Fabrication of Structures with Partially Different Wettability by Incorporating Moth-eye Structures and Their Applications

Minuscule water droplets have been extensively used for drug screening. Smaller droplet volumes accelerate the development process and reduce costs. These minuscule droplets, with volumes ranging from a few femtoliters to several hundred microliters, are also employed in applications such as inkjet printing and femtoreactors. Owing to the continuous increase in the demand for precisely controlled small-volume droplets, we developed a film capable of arranging such droplets in a regular pattern, inspired by the surface structures of tenebrionid beetles and moth eyes. Tenebrionid beetles are known for their ability to collect water from fog through regions of contrasting wettabilities, and the nanostructure of the moth eyes enhances surface wettability. In our method, hydrophilic regions are first patterned onto a moth-eye-structured surface via photolithography. Then, the hydrophilic regions are separated using a hydrophobic resin via UV nanoimprint lithography (UV-NIL). This process yielded a film featuring a hydrophobic moth-eye surface with partially hydrophilic moth-eye regions. The resulting wettability contrast enables the alignment of miniscule water droplets on the film.