Investigations on micro-blast wave assisted metal foil forming for biomedical applications

The deformation dynamics of metal foils (<0.25 mm thick) subjected to micro-blast wave are presented in this paper. The energy of micro-blast wave emanating from the open end of a polymer tube is used to deliver micro-particles for bio-medical applications. In these experiments metal foils are used to transfer the energy of the micro-blast wave to the micro-particles. Using cubic root scaling law the over pressure of the blast wave at the open end of the polymer tube is estimated and using this peak plate over pressure is estimated. The finite element analysis is used to estimate the velocity profile of the deforming metal foils. The finite element analysis results are compared with experimental results for the maximum deformation and deformed shape. Based on the deformation velocity, metal foil to be used for experiments is selected. Among the materials investigated 0.1 mm thick brass foil has the maximum velocity of 205 m/s and is used in the experiments. It is found from finite element analysis that the particles deposited within a radius of 0.5 mm will leave the foil with nearly equal velocity (error <5%). The spray cone angle which is the angle of deviation of the path of particles from the axis of the polymer tube is also estimated and found to be less than 7° up to a radius of 0.75 mm. Illustrative experiments are carried out to deliver micro particles (0.7 μm diameter tungsten) into plant tissues. Particle penetration depth up to 460 μm was achieved in ground tissue of potato tuber.

► The deformation dynamics of metal foils (aluminium, brass and copper foils thickness <0.25 mm) subjected to micro-blast wave is studied.
► Brass foil of thickness 0.1 mm has maximum deformation velocity (204 m/s) among those foils which did not fail.
► The angle of deviation from axis of penetration varies from zero at the midpoint to about 7° at a radius of 0.75 mm for brass foil of 0.1 mm thickness.
► Tungsten particles of 0.7 μm diameter were successfully delivered in to plant tissue (potato tuber) with a depth of penetration up to 460 μm.