Can secondary nucleation exist in ice banding of freezing colloidal suspensions?

The formation mechanism of ice banding in the system of freezing colloidal suspensions, which is of significance in frost heaving, ice-templating porous materials and biological materials, still remains a mystery. Recently, the theory of secondary nucleation and growth of ice has been proposed to explain the emergence of a new ice lens. However, this theory has not been quantitatively examined. Here, we quantitatively measured the initial interfacial undercooling of a new ice lens and the nucleation undercoolings of suspensions. We found that the interfacial undercooling can not satisfy the nucleation undercooling of ice and hence disprove the secondary nucleation mechanism for ice banding.