(143g) Simulation of Electrospray Particle Deposition Process in Pharmaceutical Micro-Patterning

Electrospray particle deposition on a substrate through a mask is a simple (single-step) yet versatile and robust approach to generate biodegradable polymeric particle patterns. Different methods including photolithography, soft lithography and ink jetting have been employed for automated micropattern fabrication; however, most of them are limited to the investigation of material properties of substrates with high-cost and complex procedures.

In electrospray particle deposition process for pharmaceutical micro-patterning, the sample consists of an aqueous solution of the polymer, solvent and drug. The sample is infused at atmospheric pressure with a syringe which is connected to a syringe pump. The major stages of electrospray process are generally divided in three steps: droplet formation, droplet fission and production of ions. The electrospray capillary containing the solution is maintained at a potential of a few kilovolt, and is located a few centimeters above the substrate, which is generally grounded. A mask with a special pattern is placed on the substrate which is also connected to electrical potential generator. The strong electric field causes an electrophoretic movement of the ions inside the liquid, and charged droplets are emitted at the tip of the capillary. Finally, the charge particles will deposit on the substrate and form the special pattern of the mask.

In this study, electrospray particle deposition process is used to form pharmaceutical micropatterns. The trajectories of particle motion are simulated by solving electric field lines in COMSOL, based on the assumption that particle motion is governed predominantly by the electric filed force. In this project the impact of mechanical forces such as gravitational force, buoyancy force and drag force as well as electric forces such as repulsive columbic force and image force have been considered.

The aim of this project is to determine a set of parameters that can achieve most focused micropatterns of drug particles on the substrate. The issues of traditional electrospray deposition such as reducing the loss of raw materials, enhancing the deposition efficiency, increasing the spot density, and reducing the large inherent inter-spot distance are also investigated.