Anion Intercalation into Graphite Drives Surface Wetting

The unique layered structure of graphite with its tunable interlayer distance establishes almost ideal conditions for the accommodation of ions into its structure. The smooth and chemically inert nature of the graphite surface also means that it is an ideal substrate for electrowetting. Here, we combine these two unique properties of this material by demonstrating the significant effect of anion intercalation on the electrowetting response of graphitic surfaces in contact with concentrated aqueous and organic electrolytes as well as ionic liquids. The structural changes during intercalation/deintercalation were probed using in situ Raman spectroscopy, and the results were used to provide insights into the influence of intercalation staging on the rate and reversibility of electrowetting. We show, by tuning the size of the intercalant and the stage of intercalation, that a fully reversible electrowetting response can be attained. The approach is extended to the development of biphasic (oil/water) systems that exhibit a fully reproducible electrowetting response with a near-zero voltage threshold and unprecedented contact angle variations of more than 120 degrees within a potential window of less than 2 V.

Automated summary

The unique layered structure of graphite and its tunable interlayer distance allow for the accommodation of ions into its structure. The smooth and chemically inert nature of the graphite surface makes it an ideal substrate for electrowetting. This study combines these two properties and explores the significant effect of anion intercalation on the electrowetting response of graphitic surfaces. Through in situ Raman spectroscopy, the structural changes during intercalation/deintercalation were studied, providing insights into the influence of intercalation staging on the rate and reversibility of electrowetting. By tuning the intercalant size and stage of intercalation, a fully reversible electrowetting response can be achieved. The approach is extended to biphasic (oil/water) systems, allowing for a fully reproducible electrowetting response with a near-zero voltage threshold and unprecedented contact angle variations.