V. Menezes

Laser-ablation-assisted microparticle acceleration for drug delivery

Localized drug delivery with minimal tissue damage is desired in some of the clinical procedures such as gene therapy, treatment of cancer cells, treatment of thrombosis, etc. We present an effective method for delivering drug-coated microparticles using laser ablation on a thin metal foil containing particles. A thin metal foil, with a deposition of a layer of microparticles is subjected to laser ablation on its backface such that a shock wave propagates through the foil. Due to shock wave loading, the surface of the foil containing microparticles is accelerated to very high speeds, ejecting the deposited particles at hypersonic speeds. The ejected particles have sufficient momentum to penetrate soft body tissues, and the penetration depth observed is sufficient for most of the pharmacological treatments. We have tried delivering 1 \mu m tungsten particles into gelatin models that represent soft tissues, and liver tissues of an experimental rat. Sufficient penetration depths have been observed in these experiments with minimum target damage.

Shock‐wave‐based biolistic apparatus

A shock‐wave‐based biolistic device has been developed to deliver DNA/drug‐coated micro‐projectiles into soft living targets. The device consists of an Nd:yttrium aluminum garnet laser, equipped with a suitable optical setup and a thin aluminum (Al) foil (typically 100‐μm thick). The powdered vaccines to be delivered are deposited on the anterior surface of the foil and the posterior surface of the foil is ablated using the laser beam. The ablation launches a shock wave through the foil that imparts an impulse to the foil surface, due to which the deposited particles accelerate to high velocities that are sufficient to enable them to penetrate soft targets. The device has been tested for in vivo DNA delivery by delivering plasmid‐coated, 1‐μm size, gold (Au) particles into onion and tobacco cells. The GUS activity was detected in the onion and tobacco cells after the addition of an artificial substrate. The present device is totally nonintrusive in nature and has a potential to get miniaturized to suit the existing medical procedures for drug delivery.

Drag reduction by controlled base flow separation for missile shaped bodies flying at hypersonic Mach number

The problem of wake flow at high speeds and the drag associated with it are a significant source of observation in the design of missiles, projectiles and other typical high speed vehicles. A large separated wake at the base of the body in flight would cause an increase in the overall drag due to reduced base pressure force, which otherwise would oppose the axial force on the body. The wake studies of high speed bodies also gain importance due to the severe aerodynamic heating problem and a high rise in the temperature of the base flow.

Heat transfer measurement and its application to CFD code evaluation

Convective heat-transfer-rates have been measured on the surface of a cylinder using platinum thin film gauges in a diaphragm-less shock tube. The measured values are compared with the simulated results of two numerical codes at different flow Mach and Reynolds numbers. The measured and simulated results give an insight into the transient flow fields around the model in the shock tube and are a valuable means to complement the numerical and experimental techniques used in the study.