Optimization of device geometry in single-plate digital microfluidics

Abstract

Digital microfluidics is a popular tool for lab-on-a-chip applications and is typically implemented in one of two formats: single-plate ͑"open"͒ devices or two-plate ͑"closed"͒ devices. Single-plate devices have some advantages relative to the more common two-plate format such as faster mixing, the capacity to move larger volumes on a given footprint, and easier access to droplets for handling or optical detection. In contrast with the two-plate format, in which ground potential is generally supplied via a top electrode, in the single-plate format, many different geometries of ground wires/ electrodes have been used. Until the present study, there has been no metric to determine which of these geometries is best suited for droplet actuation. Here, we present a combination of numerical simulations and experimental tests to compare six different single-plate designs. We applied finite element analysis, using the commercially available COMSOL software package to calculate the electrodynamic actuation forces in each of the different designs and used the results to optimize device design. Forces predicted by the electrodynamic model were in agreement with forces predicted using electromechanical models. More importantly, results were verified experimentally using a unique technique that permits indirect estimation of actuation forces on digital microfluidic devices. This work illustrates the promise of using numerical modeling to enhance the design and performance of digital microfluidic devices.

Assiut Microfluidics Laboratory

“…Electrodynamic forces induced on droplets in digital microfluidics are dependent on many factors, such as electrical properties of the liquid being manipulated, electrode shape, actuation frequency, and device geometrical parameters [ 8 ]. By simulating droplet actuation numerically, the effect of liquid properties and actuation frequency on electrodynamic forces generated on droplets and on droplet motion will be understood, which should enable more efficient device designs based on the intended application.…”

Digital Microfluidics: Techniques, Their Applications and Advantages

“…Also in the closed system, the top plate is always grounded while in single plate devices, the ground and electrodes are on the same substrate. This review is confined to close plate systems, however many open plate models have also been demonstrated [10].…”

Partially filled electrodes for digital microfluidic devices

“…These forces are generated by the electric field induced from the energized electrode beneath the droplet. 6 To increase capabilities of digital microfluidic devices, researchers have begun integrating additional elements within electrodes such as impedance spectroscopy, 7 electrophoresis electrodes for particle separation, 8 absorbance detection windows, 9 heaters, 10 field effect transistor-based biosensors, 11 and cell culture patches. 3 As these elements are added, electrode area for droplet actuation is reduced, and force generation becomes weaker.…”