Generic leak-free drug storage and delivery for microneedle-based systems

We present a generic liquid packaging method for micro-machined drug delivery systems with microneedles. Hollow microneedles are sealed with thin gold membranes at the openings on the needle tip on wafer level. This provides both a seal and an evaporation barrier to the drug delivery system on chip level. In addition, the membranes may also prevent drug delivery through needles that do not pierce the skin tissue. Applying a small voltage to the microneedle chip pressed onto the skin causes an electrochemical dissolving of membranes only at the needles that penetrated the skin tissue. The gold membrane sealed microneedles where tested for two types of operational modes. Opening the membranes by means of pressure showed that a minimum pressure of 125 kPa is needed to burst open the membranes. The removal of the gold membrane seal electrochemically was tested in vitro. The microneedle chip was opened within 2 min in the presence of an electrolyte comparable to the interstitial fluid.