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Updated: Jul 21, 2025

AC Electrokinetic Phenomena Generated by Microelectrode Structures
Published on: July 28, 2008
Electrically Mediated Static Contact Angle and Hysteresis of Polyelectrolyte Solutions
Sumit Kumar1, Patrick Martin1, Gleb Vasilyev1
1NanoEngineering Group, Department of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel.
Abstract:
Manipulating a droplet by electrowetting-on-dielectric (EWOD) is vital in various fields ranging from industrial applications to life sciences. As of now, EWOD research has focused primarily on aqueous electrolytes and ionic liquids. This paper investigates the electrowetting behavior of weak polyelectrolyte solutions containing poly(acrylic acid) (PAA). The study reveals distinct wetting behavior of weakly and fully charged PAA droplets controlled by their solution pH. Under an applied electric field, strongly ionized PAA wets more effectively than weakly charged PAA. The electrowetting hysteresis of fully ionized PAA droplets was also higher than that of weakly charged droplets. The reason may be the suppression of retraction flow near the contact line. In this thin region, the electric field aligns the stretched polymer chains perpendicular to the dielectric surface, thus affecting the bulk rheological properties. The results reveal how charge-connectivity and polyelectrolyte conformation under an external electric field can control the electrowetting gain and the hysteresis. This previously unexplored electrowetting mechanism of polyelectrolyte solutions might help order and manipulate biological polyelectrolytes, such as deoxyribonucleic acid (DNA), polypeptides, and glycosaminoglycans.
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