Functionalized Fiber-Based Strain Sensors: Pathway to Next-Generation Wearable Electronics

Abstract

Wearable strain sensors are arousing increasing research interests in recent years on account of their potentials in motion detection, personal and public healthcare, future entertainment, man–machine interaction, artificial intelligence, and so forth. Much research has focused on fiber-based sensors due to the appealing performance of fibers, including processing flexibility, wearing comfortability, outstanding lifetime and serviceability, low-cost and large-scale capacity. Herein, we review the latest advances in functionalization and device fabrication of fiber materials toward applications in fiber-based wearable strain sensors. We describe the approaches for preparing conductive fibers such as spinning, surface modification, and structural transformation. We also introduce the fabrication and sensing mechanisms of state-of-the-art sensors and analyze their merits and demerits. The applications toward motion detection, healthcare, man–machine interaction, future entertainment, and multifunctional sensing are summarized with typical examples. We finally critically analyze tough challenges and future remarks of fiber-based strain sensors, aiming to implement them in real applications.

Direct ink writing of a graphene/CNT/silicone composite strain sensor with a near-zero temperature coefficient of resistance

“…25,26 Meanwhile, compared with well-developed film/ foam-like devices, the fiber-shaped strain sensors developed by the DIW technique have the advantages of excellent flexibility, weavability, portability and suitable conformability onto uneven surfaces. [27][28][29] Consequently, in this study, we will develop a robust and highly stretchable GNP/CNT/silicone elastomer (GCE) fiber with small or near-zero TCR by a facile DIW technique. A non-temperature interference property of the resultant GCE strain sensor will be realized through the combination of GNPs and CNTs with opposite TCRs.…”

“…25,26 Meanwhile, compared with well-developed film/foam-like devices, the fiber-shaped strain sensors developed by the DIW technique have the advantages of excellent flexibility, weavability, portability and suitable conformability onto uneven surfaces. 27–29…”

An All-In-One Multifunctional Touch Sensor with Carbon-Based Gradient Resistance Elements

“…A growing trend for human–machine interfaces (HMIs) hinges on the progress of a full-body immersive experience [ 1 – 3 ]. HMIs are medium to transmit and exchange information between human and machines for the accomplishment of a defined task [ 4 – 6 ].…”

A sensitive and flexible interdigitated capacitive strain gauge based on carbon nanofiber/PANI/silicone rubber nanocomposite for body motion monitoring

“…CSGs with parallel electrodes are sensors composed of a dielectric layer sandwiched by two parallel conductive electrodes. The capacitance changes of CSGs mostly rely on geometry changes between the electrodes and the dielectric layer, calculated by C = e e 0 r A/d, where (A) is the overlap area between two electrodes, (d) is the thickness of the dielectric layer, (e 0 ) is vacuum permittivity and (e r ) is the relative permittivity of the dielectric layer [37][38][39]. Commercial CSGs typically have had a parallel plate design.…”

“…The following relation for interdigitated capacitive strain gauges has been derived from other work [6,39,42]. According to figure 1, the initial capacitance C 0 of the interdigitated capacitive strain gauge is expressed by:…”