Manufacturing of Sapphire Crystals with Variable Shapes for Cryosurgical Applications

Abstract

Consideration of sapphire shaped crystals as the material for manufacturing of medical instruments expands the opportunities of various approaches for diagnostics, exposure and treatment. Due to physical, mechanical and chemical properties of sapphire, as well as to its complex shape, such instruments are capable to demonstrate better performance for medical applications comparing to common tools. However, the manufacturing of high quality sapphire crystal with such geometry is still a complex issue, that usually requires application of various crystal growth techniques assisted with the automated weight control system. In this work, we consider one of such cases, that is the growth of a sapphire crystal, which can be applied for cryosurgery as an applicator due to a hollow-monolithic shape transition. Its hollow part can be filled with coolant in order to enable fast freezing of biological tissue during application. For this aim, it is of high importance to exclude the appearance of inclusions during the shape transition. To overcome this problem, we suggest using of noncapillary shaping (NCS) technique of crystal growth and study the weight signal measured during the manufacturing. We obtain the analytical description of the weight signal alteration that can be used as the program equation to control the crystal shape. We experimentally demonstrate the advantage of using such crystal for cryosurgery and obtaining faster ice-ball formation inside the model gelatin-based medium in comparison with the usage of the monolithic sapphire applicator of the same diameter. The demonstrated ability can be applied for future development of cryosurgical tools, while the analytical description of the weight signal could find its application for NCS manufacturing of sapphire crystals for other purposes.