A slim, powerless microfluidic patch-pump for transdermal drug delivery*

The delivery of many pharmaceuticals and biologicals remains a challenge. A significant portion of these materials can be delivered orally, yet others, especially macromolecular drugs that are degraded during first-pass metabolism, must rely on transdermal injection. For insulin delivery, conventional syringe injections and battery-powered pumps are associated with non-adherence due injection site pain and inconvenience. Using soft lithography and stereolithographic 3D printing techniques, we have developed multilayer microfluidic devices based on the principles of insect respiration that can be actuated by the wearer's arterial pulse and can act as painless drug delivery vehicles when coupled with 3D-printed microneedle arrays. Pressurized air that mimicked the human radial pulse was used to drive the flow at 12 different actuation frequencies and 7 different pressures. We found that the flow rate of fluid increased with increasing actuation frequency for some device designs but decreased (ideal for insulin delivery) for others. The flow rate generally exhibited a positive relationship with the actuation pressure. We have assembled these microfluidic devices, together with 3D-printed, hollow microneedle arrays, into integrated prototype patch-pumps for drug delivery.