Digital Microfluidic Mixing via Reciprocating Motions of Droplets Driven by Contact Charge Electrophoresis

Abstract

Contact charge electrophoresis (CCEP) is an electrically controllable manipulation technique of conductive droplets and particles by charging and discharging when in contact with the electrode. Given its straightforward operation mechanism, low cost, and ease of system construction, it has gained traction as a versatile and potential strategy for the realistic establishment of lab-on-a-chip (LOC) in various engineering applications. We present a CCEP-based digital microfluidics (DMF) platform with two parallel electrode modules comprising assembled conventional pin header sockets, allowing for efficient mixing through horizontal and vertical shaking via droplet reciprocating motions. The temporal chromic change caused by the chemical reaction between the pH indicator and base solutions within the shaking droplets is quantitatively analyzed under various CCEP actuation conditions to evaluate the mixing performance in shaking droplets by vertical and horizontal reciprocating motions on the DMF platform. Furthermore, mixing flow patterns within shaking droplets are successfully visualized by a high-speed camera system. The suggested techniques can mix samples and reagents rapidly and efficiently in droplet-based microreactors for DMF applications, such as biochemical analysis and medical diagnostics.

Electropatterning—Contemporary developments for selective particle arrangements employing electrokinetics

“…The controlled transport of electrically charged liquid droplets has important applications in controlled drug delivery and in the separation of micro/macro molecules [73][74][75][76][77]. Charged liquid droplets suspended in an immiscible fluid can be manipulated employing EFs [78].…”

“…Recent studies have used EPDD for merging aqueous droplets and minimizing direct liquidsolid contact. A recent study by Kim et al [74] reported the electrocoalescence and merging of droplets by employing a programmable digital microfluidics device. Their digital device consisted of two parallel electrode modules that enabled 3D programmable droplet handling.…”

“…Source : (A) Adapted from Ref. [74], open access article distributed under the Creative Commons Attribution (CC BY) License (2022). (B) Adapted with permission from Ref.…”

Graphene Oxide Paper Manipulation of Micro-Reactor Drops

“…Channel-based microfluidics suffer from clogging issues due to the narrow sizes of the channels [ 7 , 8 ]. Digital microfluidics, which relies on the movement of drops, is, alternatively, relatively more immune to this problem [ 9 , 10 , 11 , 12 ]. One of the exciting areas of application of digital microfluidics is in the creation of micro-reactors [ 13 , 14 , 15 ].…”

Utilization of charged microdroplets for the controlled rapid synthesis of hollow sodium chloride single crystals

“…Consequently, they have gained widespread utility in microfluidic control, drug delivery, and biomedical research. [8][9][10] Furthermore, in contrast to bulk phases, charged microdroplets possess unique attributes such as the presence of an interface double layer, high electric fields, pH gradients, and rapid mixing and diffusion of surface molecules. [11][12][13][14] This micro-environment resembles a confined cell, promoting chemical reactions, including acceleration, selectivity control, and the facilitation of challenging reactions under conventional conditions.…”