Interferometry‐based direct comparison of transport phenomena associated with the growth processes of organic and inorganic crystals

Abstract

Non‐intrusive dynamic measurements of concentration fields around solution‐grown protein and inorganic crystals using a Mach‐Zehnder interferometer have been reported. Sodium chlorate (inorganic) and hen‐egg‐white lysozyme (protein) crystals have been employed as model materials. Mass transport phenomenon during the growth process is visualized in the form of interferometric images. Development of concentration boundary layers in the vicinity of the two types of crystals has been investigated. Results are presented in the form of interferometric images, contours of two‐ dimensional concentrations and gradient fields. Primary findings of the experimental study clearly reveal the differences in the transport phenomena associated with the growth processes of inorganic and protein crystals. Fringe patterns recorded during the growth of inorganic crystal showed substantial deformation in the vicinity of the crystal top surface whereas the fringe deformation was seen to be very mild in the case of protein crystals. Qualitative interpretation of the images revealed strong concentration gradients in the vicinity of the growing NaClO3 crystal as compared to those observed for the lysozyme crystals. Based on the interferometric observations, the strength of transport phenomena associated with the two categories of crystals has been quantified and reported in terms of non‐dimensional parameters such as the Rayleigh number.