|Publication number||US20060015061 A1|
|Application number||US 10/994,105|
|Publication date||19 Jan 2006|
|Filing date||19 Nov 2004|
|Priority date||16 Jul 2004|
|Also published as||US7712198, US20070233016|
|Publication number||10994105, 994105, US 2006/0015061 A1, US 2006/015061 A1, US 20060015061 A1, US 20060015061A1, US 2006015061 A1, US 2006015061A1, US-A1-20060015061, US-A1-2006015061, US2006/0015061A1, US2006/015061A1, US20060015061 A1, US20060015061A1, US2006015061 A1, US2006015061A1|
|Inventors||Shih-Chi Kuo, Yu-Kon Chou|
|Original Assignee||Shih-Chi Kuo, Yu-Kon Chou|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (18), Classifications (14), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention generally relates to a microneedle array structure, and more specifically to a microneedle array device, and a method of forming the same.
The current microneedle array may be made of silicon (Si substrate), metal or polymer. The manufacturing methods of Si substrate microneedle array can further be categorized as using wet etching or dry etching. The manufacturing process of metal microneedle array can further be categorized as using electroplating or deposition. The manufacturing process of polymer microneedle array can be further categorized as using molding or photolithography.
Among the methods of microneedle array, the most widely adopted is using Si substrate to fabricate the hollow needles or mold. However, the fabrication process of using Si substrate is more complicated, as disclosed in WO0217985, and requires many steps of wet/dry etching and thin film deposition. As it takes a longer time to fabricate, the yield rate is low and the cost is high. U.S. Pat. No. 6,334,856 disclosed a method of fabricating a microneedle array having flat needle tips and tapered tube, as shown in
The tip of the hollow microneedle in most prior arts is designed as flat, except the design disclosed in WO0217985 (see
Kim et al. disclosed a method for fabricating metal microneedle array in Journal of Micromechanics and Micro engineering in 2004. They spread two layers of SU-8 on a glass substrate and used a back exposure to separately bake the two layers of SU-8. They also used reactive ion etching to obtain an SU-8 pillar array structure, and then used sputtering, electroplating, planarization and polishing to fabricate a tapered metal hollow microneedle array, as shown in
U.S. Pat. No. 6,663,820 disclosed another method of using lithography and photolithography to fabricate polymer microneedle array, as shown in
Numerous methods of fabricating microneedle array have been proposed. Regardless of the material used, the object of the microneedle array includes the capability to penetrate the human skin for micro-injection or micro-sampling painlessly, easy to fabricate, low in fabrication cost and safe to use.
The present invention has been made to overcome the aforementioned drawback of conventional bonding methods of fabricating microneedle array. The primary object of the present invention is to provide a microneedle array device, including a supporting pad and a plurality of microneedles. The supporting pad has an upper surface. Each microneedle has a slant or concave top portion with a via thereon, thereby the microfluid may flow in or out. The intersection between the top portion and the inner tube of a microneedle forms a convex needle structure. Each microneedle stands on the upper surface of the supporting pad and is almost perpendicular to the upper surface. A hollow closed tube is formed between the top portion and the supporting pad.
The supporting pad further includes a bottom portion and at least a layer of reservoir. The reservoir is located above the bottom portion and below the microneedle. The reservoir can be further divided, if necessary, into a plurality of reservoir units, with reservoir units separated from one another to prevent the microfluid flowing from one unit to another. The monolithic metal structure of the present invention includes convex needle structure formed by the intersection of the slant or concave top portion of each microneedle and the inner tube of a microneedle. The main feature of the present invention includes the safety of use and the improvement of pain. Furthermore, the rigidity and the slant uniformity of the microneedle with slant top portion are both improved so that it is suitable for molding and mass production.
Another object of the present invention is to provide a method of fabricating a microneedle array device, including the steps of: (1) providing a substrate, and forming a plurality of concave areas on a surface of the substrate; (2) spreading a layer of photo-sensitive material on the substrate and covering a layer of light transmission material on top of the photo-sensitive material; (3) using a patterned mask for exposing and lithography of the light transmission material to obtain a polymer hollow microneedle array mold based on the light transmission material; and (4) using the polymer hollow microneedle array mold to form a microneedle array device.
According to the present invention, there are several techniques to be used in step (1) of forming a plurality of concave areas, including etching, X-ray photo-etching, ultra-violet etching, ion beam etching and excimer laser micromachining. Step (4) of the method further includes the following substeps: (4a) coating a layer of metal on the outer surface of the polymer hollow microneedle array mold and the light transmission material to form a microneedle array; and (4b) removing the polymer hollow microneedle array mold from the microneedle array. In step (4), the techniques for coating metal to the surface of the polymer hollow microneedle array mold include electroplating, electroless plating, evaporation, and sputtering. The metal used can be Cu, Cr, Ni, Fe, Au, Pt, Pd, stainless steel and their alloys. The present invention uses the coating of photo-sensitive polymer on the concave areas of the substrate and covering with a light transmission material, which is exposed to define an outline of the microneedle and using lithography to obtain a polymer hollow microneedle array mold using the high light transmission material as the base for further fabrication of a metal microneedle array. The advantages of the fabrication method of the present invention are simple process and low in cost.
The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings.
As shown in
Before the coating of photo-sensitive material 720, a sacrificial layer or mold release layer 715 is coated on top of substrate 700 for the subsequent mold release, as shown in
The next step is to spread a photo-sensitive material 720 on top of sacrificial layer 715, and a light transmission material 730 on top of photo-sensitive material layer 720, as shown in
The next step is exposure and lithography to obtain a polymer hollow microneedle array mold 760 using light transmission material 730 as a base. As shown in
Finally, polymer hollow microneedle array mold 760 is used to form a microneedle array device 50, as shown in
Similarly, before the coating of metal layer 780 in sub-step (a), a sacrifical layer or mold release layer 770 is deposited on the outer surfaces of polymer hollow microneedle array mold 760 and light transmission material layer 730, and a starting layer 771 (
In sub-step (a), the electroplating, electroless plating, evaporation and sputtering is used to plate metal layer 780 on the upper surface (
In sub-step (b), the technique for removing polymer hollow microneedle array mold 760 from microneedle array device 50 is to remove sacrificial layer 770 deposited on the outer surfaces of polymer hollow microneedle array mold 760 and light transmission material layer 730. The technique includes oxygen plasma removal, thermal removal, solvent removal, aqueous removal or photo-degradation removal.
Similarly, microneedle array device 100 in
The fabrication method of the second embodiment is similar to that of first embodiment. The only difference is in the exposure and development step. Because the second embodiment has a reservoir layer 91 in the structure, the second embodiment requires an additional exposure than the first embodiment. During the second exposure, a corresponding patterned mask 750 a is used to define reservoir layer 91 and the shape of reservoir units 93 within. By adjusting the exposure dosage to control the depth “a” of the reservoir layer, the result of this step is to obtain a polymer hollow microneedle array mold 160. The remaining steps of the fabrication are identical to those in
The fabrication method of the third embodiment is also similar to that of first embodiment The only difference is still in the exposure and development step. Similarly, because the third embodiment has two more reservoir layers 101 in the structure, the third embodiment requires two additional exposures than the first embodiment. During the second and third exposures, a corresponding patterned mask 750 a, 750 b is used to define, respectively, each reservoir layer 101 and the shape of reservoir units 103 within. By adjusting the exposure dosage to control the depths “a” and “b” of the reservoir layers, the result of this step is to obtain a polymer hollow microneedle array mold 260. Therefore, according to the present invention, the first exposure is to form the shape and the structure of the microneedles, and the second and subsequent exposures are for forming the shape and the structure of the reservoir layer. The remaining steps of the fabrication are identical to those in
In summary, compared to the other molding techniques, the present invention directly applies photo-sensitive polymer on the concave areas of the substrate to form a polymer hollow microneedle array mold having slants and concave curvy surface. Then, the polymer hollow microneedle array mold is used with the evaporation and electroplating techniques to fabricate metal microneedle array device. This method greatly reduces the complexity of the fabrication and the cost of the material. The metal microneedle array electroplated on the polymer hollow microneedle array mold has a good rigidity and slant uniformity, and is suitable for mass production. The present invention may be widely used in blood sampling, micro-sampling and medication injection systems.
Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
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|U.S. Classification||604/47, 604/173|
|Cooperative Classification||Y10T29/308, Y10T29/302, Y10T29/304, Y10T29/49982, A61M37/0015, A61M2037/0053, B81B2201/055, B81C1/00111, A61B17/205|
|European Classification||A61B17/20B, B81C1/00C2T|
|19 Nov 2004||AS||Assignment|
Owner name: INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE, TAIWAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KUO, SHIH-CHI;CHOU, YU-KON;REEL/FRAME:016017/0963
Effective date: 20040901