Simple and fast wettability control of aminosilanized surfaces with carboxylic acids

• Reversible wetting of glass achieved using acid–amine surface ion pairs • Contact angle switches rapidly with simple acid or base treatment • Long-chain acids enable PFAS-free hydrophobic surfaces • Surface remains stable over 50+ wettability-switch cycles • No complex equipment or long processing times This study investigates the rapid and reversible transition between hydrophilic and hydrophobic states on aminosilanized glass substrates using ion pair formation between surface-bound amines and organic/inorganic acids. Glass surfaces were prepared via piranha solution treatment, followed by drying and chemical vapor deposition of 3-aminopropyltrimethoxysilane. Water contact angle measurements revealed a sharp transition in surface wettability upon treatment with mineral acids while treatment with carboxylic acids shows a strong dependence on carbon chain length. This approach utilizes non-fluorinated long-chain carboxylic acids as environmentally friendly alternatives to PFAS, aligning with current global efforts for sustainable engineering. The system's ability to cycle between hydrophilic and hydrophobic states within min per cycle demonstrates the efficiency of this ion pair-driven approach compared to conventional methods. Work offers insights into optimizing surface modifications for applications such as self-cleaning, anti-icing, microfluidics and dynamic wettability control without the need for prolonged processing times and complicated and expensive equipment.