High density 3D printed microfluidic valves, pumps, and multiplexers

In this paper we demonstrate that 3D printing with a digital light processor stereolithographic (DLP-SLA) 3D printer can be used to create high density microfluidic devices with active components such as valves and pumps. Leveraging our previous work on optical formulation of inexpensive resins ( RSC Adv. , 2015, 5 , 106621), we demonstrate valves with only 10% of the volume of our original 3D printed valves ( Biomicrofluidics , 2015, 9 , 016501), which were already the smallest that have been reported. Moreover, we show that incorporation of a thermal initiator in the resin formulation along with a post-print bake can dramatically improve the durability of 3D printed valves up to 1 million actuations. Using two valves and a valve-like displacement chamber (DC), we also create compact 3D printed pumps. With 5-phase actuation and a 15 ms phase interval, we obtain pump flow rates as high as 40 μL min −1 . We also characterize maximum pump back pressure ( i.e. , maximum pressure the pump can work against), maximum flow rate (flow rate when there is zero back pressure), and flow rate as a function of the height of the pump outlet. We further demonstrate combining 5 valves and one DC to create a 3-to-2 multiplexer with integrated pump. In addition to serial multiplexing, we also show that the device can operate as a mixer. Importantly, we illustrate the rapid fabrication and test cycles that 3D printing makes possible by implementing a new multiplexer design to improve mixing, and fabricate and test it within one day. We demonstrate that a custom resin with the right optical properties enables a digital light processor stereolithographic (DLP-SLA) 3D printer to fabricate microfluidic devices with densely integrated active elements in a 3D layout.