High-fidelity replication of thermoplastic microneedles with open microfluidic channels

Abstract

Development of microneedles for unskilled and painless collection of blood or drug delivery addresses the quality of healthcare through early intervention at point-of-care. Microneedles with submicron to millimeter features have been fabricated from materials such as metals, silicon, and polymers by subtractive machining or etching. However, to date, large-scale manufacture of hollow microneedles has been limited by the cost and complexity of microfabrication techniques. This paper reports a novel manufacturing method that may overcome the complexity of hollow microneedle fabrication. Prototype microneedles with open microfluidic channels are fabricated by laser stereolithography. Thermoplastic replicas are manufactured from these templates by soft-embossing with high fidelity at submicron resolution. The manufacturing advantages are (a) direct printing from computer-aided design (CAD) drawing without the constraints imposed by subtractive machining or etching processes, (b) high-fidelity replication of prototype geometries with multiple reuses of elastomeric molds, (c) shorter manufacturing time compared to three-dimensional stereolithography, and (d) integration of microneedles with open-channel microfluidics. Future work will address development of open-channel microfluidics for drug delivery, fluid sampling and analysis.

A method for large-scale implantation of 3D microdevice ensembles into brain and soft tissue

“…We produced arrays of needles using IP-S photoresist (Nanoscribe IP-S, Nanoscribe GmbH) at a 1 µm process resolution, with each needle measuring 125 µm by width and 550 µm by height at a 500 µm separation between needles (center-to-center). For additional details of this process, refer to the methods of Faraji Rad et al 34 Molding of PEG Molds adopting the shape of the microfabricated stamps were formed using PDMS (Sylgard 184, Dow Corning, Michigan, USA), which was mixed at a 1:7 ratio of hardener to elastomer for adequate stiffness. Once degassed, the PDMS was cured at 50°C for 6 h to form a mold around the selected stamp, and each mold was then annealed at 120°C for 24 h after the stamp was retrieved.…”

A method for large scale implantation of 3D microdevice ensembles into brain and soft tissue

“…We produced arrays of needles using the IP-S photoresist (Nanoscribe IP-S, Nanoscribe GmbH) at 1 m process resolution, with each needle measuring 125 m by width and 550 m by height at 500 m separation between needles (center-to-center). The details of the process resemble those reported by Faraji Rad et al 22 This method of stamp microfabrication was explored as a more accessible and customizable option for custom stamp fabrication over the silicon based process. The silicon microfabrication process had the advantage in terms of throughput however as the nanoprinting process, by currently available moderate throughput and moderate cost equipment, would take several hours to produce even a relatively small stamp form factor (6×6 array, short needles).…”

Simple and customizable method for fabrication of high-aspect ratio microneedle molds using low-cost 3D printing

“…Vat photopolymerization-based AM methods in which a liquid photopolymer vat is selectively cured using light also display better resolution compared with FFF. Certain vat photopolymerization-based methods have been shown to directly print very sharp microscale needles, including two-photon polymerization 39,40 and continuous liquid interface production 36 . However, these methods are costly, not readily available and therefore not convenient for in-house microneedle manufacture by most researchers interested in microneedle applications.…”