Drug Delivery

Drug delivery via intravenous needles is commonplace in a doctor’s office or hospital. Whether you are getting your vaccinations as a child or getting an updated tetanus shot, many drugs are administered with needles. Shown here is a transient, free-surface simulation of an injection needle modeled using cylindrical coordinates in conjunction with FLOW-3D’s Moving Objects Model. The needle itself is a few hundred micrometers wide while the syringe section is a few millimeters. A time-dependent prescribed velocity is applied to the plunger to generate the motion. In this application it is important to understand the injection force required on the plunger while squeezing out a shear thinning fluid. FLOW-3D‘s non-Newtonian viscosity model is used to account for these effects. FLOW-3D can include other viscous effects such as thixotropic fluids, temperature-dependent viscosity, a Carreau model or power law. Strain and shear stress are calculated to determine whether proteins and/or cells are damaged.

Drug delivery systems
Pressure and velocity contours in a injection syringe squeezing a shear thinning fluid

FLOW-3D is used to predict transient injection forces on a plunger and strain rate for various solutions of shear thinning medical fluid. Medical fluids contain essential components that undergo high strain through shear thinning at the syringe-needle interface. FLOW-3D can be used to model various syringe-needle geometries and fluids to analyze the strain experienced by fluid in passage through the needle as well as the force generated on the plunger for automated injections.

Simulation of a medical injection needle where the injection force on the plunger is computed while squeezing out a shear thinning fluid.