system studied in our previous work. [ 30 ] Herein, we reported a flexible CPS based on PVDF/rGO films with multilayer and hierarchical microstructures (150/400/800 CW films‐3L) composed of irregular protrusions and the successive roughness (remarked as 150 Cw, 400 Cw, 800 Cw). Due to the synergistic effect of the structural compressibility and effective stress distribution of stacked multilayers under pressure, the sensor has a good sensitivity (0.18 kPa −1 ) in a wide linear range of 0.1 kPa–11 kPa, and is not easy to be saturated in the high‐pressure range of 360 kPa.…”

A flexible pressure sensor with highly customizable sensitivity and linearity via positive design of microhierarchical structures with a hyperelastic model

“…The passive design of irregular microstructures with multiscale hierarchical properties offers an optimal solution for realizing continuous deformation with pressure 20,21 . Previously, methods of inverting naturally occurring microstructural templates (e.g., pollen grains 22 or petals 23 , human skin 24,25 , abrasive paper 26 , and kirigami patterns 27 ) or MEMS-fabricated artificial patterns [28][29][30][31] have been introduced for piezoresistive sensors to fabricate active layers. For example, Geng et al reported an ordered multilevel microstructure and explored the regulations of its radius and spatial distribution impacting the sensor performance merely via simulations and experiments 32 , rather than from a quantitative perspective.…”

Designing wearable capacitive pressure sensors with arrangement of porous pyramidal microstructures

“…The advantages of using capacitive pressure sensors are notable. Firstly, they exhibit low energy consumption, making them suitable for battery-operated devices and applications where power efficiency is critical [22]. Secondly, capacitive sensors offer high repeatability, ensuring consistent and reliable measurements over time [23].…”