Using capacitance measurements in EWOD devices to identify fluid composition and control droplet mixing

SENSORS AND ACTUATORS B-CHEMICAL

卷:145

Article

Schertzer, M. J.¹  Ben-Mrad, R.¹  Sullivan, P. E.¹ 

[1] Univ Toronto, Dept Mech & Ind Engn, Toronto, ON M5S 3G8, Canada

关键词: Electrowetting on dielectric;    Microfluidics;    Mixing;    Composition;    Capacitance;    Void fraction;    Control;    Automation;   

DOI  :  10.1016/j.snb.2009.12.019

来源: Elsevier

【 摘 要 】

The use of capacitance measurements to identify the composition of droplets and monitor mixing in electrowetting on dielectric devices is examined here. Measurements were repeatable at each addressable location, with standard deviations on the order of 0.1 pF and a two-point calibration allowed repeatable differentiation of water-methanol solutions as the capacitance was linear with concentration. Capacitance at addressable locations was monitored throughout the mixing of water-methanol solutions. It was shown analytically and experimentally that the dimensionless capacitance is approximately equal to the dimensionless dielectric constant for practical EWOD applications. The number of cycles required for complete mixing remained constant for periods of actuation between 400 and 1000 ms and applied voltages between 90 and 110 V-RMS. Although minimizing actuation period and maximizing droplet velocity decreases mixing time, these parameters have little affect on the number of cycles necessary to achieve mixing in EWOD devices. This shows mixing efficiency in EWOD devices is better described by the number of cycles, not the time, required for full mixing. (C) 2009 Elsevier B.V. All rights reserved.

【 授权许可】

Free