Abstract
The development of anti-icing, anti-frosting transparent plates is important for many reasons, such as poor visibility through the ice-covered windshields of vehicles. We have fabricated new glass surfaces coated with polypeptides which mimic a part of winter flounder antifreeze protein. We adopted glutaraldehyde and polyethylene glycol as linkers between these polypeptides and silane coupling agents applied to the glass surfaces. We have measured the contact angle, the temperature of water droplets on the cooling surfaces, and the frost weight. In addition, we have conducted surface roughness observation and surface elemental analysis. It was found that peaks in the height profile, obtained with the atomic force microscope for the polypeptide-coated surface with polyethylene glycol, were much higher than those for the surface without the polypeptide. This shows the adhesion of many polypeptide aggregates to the polyethylene glycol locally. The average supercooling temperature of the droplet for the polypeptide-coated surface with the polyethylene glycol was lower than for the polypeptide-coated surface with glutaraldehyde and the polyethylene-glycol-coated surface without the polypeptide. In addition, the average weight of frost cover on the specimen was lowest for the polypeptide-coated surface with the polyethylene glycol. These results argue for the effects of combined polyethylene glycol and polypeptide aggregates on the locations of ice nuclei and condensation droplets. Thus, this polypeptide-coating with the polyethylene glycol is a potential contender to improve the anti-icing and anti-frosting of glasses.
Highlights
The development of anti-icing, anti-frosting surfaces is of importance because surfaces covered with ice layers and frost layers often cause serious issues, such as (1) poor visibility through the windshields of aircraft, trains and automobiles; (2) poor visibility of traffic lights and surveillance cameras; (3) decreases in efficiency of the heat exchanger and power generation efficiency of solar panels; (4) breaking of power transmission lines in winter; (5) deterioration of the aerodynamic performance of aircraft wings
We previously conducted experiments on the freezing of water droplets on glass surfaces coated with this polypeptide, and showed delays in the freezing and a decrease in adhesion strength [16,18]. We argued that these changes occurred as a result of the surfaces consisting of smooth hydrophobic areas and many hydrophilic protrusions produced by the adhesion of the polypeptide aggregates
By taking account of the slight lowering of the contact angle for the SS coating, many non-aggregated SSs, and the SS aggregates shown in Figure 4d, were immobilized to PEG. This is because the hydrophobic amino acid residues of the non-aggregated SS are exposed on the smooth surfaces, while the hydrophilic amino acid residues are exposed on the surfaces of aggregates [16]
Summary
The development of anti-icing, anti-frosting surfaces is of importance because surfaces covered with ice layers and frost layers often cause serious issues, such as (1) poor visibility through the windshields of aircraft, trains and automobiles; (2) poor visibility of traffic lights and surveillance cameras; (3) decreases in efficiency of the heat exchanger and power generation efficiency of solar panels; (4) breaking of power transmission lines in winter; (5) deterioration of the aerodynamic performance of aircraft wings. Lubricant-infused surfaces [1,2,3] and surfaces with micro-scale roughness [4,5,6] showed remarkable ice-phobicity, including a lengthening in the lag time to reach the coldest supercooling temperature [2,4,5] These functional surfaces are generally unsuitable for the applications mentioned above, due to problems such as (1) the deterioration of visibility by the lubricant and microstructure, (2) the loss of lubricant by water droplets [1], frost [7] and ice particles [8], and (3) the promotion of vapor condensation by micro-structured surfaces [9]. The polypeptide will be abbreviated as SS, which is associated with the fact that Kun and Mastai called the polypeptide “short segment” in [17]
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