nn6b06463_si_001.pdf (2.24 MB)
Rational Design of Hyperbranched Nanowire Systems for Tunable Superomniphobic Surfaces Enabled by Atomic Layer Deposition
journal contribution
posted on 2016-11-30, 14:40 authored by Ashley
R. Bielinski, Mathew Boban, Yang He, Eric Kazyak, Duck Hyun Lee, Chongmin Wang, Anish Tuteja, Neil P. DasguptaSuperomniphobic
surfaces display contact angles of θ* > 150°
and low contact angle hysteresis with virtually all high and low surface
tension liquids. The introduction of hierarchical scales of texture
can increase the contact angles and decrease the contact angle hysteresis
of superomniphobic surfaces by reducing the solid–liquid contact
area. Thus far, it has not been possible to fabricate superomniphobic
surfaces with three or more hierarchical scales of texture where the
size, spacing, and angular orientation of features within each scale
of texture can be independently varied and controlled. Here, we report
a method for tunable control of geometry in hyperbranched ZnO nanowire
(NW) structures, which in turn enables the rational design and fabrication
of superomniphobic surfaces. Branched NWs with tunable density and
orientation were grown via a sequential hydrothermal
process, in which atomic layer deposition was used for NW seeding,
disruption of epitaxy, and selective blocking of NW nucleation. This
approach allows for the rational design and optimization of three-level
hierarchical structures, in which the geometric parameters of each
level of hierarchy can be individually controlled. We demonstrate
the coupled relationships between geometry and contact angles for
a variety of liquids, which is supported by mathematical models. The
highest performing superomniphobic surface was designed with three
levels of hierarchy and achieved the following advancing/receding
contact angles with water 172°/170°, hexadecane 166°/156°,
octane 162°/145°, and heptane 160°/130°.