Significant advancements in microfluidics have enabled miniaturization of microfluidic and nanofluidic biosensors for applications in DNA analysis, genomics study, and more. This project seeks to reduce fabrication complexity of microfluidic devices by combining reactive ink chemistries with drop-on-demand printing. In this work, we demonstrate Drop on Demand (DOD) fabrication of microfluidic mixer devices with integrated sensors using Polydimethyl Siloxane (PDMS) reactive inks, silver reactive inks, and fugitive inks. Fugitive phase change inks were used to define the microfluidic channels. Ag reactive inks were used to define sensing electrodes at the inlet and outlets of the device to quantify the degree of mixing of two electrolytic solutions. PDMS reactive inks were used to both confine the fugitive inks and print caps between layers for multi-layer devices.
A fully functional microfluidic mixer device was fabricated using DOD technique, calibrated and tested using NaCl solutions with concentrations ranging from 0.01 M to 1.0 M to show that electrolyte concentration and mixing completeness can be accurately measured. Overall, this work demonstrates a simple and inexpensive process to fabricate a passive microfluidic mixer device with integrated electronics using affordable phase changing materials and reactive inks that can be mixed in the lab. Unlike paper-based microfluidic devices often fabricated using printers, our process demonstrates that flushable, “hard” microfluidic devices can be fabricated using drop-on-demand printing. This process should facilitate low-cost microfluidic prototyping and fabrication.