Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Department of Electrical and Computer Engineering, Shinshu University, 4-17-1, Wakasato, Nagano City, Nagano, 380-8553, Japan.
Adv Sci (Weinh). 2022 Oct;9(30):e2202312. doi: 10.1002/advs.202202312. Epub 2022 Sep 4.
Flexible sensors enable on-skin and in-body health monitoring, which require flexible thermal protection circuits to prevent overheating and operate the devices safely. Here, ultrathin fiber-mesh polymer positive temperature coefficient (PTC) thermistors via electrospinning are developed. The fiber-type thermistors are composed of acrylate polymer and carbon nanofibers. The fibrous composite materials are coated with a parylene to form a core-sheath structure, which improves the repeatability of temperature characteristics. Approximately 5 µm thick fiber-type thermistors exhibit an increase in the resistance by three orders of magnitude within ≈2 °C and repeatable temperature characteristics for up to 400 cycles. The mesh structure enables the thermistor layer to be ultra-lightweight and transparent; the mesh-type thermistor operates with a fiber density of 16.5 µg cm , whose fiber layer has a transmittance of more than 90% in the 400-800 nm region. By fabricating the mesh thermistor on a 1.4 µm thick substrate, the thermistor operates without degradation when wrapped around a 280 µm radius needle. Furthermore, the gas-permeable property is demonstrated by fabricating the fibrous thermistor on a mesh substrate. The proposed ultrathin mesh polymer PTC thermistors form the basis for on-skin and implantable devices that are equipped with overheat prevention.
柔性传感器可实现皮肤和体内健康监测，但需要灵活的热保护电路来防止过热，以安全地运行这些设备。在此，通过静电纺丝开发了超薄纤维网聚合物正温度系数（PTC）热敏电阻器。纤维型热敏电阻器由丙烯酯聚合物和碳纳米纤维组成。纤维状复合材料涂有聚对二甲苯，形成芯鞘结构，从而提高了温度特性的可重复性。厚度约为 5 µm 的纤维型热敏电阻器在 ≈2°C 内电阻增加了三个数量级，并且在 400 次循环内具有可重复的温度特性。网状结构使热敏电阻层超轻且透明；网型热敏电阻在纤维密度为 16.5 µg cm 的情况下工作，其纤维层在 400-800nm 区域的透光率超过 90%。通过在 1.4 µm 厚的基底上制造网状热敏电阻器，当将其包裹在 280 µm 半径的针上时，热敏电阻器不会因弯曲而降级。此外，通过在网状基底上制造纤维状热敏电阻器，展示了透气性能。所提出的超薄网状聚合物 PTC 热敏电阻器为配备过热预防功能的皮肤和植入式设备奠定了基础。
