Sensitive and Fast Humidity Sensor Based on A Redox Conducting Supramolecular Ionic Material for Respiration Monitoring

Abstract

Real-time monitoring of respiratory rate (RR) is highly important for human health, clinical diagnosis, and fundamental scientific research. Exhaled humidity-based RR monitoring has recently attracted increased attention because of its accuracy and portability. Here, we report a new design of an exhaled humidity sensor for the real-time monitoring of the RR based on a synthetic redox conducting supramolecular ionic material (SIM). The humidity-dependent conducting SIM is prepared by ionic self-assembly in aqueous solutions of electroactive 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,10-bis(3-methylimidazolium-1-yl) decane (C(mim)). By taking full advantage of the high hygroscopicity and water stability arising from the ionic and hydrophobic interactions between two building blocks (i.e., ABTS and C(mim)), the SIM-based humidity sensor exhibits both high sensitivity (less than 0.1% relative humidity) and fast response time (∼37 ms). These excellent properties allow this humidity sensor to noninvasively monitor the RRs of not only humans but also rats that have a much faster RR and much smaller tidal volume than humans. Moreover, this sensor could also be efficiently used for the real-time monitoring of the recovery process of rats from anesthesia.

All-Painting Process To Produce Respiration Sensor Using Humidity-Sensitive Nanoparticle Film and Graphite Trace

“…The thickness of the NP film is approximately 400 nm from line profiles in Figure S1. The scanning electron microscope image of a NP film and a graphite electrode is shown in Figure S1 For evaluating dynamic response of resistance of SiO2 NP films, we used a saturated KCl solution in a closed vessel which had 84 % RH 41,42 . We monitored resistance of the films while taking the sensor into and out of the vessel.…”

Sensing Systems for Respiration Monitoring: A Technical Systematic Review

“…For that, Agcayazi et al [ 123 ] used a mannequin equipped with an inflatable cuff bladder that emulated breathing cycles, which is similar to the prototype of Koch et al [ 90 ]. For humidity sensors, authors designed controlled humidity chambers using humidifiers and dry air compressors [ 74 ] or switches for controlling nitrogen flow and a motor to control the dispersion of water vapor [ 97 ]. Finally, other studies presented artificial validation prototypes adapted to the specific sensors used for respiration monitoring.…”

“…It was called “human observation”, since an expert provided a value of the breathing parameter from direct observation of the signals recorded by the sensors. Figure 28 shows that validation using a reference device was the predominant approach (adopted by 67% of the studies that performed validation), followed by the use of an artificial validation prototype (10%) [ 69 , 74 , 77 , 90 , 93 , 97 , 110 , 114 , 116 , 119 , 123 , 135 , 141 , 146 , 150 , 226 ]. It is also worth noting that 53 studies presented the sensing systems without providing evidence of their validation.…”

Water Adsorption and Transport on Oxidized Two‐Dimensional Carbon Materials

“…Humidity measurements are critical in a wide range of applications such as climatology, agriculture, architecture, and human comfort . So far, various humidity sensors built on different transduction mechanisms have been proposed and developed . Thanks to their rich surface chemistry and structure designability, carbon materials are considered to be particularly attractive in humidity sensing.…”

“…[59] So far,v arioush umiditys ensors built on different transduction mechanisms have been proposed and developed. [60,61] Thankst ot heir rich surfacec hemistry and structure designability,carbon materials are considered to be particularly attractive in humidity sensing.In2012, Nair et al demonstrated the selective superpermeability of the GO membrane to water molecules, [53a] suggesting applications such as humidity sensing. As the aqueous solution of GO turned out to be acidic, [62] protons generated throught he reaction of water molecules with the GO surface functional groups result in ad ecrease in the electrical impedance.P reviously,t he measured proton con- Figure 5.…”