Understanding the effect of superhydrophobic coatings on energy reduction in anti-icing systems

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

“…Efforts in the past decades have explored controllable fabrication, functionality, and performance optimization of bionic superhydrophobic surfaces with a contact angle above 150°, and they have resulted in technological innovations such as self-cleaning, drag-reduction, anticorrosion, antifogging, antifreezing and oil-water separation. [15][16][17][18][19] Recently, intensive www.advmat.de www.advancedsciencenews.com demonstration of their technological potential for enhancement of heat transfer, [20][21][22][23][24][25] energy saving, [26][27][28] and electrostatic energy harvesting. [29] Currently, this multidisciplinary research direction, which includes biology, chemistry, physics, materials science, and engineering, is still in its infancy, but it has exhibited significance and vigor in both fundamental and technological aspects.…”

“…Example applications are the enhancement of condensation heat transfer for high-efficiency thermal management and energy utilization, [20][21][22][23][24][25] energy-effective antifreezing for airconditioner heat exchangers and aircraft wings, [26][27][28] and electrostatic energy harvesting. [29] In general, condensate drops on typical flat hydrophobic surfaces are only shed off under gravity when their sizes are comparable to the capillary length (≈2.7 mm for water), [30] which creates undesirable effects such as large thermal resistance [20][21][22][23][24][25] and the freezing of subcooled drops.…”

“…[29] In general, condensate drops on typical flat hydrophobic surfaces are only shed off under gravity when their sizes are comparable to the capillary length (≈2.7 mm for water), [30] which creates undesirable effects such as large thermal resistance [20][21][22][23][24][25] and the freezing of subcooled drops. [26][27][28] Clearly, a great challenge is the timely removal of condensate drops at the microscale where the gravitational effect does not work. The latest research has indicated that these small-scale condensate microdrops may self-remove via mutual coalescence as long as the coalescence-released excess surface energy is larger than the interface adhesion-induced energy dissipation.…”

The challenge of removing snow downfall on photovoltaic solar cell roofs in order to maximize solar energy efficiency—Research opportunities for the future

“…added liquid is pressed from the capillaries, which then is able to remove contaminant particles on its escape from the material surface, thus inducing a self-cleaning effect. Figure 19 shows various states a drop may have on a surface, illustrating an increased hydrophobicity (and larger contact angle) on a coarse surface compared to a smooth surface, also depicting the Wenzel state, the CassieBaxter state and a combined state (Antonini et al [1] Several studies have fabricated various artificial coarse superhydrophobic surfaces, where some examples are shown by scanning electron microscope (SEM) images in fig.20 (Dash et al [12]). A comparison of poly(dimethylsiloxane) (PDMS) templates and the natural lotus leaf with respect to surface morphology and hydrophobicity is given in fig.21, depicting SEM images of the surface structure of (a) the lotus leaf, (b) the superhydrophobic surface, and (c) the negative template, with droplets on the corresponding surfaces (d, e, f).…”

“…The commercial factory-finished products are normally based on photocatalytic hydrophilic coatings or surfaces, whereas the user-finished products are usually based on the creation of hydrophobic coatings on the desired surfaces. Figure 17 depicts the different water drop shapes on a hydrophilic and a superhydrophobic surface (Antonini et al [1]). The photocatalytic hydrophilic self-cleaning products of today normally apply titanium dioxide (TiO 2 ) as the photocatalytic layer, utilizing UV solar radiation to break down chemical bonds in organic dirt fastened on the surface, thereafter utilizing rain water to wash off the loosened dirt over the hydrophilic surface.…”