Intermediate layer-based bonding techniques for polydimethylsiloxane/digital light processing 3D-printed microfluidic devices

There is profound potential in developing novel microfluidic devices by integrating 3D-printed structures with polydimethylsiloxane (PDMS) to reap the advantages. One important aspect of the successful development of such microfluidic devices is to achieve a uniform and strong bond between PDMS and the 3D-printed structure. In this paper, we present the measurement results of the bonding strength between PDMS and digital light processing 3D-printed structures using intermediate layer-based bonding techniques. Five different intermediate layers were investigated: double-sided tape, a PDMS/tape composite, UV glue, (3-Aminopropyl) triethoxysilane (APTES), and sputter-coated SiO2. A simple burst test structure was designed and fabricated. Out of five available resins from the manufacturer, we chose the yellow resin to compare the bonding strengths with those intermediate layers. The burst test system consisted of a computer-controlled solenoid valve, pressure regulators, and a microscope for inspection. The sputter-coated SiO2 intermediate layer with a thickness of 77 nm demonstrated the highest bonding strength compared to other intermediate layers. The burst pressure with this SiO2 intermediate layer was greater than 436.65 kPa. Furthermore, we measured the burst pressure using the same SiO2 intermediate layer process for two other resins (emerald and black). The burst pressures for these were less than that of the yellow resin. The results indicate that the intermediate layer thickness and oxygen treatment processes have to be optimized for each resin.