Project 1

Droplet evaporation on microfluidic pedestals

(PROF. Stuart Williams, ME)

The physics of droplet evaporation has a variety of applications including coatings, heat transfer, and microfluidics. Dispensing small droplets (< 1 mL) manually using a pipette is a challenge which is why our group recently created an acoustic droplet dispenser (inspired by [1]) and measured nanoliter droplets volumes from digital images. These nanoliter droplets were used to build a larger microliter sessile droplet. Droplet evaporation was measured using an optical distortion technique where the curvature of the droplet acted as a lens to magnify underlying microfeatures [2,3] and the size of these features correlated to droplet volume. For this REU project, we want to study the evaporation of microliter droplets that were deposited onto a transparent micro-pedestal whose sharp edges are used to constrain the sessile droplet and prevent it from spreading. The fundamental physics of constrained droplet evaporation will be explored using different concentrations of water and ethanol.

REFERENCES:

[1] N. Ionkin and D.M. Harris, “Note: A versatile 3D-printed droplet-on-demand generator,” Rev. Sci. Instrum. 89, 116103 (2018)

[2] J.J. Kilbride, K.E. Fagg, F.F. Ouali, and D.J. Fairhurst, “Pattern-distortion technique: Using liquid-lens magnification to extract volumes of individual droplets or bubbles within evaporating two-dimensional arrays,” Phys. Rev. Applied 19, 044030 (2023)

[3] A. Iqtidar, J.J. Kilbride, F.F. Ouali, D.J. Fairhust, H.A. Stone, and H. Masoud, “Drying dynamics of sessile-droplet arrays,” Phys. Rev. Fluids 8, 013602 (2023)