Nanomaterial‐Enabled Flexible and Stretchable Sensing Systems: Processing, Integration, and Applications

Abstract

Nanomaterial‐enabled flexible and stretchable electronics have seen tremendous progress in recent years, evolving from single sensors to integrated sensing systems. Compared with nanomaterial‐enabled sensors with a single function, integration of multiple sensors is conducive to comprehensive monitoring of personal health and environment, intelligent human–machine interfaces, and realistic imitation of human skin in robotics and prosthetics. Integration of sensors with other functional components promotes real‐world applications of the sensing systems. Here, an overview of the design and integration strategies and manufacturing techniques for such sensing systems is given. Then, representative nanomaterial‐enabled flexible and stretchable sensing systems are presented. Following that, representative applications in personal health, fitness tracking, electronic skins, artificial nervous systems, and human–machine interactions are provided. To conclude, perspectives on the challenges and opportunities in this burgeoning field are considered.

In Situ Dynamic Manipulation of Graphene Strain Sensor with Drastically Sensing Performance Enhancement

“…In Figure 4f, various strain sensors based on graphene and carbon material are compared in the aspects of GF and the maximum applied strain. Compared with other strain sensors that have been reported, [ 8,13,24–26,32,35–43 ] our graphene sensor reaches a satisfying balance between wide detect strain range and high sensitivity.…”

Surface and Interface Designs in Copper-Based Conductive Inks for Printed/Flexible Electronics

“…Cu-based inks/pastes are recognized as having a low reliability due to oxidation. As a result, there are few reports on the application of Cu-based inks/pastes on flexible electronics applications, compared with those of Ag-based inks/pastes and carbon nanotube-(CNT) or graphene-based inks/pastes [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. However, the recent development of Cu-based inks/pastes described in this review would allow a real application of flexible devices such as smart robotics, electronic skin, optoelectronics, human motion, health monitoring systems, and human–machine interactive systems in the future.…”

“…Recent printing technologies, including flexography, offset, gravure, screen printing, and inkjet printing, offer the direct deposition of conductive materials on flexible substrates for the cost-effective/large-scale fabrication of flexible electronics [ 2 ]. Printed electronics are essential to facilitate the widespread use of flexible electronics and, more recently, stretchable electronics, such as sensors, electronic displays, solar cells, thin-film transistors, and supercapacitors [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Printable conductive electrodes on flexible substrates require the following characteristics for the application of printed electronics: (i) a high conductivity, (ii) cost-effectiveness, (iii) durability under extreme environmental conditions (heat and moisture), and (iv) printing processability on low-cost plastic substrates (indispensably, PET for productive roll to roll (R2R) processes).…”

“…In the past decade, numerous researchers have developed stable Cu-based inks/pastes. Many excellent review articles on the widespread use of flexible/stretchable electronics have been reported [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], as well as on Cu-based conductive inks/pastes [ 26 , 27 , 28 ]. Specifically, we adopt the viewpoints of the surface and interface designs for Cu-based inks/pastes in this review, as summarized in Figure 1 .…”

Structural Innovations in Printed, Flexible, and Stretchable Electronics

“…Microfabrication techniques (e.g., photolithography and chemical/physical vapor deposition), subtractive manufacturing (e.g., computer numerical control (CNC) machining and laser ablation), and additive manufacturing (e.g., inject molding, thick‐film printing, and 3D printing), have all shown remarkable capabilities toward the fabrication of stretchable electronics. [ 29,30 ] Among them, microfabrication techniques have pioneered and advanced the development of soft electronics, and related fabrication techniques, mechanical behavior, and electrical performance have been studied extensively. [ 31 ] Yet, such processes are challenged by their high material and device cost, limited material compatibility, complex fabrication procedures, or low throughput, which hinder their ability to enter the market with sufficient scalability and competitive price.…”