Experimental investigations into immersive ice nucleation

Abstract

Ice nucleation has a significant role in many fields of research, with many questions of its behaviour still unanswered. The purpose of this thesis was to investigate three different aspects of immersive ice nucleation. These included the development of a cold stage that could be used with microfluidics, an investigation into the affects of salinity on the freezing temperature of snow and a determination on whether Homogentisate-1,2-dioxygenase (HGD) acts as an ice nucleator or an anti-freeze protein. These each pose important implications on areas such as climate change and cryopreservation. The cold stage or Automated Lag-Time Apparatus (ALTA) was successfully able to reach temperatures as low as -28.7°C with the use of a thermally conductive paste, making it a viable option for linear and isothermal experiments in the future. Further incorporating this with microfluidics will provide large sample sizes of small droplets giving statistically valuable data sets. The results from the British Antarctic Survey portrayed a minimal effect of salinity on the Arctic snow samples, with no significant freezing point depression observed. Where the freezing point increased due to INPs, it was most likely caused by biological particles such as ultramicrobacteria or exudates from phytoplankton. Finally, HGD was shown to act as an ice nucleator, increasing the freezing rate and causing the sample to freeze at a higher temperature. The HGD samples also experienced dendritic ice formation, causing a two step freezing pattern. Theories surrounding these results are discussed as well as suggestions for future experiments.

Date of Award	24 Jan 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Walther Schwarzacher (Supervisor) & Alison C Rust (Supervisor)