Imaging ice growth and nucleation inside non-transparent materials using micro-thermography

Ice nucleation and recrystallization plays a central role in our daily lives and understanding these processes will have great implications. The measurement of ice nucleation, growth and melting is usually done using light microscopy in liquid and transparent samples. However, crystal growth inside solid materials such as food products, cementitious materials and biological samples is more complex. Imaging ice inside these non-transparent materials would be beneficial in many ways since rapid ice growth leads to structural damage of food, and the weakening of the final structure of cementitious materials. Thermography is a technique that uses thermal (Infra-red) cameras to monitor temperature changes in a material, and it has been used to provide qualitative description of ice propagation and nucleation with a spatial resolution of millimeters. Here, the use of a novel micro-thermography system to image ice nucleation, growth and melting inside non-transparent samples with an emphasis on biological samples is described. This method relies on two major players; a cold stage with accurate temperature control (±0.001 ºC) coupled to a high-resolution (both temperature and spatial) thermal camera. The coupling of these instruments brings about the ability to measure the kinetics of ice growth and nucleation inside a variety of non-transparent samples. These experiments provide strong evidence for the high-quality imaging of ice growth, thus leading to quantitative measurements of ice growth velocity and ice nucleation in solid materials.