Electrohydrodynamic Printed Ultramicro AgNPs Thin-Film Temperature Sensor

To achieve high-density and arrayed temperature sensing, thin-film temperature sensors require a multilayer structure and miniaturized preparation technology. Currently, screen printing, direct writing by squeeze, and MEMS are the main methods for preparing thin-film sensors; however, the film linewidth produced by screen printing or direct writing by squeeze is impossible to achieve width within $10 \mu \text{m}$ , while MEMS is costly, and limited in terms of target materials. Electrohydrodynamic (EHD) printing is a promising alternative due to its ability to print multiple materials and multilayer structures with patterned films less than $10 \mu \text{m}$ width. In this study, we propose a method using only EHD printing to prepare ultramicro thin-film temperature sensors, including an AgNPs sensitive layer and polydimethylsiloxane (PDMS) encapsulation layer. The area of the AgNPs film sensitive layer is less than $120\times 120\,\,\mu \text{m}$ , with an average linewidth of less than $10 \mu \text{m}$ , and a film thickness of less than 200 nm. The printing range of the PDMS encapsulation layer is $300\times 300\,\,\mu \text{m}$ , with a minimum film thickness of 567 nm. The performance test results show that the ultramicro AgNPs thin-film temperature sensor after EHD printing of PDMS encapsulation has a higher temperature measurement upper limit. The hysteresis error was ±0.1309%, and the repeatability error was ±0.3311%, both much lower than previously reported. The successful fabrication of ultramicro thin-film temperature sensors using EHD printing suggests the potential of this method to supercede MEMS for achieving high-density and arrayed temperature sensing in limited space.