Periodic Burst Freezing in a Water-Filled Capillary Tube

Water-filled porous structures are ubiquitous components in life sciences and engineering. At sufficiently low temperatures, the water inside the porous structures can freeze, triggering the frost heave effect and causing problems such as permafrost, frost damage, and frostbite. In this study, we report a unique pattern of frost heat release through periodic bulging and bursting at the end of a water column inside a capillary tube. When water freezes, it expands in volume and attempts to drain out. However, surface tension can hinder the flow of water, resulting in the formation of a bulge that periodically bursts when the spherical molecule reaches a critical threshold. We determined that the critical contact angle of the bulge is approximately 135°, which is balanced by the surface tension at the three-phase line of contact. The size of the bulge increases nonlinearly with the diameter of the capillary tube, while the number of periodic repetitions is inversely proportional to the tube diameter and directly proportional to the length of the water column. These findings provide insights into the interaction between surface tension and frost heave, which has important implications for the design and optimization of microfluidic devices with improved resistance to freezing.