Enhanced performance of METES-modified halloysite nanotube-coated glass surfaces via sol-gel deposition in supercritical CO2 environments

Thin film coatings enhance surface functionality in diverse applications such as semiconductors, biosensors, optoelectronics, and microfluidics. The sol-gel method is particularly attractive for its low-temperature processability and ability to yield functional hybrid films. However, conventional techniques struggle to achieve uniform and durable coatings, especially on complex geometries like microelectromechanical systems (MEMS), microreactors, and lab-on-chip (LOC) devices. To overcome these challenges, this study presents an innovative drainage-based sol-gel coating method developed under supercritical CO2 (scCO2) conditions. In literature, this technique was applied for the first time to coat the surface of glass with the coating formulation including halloysite nanotube (HNT) and methyltriethoxysilane (METES). It enabled the successful deposition of HNT-METES hybrid structures onto glass surfaces, yielding coatings with low surface roughness (RMS approximate to 47 nm), high optical transmittance, and tunable surface hydrophobicity. This technique, applied fort he first time, enabled the successful deposition of HNT-METES hybrid structures onto glass surfaces, yielding coatings with low surface roughness (RMS approximate to 47 nm), high optical transmittance, and tunable surface hydrophobicity. Thanks to the low surface tension, high diffusivity, and environmentally friendly nature of scCO2, this approach emerges as a promising alternative for next-generation conformal coating applications that demand precise control at the micro-and nanoscale.