Resistance Temperature Detector for INHA RoSAT Rollable Solar Panel Using Electrohydrodynamic Inkjet Printing

Rollable solar panels can increase the available photovoltaic area of CubeSats, but their flexible structure requires a flexible sensor for monitoring surface temperature during operation. In this study, an Ag-based flexible resistance temperature detector (RTD) was fabricated by electrohydrodynamic (EHD) inkjet printing for the rollable solar panel of the 3U CubeSat INHA RoSAT. The sensor was formed on a polyimide (PI) substrate and protected with a PI coating. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to assess the imidization, residual solvent removal, and thermal stability of the coating. The sensor was then evaluated through an eight-cycle thermal cycling test from -25 to 125 °C, tailored with reference to MIL-STD-1540. The coating, heat-treated up to 250 °C, showed clear imide formation and no notable mass loss below 500 °C. During thermal cycling, the sensor exhibited stable resistance behavior with a drift rate of 0.032%/h. The derived calibration equation yielded a mean absolute error of 1.44 °C, while the temperature coefficient of resistance and hysteresis were 0.269%/°C and 1.2% of full-scale output (FSO), respectively. These results support the feasibility of the sensor for integration with rollable solar panels and future on-orbit temperature estimation.