Preparation of PDMS microfluidic devices based on drop-on-demand generation of wax molds

Polydimethylsiloxane (PDMS) microfluidic devices have been widely used in micro total analysis systems (mu-TAS) for various types of analytical, diagnostic and therapeutic applications. With the increasing use of these systems in various fields, the development of low-cost and easy to manipulate methods for fabricating PDMS microdevices is emerging as an important challenge in their widespread use. This article describes a simple method for wax molds used in the preparation of PDMS microfluidic devices based on a PZT (lead zirconate titanate) drop-on-demand droplet generator. Wax was jetted in the form of droplets, linked with each other and formed into wax molds on a glass sheet with the PZT actuator and a glass nozzle. The glass nozzle fabricated by a homemade micronozzle puller without complicated fabrication technology was low cost, simple and easily made. The coefficient of variation of the jetted wax droplet diameter was less than 4.0%, which showed good reproductivity. The geometry and surface topography of wax molds were experimentally studied by changing the driving voltage, nozzle diameter, degree of overlapping and wax layers. In addition, wax molds with aspect ratios ranging from 1 to 2.6 were prepared through multilayers of wax droplets. PDMS channels with depths of 200-700 mm and widths of 200 and 250 mu m were prepared by the replication of wax molds. The micromixing of blue and yellow dyes was realized with the prepared PDMS microfluidic devices. The wax-droplet-generating system supplied a low-cost, simple, easy-to-use and fast fabrication method for the PDMS microfluidic devices.