Surface Acoustic Waves to Control Droplet Impact onto Superhydrophobic and Slippery Liquid-Infused Porous Surfaces

Abstract

Superhydrophobic coatings and slippery liquid-infused porous surfaces (SLIPS) have shown their potentials in self-cleaning, anti-icing, antierosion, and antibiofouling applications. Various studies have been done on controlling the droplet impact on such surfaces using passive methods such as modifying the lubricant layer thickness in SLIPS. Despite their effectiveness, passive methods lack on-demand control over the impact dynamics of droplets. This paper introduces a new method to actively control the droplet impact onto superhydrophobic and SLIPS surfaces using surface acoustic waves (SAWs). In this study, we designed and fabricated SLIPS on ZnO/aluminum thin-film SAW devices and investigated different scenarios of droplet impact on the surfaces compared to those on similar superhydrophobic-coated surfaces. Our results showed that SAWs have insignificant influences on the impact dynamics of a porous and superhydrophobic surface without an infused oil layer. However, after infusion with oil, SAW energy could be effectively transferred to the droplet, thus modifying its impact dynamics onto the superhydrophobic surface. Results showed that by applying SAWs, the spreading and retraction behaviors of the droplets are altered on the SLIPS surface, leading to a change in a droplet impact regime from deposition to complete rebound with altered rebounding angles. Moreover, the contact time was reduced up to 30% when applying SAWs on surfaces with an optimum oil lubricant thickness of ∼8 μm. Our work offers an effective way of applying SAW technology along with SLIPS to effectively reduce the contact time and alter the droplet rebound angles.

Novel Intrinsic Self‐Healing Poly‐Silicone‐Urea with Super‐Low Ice Adhesion Strength

“…[11,12] For example, lubrication oil or low freezing point liquids infused with low ice adhesion coating are often damaged mechanically causing the fast run-off of lubricating oil or low freezing point liquids. [13,14] Moreover, the hydrophobic materials-based low ice adhesion coatings are often easily damaged resulting in lost de-icing properties. [15,16] It is believed that to achieve long-time de-icing properties of these low ice adhesion coatings, mechanical durability, and smart function should be integrated into the material, [17,18,19,20,21,22] which are not solved until now.…”

Dynamic Mitigation Mechanisms of Rime Icing with Propagating Surface Acoustic Waves

“…Based on the above background information, Biroun et al 45 reported that there is a large impedance mismatch between the surface of the SAW devices along with the wave propagation and the porous superhydrophobic nanoparticle layer coating (ϕ ≈ 0.57), which results in a wave reflection coefficient of 0.998, calculated using …”

“…This low wave reflection coefficient indicates a weak transmission of acoustic energy at the substrate–porous layer interface. Although it is challenging to quantify the porosity of the rime ice layer, we can reasonably assume that the porosity of the rime ice will be higher than that of the nanoparticle porous coating in ref ( 45 ). Therefore, in our case, the SAW acoustic energy will not easily be transmitted through the rime ice layer; thus, the energy will be dissipated significantly into the interfacial layer and the rime ice layer.…”

Surface acoustic wave-based generation and transfer of droplets onto wettable substrates

“…A theoretical model is presented that predicts the average initial size of the transferred droplets on the wettable substrates. During these experiments, the wettability of the LiNbO 3 substrate is unaltered since literature 54 suggests that as the wettability of the LiNbO 3 substrate is changed to hydrophobic/superhydrophobic the area fraction through which the surface acoustic waves leak into the droplet decreases and there will be no effect of surface acoustic waves. Finally, the potential application of the technique is demonstrated by transferring streptavidin protein molecules.…”