Leveraging the Coffee Ring Effect for a Defect-Free Electroformation of Giant Unilamellar Vesicles

We took advantage of the microflow hydrodynamics in the evaporation of sessile droplets to increase the height uniformity of thin lipid films for the subsequent electroformation of defect-free giant unilamellar vesicles (GUV). By serially casting progressively larger liposome suspension droplets on the same spot of an indium-tin-oxide (ITO) electrode, we managed to leverage the coffee ring effect (CRE) in the evaporation of each droplet to generate a smeared multilayer film of uniform thickness. This multidroplet technique of lipid film formation outperformed the traditional single-droplet deposition, improving the final quality of electroformed GUV samples. The proposed film formation technique constitutes a solvent-free method that results in a dramatic reduction (∼20×) in the appearance of undesirable structures like nonspherical (NSV), multilamellar (MLV), and multivesicular (MVV) vesicles.