Review of Fiber- or Yarn-Based Wearable Resistive Strain Sensors: Structural Design, Fabrication Technologies and Applications

Abstract

Flexible textile strain sensors that can be directly integrated into clothing have attracted much attention due to their great potential in wearable human health monitoring systems and human–computer interactions. Fiber- or yarn-based strain sensors are promising candidate materials for flexible and wearable electronics due to their light weights, good stretchability, high intrinsic and structural flexibility, and flexible integrability. This article investigates representative conductive materials, traditional and novel preparation methods and the structural design of fiber- or yarn-based resistive strain sensors as well as the interconnection and encapsulation of sensing fibers or yarns. In addition, this review summarizes the effects of the conductive materials, preparation strategy and structures on the crucial sensing performance. Discussions will be presented regarding the applications of fiber- or yarn-based resistive strain sensors. Finally, this article summarizes the bottleneck of current fiber- or yarn-based resistive strain sensors in terms of conductive materials, fabrication techniques, integration and performance, as well as scientific understanding, and proposes future research directions.

A Review on Knitted Flexible Strain Sensors for Human Activity Monitoring

“…Otherwise, irreversible recovery can lead to inaccuracy of the next signal acquisition and drift of the data. [ 130 ]…”

“…[76] The smaller the standard deviation, the better the stability, and repeatability of the KFSS. [129] The initial resistance of the sensor generally increases slightly in the later stretching cycle, [130] demonstrating that the strain sensor does not return to its original unstretched state after the repeated stretching. This results in an overall increase in the range of the rate of change of resistance with the number of cycles as well.…”

“…Otherwise, irreversible recovery can lead to inaccuracy of the next signal acquisition and drift of the data. [130] The hysteresis of a KFSS is related to the degree and times of strain. The adhesion of the knitted sensor itself and the interaction between the loops during stretching are the two main factors that contribute to hysteresis.…”

Advances in the Robustness of Wearable Electronic Textiles: Strategies, Stability, Washability and Perspective

“…The interconnections among different wearable components can be achieved via physical (soldering, conductive/nonconductive paste, crimp) or mechanical (embroidery, printing, sewing) bonding of the interconnects with the clothing/garment embedded into the complete wearable system. The physical methods are mostly adopted for interconnecting commercial rigid electronic components which involve a high welding temperature (soldering), may easily break under greater deformation (clamp), and may easily be affected by humidity and temperature (adhesive paste) [199], etc. These interconnection techniques are not suitable for designing flexible and comfortable wearable systems.…”

Strain‐Driven Negative Resistance Switching of Conductive Fibers with Adjustable Sensitivity for Wearable Healthcare Monitoring Systems with Near‐Zero Standby Power

“…[18][19][20][21][22] At this point, it can maintain a low resistance value of ≈1000 Ω or less to continuously transmit signals to the system, resulting in continuous high-power consumption even throughout the long standby time where no deformation has occurred. [18,19,23] In an effort to address the power consumption issue, some researchers have explored the use of piezoelectric materials to develop self-powered fiber sensors. [24] However, most piezoelectric materials, such as BaTiO 3 or PZT (PbZr x Ti 1-x O 3 ), present challenges for textile-based strain-sensor fabrication due to their complex deposition methods as well as their relatively rigid and fragile nature under strain.…”