Cu Microbelt Network Embedded in Colorless Polyimide Substrate: Flexible Heater Platform with High Optical Transparency and Superior Mechanical Stability

Metal nanowires have been considered as essential components for flexible transparent conducting electrodes (TCEs) with high transparency and low sheet resistance. However, large surface roughness and high interwire junction resistance limit the practical use of metal wires as TCEs. Here, we report Cu microbelt network (Cu MBN) with coalescence junction and low surface roughness for next-generation flexible TCEs. In particular, the unique embedded structure of Cu MBN in colorless polyimide (cPI) film was achieved to reduce the surface roughness as well as enhance mechanical stability. The TCEs using junction-free Cu MBN embedded in cPI exhibited excellent mechanical stability up to 100 000 bending cycles, high transparency of 95.18%, and a low sheet resistance of 6.25 Ω sq^–1. Highly robust Cu MBN-embedded cPI-based TCE showed outstanding flexible heater performance, i.e., high saturation temperature (120 °C) at very low voltage (2.3 V), owing to the high thermal stability of cPI and excellent thermal conductivity of the Cu MBN

Selective Diagnosis of Diabetes Using Pt-Functionalized WO₃ Hemitube Networks As a Sensing Layer of Acetone in Exhaled Breath

Thin-walled WO₃ hemitubes and catalytic Pt-functionalized WO₃ hemitubes were synthesized via a polymeric fiber-templating route and used as exhaled breath sensing layers for potential diagnosis of halitosis and diabetes through the detection of H₂S and CH₃COCH₃, respectively. Pt-functionalized WO₃ hemitubes with wall thickness of 60 nm exhibited superior acetone sensitivity (<i>R</i>_air/<i>R</i>_gas = 4.11 at 2 ppm) with negligible H₂S response, and pristine WO₃ hemitubes showed a 4.90-fold sensitivity toward H₂S with minimal acetone-sensing characteristics. The detection limit (<i>R</i>_air/<i>R</i>_gas) of the fabricated sensors with Pt-functionalized WO₃ hemitubes was 1.31 for acetone of 120 ppb, and pristine WO₃ hemitubes showed a gas response of 1.23 at 120 ppb of H₂S. Long-term stability tests revealed that the remarkable selectivity has been maintained after aging for 7 months in air. The superior cross-sensitivity and response to H₂S and acetone gas offer a potential platform for application in diabetes and halitosis diagnosis