Division of Mechanophysics, Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Japan.
Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Japan.
PLoS One. 2018 Oct 5;13(10):e0204686. doi: 10.1371/journal.pone.0204686. eCollection 2018.
The development of ice-phobic, glass-substrate surfaces is important for many reasons such as poor visibility through the ice-covered windshields of vehicles. The present authors have developed new glass surfaces coated with a silane coupling agent and polypeptides whose amino-acid sequence is identical to a partial sequence of winter flounder antifreeze protein. We have conducted experiments on the freezing of sessile water droplets on the glass surfaces, and measured the droplet temperature, contact angle, contact area and surface roughness. The results show that the supercooling temperature decreased noticeably in the case where a higher concentration solution of polypeptide was used for the coating. The adhesion strength of frozen droplets was lowest in the same case. In addition, we observed many nanoscale humps on the coated surface, which were formed by polypeptide aggregates in the solution. We argue that the combination of the hydrophilic humps and the hydrophobic base surfaces causes water molecules adjacent to the surfaces to have a variety of orientations in that plane, even after the ice layer started to grow. This then induces a misfit of water-molecule spacing in the ice layers and consequent formation of fragile polycrystalline structure. This explains the lower values of ice adhesion strength and supercooling enhancement in the cases of the polypeptide-coated glass plates.
防冰、玻璃基底表面的开发具有重要意义，例如，车辆挡风玻璃结冰会导致能见度降低。本文作者开发了一种新的玻璃表面，其表面涂有硅烷偶联剂和多肽，多肽的氨基酸序列与冬比目鱼抗冻蛋白的部分序列相同。我们在玻璃表面上进行了附着水滴滴冻结的实验，测量了液滴的温度、接触角、接触面积和表面粗糙度。结果表明，使用较高浓度的多肽溶液进行涂层时，过冷温度明显降低。在同样的情况下，冻结液滴的附着力最低。此外，我们在涂层表面观察到许多纳米尺度的凸起，这些凸起是溶液中的多肽聚集体形成的。我们认为，亲水凸起和疏水基底表面的结合导致与表面相邻的水分子在该平面上具有多种取向，即使在冰层开始生长之后也是如此。这导致冰晶层中水分子间距失配，并形成易碎的多晶结构。这解释了在多肽涂覆的玻璃板的情况下，冰附着强度和过冷度增强的降低的原因。
