Nitrocellulose as a Protective Dielectric Layer for Optimized Cu/Ni Cryogenic Sensors

Although the potential of Cu/Ni materials and nitrocellulose coatings for cryogenic temperature sensors is acknowledged, a significant knowledge gap persists regarding the quantitative impact of nitrocellulose coating thickness variations on the electrical and thermal performance of Cu/Ni-based sensors at cryogenic temperatures. This work investigates the protective function of nitrocellulose (NC) layers in Cu/Ni-based cryogenic temperature sensors, emphasizing the impact of coating thickness (0–0.74 mm) on thermal and electrical performance. The sensors were fabricated by electroplating nickel onto copper substrates, followed by NC spray coating. Key parameters, including voltage range, response time, activation energy, hysteresis loss, and absolute sensitivity, were evaluated over the temperature range of 0 °C to −160 °C. The results show that NC layers provide both mechanical and chemical protection while modulating heat transfer and charge transport. An optimal thickness (0.30–0.43 mm) balances protection, high sensitivity, and rapid thermal response, with a peak voltage range of 0.17 V and increased activation energy. Thicker layers (>0.43 mm) improve cryogenic sensitivity (>6 Ω/°C at −160 °C) but reduce performance at higher temperatures. A multivariate logarithmic regression model accurately predicts sensitivity from physical parameters, enabling design optimization. These findings highlight NC thickness control as a practical approach to enhancing durability and sensitivity in cryogenic sensor applications.