Highly sensitive temperature sensors are designed by exploiting the interparticle distance-dependent transport mechanism in nanocrystal (NC) thin films based on a thermal expansion strategy. The effect of ligands on the electronic, thermal, mechanical, and charge transport properties of silver (Ag) NC thin films on thermal expandable substrates of poly(dimethylsiloxane) (PDMS) is investigated. While inorganic ligand-treated Ag NC thin films exhibit a low temperature coefficient of resistance (TCR), organic ligandtreated films exhibit extremely high TCR up to 0.5 K −1 , which is the highest TCR exhibited among nanomaterial-based temperature sensors to the best of the authors' knowledge. Structural and electronic characterizations, as well as finite element method simulation and transport modeling are conducted to determine the origin of this behavior. Finally, an all-solution based fabrication process is established to build Ag NC-based sensors and electrodes on PDMS to demonstrate their suitability as low-cost, high-performance attachable temperature sensors.
In this study, multifunctional light-emitting and passive radiative cooling (LEPC) materials and devices are designed by embedding chemically designed perovskite nanocrystals (NCs) into the radiative polymer layer. Lead halide perovskite NCs are chosen as the light-emitting material, owing to their high photon radiation rate and low phonon generation. To integrate the perovskite NCs into the radiative polymer layers, a surface passivation is achieved by coating the NCs with silica. The silica shell synergistically improves the chemical stability and cooling efficiency. Both outdoor experimental and simulation results demonstrate that the fabricated LEPC devices show better cooling performance than conventional cooling devices. The LEPC devices are easily patterned by utilizing pixelating, assembling, and simple cutting or drawing techniques with the LEPC materials. This study also demonstrates the potential applications of these materials as components of smart building systems, in smart window displays, or for anticounterfeiting cooling systems, thus proving the practicality of these multifunctional LEPC devices.
In this study, non-temperature interference strain gauge sensors, which are only sensitive to strain but not temperature, are developed by engineering the properties and structure from a material perspective. The environmental interference from temperature fluctuations is successfully eliminated by controlling the charge transport in nanoparticles with thermally expandable polymer substrates. Notably, the negative temperature coefficient of resistance (TCR), which originates from the hopping transport in nanoparticle arrays, is compensated by the positive TCR of the effective surface thermal expansion with anchoring effects. This strategy successfully controls the TCR from negative to positive. A near-zero TCR (NZTCR), less than 1.0 × 10 −6 K −1 , is achieved through precisely controlled expansion. Various characterization methods and finite element and transport simulations are conducted to investigate the correlated electrical, mechanical, and thermal properties of the materials and elucidate the compensated NZTCR mechanism. With this strategy, an all-solution-processed, transparent, highly sensitive, and noninterference strain sensor is fabricated with a gauge factor higher than 5000 at 1% strain, as demonstrated by pulse and motion sensing, as well as the noninterference property under variabletemperature conditions. It is envisaged that the sensor developed herein is applicable to multifunctional wearable sensors or eskins for artificial skin or robots.
In recent times, wearable sensors have attracted significant attention in various research fields and industries. The rapid growth of the wearable sensor related research and industry has led to the development of new devices and advanced applications such as bio-integrated devices, wearable health care systems, soft robotics, and electronic skins, among others. Nanocrystals (NCs) are promising building blocks for the design of novel wearable sensors, due to their solution processability and tunable properties. In this paper, an overview of NC synthesis, NC thin film fabrication, and the functionalization of NCs for wearable applications (strain sensors, pressure sensors, and temperature sensors) are provided. The recent development of NC-based strain, pressure, and temperature sensors is reviewed, and a discussion on their strategies and operating principles is presented. Finally, the current limitations of NC-based wearable sensors are discussed, in addition to methods to overcome these limitations.
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