A new capacitive‐type humidity sensor is proposed using novel materials and fabrication process for practical applications in sensitive environments and cost‐effective functional devices that require ultrasensing performances. Metal halide perovskites (CsPbBr3 and CsPb2Br5) combined with diverse ceramics (Al2O3, TiO2, and BaTiO3) are selected as sensing materials for the first time, and nanocomposite powders are deposited by aerosol deposition (AD) process. A state‐of‐the‐art CsPb2Br5/BaTiO3 nanocomposite humidity sensor prepared by AD process exhibits a significant increase in humidity sensing compared with CsPbBr3/Al2O3 and CsPbBr3/TiO2 sensors. An outstanding humidity sensitivity (21426 pF RH%−1) with superior linearity (0.991), fast response/recovery time (5 s), low hysteresis of 1.7%, and excellent stability in a wide range of relative humidity is obtained owing to a highly porous structure, effective charge separation, and water‐resistant characteristics of CsPb2Br5. Notably, this unprecedented result is obtained via a simple one‐step AD process within a few minutes at room temperature without any auxiliary treatment. The synergetic combination of AD technique and perovskite‐based nanocomposite can be potentially applied toward the development of multifunctional sensing devices.

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Inter-digital capacitors (IDCs) with aerosol-deposition (AD) high-k dielectric layer were compared via simulation and measurements of bare IDCs and AD IDCs at room temperature and subjected to a post-annealing process for realizing capacitive super-sensing applications. IDCs with thin AD films can provide higher capacitive intensity and improvements for other dielectric performances. Therefore, IDC patterns with AD high-k dielectric layers were fabricated by varying the finger widths and gap. Moreover, we analyzed the layer microstructure design patterns using simulations and experiments with AD BaTiO3 as-deposited IDCs and IDCs subjected to annealing at 500 °C. These three different IDCs were measured using an impedance analyzer; furthermore, the AD BaTiO3 films were evaluated using X-ray diffraction, atomic force microscopy, and traveling electron microscopy. The results for the IDCs with the AD BaTiO3 film show the highest capacitance when compared with other thin layer capacitors, which is expected to be useful in realizing super-sensing applications in the future.

In this paper, we demonstrated the feasibility of the Aerosol Deposition (AD) method which can be adapted as a future fabrication process for flexible electronic devices. On the basis of this method’s noticeable advantages such as room-temperature processing, suitability for mass production, wide material selectivity, and direct fabrication on a flexible substrate, we fabricated and evaluated a flexible conductive bridge random access memory (CBRAM) to confirm the feasibility of this method. The CBRAM was fabricated by the AD-method, and a novel film formation mechanism was observed and analyzed. Considering that the analyzed film formation mechanism is notably different with previously reported for film formation mechanisms of the AD method, these results of study will provide strong guidance for the fabrication of flexible electronic device on ductile substrate.

Respiration monitoring and human sweat sensing have promising application prospects in personal healthcare data collection, disease diagnostics, and the effective prevention of human-to-human transmission of fatal viruses. Here, we have introduced a unique respiration monitoring and touchless sensing system based on a CsPb 2 Br 5 /BaTiO 3 humidity-sensing layer operated by water-induced interfacial polarization and prepared using a facile aerosol deposition process. Based on the relationship between sensing ability and layer thickness, the sensing device with a 1.0 μm thick layer was found to exhibit optimal sensing performance, a result of its ideal microstructure. This sensor also exhibits the highest electrical signal variation at 0.5 kHz due to a substantial polarizability difference between high and low humidity. As a result, the CsPb 2 Br 5 /BaTiO 3 sensing device shows the best signal variation of all types of breath-monitoring devices reported to date when used to monitor sudden changes in respiratory rates in diverse situations. Furthermore, the sensor can effectively detect sweat evaporation when placed 1 cm from the skin, including subtle changes in capacitance caused by finger area and motion, skin moisture, and contact time. This ultrasensitive sensor, with its fast response, provides a potential new sensing platform for the longterm daily monitoring of respiration and sweat evaporation.