Project 12
Controlled collapse and patterning of monolayers using patterned hydrophobic surfaces
(dr. Stuart Williams, ME)
Patterns created from evaporationg a 1 microliter droplet of diluted bourbon whiskey.Three different brands were used. From [1].
Our group recently discovered that the evaporation of diluted bourbon whiskey droplets yielded interesting patterns that are correlated with their chemical composition [1]. We determined that these patterns were the result of monolayers that formed at the liquid-air interface and subsequently collapsed/folded as the surface area reduced during evaporation. The chemical composition of the liquid has an obvious impact on monolayer composition and connectivity, thus resulting in different patterns. Its heterogeneity, including contaminants, plays a role in the formation of the collapsed structure [2, 3]. Previous reports with relevance to this study have shown that whiskey inherently contains chemicals that facilitate the generation of interfacial monolayers [4] and dilution of whiskey with water facilitates the transport of chemicals to the interface [5].
The goal of this project is to pattern hydrophobic wells of different patterns (ex: circular triangles, horned triangles, etc.) that will contain droplets. The students will create these hydrophobic/hydrophilic patterns on a glass surface using traditional microfabrication techniques. These “virtual wells” will be designed to induce areas of increased stress on the surface of the droplet during evaporation, thus controlling the sites of monolayer collapse. Such control will enable the future design of droplet-based systems that can investigate the fundamentals of monolayer collapse at high throughput.
REFERENCES:
Williams, S.J., M.J. Brown VI, and A.D. Carrithers, Whiskey webs: microscale "fingerprints" of bourbon whiskey. Physical Review Fluids, 2019. 4: p. 100511.
Ybert, C., W.X. Lu, G. Moller, and C.M. Knobler, Kinetics of phase transitions in monolayers: collapse. Journal of Physics-Condensed Matter, 2002. 14(19): p. 4753-4762.
Lee, K.Y.C., Collapse mechanisms of Langmuir monolayers. Annual Review of Physical Chemistry, 2008. 59: p. 771-791.
Kelly, A.G., V. Vega-Mayoral, J.B. Boland, and J.N. Coleman, Whiskey-phase exfoliation: exfoliation and printing of
