Drawing Lithography: Three‐Dimensional Fabrication of an Ultrahigh‐Aspect‐Ratio Microneedle

Lee, Kwang; Lee, Hyun Chul; Lee, Dae Sik; Jung, Hyungil

doi:10.1002/adma.200902418

Cited by 165 publications

(65 citation statements)

References 27 publications

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“…To date, it has been applied to polystyrene 11 , PMMA 12 , PTT 13 , nylon 14 , sucrose 15 , polyurethane 16 , SU-8 (ref. 17) and adhesives 18 . Its application to PDMS, however, has not been reported due mainly to the material's softness and slow solidification rate.…”

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confidence: 99%

Microsphere-assisted fabrication of high aspect-ratio elastomeric micropillars and waveguides

Paek

Kim

2014

Nat Commun

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High aspect-ratio micropillars are in strong demand for microtechnology, but their realization remains a difficult challenge, especially when attempted with soft materials. Here we present a direct drawing-based technique for fabricating micropillars with poly(dimethylsiloxane). Despite the material's extreme softness, our technique enables routine realization of micropillars exceeding 2,000 mm in height and 100 in aspect-ratio. It also supports in situ integration of microspheres at the tips of the micropillars. As a validation of the new structure's utility, we configure it into airflow sensors, in which the micropillars and microspheres function as flexible upright waveguides and self-aligned reflectors, respectively. Highlevel bending of the micropillar under an airflow and its optical read-out enables mm s À 1 scale-sensing resolution. This new scheme, which uniquely integrates high aspect-ratio elastomeric micropillars and microspheres self-aligned to them, could widen the scope of soft material-based microdevice technology.

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confidence: 99%

Microsphere-assisted fabrication of high aspect-ratio elastomeric micropillars and waveguides

Paek

Kim

2014

Nat Commun

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“…Another interesting tweak in SU-8 lithography is "drawing lithography" [37]. This is not a traditional UV lithography technique, but utilizes mechanical pulling of soft-baked (at 120 °C) SU-8 layer to create extremely tall (~2 mm) high aspect ratio (>100:1) microneedles.…”

Section: Drawing Lithographymentioning

confidence: 99%

Innovative SU-8 Lithography Techniques and Their Applications

2014

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SU-8 has been widely used in a variety of applications for creating structures in micro-scale as well as sub-micron scales for more than 15 years. One of the most common structures made of SU-8 is tall (up to millimeters) high-aspect-ratio (up to 100:1) 3D microstructure, which is far better than that made of any other photoresists. There has been a great deal of efforts in developing innovative unconventional lithography techniques to fully utilize the thick high aspect ratio nature of the SU-8 photoresist. Those unconventional lithography techniques include inclined ultraviolet (UV) exposure, back-side UV exposure, drawing lithography, and moving-mask UV lithography. In addition, since SU-8 is a negative-tone photoresist, it has been a popular choice of material for multiple-photon interference lithography for the periodic structure in scales down to deep sub-microns such as photonic crystals. These innovative lithography techniques for SU-8 have led to a lot of unprecedented capabilities for creating unique micro-and nano-structures. This paper reviews such innovative lithography techniques developed in the past 15 years or so.

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“…To simplify the fabrication process of microneedle arrays, various micromanufacturing methods, including drawing lithography [5][6][7] , deep X-ray lithography of Lithographie Galvanoformung Abformung (LIGA) 8,9 , and ultraviolet (UV) lithography [10][11][12][13][14][15] , have been studied. Compared with other methods, UV lithography provides a simple, easily accessible, and conventional fabrication process for the creation of wide-area microneedle arrays.…”

Section: Introductionmentioning

confidence: 99%

Scalable fabrication of microneedle arrays via spatially controlled UV exposure

et al. 2016

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This paper describes a theoretical estimation of the geometry of negative epoxy-resist microneedles prepared via inclined/rotated ultraviolet (UV) lithography based on spatially controlled UV exposure doses. In comparison with other methods based on UV lithography, the present method can create microneedle structures with high scalability. When negative photoresist is exposed to inclined/rotated UV through circular mask patterns, a three-dimensional, needle-shaped distribution of the exposure dose forms in the irradiated region. Controlling the inclination angles and the exposure dose modifies the photo-polymerized portion of the photoresist, thus allowing the variation of the heights and contours of microneedles formed by using the same mask patterns. In an experimental study, the dimensions of the fabricated needles agreed well with the theoretical predictions for varying inclination angles and exposure doses. These results demonstrate that our theoretical approach can provide a simple route for fabricating microneedles with on-demand geometry. The fabricated microneedles can be used as solid microneedles or as a mold master for dissolving microneedles, thus simplifying the microneedle fabrication process. We envision that this method can improve fabrication accuracy and reduce fabrication cost and time, thereby facilitating the practical applications of microneedle-based drug delivery technology.

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Drawing Lithography: Three‐Dimensional Fabrication of an Ultrahigh‐Aspect‐Ratio Microneedle

Cited by 165 publications

References 27 publications

Microsphere-assisted fabrication of high aspect-ratio elastomeric micropillars and waveguides

Microsphere-assisted fabrication of high aspect-ratio elastomeric micropillars and waveguides

Innovative SU-8 Lithography Techniques and Their Applications

Scalable fabrication of microneedle arrays via spatially controlled UV exposure

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