Integrated heating & sensing for PCB EWOD chips on a digital microfluidics cloud platform

Digital microfluidics (DMF) based on electrowetting-on-dielectric (EWOD) is a versatile platform that offers automated and precise droplet handling. Despite advances, one of the critical components-an integrated thermal module-remains underdeveloped, limiting the accuracy and reliability of bioassays. This paper presents a new thermal management module compatible with printed circuit board (PCB)-based DMF devices co-fabricated through standard PCB manufacturing. It integrates a microheater and sensor pair interfaced with a closed-loop control system for individual droplet's temperature control. Numerical simulations were performed to understand heat transfer from the embedded microheaters to the droplets for optimized microheater design. Experiments were performed to evaluate key performance metrics of the module, including temperature accuracy, control stability, response time, crosstalk, and heat localization. Finally, a glucose assay was conducted on-chip to demonstrate the module's applicability. The co-fabricatable heating-sensing module design presented in this paper offers seamless integration of thermal management for PCB-based DMF chips at little additional manufacturing cost while supporting the cloud-based platform established to democratize DMF.