Electrohydrodynamic-Printed AgNPs/PR Thin-Film Temperature Sensors With Micro Dimensions and Higher Temperature Measurement Capabilities

Abstract

Conflicts between the existing temperature-resistant ink and printing window currently prevent electrohydrodynamic (EHD) printed thin film temperature sensors from achieving both fine line width and a higher temperature measurement limit simultaneously. In this study, we propose a method to adjust the existing AgNPs ink to prepare thin film temperature sensors with micro dimensions and enhanced temperature measurement capabilities. The method involves leveraging the solubility of Polyester resins (PR) in alcohol-ether solvent to incorporate PR into a nano-silver solution in the same solvent system. This allows for easy printing while utilizing the temperature-resistant properties of PR to anchor conductive networks. The AgNPs/PR film sensitive layer has an area less than 800 μm×800 μm, with an average line width of under 50 μm and a film thickness of approximately 700 nm. The unencapsulated AgNPs/PR film sensitive layer demonstrates long-term conductivity at 400°C, while maintaining its structural integrity. Furthermore, performance test results indicate that AgNPs/PR film temperature sensors without encapsulation have a temperature measurement upper limit of 400°C, but they are susceptible to oxidation drift at this temperature. To eliminate oxidation, SiO ₂ encapsulation is prepared. Experimental results demonstrate that AgNPs/PR film temperature sensors with SiO ₂ encapsulation achieve a temperature measurement upper limit of 407°C. At this temperature, the resistance drift rate is -0.0496% per hour. After three rounds of testing, the change rate of the sensor resistance at 100°C was -0.281%. The successful fabrication of the sensor using EHD printing suggests the potential of this sensor for applications in high-density temperature sensing requirements.