(1020-A) A Versatile Control System to Accelerate Digital Microfluidics Chip Prototyping for Diverse Lab-on-a-Chip Applications

Abstract: Digital microfluidics (DMF) emerged as a revolutionary advancement in the microfluidics field, enabling independent control over individual droplets. Resembling the revolutionary impact of digital integrated circuit (IC) on electronics, DMF was anticipated to enable numerous lab-on-a-chip (LoC) devices for a variety of applications. Enabling control over various types of liquid by electrical signals alone, electrowetting-on-dielectric (EWOD) has become the most popular technology for DMF. However, despite a wealth of research and publications, EWOD DMF has not seen the anticipated wide adoption, and chip prototyping has been slow. It often takes 3-5 years for a startup to develop DMF chip prototypes. We identified that the absence of a versatile control system that operates diverse DMF chips is one of the culprits. Operating a DMF chip tends to require a relatively high voltage (i.e., more than 50 V) to power many electrodes independently. During the prototyping stage, one often needs to test many different chip parameters (e.g., substrate type, thickness, size, shapes, and electrode layout). However, existing general-purpose systems such as OpenDrop and Dropbot only work with their own DMF chips, lacking the versatility to support iterative chip prototyping for widely different demands. Furthermore, their limited control channels (~100) preclude complex droplet protocols.
To address this issue, we have developed a versatile control system capable of operating diverse DMF chips. Most existing systems use a fine-pitch edge connector or chip slot for chip installment and electrical connection, which tends to restrict the chip thickness, size, and shape. Our system employs a unique hinge structure for chassis design with pogo pin arrays as chip-system interface, which enables unprecedented compatibility of various substrate types (e.g., glass, silicon, PCB, paper), shapes (e.g., even irregular), sizes (1–20 cm range), and thicknesses (≤ 2.0 mm). An aperture-based alignment stencil enables quick and easy installation of various DMF chips. The control circuit, utilizing HV3418 serial-to-parallel high-voltage converters, offers 80–360 Vpk-pk square waves up to 10 kHz or 40–180 V in DC via 256 independently controlled channels, doubling the maximum channel count (i.e., 128) in the existing general-purpose systems.
Accessible online, the GUI enables users to create arbitrary electrode layouts on a virtual canvas so that they can operate chips with any electrode layouts – a level of flexibility not offered by any existing system. Users can program actuation sequences by selecting electrodes for activation or deactivation for each step which are, then, transferred to the control circuit via a USB-C cable.
With unprecedented versatility, this control system has been developed to serve a diverse user base with widely different demands and to significantly accelerate iterative DMF chip prototyping.