Fabrication of flexible inkjet-printed copper electrowetting valve for capillary-driven microfluidic devices

Research in microfluidic valves has led to advances in the control of liquids in capillary-driven microfluidic devices. Herein, we fabricated low-voltage-activated microfluidic valve on a flexible substrate based on the principle of electrowetting on dielectric. Using inkjet printing technique, copper-based electrodes were deposited on poly(ethylene terephthalate) substrate, followed by coating a thin layer of poly(perfluorooctyl methacrylate) (pPFOM) on top of electrodes via initiated chemical vapor deposition (i-CVD). pPFOM coating thicknesses were well controlled from 20 nm to 200 nm. A droplet was placed on top of the electrode and a voltage was applied in between of the droplet and the electrode to polarize the pPFOM thin film, thus cause a contact angle decrease of the droplet. The results show that the contact angle decreasing process has a faster response under thinner pPFOM coating thickness and higher applied voltage. Finally, the valve can be actuated under 2V, which is among the best results in the literature. Furthermore, a microfluidic device with the designed pattern is demonstrated for potential bioelectronic applications.