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Abstract

The evaporation of droplets on patterned surfaces occurs in a large variety of natural and technological processes such as medical diagnostics, agriculture, food industry, printing, and catalytic reactions. Here we experimentally and computationally examine the micro-droplet evaporation on lyophilic elliptical patches. In the experiments, the drops of various volumes are placed on elliptical chemical patterns of different aspect ratios and imaged in 3D using laser scanning confocal microscopy extracting the droplet's shape. In the corresponding numerical simulations, we minimize the interfacial free energy of the droplet, employing Surface Evolver. The numerical results are in good qualitative agreement with our experimental data and can be used for the design of micro-patterned structures, potentially suggesting or excluding certain morphologies for particular applications. However, the experimental results show the effects of pinning and contact angle hysteresis, which are obviously absent in the numerical energy minimization.The work culminates with the morphology diagram in the aspect ratio vs relative volume parameter space, comparing the predictions with the actual measurements.