This study was supported by a Singapore National Research Foundation (NRF) Grant NRF2012NRF-POC001-043.

1. Photomask Fabrication
<ol>
	<li>Clean a 4&#8221; glass wafer with piranha solution (H2SO4/H2O2 in 2:1 ratio) for 20 min at 120 &#176;C by immersion in a quartz tank.</li>
	<li>Deposit a layer of Chromium/Gold (30 nm of Cr/1 &#181;m of Au) layer on the glass wafer using an e-beam evaporator7 (Figure 1A).
	<ol>
		<li>Place the wafers in an e-beam evaporator. Once the vacuum reaches 5 x 10-6 Torr, turn on the high voltage source (10 kV)....

<ol>
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The protocol described above for fabrication of the MNs array has been presented to fabricate the MNs array of ~1 cm2. The arrays can be scaled up by creating a large size cavity and by using a larger photomask. The increased cavity size can be created by increasing the width between the spacers on either side. Though each step to fabricate the MN arrays in the protocol was important, the most crucial steps were: the photomask positioning, the filling of prepolymer solution, and irradiation of the setup. Posit...

Transdermal drug delivery offers an attractive alternative approach for drug administration, especially for biomolecules, which are almost exclusively administered by hypodermic injections. However, skin, especially the top layer (the stratum corneum), is a formidable barrier preventing exogenous molecules from entering the human body. Recently, MN devices have emerged as enabling tools to deliver drugs through skin. The MN devices create temporary pores inside the stratum corneum to allow the passage of drug molecules to achieve the desired physiological activity with improved patient compliance and convenience1-3.
Various fabrication methods have been adopted to fabricate polymeric MNs4. However, they usually involve complicated and multiple step processes requiring long times and/or high temperatures to fabricate MNs arrays.4 To simplify the fabrication process, a single step mold-free process using a photomask was developed recently5,6. However, with this method, fabricated MNs had blunt needle tips, as no mechanism was in place to modify the ultraviolet (UV) light path involved in photolithography.
In this study, embedded microlenses in the photomask have been proposed to define the geometry of the MNs. The protocol to fabricate photomasks consisting of embedded microlenses and subsequently MN fabrication with sharp tips using the photomask are reported.

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			<td>Poly(ethylene glycol) diacrylate (PEGDA Mn=258)</td>
			<td>SIGMA&#160;</td>
			<td>475629-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>2-hydroxy-2-methyl-propiophenone (HMP)</td>
			<td>SIGMA&#160;</td>
			<td>405655-50ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine collagen type 1, FITC conjugate&#160;</td>
			<td>SIGMA&#160;</td>
			<td>C4361</td>
			<td></td>
		</tr>
		<tr>
			<td>UV curing station&#160;&#160;&#160;</td>
			<td>EXFO Photonic Solutions Inc., Canada</td>
			<td>OmniCure S200-XL</td>
			<td></td>
		</tr>
		<tr>
			<td>Collimating Adaptor&#160;</td>
			<td>EXFO Photonic Solutions Inc., Canada</td>
			<td>EXFO 810-00042</td>
			<td></td>
		</tr>
		<tr>
			<td>24-well plate</td>
			<td>Thermo Fisher Scientific, USA</td>
			<td></td>
			<td></td>
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			<td>Nikon SMZ 1500 stereomicroscope&#160;</td>
			<td>Nikon, Japan</td>
			<td></td>
			<td></td>
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			<td>Dillon GL-500 digital force gauge&#160;</td>
			<td>Dillon, USA</td>
			<td></td>
			<td></td>
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			<td>A-1R confocal microscope&#160;</td>
			<td>Nikon, Japan</td>
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polymeric microneedle array fabrication by photolithography

This manuscript describes the fabrication of polymeric microneedle (MN) arrays by photolithography. It involves a simple mold-free process by using a photomask consisting of embedded micro-lenses. Embedded micro-lenses were found to influence MN geometry (sharpness). Robust MN arrays with tip diameters ranging between 41.5 &#181;m &#177; 8.4 &#181;m and 71.6 &#181;m &#177; 13.7 &#181;m, with two different lengths (1,336 &#181;m &#177; 193 &#181;m and 957 &#181;m &#177; 171 &#181;m) were fabricated. These MN arrays may provide potential applications in delivery of low molecular and macromolecular therapeutic agents through skin.

The geometry of the MNs can be significantly affected by the photomask characteristics and embedded microlens. The degree of refraction affects the transmission path of the UV rays, which influenced the MN geometry (Figure 2A). Each microlens was found to have a 350 &#181;m diameter, a 130 &#181;m flattened convex surface, and a 62.3 &#181;m depth (Figure 2B-D). Using the Pythagoras theorem, the radius of curvature of the first surface was found to be 272.89 &#181;m. The focal length was...

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Polymeric Microneedle Array Fabrication by Photolithography

Here, we present a protocol describing a mold-free fabrication process of the polymeric microneedles by photolithography.

This manuscript describes the fabrication of polymeric microneedle (MN) arrays by photolithography. It involves a simple mold-free process by using a ...

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11.8K vistas.  National University of Singapore. Here, we present a protocol describing a mold-free fabrication process of the polymeric microneedles by photolithography. 