Droplet sensing by measuring the capacitance between coplanar electrodes in a digital microfluidic system

Abstract

In this paper, we report a novel method of droplet sensing in a two-plate digital microfluidic system (DMS) based on coplanar capacitance measurement. The total capacitance between the two adjacent electrodes on the lower plate depends on the position of the droplet. Both numerical and experimental results show that the capacitance is maximal at the midpoint between two electrodes. The value of maximum capacitance increases with the volume of the droplet. Further, the measured capacitance is a function of the gaps between the electrodes as well as the plates. This new method of droplet sensing adds to the functionality of DMSs by allowing single plate measurement.

Evaluation of Cyanoethyl Pullulan material as the dielectric layer for EWOD devices

“…When the CEP films were dried at RT or annealed at 100 ºC in air atmosphere for an hour, it reached the lowest and highest dielectric constant of 15.5 and 19, respectively, which reaches great agreement with previous reports [12] . However, in the previous reports [13][14][15] the spin-coated CEP must be dried in vacuum and then annealed in vacuum or argon ambient. Instead, the CEP film in our work was formed just through hot-baking in air atmosphere, which shows a more convenient process without changing its main dielectric properties.…”

“…For those excellent properties, CEP has been used as the gate insulator in organic field-effect transistors (OFET) [13,14] . However, CEP was rarely used in EWOD device [15] and its performance related to electrowetting has not been well studied. Herein, we study the dielectric properties of CEP material in details with a simple thermal treatment.…”

Stationary-Mixing Field-Programmable Pin-Constrained Digital Microfluidic Biochip

“…For example, input and output (including waste production) use reservoirs that are physically placed on the perimeter of the chip; the locations and roles of the reservoirs do not change when the DMFB is in use, so they are not reconfigurable. External devices such as sensors, mixers, and heaters may be placed at any location on the chip surface [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]; such locations can still perform the five basic operations, but are now enhanced with additional capabilities. Similarly, specialized electrodes can be fabricated to perform operations such as electroporation [12] or non-uniform splitting [32].…”

Droplet Manipulations in Two Phase Flow Microfluidics

“…Nice examples are for instance the ability to print electrodes on thin films, allowing the manipulation of droplets on bent surfaces [51]. In addition, real-time detection of the droplet position by measuring the capacitance of a set of electrodes [52], or electronic paper displays [53] illustrate this point. Thin film transistor arrays used in liquid crystal displays have also been used for EWOD, giving control to over 4000 electrodes with impedance spectroscopy for droplet position detection [54].…”