title: Tuning kinetics to control droplet shapes on chemically striped patterned surfaces.
abstract: The typically elongated shape of droplets on chemically microstriped surfaces has been suggested to depend strongly on the kinetics during deposition. Here, we unequivocally establish the importance of impact kinetics by comparing the geometry of pico- to microliter droplets deposited from an inkjet nozzle with those obtained by conventional deposition from a syringe. For large Weber numbers, the strongly enhanced spreading during the impact in combination with direction-dependent pinning of the contact line gives rise to more spherical droplets with a low aspect ratio. The impact energy can be minimized by the prolonged firing of small picoliter droplets to form larger droplets or, as shown in the past, by using high-viscosity liquids. In the first case, the impact energy is absorbed by the liquid already present, therewith reducing the impact diameter and consequently forming markedly more elongated droplets.
authors.affiliation: Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: H Patrick
authors.initials: HP
authors.lastname: Jansen
authors.forename: Kai
authors.initials: K
authors.lastname: Sotthewes
authors.forename: Christian
authors.initials: C
authors.lastname: Ganser
authors.forename: Christian
authors.initials: C
authors.lastname: Teichert
authors.forename: Harold J W
authors.initials: HJ
authors.lastname: Zandvliet
authors.forename: E Stefan
authors.initials: ES
authors.lastname: Kooij