Hydrophobic Sol-Gel coatings for passive ice prevention of unmanned aerial vehicles

Unmanned aerial vehicles (UAVs), or drones, have emerged as crucial instruments for atmospheric research, offering data collection capabilities from an aerial vantage point, as well as potential search and rescue tools at high altitudes[1,2]. However, the current limitations of UAV technology confine their operation to warm and dry weather conditions[2,3]. In subzero, high-humidity environments, the propeller blades of UAVs are susceptible to accumulating significant amounts of ice, inducing aerodynamic stall and significantly reducing flight performance[4]. Existing methods designed for preventing ice accretion on full-sized flight vehicles are ill-suited for the constraints of small, power-limited drones[4–6]. Active systems, which rely on external energy input such as heating or vibration, are typically too heavy and power-intensive for UAVs, making passive strategies essential[5]. Therefore, alternative approaches to ice prevention must be explored to ensure the effective operation of UAVs in diverse and challenging atmospheric conditions. This thesis investigates a sol-gel-based approach to mitigating ice accumulation by developing hydrophobic surface coatings on silica substrates. A variety of coating formulations, primarily within the MTO and MTP series, were synthesized, applied via dip coating, heat-treated, and characterized through contact angle analysis, FT-IR, and Ellipsometry. Coatings demonstrating favorable hydrophobicity (advancing contact angle > 90°) and droplet mobility (contact angle hysteresis ≤ 15°) were further evaluated in icing/deicing experiments. Among the tested formulations, several MTO samples showed the most promising balance between water repellency and reduced droplet pinning. While no coating achieved ideal performance across all criteria, the MTO series emerged as the most robust platform, offering tunable sol-gel chemistry and process parameters for optimizing surface functionality under icing conditions, though mechanical durability under operational stress remains a critical limitation for future optimization. In particular, the MTO2_B Series exhibited good homogeneity under 150 °C thermal treatment and approximately 20% relative humidity, achieving an advancing contact angle of 90.47°, contact angle hysteresis of 11.18°, and consistent film formation, making it a leading candidate for further refinement.