Fluid injection through out-of-plane microneedles

In order to make frequent injections of insulin and other therapeutic agents more efficient, a new painless way to inject drug subcutaneously is investigated. Injecting such agents just under the stratum corneum is a painless and very effective way of drug delivery, since the nerve endings occur deeper under the skin, and the presence of a large number of capillaries help to absorb the drugs efficiently into the vascular system. The critical component for the successful development of this methodology is an array of robust, sharp, hollow microneedles. Arrays of needles that fulfill these requirements have been fabricated using a new fabrication process based on a combination of isotropic and anisotropic etching. Prototypes of these single crystal needles have been successfully tested by injection of fluid into chicken thighs. The flow characteristics of these needles have been modeled using the modified Bernoulli equation. This one-dimensional model has been validated through experimental results.