Electrochemical Detection of Droplets in an All-PDMS Microfluidic Device

Candidate: Kathy Ly
Supervisor: Dr. Darius Rackus

ABSTRACT

Microfluidics has been revolutionary, offering many advantages such as short analysis times, miniaturization, reduced costs, and lower sample consumption. Microfluidic devices can be used to generate droplets, which are treated as small reactions vessels and microreactors, ideal for single-cell encapsulation and high-throughput screening. However, determination of droplet composition is almost entirely done by optical methods, which often make use of bulky and expensive instrumentation. Electrochemistry, on the other hand, is an analytical method that relies on small and inexpensive instrumentation. Moreover, electrochemistry can be coupled with microfluidic devices by integrating electrodes within the microfluidic device. Many microfluidic devices are fabricated from polydimethylsiloxane (PDMS) using microfabrication and replica molding techniques. While not conductive itself, PDMS can be doped with conductive fillers and then same fabrication techniques can be used to generate microscale electrodes. This thesis reports on the electrochemical properties of a carbon black-doped conductive PDMS (C-PDMS). Electrodes were characterized by cyclic voltammetry (CV) and scanning electron microscopy. C-PDMS electrodes were integrated with a droplet microfluidic device and used to measure Ru(NH₃)₆³⁺ and alkaline phosphatase activity in droplets. Together, this represents the first integration of C-PDMS electrodes with a flow focusing droplet generator for the electrochemical quantitation of droplet contents.