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Low humidity detection has always been a challenge in the field of humidity detection. Humidity sensors base on ionic liquid modified metal organic frameworks (MOFs) derived polymer films were prepared in this work. The ionic liquid ligand was uniformly introduced in the frameworks of UIO-66 to enhance the hydrophilicity of sensing materials, the caused defects sites are beneficial for adsorption and desorption, and the MOFs based functional films were easily obtained by in situ photoinduced thiol-ene click reaction. The obtained humidity sensor exhibits a linear response in low relative humidity (RH) range (5% RH - 30% RH) with a tiny humidity hysteresis (~0.2% RH) and short response time to humidity change (response/recovery time is 0.6 s/1.7 s, respectively). ● Humidity sensors based on ionic liquid modified UIO-66 derived polyelectrolyte films were prepared. ● The sensors were prepared facilely in situ on the electrodes by thiol-ene click polymerization in batches. ● The sensor presents linear response under low humidity (5% RH - 30% RH) with a small hysteresis and fast response speed. ● The introduction of ILs and the resulting defect sites are the reasons for effective low humidity detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Humidity sensors based on glycidyl trimethyl ammonium chloride (EPTAC) modified cellulose paper via a facile solution method were fabricated. • The paper is used for the purpose of the humidity sensing material and the sensor substrate. • The as-fabricated paper-based humidity sensor is provided with outstanding humidity sensing properties and good stability. • The humidity sensor was applied to multifunctional applications including human breath rate, non-contact switch and skin humidity. It is of great significance to exploit a simple, cost-effective and environmentally friendly preparation method of multifunctional humidity sensors. However, most humidity sensors need complex manufacturing processes, high cost and narrow usage range. Herein, humidity sensors based on glycidyl trimethyl ammonium chloride (EPTAC) modified cellulose paper via a facile solution method were fabricated, among which the paper is used for the purpose of the humidity sensing material and the sensor substrate. The sensitivity of the obtained sensor was improved by the modification of EPTAC, the response time was decreased to 25 s, which is equivalent to the first-rate paper-based humidity sensors. In addition, the paper-based humidity sensor is provided with well flexibility and biocompatibility, and it exhibits multifunctional applications in respiratory monitoring, non-contact switch and skin humidity monitoring. The low cost and facile preparation technique in this work could provide a useful strategy for developing multifunctional humidity sensor. [ABSTRACT FROM AUTHOR]

Self-supported polymer films were fabricated by the thiol-ene click cross-linking reaction in this work. The cross-linked frameworks were used to guarantee the stability the films. The hydrophilic monomer with different contents were introduced into the self-supported thick films and uniformly dispersed in the polymer frameworks. The interdigitated electrodes were screen printed with silver paste on the self-supported films to obtain humidity sensors. Herein, the self-supported film acts as both the sensor substrate and the humidity-sensing material. The humidity sensing performances of the obtained sensors were systematically researched. By optimizing the ratio of hydrophilic monomer in the polymer films, the sensitivities of the sensors were enhanced from 1.58 to 103.75 (in the humidity from 11% RH to 95% RH), the response under low RH environment was significantly improved with good linearity. The response/recovery times of the sensor within the humidity range are measured to be 12.5 s and hundreds of seconds. The prepared flexible sensors possess certain mechanical properties, and exhibit good stability under bending and long-term tests up to 60 days. The applications of the as-prepared sensor in the detection of non-contact human skin humidity, human respiration and relative humidity of green plant were explored. The sensor shows excellent sensing performance in various applications and indicates the potential application in wearable and multifunctional devices. [Display omitted] • Self-supported polymer films were fabricated by the thiol-ene click cross-linking reaction. • Flexible and stable humidity sensors were fabricated by screen printing electrodes on the self-supported films. • The roles of the self-supported film are the substrate of the sensor, as both the humidity-sensing material. • The humidity sensing properties and the multifunctional applications of the obtained sensors were systematically researched. [ABSTRACT FROM AUTHOR]