title: Mixed mode of dissolving immersed nanodroplets at a solid-water interface.
abstract: The dissolution dynamics of microscopic oil droplets (less than 1 μm in height, i.e. nanodroplets) on a hydrophobilized silicon surface in water was experimentally studied. The lateral diameter was monitored using confocal microscopy, whereas the contact angle was measured by (disruptive) droplet polymerisation of the droplet. In general, we observed the droplets to dissolve in a mixed mode, i.e., neither in the constant contact angle mode nor in the constant contact radius mode. This means that both the lateral diameter and the contact angle of the nanodroplets decrease during the dissolution process. On average, the dissolution rate is faster for droplets with larger initial size. Droplets with the same initial size can, however, possess different dissolution rates. We ascribe the non-universal dissolution rates to chemical and geometric surface heterogeneities (that lead to contact line pinning) and cooperative effects from the mass exchange among neighbouring droplets.
authors.affiliation: School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, VIC 3001, Australia. xuehua.zhang@rmit.edu.au.
authors.forename: Xuehua
authors.initials: X
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Bao
authors.forename: Erik
authors.initials: E
authors.lastname: Dietrich
authors.forename: Roeland C A
authors.initials: RC
authors.lastname: van der Veen
authors.forename: Shuhua
authors.initials: S
authors.lastname: Peng
authors.forename: James
authors.initials: J
authors.lastname: Friend
authors.forename: Harold J W
authors.initials: HJ
authors.lastname: Zandvliet
authors.forename: Leslie
authors.initials: L
authors.lastname: Yeo
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse