Wearable Capacitive Pressure Sensor Based on MXene Composite Nanofibrous Scaffolds for Reliable Human Physiological Signal Acquisition

Abstract

In recent years, highly sensitive pressure sensors that are flexible, biocompatible, and stretchable have attracted significant research attention in the fields of wearable electronics and smart skin. However, there has been a considerable challenge to simultaneously achieve highly sensitive, low-cost sensors coupled with optimum mechanical stability and an ultralow detection limit for subtle physiological signal monitoring devices. Targeting aforementioned issues, herein, we report the facile fabrication of a highly sensitive and reliable capacitive pressure sensor for ultralow-pressure measurement by sandwiching MXene (Ti 3 C 2 T x )/poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) composite nanofibrous scaffolds as a dielectric layer between biocompatible poly-(3,4-ethylenedioxythiophene) polystyrene sulfonate /polydimethylsiloxane electrodes. The fabricated sensor exhibits a high sensitivity of 0.51 kPa −1 and a minimum detection limit of 1.5 Pa. In addition, it also enables linear sensing over a broad pressure range (0−400 kPa) and high reliability over 10,000 cycles even at extremely high pressure (>167 kPa). The sensitivity of the nanofiber-based sensor is enhanced by MXene loading, thereby increasing the dielectric constant up to 40 and reducing the compression modulus to 58% compared with pristine PVDF-TrFE nanofiber scaffolds. The proposed sensor can be used to determine the health condition of patients by monitoring physiological signals (pulse rate, respiration, muscle movements, and eye twitching) and also represents a good candidate for a next generation human−machine interfacing device.

Recent Progress on Flexible Capacitive Pressure Sensors: From Design and Materials to Applications

“…Reproduced with permission. [ 212 ] Copyright 2020, ACS. p,q) Respiration rate monitoring before and after exercise with sensor placed on the chest of subject.…”

“…Respiration monitoring in everyday can provide early detection of several diseases like emphysema, bronchitis, asthma, and sleep apnea. [ 210–212 ] Continuous monitoring of respiration can save human lives and is actually very common for athletes, and nowadays, even normal people. [ 213 ] Several researchers proposed monitoring respiration or wheezing using flexible capacitive pressure sensors.…”

“…Sharma et al performed respiration monitoring of breathing before and after exercise using composite nanofibrous scaffolds based flexible capacitive pressure sensors. [ 212 ] The sensor is attached to a mask worn by the subject (healthy 30 years old) for respiration monitoring which shows increase from 24 to 48 respiration cycles per minute for before to after exercise [Figure 11o]. The sensor shows excellent response; however, as masks are not worn constantly, a more practical system needs to be designed, such as sensor embedded in textile clothing or stuck on the chest, for respiration monitoring.…”

Textile Technology for Soft Robotic and Autonomous Garments

“…[ 482–484 ] Sharma and colleagues took advantage of the ability to electrospin MXene/PVDF‐TrFE nanofiber scaffolds to increase dielectric constant and reduce the material compression modulus to enhance pressure sensitivity. [ 485 ] Here MXene was specifically added to increase the dielectric constant, while its 2D nature allowed for more uniform dispersion within the polymer matrix. With this approach, a sensitivity of 0.51 kPa −1 could be achieved for a range of 0–1 kPa.…”

Conical Microstructure Flexible High-Sensitivity Sensing Unit Adopting Chemical Corrosion

“…In a general way, the response of flexible pressure sensors can be divided into capacitive, piezoresistive, photoelectric, hall-type, etc. [ 13 , 14 , 15 , 16 , 17 , 18 ]. Compared with other sensing methods, capacitive sensors have the advantage of low power consumption, small peripheral volume, high stability, etc.…”