Full‐Textile Wireless Flexible Humidity Sensor for Human Physiological Monitoring

Abstract

Textile-based electronic techniques that can in real-time and noncontact detect the respiration rate and respiratory arrest are highly desired for human health monitoring. Yarn-shaped humidity sensor is fabricated based on a sensitive fiber with relatively high specific surface area and abnormal cross-section. The response and recovery time of the yarnshaped humidity sensor is only 3.5 and 4 s, respectively, with little hysteresis, because of the hydrophobic property of these functional fibers and the grooves on the surface of the fibers, which is much faster than those of the commercial polyimide materials. Moreover, a batteryfree LC wireless testing system combined with the yarn-shaped sensor is fabricated, which is further successfully imbedded into the intelligent mask to detect human breath. Based on the detection of LC wireless testing system, the frequency of 50.25 MHz under the exhaled condition shifts to 50.86 MHz under the inhaled situation of humidity sensor. In essence, the functional yarns with proper structure, would be an excellent candidature to the yarn-shaped humidity sensor, in which there are good performance and wide application possibilities, eventually offering a facile method for the wireless detection of human physiological signals in the field of electronic fabrics.

Wearable humidity sensor embroidered on a commercial face mask and its electrical properties

“…3 . It can be concluded from the graph that the electrical resistance change is flatter at higher frequencies and the obtained results confirm the decreasing trend of electrical resistance of face mask sensor with the increase in frequencies suggesting high suitability of our prepared sensor for humidity monitoring [ 25 – 34 ].

Figure 3 Resistance vs frequency change of the face mask sensor at different relative humidity levels: ( a ) in the lower frequency range (1 Hz to 40 kHz); ( b ) in the higher-frequency range (40 kHz to 200 kHz)

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Surface Engineering Enabled Capacitive Gas‐Phase Water Molecule Sensors in Carbon Nanodots

“…As a result, the as‐prepared CDs‐based capacitive sensor possesses a broad detection range from 11% to 98% relative humidity (RH), with a remarkable sensitivity of 3.3 × 10 5 pF/RH at 98% RH, which is the best performances among capacitive humidity sensors (Figure 1f ). [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ] The performances of these CDs‐based sensors significantly support the hypothesis of the molecular affinity effect toward capacitive response and highlight the unique structure of CDs for the gas sensors.…”

Ultra‐Sensitive and High‐Resolution Flexible Iontronic Humidity Sensor for Detecting Subtle Moisture Differences

“…Our sensor is superior existing humidity sensors in several aspects. First, it exhibits an ultrahigh sensitivity of 1580%RH -1 within 70%-100% RH, which is two orders of magnitude greater than that reported in other studies (Figure 4f), [31,38,[45][46][47][48][49][50][51][52][53][54] and the high sensitivity gives rise to high humidity resolution of 0.01% RH. Humidity-resolution is defined as the minimum value of normalized change in humidity that causes a noticeable change in capacitance.…”