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Hysteretic DC electrowetting by field-induced nano-structurations on polystyrene films
Yogesh B Sawane1, Suwarna Datar, Satishchandra B Ogale
1Centre for Advanced Studies in Condensed Matter and Solid State Physics, Department of Physics, S P Pune University, Pune 411007, India. agb@physics.unipune.ac.in.
Soft Matter
|February 19, 2015
Summary
Electrowetting on polystyrene surfaces causes unexpected contact angle hysteresis due to electric field-induced nanostructuring. This electrowetting-driven surface modification enhances dye loading on hydrophobic materials.
Area of Science:
- Surface science
- Materials science
- Electrochemistry
Background:
- Electrowetting (EW) enables precise control of liquid droplet behavior on surfaces.
- Standard EW typically involves reversible contact angle changes.
- Previous studies have not reported significant surface modification during EW of aqueous solutions on polymers.
Purpose of the Study:
- To investigate the anomalous electrowetting behavior of aqueous drops on polystyrene (PS) dielectric surfaces.
- To understand the mechanism behind the observed contact angle hysteresis.
- To explore the potential of EW-induced surface modification for practical applications.
Main Methods:
- Experimental electrowetting measurements using direct current (DC) voltage.
- Atomic force microscopy (AFM) for surface characterization.
- Systematic variation of parameters like molecular weight, electric field, water conductivity, and pH.
Main Results:
- Aqueous droplets on PS exhibited significant contact angle hysteresis after a single DC voltage cycle.
- In situ surface modification, specifically nanostructuration, was confirmed by AFM.
- Nanostructuration was influenced by water-ion contact with the PS surface, driven by electro-hydrodynamic (EHD) instability.
- The extent of nanostructuration depended on molecular weight, electric field, water conductivity, and pH.
Conclusions:
- The observed contact angle hysteresis in electrowetting on PS is attributed to electric field-induced nanostructuration.
- EW-driven nanostructuration offers a novel method for surface modification.
- This technique was successfully applied to enhance the loading of aqueous dyes onto hydrophobic PS surfaces.
