'Cassie-Baxter to' Wenzel like transition on patterned electrodes

Hydrogen production through electrolysis is receiving widespread attention in the wake of the much-desired energy transition in our society. However, this hitherto limited to lab-scale process suffers from low productivity due to the produced hydrogen gas bubbles not 'taking off' the electrode efficiently, thereby blocking the production of the next bubble. Researchers have attempted to create patterned substrates with hydrophobic patches which would force the bubbles to limited parts of the electrode, thereby helping them take off. However, sideways movement of bubbles on these patches and subsequent coalescence between the bubbles, keep posing problems in such situations. In this work, patterned substrates have been created by photolithograhy with various hydrophobic, dielectric layers. The jump of a water droplet from the top of of a patch (a pillar) to the area next to the pillar (a valley), a phenomenon very similar to the classic Cassie-Baxter to Wenzel type transition. We observe separated regimes in the nature of the phenomenon, based on the type of dielectric layers. More importantly, the influence of an external electric potential has been investigated on the nature of the jump, since the electrodes during electrolysis also carry such potential.