Challenges and Complexities in Fabrication of Nano-dispensing Electrowetting-on-Dielectric actuated Glass Micropipettes

Since the first study of electrocapillarity by Gabriel Lippmann in 1875, the modern electrowetting-on-dielectric (EWOD) has been intensively studied and developed. The modification of wetting properties of surface allows users to exploit this phenomenon for various applications such as nano liter sized droplet generation/splitting/merging, controlled chemical reactions, and DNA/protein analysis platforms. Electrowetting-on-dielectric (EWOD) is one such phenomenon that takes advantage of hydrophobic/hydrophilic surfaces to navigate a droplet onto the desired position. EWOD based micropipette provides customization (vis-a-vis droplet dispensing) to a great extent as well as the enhanced analysis speed which is the sine qua non to meet the current demand for high throughput analysis. Despite the advantages of the technology, it is observed during reviewing that the assimilation of these digital microfluidic devices have not been successfully achieved in academia or industry and this is widely visible by looking at the fraction of EWOD devices used in industrial applications in general. This is due to various issues and complicated processes involved in the development of EWOD based micropipettes. The present study focuses majorly on the challenges involved in the fabrication of an EWOD actuated micropipette. Possible ways to circumvent issues like coating of a hydrophobic layer inside the micropipette and metal coating on curved surface are also elaborated. The complexities arising during the development of these micropipettes act as a major hindrance in mainstreaming this technology from academia to industry.