Ultrafast response humidity sensor using supramolecular nanofibre and its application in monitoring breath humidity and flow

Abstract

Measuring humidity in dynamic situations calls for highly sensitive fast response sensors. Here we report, a humidity sensor fabricated using solution processed supramolecular nanofibres as active resistive sensing material. The nanofibres are built via self- assembly of donor and acceptor molecules (coronene tetracarboxylate and dodecyl methyl viologen respectively) involved in charge transfer interactions. The conductivity of the nanofibre varied sensitively over a wide range of relative humidity (RH) with unprecedented fast response and recovery times. Based on UV-vis, XRD and AFM measurements, it is found that the stacking distance in the nanofibre decreases slightly while the charge transfer band intensity increases, all observations implying enhanced charge transfer interaction and hence the conductivity. It is demonstrated to be as a novel breath sensor which can monitor the respiration rate. Using two humidity sensors, a breath flow sensor was made which could simultaneously measure RH and flow rate of exhaled nasal breath. The integrated device was used for monitoring RH in the exhaled breath from volunteers undergoing exercise and alcohol induced dehydration.

Photopatternable PEDOT:PSS/PEG hybrid thin film with moisture stability and sensitivity

“…Figure 5a shows that the humidity sensor has been utilized as a measurement device to profile the humidity level from a water surface. The measured RH, calculated from the change of capacitance, increases with the approach to the water surface, as expected, which fits very well with the theoretical predications (a detailed calculation can be found in the Supplementary Information) 59,60 . The test continues as the humidity sensor moves away from the water surface, for which the measurement results closely follow the readings from the approaching process and show a negligible hysteretic effect overall.…”

Flexible and Stretchable Physical Sensor Integrated Platforms for Wearable Human‐Activity Monitoringand Personal Healthcare

“…For monitoring of human activity and personal healthcare, aside from the measurement of physical parameters such as temperature, pressure, and strain, an important measurement mode in such wearable sensor devices may involve the analysis of body humidity (hydration, exhaled breath), [ 170,171 ] body fl uids (blood, interstitial fl uids, sweat, saliva, and tears), [ 172 ] to gain insights into various aspects of physiological health. Measurement of the hydration levels of the skin can be important in dermatology and cosmetology as a means for analyzing various disease states (e.g., eczema, psoriasis, atopic dermatitis, and ichthyosis) and assessing factors (e.g., environmental, age, stress, and hormones) that can be associated with abnormal skin responses.…”

Humidity sensor based on electrospun (Na0.5Bi0.5)0.94TiO3–Ba0.06TiO3 nanofibers

“…The (Na 0. 5 Bi 0.5 ) (1 À x) TiO 3 -Ba x TiO 3 ((1 À x)NBT-BTx), as an ABO 3 -type complex metal oxide with the substitution of A-site ions, has been studied by many researchers. Its electrical properties can be affected by the compositions of (1À x)NBT-BTx [25].…”

“…Humidity sensors have attracted much attention for their diverse applications in industrial, agricultural, aeronautics, medicine and meteorology [1][2][3][4][5]. In recent years, more and more researchers are paying their attention to exploitation of materials for humidity sensor with excellent humidity sensing properties including high sensitivity, linear response, and fast response speed [6][7][8][9].…”