posted on 2022-03-15, 18:05authored byHaitao Liu, Xingda Song, Xiaoyu Wang, Shuhao Wang, Ni Yao, Xiong Li, Wei Fang, Limin Tong, Lei Zhang
The
monitoring of proximity-contact events is essential for human–machine
interactions, intelligent robots, and healthcare monitoring. We report
a dual-modal sensor made with two functionalized optical microfibers
(MFs), which is inspired by the somatosensory system of human skin.
The integrated sensor with a hierarchical structure gradationally
detects finger approaching and touching by measuring the relative
humidity (RH) and force-triggered light intensity variations. Specifically,
the RH sensory part shows enhanced evanescent absorption, achieving
a sensitive RH measurement with a fast response (110 ms), a high resolution
(0.11%RH), and a wide working range (10–100%RH). Enabled by
the transition from guided modes into radiation modes of the waveguiding
MF, the force sensory part exhibits a high sensitivity (6.2%/kPa)
and a fast response (up to 1.5 kHz). By using a real-time data processing
unit, the proximity-contact sensor (PCS) achieves continuous detection
of the full-contact events, including finger approaching, contacting,
pressing, releasing, and leaving. As a proof of concept, the electromagnetic-interference-free
PCS enables a smart switch system to recognize the proximity and contact
of bare/gloved fingers. Moreover, skin humidity detection and respiration
monitoring are realized. These initial results pave the way toward
a category of optical collaborative devices ranging from human–machine
interfaces to multifunctional on-skin healthcare sensors.