Fabrication Of Hollow Microneedles Research Articles

Fabrication of hollow microneedles with jagged edges mimicking mosquitoes’ needles using a thermal nanoimprinting method and 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 μm; height: 1,000 μm) with a sharp tip and jagged edge was successfully achieved.

One-Shot Fabrication of Polymeric Hollow Microneedles by Standard Photolithography.

Microneedles (MNs) are an emerging technology in pharmaceutics and biomedicine, and are ready to be commercialized in the world market. However, solid microneedles only allow small doses and time-limited administration rates. Moreover, some well-known and already approved drugs need to be re-formulated when supplied by MNs. Instead, hollow microneedles (HMNs) allow for rapid, painless self-administrable microinjection of drugs in their standard formulation. Furthermore, body fluids can be easily extracted for analysis by a reverse use of HMNs, thus making them perfect for sensing issues and theranostics applications. The fabrication of HMNs usually requires several many-step processes, increasing the costs and consequently decreasing the commercial interest. Photolithography is a well-known fabrication technique in microelectronics and microfluidics that fabricates MNs. In this paper, authors show a proof of concept of a patented, easy and one-shot fabrication of two kinds of HMNs: (1) Symmetric HMNs with a “volcano” shape, made by using a photolithographic mask with an array of transparent symmetric rings; and (2) asymmetric HMNs with an oblique aperture, like standard hypodermic steel needles, made by using an array of transparent asymmetric rings, defined by two circles, which centers are slightly mismatched. Simulation of light propagation, fabrication process, and preliminary results on ink microinjection are presented.