Fabrication and performance study of BST/Teflon nanocomposite thin film for low voltage electrowetting devices

A simple and cost effective method for fabrication of electrowetting device which operates in low voltage is presented. A nanocomposite thin film of Barium Strontium Titanate (BST) and Teflon®AF is synthesized to achieve the low voltage operation. First, crystallized BST nanopowder is prepared from sol-gel method, and thereafter, a nanocomposite is prepared by using Teflon®AF as matrix and BST as the filler material. The solution is spin coated for depositing thin film on coplanar metal electrodes, used for droplet transport. A thorough charaterization of the film is carried out using XRD, TEM, EDX, FESEM and AFM which shows smooth, uniform and crack free hydrophobic film (contact angle ≈ 115°) with high dielectric constant (ϵr≈ 9.1). Using the nanocomposite film, only single layer of coating is required on the actuating electrodes to make the EWOD device (at 80 °C). It is able to actuate liquid droplet of 5 μl at 30 V, and showed repeatable and consistent result for more than two hundred actuations.