Electro-drawn polymer microneedle arrays with controlled shape and dimension

Biodegradable polymer microneedles are recognized as a valuable route for transdermal drug delivery as well as for cutaneous treatments. According to the industrial needs, the present trend is to fabricate microneedles through stamp-less techniques. Electro-drawing has been recently proposed as an alternative fast and mild temperature strategy to the stamp based techniques for the fabrication of biodegradable polymer microneedles. However, previously presented electro-drawn microneedles were fabricated by a point-like thermal stimulation, thus, they could not be electro-drawn in parallel and displayed a pedestal at their basis. Here, we present a novel electro-drawing set up and strategy to parallelize the process and to avoid the pedestal at the microneedle basis. The new set-up is based on titanium micro-heaters integrated onto the pyroelectric substrate which is the electric field generator enabling the electro-drawing. The micro-heaters configuration has been chosen starting from numerical simulations to guarantee uniform heating on large areas, in contrast to the local heating by hot tip, allowing the generation of a uniform electric field which is a basic condition for an in parallel fabrication of microneedles. Additionally, thanks to the stronger electric field, it was possible to apply a double step electro-drawing, where the second step is carried out at higher distance in order to avoid microneedle shrinkage while avoiding further growing of the microneedles.