Long-term deep supercooling of large-volume water via surface sealing with immiscible liquids

TL;DR

This study demonstrates a surface sealing method using immiscible liquids to achieve long-term, large-volume supercooling of water at temperatures as low as -20°C for up to 100 days, overcoming previous nucleation barriers.

Contribution

The paper introduces a novel surface sealing technique with oils and alcohols to enable long-term deep supercooling of large water volumes, surpassing prior limitations.

Findings

Achieved -20°C supercooling of 100 ml water for 100 days.

Surface sealing drastically reduces heterogeneous nucleation.

Alcohols and alkanes show different effects based on chain length and interfacial structure.

Abstract

Supercooling of aqueous solutions below their melting point without any crystallization is a fundamentally and practically important physical phenomenon with numerous applications in biopreservation and beyond. Under normal conditions, heterogeneous nucleation mechanisms critically prohibit the simultaneous long-term (> 1 week), large volume (> 1 ml) and low temperatures (< -10 oC) supercooling of aqueous solutions. Here, in order to overcome this bottleneck and enable novel and practical supercooling applications, we report on the use of surface sealing of water by an oil phase to drastically diminish the primary heterogeneous nucleation at the water/air interface. Using this approach, we have achieved deep supercooling (as low as -20 oC) of large-volumes of water (up to 100 ml) for long periods (as long as 100 days) simultaneously. Since oils are mixtures of various hydrocarbons we also report on the use of pure alkanes and primary alcohols of various lengths to achieve the same. All alcohols and some of the longer alkane chains we studied show high capacity to inhibit freezing. The relationship of this capacity with the chain length, however, shows opposite trends for alcohols and alkanes due to their drastically different interfacial structures with the water molecules. We find that the deeply supercooled water (at -20 oC) can withstand vibrational and thermal disturbances with all sealing liquids used, and even an extreme disturbance, ultrasonication, when alcohols are used as the sealing phase. The deep supercooling approach we developed here, for large samples and long periods, is expected to enable novel applications of supercooling in a variety of areas including biopreservation and food storage among others.