The preparation of urchin-like La2O3 film and the superlow voltage electrowetting-on-dielectric response

An effective one-step solvothermal process is developed to fabricate La2O3 film on Ti substrate at 130 °C. The surface morphology and roughness are controlled from urchin-like nanosphere to dense film by the reaction duration. The as-prepared La2O3 film has low surface free energy and a large initial contact angle (CA), about 120°. Due to the uniform distribution of the urchin-like nanosphere on the surface, the water droplet starts to be adsorbed into the interspace of film surface, and the wetting state gradually transforms from Cassie to Wenzel state as soon as the low voltage less than 1 V is applied. Obviously, the DC EWOD response with superlow voltage can be realized, and large CA modulation about 58° is also acquired.