University of Twente Student Theses


Characterization of needle-free injection into soft matter and skin with continuous jets

Boom, B. and Groendijk, H. (2013) Characterization of needle-free injection into soft matter and skin with continuous jets.

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Abstract:For the pharmaceutical industry needle-free injection methods of liquids are of great importance. Despite the potential there are still many problems that need to be investigated before needle-free injection can be succesfully used. It is still unknown how much air is entrained with injection and not much is known about the shape of liquid impacts in skin. In this report, a high-pressure pump will be used to inject controllable liquid jets with constant velocity into 5 mass percent gelatin as a model for soft human tissue. The penetration depth, amount of entrained air and impact characteristics are investigated by recording the impacts with high-speed imaging. The temporal evolution of the impact shape has been studied and two distinct regimes can be distinguished. In the first regime the penetration can be modelled by a viscous shear stress model and the cylindrical shape of the jet is maintained. During the second penetration regime a spheroidal crater is formed at the end of the cylindrical cavity that was formed in the first regime. The final depth of the impact is strongly dependent on the jet velocity and increases for higher jet velocity. At a certain jet velocity, v0, the morphology of the final impact changes. This velocity is 56ms−1 for a 20 μm capillary and 27ms−1 for a 50 μm capillary for 5 mass percent gelatine. The crater volume of the impact is also strongly dependent on the jet velocity. Again two regimes can be seen that are related to the shape of the final impact crater. For high jet velocities the ratio Vair/Vl iquid can increase up to 6. Measurements with artificially grown human skin samples show that the skin doesn’t rupture directly on jet impact. Skin rupture times decrease with increasing jet velocity and show a large spread. No penetration of skin was observed with jet velocities below 60ms−1.
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics BSc (56962)
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