Characteristics Of Phase Interface Movement Of Materials Under Cooling

Under the cold driving of the materials,ice crystals will be produced in the cells of biomaterials.The formation of ice crystals in cells will cause serious cell damage and destroy the quality of life materials.The shape,size,growth rate and direction of ice crystals in cells will affect the cells and the intercellular space.However,most of the existing available information is mainly limited to animal cells.The information of plant materials at low temperature needs more in-depth research,and the basic research at the cell level is an essential part.Therefore,it is necessary to understand the formation process of ice in cells,the causes of ice formation and the extent of cell damage,especially the observation and study of the characteristics of the phase interface movement in cells,so as to obtain the information of life materials driven by cold can provide an important theoretical basis for the preservation of life materials at low temperature.In order to facilitate the quantitative study,onion cells with large volume and easy to observe were used as the research object.Different cooling rates,different ways of seeding ice crystals were used,and a low-temperature microsystem was used with a high-speed camera to visualize the clear phase interface movement process in the cells.At the same time,in order to further understand the formation of intracellular ice in different plant materials,Vicia faba seeds were used as the research object,cytoskeleton was dissolved by cytochalasin B,and cryopreservation experiments were carried out under different cooling rates with a low-temperature microsystem.The growth process of ice in cells was recorded by digital image correlation method.The frequency of ice crystals in cells and the effect of different freezing methods on ice growth were calculated.The ice crystal growth process was observed by high-speed camera,and three modes of ice crystal growth were found.Mode a: the cell wall continues to crystallize at the edge after crystallizing;mode B: the cell wall diffuses to the center after crystallizing and crosses the center position;mode C: the center first crystallizes and diffuses to the cell edge.The growth rates of ice crystals in three different processes were calculated and analyzed by means of statistics.It is found that the freezing mode plays a key role in the formation of ice crystals in cells and the growth rate of ice crystals.The cooling rate affects the growth mode of ice crystals in cells.When the crystallization temperature is the same,the probability of mode a is the highest.As the cooling rate increases,the probability of mode a decreases,and the probability of mode B and mode C increases.In the same mode,the higher the cooling rate,the faster the growth rate of ice crystal;in the same cooling rate,the fastest growth rate of mode B.The results show that the growth of ice is affected by the cooling rate,and the probability of ice crystal appearing in cells at the same temperature decreases with the increase of cooling rate.However,the growth rate of ice crystals on the edge of cells increased with the increase of cooling rate.It was found by the analysis of light intensity diagram that the ice crystals at this time increased the damage degree of cells.The formation of ice crystals in cells is related to the structure of cytoskeleton.The experimental results show that the cells treated with cytochalasin B crystallize at a higher temperature and a shorter time.However,the structure of cytoskeleton has little effect on the growth pattern of ice crystals.Finally,in order to fully understand the damage degree of plant materials in the whole freezing process,the gray detection method was used to measure and draw the deformation of cells.By comparing the deformation field of cells before and after freezing,it was found that the damage degree of cells was different with the setting of different freezing parameters.With the increase of cooling rate,the deformation degree of cells decreased It can reduce the deformation of cells.