Hollow microneedles for intradermal injection fabricated by sacrificial micromolding and selective electrodeposition

Abstract

Limitations with standard intradermal injections have created a clinical need for an alternative, low-cost injection device. In this study, we designed a hollow metal microneedle for reliable intradermal injection and developed a high-throughput micromolding process to produce metal microneedles with complex geometries. To fabricate the microneedles, we laser-ablated a 70 μm × 70 μm square cavity near the tip of poly(lactic acid-co-glyoclic acid) (PLGA) microneedles. The master structure was a template for multiple micromolded PLGA replicas. Each replica was sputtered with a gold seed layer with minimal gold deposited in the cavity due to masking effects. In this way, nickel was electrodeposited selectively outside of the cavity, after which the polymer replica was dissolved to produce a hollow metal microneedle. Force-displacement tests showed the microneedles, with 12 μm thick electrodeposition, could penetrate skin with an insertion force 9 times less than their axial failure force. We injected fluid with the microneedles into pig skin in vitro and hairless guinea pig skin in vivo. The injections targeted 90% of the material within the skin with minimal leakage onto the skin surface. We conclude that hollow microneedles made by this simple microfabrication method can achieve targeted intradermal injection.

Rapid prototyping of multi-scale biomedical microdevices by combining additive manufacturing technologies

“…This shrinking can be reduced to values of around 1-2 % by incorporating some additional outer pillars connected to the surface. These pillars act as support structures and absorb stress, as previous research has shown (Norman et al 2013).…”

“…for micromolding (Norman et al 2013), and they can be Fig. 4 Overview of the multiscale biomedical microsystem, with the outer structure obtained using the Heidelberg Laser Writer and with the textured channels obtained using the NanoScribe system …”

Feasibility Study of Carbon Nanotube Microneedles for Rapid Transdermal Drug Delivery

“…Typical master structures for micromolding are fabricated by micromachining or laser drilling of a bulk material which can be time consuming and ultimately limits the minimum feature size of the needle [1,9]. However after the master structure is complete, the micromolding process allows for fast fabrication of large numbers of microneedles.…”

An array of individually addressable micro-needles for mapping pH distributions

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Silicon has been used predominantly for fabrication of microneedles, however the fragility and the cost of the microfabrication process are major drawbacks for this material. [1][2][3][4] Injection molding has instead emerged as an alternative fabrication process offering advantages such as cost and robustness. 16,17 Microneedles can offer minimally invasive tools in the field of analytic a l science for example in order to achieve high-density chemical mapping thus to measure chemical heterogeneities in biological systems such as in tissues and organs.…”