Highly Linear and Stable Flexible Temperature Sensors Based on Laser‐Induced Carbonization of Polyimide Substrates for Personal Mobile Monitoring

Abstract

Wearable on‐skin electronic devices that can monitor temperature in real time are of significant interest for personalized mobile health monitoring. Here, a flexible temperature sensor directly patterned by laser‐induced carbonization on Kapton polyimide films integrated with flexible printed circuit boards is reported. The proposed sensor design possessing high resistance values exhibits high‐linear and stable response to temperatures when integrated with flexible printed circuit boards (FPCBs) to enable continuous monitoring. The anisotropic conductive film bonding technique is used to obtain the stable real‐time monitoring data under various complex environments. The sensor integration with a wearable patch based FPCB establishes conformal contacts with human skin and allows wireless sensing capabilities smoothly in real time. This kind of approach can enable multifunctional sensors to be directly laser patterned on FPCBs without any additional interfacing.

Laser-Induced Graphene Based Flexible Electronic Devices

“…On this basis, as shown in Figure 2 d they have improved the micro-supercapacitors (MSC) with interdigitated electrodes using a hybrid composite of LIG [ 49 ]. A highly stable and linear LIG-based flexible temperature sensor capable of delivering the real-time monitor of human skin temperature was shown in Figure 2 e [ 81 ]. Benefiting from the fast electron transfer between the Cu nanoparticles and the porous graphene, a novel LIG-based glucose biosensor provides a new platform for the fabrication of the flexible non-enzymatic glucose sensors (as shown in Figure 2 f) [ 82 ].…”

“…Furthermore, the microstructure and the electrical conductivity of the prepared porous graphene films can also be preciously designed by controlling the laser-scanning parameters. At present, various types of LIG-based electronic devices have been successfully proposed to monitor mechanical [ 16 , 18 , 37 , 58 , 78 , 79 , 83 , 84 , 87 , 88 , 89 , 90 , 94 , 95 , 96 ], environmental [ 80 , 81 , 84 , 97 , 98 , 99 , 100 , 101 , 102 ] and biochemical signals [ 19 , 67 , 82 , 85 , 90 , 103 , 104 , 105 , 106 , 107 ].…”

“…Electrical conductivity changes caused by the electron-phonon scattering and thermal velocity of electrons in response to temperature variations can be adopted for developing LIG-based temperature sensors [ 81 ]. As shown in Figure 4 a, an integrated, flexible wireless temperature sensing system is proposed with a high linearity LIG-based temperature sensor.…”

Research of a Novel Ag Temperature Sensor Based on Fabric Substrate Fabricated by Magnetron Sputtering

“…In recent years, there have been a few reports on the fabrication of flexible temperature sensors based on textile substrates by magnetron sputtering. Most researchers used polymer films as the substrate, such as polyimide [21], polyethylene terephthalate [22], and polyethylene naphthalate [23] etc. Joon et al [24] applied the magnetron sputtering method to produce a flexible temperature sensor with Pt as the temperature sensing layer and polyimide as the substrate.…”

Flexible Hybrid Sensor Systems with Feedback Functions

“…[ 77 ] Another advantage of the LIG technique is that it can be almost transferred from the PI to soft materials, such as PDMS or Ecoflex that features greater flexibility and stretchability. [ 78–81 ] Until now, LIG has been applied in versatile flexible sensors to measure strain, [ 82,83 ] pressure, [ 84 ] humidity, [ 85 ] temperature, [ 86 ] sweat biomarkers, [ 87 ] and urine. [ 88 ] Representative research has focused on employing LIG for voice recognition, [ 89 ] human sweat analysis, [ 77,90 ] and gas sensing.…”