A digital microfluidic chip with programmable open system actuation and enhanced optical annealing with near-infrared light

This work investigates a digital microfluidic chip and presents an advancement to microfluidic optical annealing methods through the application of whispering gallery mode (WGM) with near infrared excitation. Establishing a microfluidic chip with point-of-care capabilities, including actuation and annealing, has proven to be important. Unfortunately, poor heat absorption due to the long optical penetration depth of near infrared light creates scaling limitations for applications in optical-based microfluidics. Through the application of WGM, the interaction length between the droplet and light is increased beyond the droplet diameter to improve heating and optical absorption. This is supported by finite-difference time-domain electromagnetic simulations and experimental results showing a greatly improved temperature change. Such a system is implemented in an open system digital microfluidic chip, to facilitate annealing via side illumination of droplets. The open system digital microfluidic chip is programmable for droplet actuation. The fundamental experiment of preprogrammed actuation of microdroplets is demonstrated in a 36 electrode grid. The results of annealing and actuation show potential for implementation in point-of-care microfluidic devices.

Automated summary

This study proposes an advancement to microfluidic optical annealing methods through the application of whispering gallery mode (WGM) with near infrared excitation in a digital microfluidic chip. The use of WGM increases the interaction length between the droplet and light to improve heating and optical absorption, addressing the scaling limitations in optical-based microfluidics. The implementation of this system in an open system digital microfluidic chip shows potential for point-of-care microfluidic devices.