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Fabrication of sharp silicon hollow microneedles by deep-reactive ion etching towards minimally invasive diagnostics

Yan Li1Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 CanadaHang Zhang1Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 CanadaRuifeng Yang1Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 CanadaYohan LaffitteExVivo Labs Inc., 3 Regina Street North, Waterloo, ON N2J 2Z7 CanadaUlises SchmillExVivo Labs Inc., 3 Regina Street North, Waterloo, ON N2J 2Z7 CanadaWenhan Hu1Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 CanadaMoufeed KaddouraExVivo Labs Inc., 3 Regina Street North, Waterloo, ON N2J 2Z7 CanadaEric J. M. BlondeelExVivo Labs Inc., 3 Regina Street North, Waterloo, ON N2J 2Z7 CanadaBo Cui1Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 Canada

2019en

ABI

Annotatsiya

Microneedle technologies have the potential for expanding the capabilities of wearable health monitoring from physiology to biochemistry. This paper presents the fabrication of silicon hollow microneedles by a deep-reactive ion etching (DRIE) process, with the aim of exploring the feasibility of microneedle-based in-vivo monitoring of biomarkers in skin fluid. Such devices shall have the ability to allow the sensing elements to be integrated either within the needle borehole or on the backside of the device, relying on capillary filling of the borehole with dermal interstitial fluid (ISF) for transporting clinically relevant biomarkers to the sensor sites. The modified DRIE process was utilized for the anisotropic etching of circular holes with diameters as small as 30 μm to a depth of >300 μm by enhancing ion bombardment to efficiently remove the fluorocarbon passivation polymer. Afterward, isotropic wet and/or dry etching was utilized to sharpen the needle due to faster etching at the pillar top, achieving tip radii as small as 5 μm. Such sharp microneedles have been demonstrated to be sufficiently robust to penetrate porcine skin without needing any aids such as an impact-insertion applicator, with the needles remaining mechanically intact after repetitive penetrations. The capillary filling of DRIE-etched through-wafer holes with water has also been demonstrated, showing the feasibility of use to transport the analyte to the target sites.

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DOI: 10.1038/s41378-019-0077-y

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