Yang Shaohua, Gerber Dominic, Feng Yanxia, Bain Nicolas, Kuster Matthias, de Lorenzis Laura, Xu Ye, Dufresne Eric R, Style Robert W
School of Mechanical Engineering and Automation, Beihang University, Beijing, China.
Department of Materials, ETH Zürich, 8093 Zürich, Switzerland.
Sci Adv. 2024 Aug 23;10(34):eado7750. doi: 10.1126/sciadv.ado7750.
It is widely known that freezing breaks soft, wet materials. However, the mechanism underlying this damage is still not clear. To understand this process, we freeze model, brittle hydrogel samples, while observing the growth of ice-filled cracks that break these apart. We show that damage is not caused by the expansion of water upon freezing or the growth of ice-filled cavities in the hydrogel that exert pressure on the surrounding material. Instead, local ice growth dehydrates the adjacent hydrogel, leading to drying-induced fracture. This dehydration is driven by the process of cryosuction, whereby undercooled ice sucks nearby water toward itself, feeding ice growth. Our results highlight the strong analogy between freezing damage and desiccation cracking, which we anticipate being useful for developing an understanding of both topics. Our results should also give useful insights into a wide range of freezing processes, including cryopreservation, food science, and frost heave.
众所周知，冷冻会破坏柔软、潮湿的材料。然而，这种破坏背后的机制仍不清楚。为了理解这一过程，我们对脆性水凝胶模型样品进行冷冻，同时观察使这些样品破裂的充满冰的裂缝的扩展情况。我们发现，破坏并非由冷冻时水的膨胀或水凝胶中充满冰的空洞的生长对周围材料施加压力所致。相反，局部冰的生长使相邻的水凝胶脱水，导致干燥引起的断裂。这种脱水是由低温抽吸过程驱动的，即过冷冰将附近的水吸向自身，为冰的生长提供水分。我们的研究结果突出了冷冻损伤与干燥开裂之间的强烈相似性，我们预计这将有助于对这两个主题的理解。我们的研究结果还应为包括低温保存、食品科学和冻胀在内的广泛冷冻过程提供有用的见解。
