Recent Advances in Flexible Piezoresistive Arrays: Materials, Design, and Applications

A Flexible Double-Sided Curvature Sensor Array for Use in Soft Robotics

This paper describes the design, fabrication, integration, characterization, and demonstration of a novel flexible double-sided curvature sensor array for use in soft robotics. The paper explores the performance and potential applications of a piezoresistive sensor array consisting of four gold strain gauges on a flexible polyimide (PI) substrate arranged in a Wheatstone bridge configuration. Multiple sensor strips were arranged like the fingers of a hand. Integrating Shape Memory Alloy (SMA) foils alongside the fingers was explored to mimic a human hand-gripping motion controlled with temperature, while curvature sensor array strips measure the resulting finger shapes. Moreover, object sensing in a flexible granular material gripper was demonstrated. The sensors were embedded within Polydimethylsiloxane (PDMS) to enhance their tactile feel and adhesive properties. The findings of this study are promising for future applications, particularly in robotics and prosthetics, as the ability to accurately mimic human hand movements and reconstruct sensor surfaces paves the way for robotic hand functionality.

A Novel Resistive Sensor Network Utilizing an SAP-Enhanced Ionic Layer and CNT Doping for Multipoint Pressure Measurement

Amidst the rapid advancements in flexible electronics, flexible pressure sensors have achieved widespread applications in fields such as wearable devices and motion monitoring. Nevertheless, it is still a challenge to design a sensor with high sensitivity, cost-effectiveness, and a simplified manufacturing process. This paper introduces a piezoresistive sensor built upon a composite conductive filler. The sensor incorporates a super absorbent polymer (SAP) to absorb a phosphoric acid solution and doped carbon nanotubes as the composite conductive filler. In contrast to conventional rigid conductive fillers, the elastic polymer SAP enhances the sensor's stability significantly by exhibiting superior compatibility with the polydimethylsiloxane matrix, all the while reducing its Young's modulus. This work aims to theoretically elucidate the underlying principles that enable the sensor to achieve high sensitivity. It focuses on the induction of charge carriers due to pressure, which leads to the formation of a conductive pathway and subsequent changes in resistance, thus facilitating precise pressure detection. The paper also discusses the effects of piezoresistive layers with varying thicknesses and conductive fillers on the sensor's output performance. The results highlight the sensor's high sensitivity (0.094 kPa-1), rapid response time (105 ms), and exceptional cyclic load/unload stability (>5000 cycles). Furthermore, this paper establishes a versatile sensing network by integrating a portable inductance, capacitance, and resistance instrument with a programmable logic controller module. Compared to individual sensors, this system enables multipoint measurements, offering high spatial resolution and real-time monitoring capabilities, significantly expanding its overall practicality.