Inscribing Wettability Gradients Onto Superhydrophobic Carbon Nanotube Surfaces

Tunable wettability of carbon nanotube (CNT) arrays on the nanoscale is the key to move water droplets on such surfaces on a macroscopic scale. A novel type of superhydrophobic CNT surface for guided droplet transport, a key issue for future microfluidic systems, is demonstrated. It is accomplished by tailoring the required surface roughness using a process employing CNT regrowth, chemical passivation, and corona discharge.