Preparation of paper micro-fluidic devices used in bio-assay based on drop-on-demand wax droplet generation

Paper microfluidic devices are a promising technology in developing analytical devices for point-of-care diagnosis in the developing world. This article describes a simple method for paper microfluidic devices based on a PZT drop-on-demand droplet generator. Wax was jetted in the form of droplet, linked with each other and formed into wax pattern on filter paper with a PZT actuator and a glass nozzle. The heated wax pattern became a hydrophobic barrier for reagent used in bio-assay. The glass nozzle fabricated by a home-made micronozzle puller without complicated fabrication technology was low cost, simple and easily made. Coefficient of variation of the jetted wax droplet diameter was 4.0% which showed good reproducibility. The width of wax line was experimentally studied by changing the driving voltage, nozzle diameters and degree of overlapping. The wax line with width of 700-1700 mm was prepared for paper based microfluidic devices. Multi-assay of glucose, protein and pH and 3 x 3 arrays of glucose, protein and pH assay were realized with the prepared paper microfluidic devices. The wax droplet generating system supplied a low-cost, simple, easy-to-use and fast fabrication method for paper microfluidic devices.