A review of electrochemical sensing in droplet systems: Droplet and digital microfluidics.

Background: Microfluidic technologies based on droplets provide discrete volumes within which chemical and/or biological processes can take place. Two major platforms in this space include droplet microfluidics (emulsions within channels) and digital microfluidics (discrete droplet manipulation by electric fields). The integration of electrochemical sensing with both microfluidic platforms offers advantages in miniaturization and portability, as sensors can be integrated directly within the microfluidic devices and instrumentation is relatively compact.

Results: This review provides background on droplet and digital microfluidic technologies and electrochemical sensing before moving to methods and applications. A discussion of the various strategies to integrate sensing electrodes with both droplet and digital microfluidics and the merits of each method are included. A review of the many different applications of these integrated systems is provided.

Significance And Novelty: To date, there are no reviews that solely focus on the integration of electrochemical sensing with droplet and digital microfluidics. There are many advantages to combining electrochemical sensing with these platforms, especially for applications where portability or small form factors are paramount. While early reports on integrating electrochemical sensing with droplet and digital microfluidics are more than a decade old, the field is still relatively nascent, offering opportunity for many applications.