Breathable Strain/Temperature Sensor Based on Fibrous Networks of Ionogels Capable of Monitoring Human Motion, Respiration, and Proximity

Abstract

Wearable strain and temperature sensors are desired for human−machine interfaces, health monitoring, and human motion monitoring. Herein, the fibrous mat with aligned nanofibers of ionic liquid (IL)/thermoplastic polyurethane (TPU) ionogels is fabricated via an electrospinning technique. The resultant fibrous mat is cut into a rectangle specimen and electrodes are loaded along the direction perpendicular to the nanofiber orientation to design a high-performance multimodal sensor based on an ionic conducting mechanism. As a strain sensor, the obtained sensor exhibits a wide strain working range (0−200%), a fast response and recovery (119 ms), a low detection limit (0.1%), and good reproducibility because of the reversible and deformable ionic conductive pathways of the sensor. Moreover, the sensor also exhibits excellent temperature-sensing behaviors, including a monotonic thermal response, high sensitivity (2.75% °C−1 ), high accuracy (0.1 °C), a fast response time (2.46 s), and remarkable repeatability, attributable to the negative temperature coefficient behavior of the IL/TPU fibrous mat. More interestingly, the IL/TPU fibrous sensor possesses good breathability, which is desired for wearable electronics. Because of these excellent sensing capabilities in strain and temperature, the sensor can not only monitor tiny and large human motions but also detect respiration and proximity, exhibiting enormous potential in wearable electronics.

An ultra-wide sensing range film strain sensor based on a branch-shaped PAN-based carbon nanofiber and carbon black synergistic conductive network for human motion detection and human–machine interfaces

“…5d), respectively, which were faster compared with numerous previous resistance-based strain-type film sensors. 42,46,47 There is no doubt that the rapid response and recovery times can meet the requirements for the real-time monitoring of human motion. In addition, good long-term stability of a film sensor is critical for the practical utilization of wearable electronics, as this can reduce costs and expand the e-products market remarkably.…”

Transparent Conducting Films Based on Carbon Nanotubes: Rational Design toward the Theoretical Limit

“…Applications of SWCNT networks in thin-film transistors and integrated circuits, as stretchable TCFs in various sensors and devices, and as stretchable electrode materials owing to new form factors such as flexibility and stretchability are already shown by various research groups. [64,180,[191][192][193][194] The key points for further research in this area are also to improve optoelectronic performance, deeper understand the microstructural origin of resistance-strain dependence, and integrate such stretchable SWCNT-based structures along with other compliant rigid interfaces. Developing a stretchable electrode that is transparent as well is especially important for prospective applications in the rapidly growing fields of wearable electronics and Internet of Things, which are shaping the function and view of future electronic devices.…”

Organic ionic fluid-based wearable sensors for healthcare

“…A successful application case is to prepare a film with good air permeability by electrospinning a composite solution of a polymer and ionic fluid materials. 58,61 Broadly speaking, the existing device processing technology still cannot perfectly meet the actual application requirements. Particularly, device miniaturization processing is currently facing a bottleneck.…”