Fabrication of hollow microneedles with jagged edges mimicking mosquito's needles by thermal nanoimprint method using a mold combining soft and hard materials

In the aim of realizing minimally invasive needles, a hollow microneedle mimicking a mosquito’s proboscis was developed by a thermal nanoimprinting method using the polylactic acid (PLA) of a biodegradable thermoplastic. A mold was proposed and developed, which consisted of a soft polydimethylsiloxane (PDMS) body and a hard acrylic center pillar for creating the hole. Note that, if a mold is made of a single PDMS, the pillar cannot withstand the imprint pressure and tilts. By imprinting the mold against a PLA sheet, a hollow structure with a high aspect ratio of five (i.e., outer/inner diameter: 200/100 μ m; height: 1,000 μ m) with a sharp tip and jagged edge was successfully achieved.