Drug dosage for microneedle‑based transdermal drug delivery systems utilizing evaporation‑induced droplet transport

We present a setup for directed loading of standard microneedle arrays for transdermal drug delivery with the respective therapeutic agent. The necessity to dose medical drugs according to their particular utilization requires an exact volumetric measure of the particular drug, which is usually provided as a liquid. This is achieved by arranging a metallic plate above the array featuring a set of holes aligned with the microneedles underneath. The plate is coated with a superhydrophobic layer. To initiate the filling, droplets are deposited on said holes, where the volume needs to be above the desired load for an individual needle, but the exact dosage is not required. Evaporation of these sessile droplets, after some time, leads to the falling of the droplets through the microfluidic plate, delivering an exact amount of liquid drug to the needles underneath. The proposed setup is easy to implement and parallelize, assisting in the task of accurate and high throughput coating of microneedle-based transdermal drug delivery devices.