A Cost-Effective Microfluidic Device to Teach the Principles of Electrophoresis and Electroosmosis

Abstract

Electrophoresis is integral to analytical and biochemistry experiences in undergraduate education; however, fundamental principles of the method are often taught in upper-level laboratories through hands-on experiences. A laboratory activity is reported that teaches the concepts of electrophoretic mobility and electroosmotic flow. A single reuseable instrument, called a mini-E, costs 37 USD and consists of a DC power supply, a voltmeter, platinum electrodes, and a chip cast in polydimethylsiloxane. This activity uses common reagents costing only 0.02 USD per student. Experiments are devised that allow students to investigate the properties of electrophoretic flow and electroosmotic flow by separating the two commonly used food dyeing agents Brilliant Blue FCF and Allura Red AC in vinegar and in a solution of ammonium hydroxide. A dark-purple mixture of these dyes is separated into red and blue bands that are easily visualized. The migration order of the dyes differs when the separation is performed under conditions of reversed polarity and suppressed electroosmotic flow (vinegar) compared to conditions of normal polarity and active electroosmotic flow (ammonium hydroxide). When delivered to chemistry majors, students had a significant gain in their ability to apply the concepts of electroosmosis and electrophoresis to predict analyte migration. Although this activity targets upper-level chemistry content, it can also be adapted for other laboratory experiences.

Electrochemical Nucleic Acid Biosensor on a Microfluidic Chip to Understand the Coupling between Electrochemistry and Microfluidics

“…While previously published work focuses mainly on microfluidic chip fabrication, − this article aims at providing in-depth theoretical and practical knowledge of electrochemistry coupled with microfluidics. This laboratory experiment not only shows how flow rates impact electrochemical measurements but also explains the phenomenon behind it (e.g., the impact of forced convection on the diffusion layer and on the biosensor’s detection limit), as well as how the diffusion layer shrinks under forced convection and the consequences on the biosensor’s detection.…”

“…General principles of electrochemistry and microfluidics ,, (mass transport, chemical kinetics) should be acquired prior to this laboratory experiment. This practical workshop could be addressed to high-level undergraduates or postgraduates.…”