Dielectric-free electrowetting on graphene

Area of Science:

• Surface science
• Materials science
• Physical chemistry

Background:

• Electrowetting typically requires a dielectric layer between electrolytes and conductors.
• Recent studies demonstrate reversible electrowetting directly on conductors like graphite.
• Ion-surface interactions are key to understanding electrowetting on conductive surfaces.

Purpose of the Study:

• Investigate electrowetting on graphene surfaces of varying thickness.
• Understand the role of ion adsorption and surface impurities in direct electrowetting.
• Analyze the influence of anion-graphene interactions on wetting behavior and dynamics.

Main Methods:

• Fabrication of graphene samples using chemical vapor deposition.
• Application of highly concentrated aqueous and non-aqueous electrolytes.
• Contact angle measurements to quantify electrowetting response.
• Monitoring wetting dynamics to identify irreversible behaviors.

Main Results:

• Concentrated electrolytes induce a subtle electrowetting response on graphene by suppressing surface impurity effects.
• Strongly adsorbed/intercalated anions amplify the wetting response in both aqueous and non-aqueous electrolytes.
• Wetting dynamics reveal irreversible behavior attributed to anion adsorption and/or intercalation.

Conclusions:

• Direct electrowetting on graphene is feasible with concentrated electrolytes, modulated by ion-surface interactions.
• Anion-graphene interactions play a crucial role in enhancing and altering electrowetting phenomena.
• The observed irreversibility highlights the impact of adsorption/intercalation processes on wetting dynamics.