Ultrathin Fiber‐Mesh Polymer Thermistors

Abstract

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 −2 , 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.

Technology Roadmap for Flexible Sensors

“…For example, accidental ingestion is a big risk for small, wireless monitoring devices used on infants . Catastrophic battery failure or circuit overloading could lead to injurious thermal loads on the skin . Repeated application/removal of skin-interfaced devices can lead to skin injuries in vulnerable populations .…”

“…919 Catastrophic battery failure or circuit overloading could lead to injurious thermal loads on the skin. 920 Repeated application/removal of skininterfaced devices can lead to skin injuries in vulnerable populations. 568 Furthermore, there should also be data privacy regulations to prevent data breach and misuse.…”

Toward a new generation of permeable skin electronics

“…Immense efforts have been dedicated to developing breathable skin-mountable temperature sensors. 190–192…”

“…Immense efforts have been dedicated to developing breathable skin-mountable temperature sensors. [190][191][192] Typical breathable skin-mountable temperature sensors are thermo-sensitive conductive composites and conductors. Nanofibres/fabrics have been used as porous substrates for the fabrication of breathable skin-mountable temperature sensors.…”

Polymer Boosts High Performance Perovskite Solar Cells: A Review

“…[38][39][40] According to the shape of the chain, they can be divided into linear polymers, branch polymers, network polymers, star polymers, and tree polymers (as shown in Figure 2a). [41][42][43][44][45] According to the conductivity they can be divided into insulating polymers, semiconductor polymers, and conductive polymers. [46][47][48] Insulating polymers can be divided into crystalline polymers and amorphous solid polymers.…”