The status and perspectives of nanostructured materials and fabrication processes for wearable piezoresistive sensors

Abstract

The wearable sensors have attracted a growing interest in different markets, including health, fitness, gaming, and entertainment, due to their outstanding characteristics of convenience, simplicity, accuracy, speed, and competitive price. The development of different types of wearable sensors was only possible due to advances in smart nanostructured materials with properties to detect changes in temperature, touch, pressure, movement, and humidity. Among the various sensing nanomaterials used in wearable sensors, the piezoresistive type has been extensively investigated and their potential have been demonstrated for different applications. In this review article, the current status and challenges of nanomaterials and fabrication processes for wearable piezoresistive sensors are presented in three parts. The first part focuses on the different types of sensing nanomaterials, namely, zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) piezoresistive nanomaterials. Then, in second part, their fabrication processes and integration are discussed. Finally, the last part presents examples of wearable piezoresistive sensors and their applications.

Porous Nanocomposites with Enhanced Intrinsic Piezoresistive Sensitivity for a Highly Integrated Multimodal Tactile Sensor

“…11,12 Material systems suitable for producing PPEN include thermoplastic urethanes (TPU), Polydimethylsiloxane (PDMS), Epoxy, and conductive fillers like carbon nanoparticles (CNs), carbon nanotubes (CNTs), nanowires, and graphene, etc. 13 Sophisticated fabrication techniques, leveraging advanced principles of chemistry and physics, have been employed to achieve specific structural characteristics, such as Chemical or physical foaming, sacrificial poremaking method, freeze drying, soaking adhesion, electroless plating, physical vapor deposition, 3D printing, among others. 6,11,14,15 , giving rise to a variety of mechanical structures including open-cell, closed-cell, and negative Poisson's ratio cell.…”

Tuning the Piezoresistive Behavior of Graphene-Polybenzoxazine Nanocomposites: Toward High-Performance Materials for Pressure Sensing Applications

“…To overcome the limitations of traditional pressure sensors based on metals and semiconductors, e.g., rigidity, high production costs, and cumbersome processability, research efforts are currently focused on the development of novel systems comprising flexible components and featuring superior mechanical properties and cost-effective and scalable production and processing. Various nanomaterial-based systems (including MoS 2 , MXene, and gold nanoparticles) are being explored as candidates for pressure-sensitive active materials that, once integrated into a device with appropriate flexible substrates and electrodes, can ensure high sensitivity, durability, and fulfillment of all the aforementioned characteristics. , Among them, graphene and its derivatives are particularly appealing since they display excellent electrical and mechanical properties, high flexibility, and lightweight, rendering graphene-based materials particularly suitable for application in pressure sensing . One common approach to integrating graphene-based materials in a pressure sensor consists in their incorporation into flexible or elastic substrates, such as rubbers, , fibers, , fabrics, , or polymer matrices. ,, With this approach, various types of pressure sensors featuring different structures have been integrated into capacitive, , piezorestistive, , and piezoelectric , sensors.…”

“…One common approach to integrating graphene-based materials in a pressure sensor consists in their incorporation into flexible or elastic substrates, such as rubbers, , fibers, , fabrics, , or polymer matrices. ,, With this approach, various types of pressure sensors featuring different structures have been integrated into capacitive, , piezorestistive, , and piezoelectric , sensors. Piezoresistive sensors are particularly promising for technological implementation, given their simple sensing mechanism and design, low power consumption, and easy readout. ,, …”

“…Piezoresistive sensors are particularly promising for technological implementation, given their simple sensing mechanism and design, low power consumption, and easy readout. 15,16,29 For applications in flexible electronics, a high sensitivity in the low-pressure regime (i.e., 0.1−10 kPa, compatible with tactile perception) is crucial. In piezoresistive devices, the sensing mechanism relies on variations of the active material electrical resistance (tunneling resistance or contact resistance); briefly, the application of compressive stresses causes changes in the material microstructure and consequently variations in the electrically conductive pathways within the sensing material.…”

“…Various nanomaterial-based systems (including MoS 2 , MXene, and gold nanoparticles) are being explored as candidates for pressure-sensitive active materials that, once integrated into a device with appropriate flexible substrates and electrodes, can ensure high sensitivity, durability, and fulfillment of all the aforementioned characteristics. , Among them, graphene and its derivatives are particularly appealing since they display excellent electrical and mechanical properties, high flexibility, and lightweight, rendering graphene-based materials particularly suitable for application in pressure sensing . One common approach to integrating graphene-based materials in a pressure sensor consists in their incorporation into flexible or elastic substrates, such as rubbers, , fibers, , fabrics, , or polymer matrices. ,, With this approach, various types of pressure sensors featuring different structures have been integrated into capacitive, , piezorestistive, , and piezoelectric , sensors. Piezoresistive sensors are particularly promising for technological implementation, given their simple sensing mechanism and design, low power consumption, and easy readout. ,, …”