Development and surface characterization of an electrowetting valve for capillary-driven microfluidics

This article presents the development of a microfluidic valve to be used in capillary flow microfluidic devices. The valve used the principle of electrowetting and was able to be actuated at low voltage. The valve consisted of two inkjet-printed silver electrodes which were encountered in series within a microfluidic channel. The second electrode was modified with a hydrophobic monolayer resulting in a cessation of capillary flow. A potential of 4 V resulted in a 70° reduction in apparent water contact angle within 10 s which allowed capillary flow to continue. The electrode surface chemistry was investigated prior to monolayer deposition, after monolayer deposition and following the application of the 4 V potential. The flexible microfluidic channel consisted of two layers of polyethylene terephthalate bonded by a pressure sensitive adhesive layer which was patterned with a laser ablated microfluidic channel. The final device represented a microfluidic valve for capillary flow microfluidics realized on a flexible substrate. The valve was designed to allow timed fluid delivery for low-cost lab-on-a-chip applications.