Combination of channel- and droplet-based microfluidics for complex PoC devices

This paper presents a microfluidic device addressing the field of ambulant diagnostics in rural areas. Often, the diagnostic approach of micro-channel based point of care devices (PoCD) will target a certain marker — if e.g. on site another marker is to be checked against, the visiting doctor needs to use another test device. With the number of markers growing on a steady basis this will incur the need to transport a large number of individual test strips/cartridges, making the PoCD concept useless for this specific setting. The basis of the proposed novel device is a hybrid system combining the advantages of conventional channel-based fluidics with those of digitally controlled droplet-based fluidics. This hybrid concept uses a micro-channel based delivery partition for stored reagents with a disposable reaction partition based on electrowetting-on-dielectric to run the actual test protocol. It promises to realize a low cost approach for a Point-of-Care system with easy deployability. Conceptual implementation was done by roll embossing for the microchannels and direct structuring of the electrode elements for the EWOD substrate. The latter was laminated with a PTFE-film or coated with a nanoparticle loaded lacquer for hydrophobization. A variety of reagents were handled using a two-phase containment on the EWOD substrate, overcoming the issues associated with low surface energy fluids.