A research achievement by Dr. Harutoshi Asakawa, Assistant Professor of the Crystal Engineering Laboratory, Applied Chemistry in Engineering at the Graduate School of Sciences and Technology for Innovation, has been introduced in "Research Highlights" in Nature Physics, Nature's sister journal.
He studied the behavior of water films (Fig. 2) on ice surfaces formed below the melting point (0°C) under various water vapor pressures, using a special optical microscope (Fig. 1) which is able to detect one-molecular height (0.37nm) on ice surfaces. As a result, they found that the two types of water films on ice surfaces are formed not by the melting of the ice, but by the deposition of water vapor. In the conventional picture, it had been thought that these water films are formed by "surface melting," where the ice melts. However, this research achievement turned the long-believed "surface melting" picture on its head (Fig. 3).
This achievement was published in Proceedings of the National Academy of Sciences of the United States of America (impact factor: 9.7; PNAS, 113 (7), 1749-1753, 2016), and was also selected by Nature Physics, sister journal of Nature, to have its abstract printed in "Research Highlights." (Nature Physics, 12 (3), 201, 2016)
Such liquid films are also observed on metal crystals, semiconductor crystals, organic crystals, etc. Hence, these findings are expected to contribute to the elucidation of interface phenomena which occur just below the melting points of these crystal materials.

Article URL:
http://www.pnas.org/content/113/7/1749.full?sid=427f55bd-b95a-4b00-96be-84b27d45a630

Figure 1. A laser confocal microscope combined with differential interference contrast microscope, which can visualize one-molecular height (0.37nm) on ice surfaces.

Figure 2. Thin layers and droplets covering an ice surface.

Figure 3. Relation between the appearance of the two types of water films and water vapor pressure. This achievement is shown on the left, and the conventional picture is also shown on the right. Under high water vapor pressure, thin layers and droplets appeared (A). With decreasing water vapor pressure, the thin layers first disappeared (B), and then droplets disappeared under low supersaturation conditions (C).