Fabrication process for tall, sharp, hollow, high aspect ratio polymer microneedles on a platform (original) (raw)
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Journal of Microelectromechanical Systems, 2000
Drug delivery through micromachined needles is an attractive alternative to intramuscular and subdermal injection by hypodermic needles, due to the potential for reduced pain caused by the micro-sized needles. In this paper, a polymerbased fabrication process using UV lithography into micromolds is developed, allowing the fabrication of microneedle (MN) shafts, tips, lumens, and substrate baseplate using lithography. Using UV lithography into micromolds allows complex three-dimensional structures to be defined, since both mask patterns and mold topography are available to define the structures. A hollow MN array and baseplate, in which the needle lumens extend through the thickness of the baseplate, are demonstrated. Fabricated SU-8 MNs are 825 μm in height and 400 μm in width, with a pyramidal tip; the needle lumen, 120 μm in diameter, intersects with one of the faces of the pyramidal tip. Mechanical characterization of the fabricated MNs shows that the fracture force of a single needle against a rigid surface is 12.0 N. The insertion force of a single needle into porcine skin is empirically determined to be 2.4 N. The fracture force of the needle against porcine skin is observed to be in excess of 90 N.
Hypodermic-needle-like hollow polymer microneedle array using UV lithography into micromolds
2011
This paper presents a polymer hollow microneedle array for transdermal drug delivery that is fabricated using UV photolithography and a single-step micromolding technique. This fabrication process patterns a 6×6 array of 1mm tall high-aspect-ratio hollow microneedles with sharp beveled tips and 150μm diameter side-opened lumens. The geometry of the beveled tip and the position of the lumen are defined simultaneously by a two-dimensional lithography mask pattern and the topography of the micromold. This three-dimensional geometry improves insertion performance and potentially the drug delivery efficiency without additional fabrication processes. These hypodermic-needle-like microneedles have been successfully constructed, packaged, and tested for fluidic functionality and skin penetrability.
Integrated Lithographic Molding for Microneedle-Based Devices
Journal of Microelectromechanical Systems, 2007
This paper presents a new fabrication method consisting of lithographically defining multiple layers of high aspect-ratio photoresist onto preprocessed silicon substrates and release of the polymer by the lost mold or sacrificial layer technique, coined by us as lithographic molding. The process methodology was demonstrated fabricating out-of-plane polymeric hollow microneedles. First, the fabrication of needle tips was demonstrated for polymeric microneedles with an outer diameter of 250 µm, through-hole capillaries of 75-µm diameter and a needle shaft length of 430 µm by lithographic processing of SU-8 onto simple v-grooves. Second, the technique was extended to gain more freedom in tip shape design, needle shaft length and use of filling materials. A novel combination of silicon dry and wet etching is introduced that allows highly accurate and repetitive lithographic molding of a complex shape. Both techniques consent to the lithographic integration of microfluidic back plates forming a patchtype device. These microneedle-integrated patches offer a feasible solution for medical applications that demand an easy to use Point-of-Care sample collector, for example, in blood diagnostics for lithium therapy. Although microchip capillary electrophoresis glass devices were addressed earlier, here, we show for the first time the complete diagnostic method based on microneedles made from SU-8.
An overview of microneedle applications, materials, and fabrication methods
Beilstein Journal of Nanotechnology
Microneedle-based microdevices promise to expand the scope for delivery of vaccines and therapeutic agents through the skin and withdrawing biofluids for point-of-care diagnostics – so-called theranostics. Unskilled and painless applications of microneedle patches for blood collection or drug delivery are two of the advantages of microneedle arrays over hypodermic needles. Developing the necessary microneedle fabrication processes has the potential to dramatically impact the health care delivery system by changing the landscape of fluid sampling and subcutaneous drug delivery. Microneedle designs which range from sub-micron to millimetre feature sizes are fabricated using the tools of the microelectronics industry from metals, silicon, and polymers. Various types of subtractive and additive manufacturing processes have been used to manufacture microneedles, but the development of microneedle-based systems using conventional subtractive methods has been constrained by the limitations...
Transdermal drug delivery through microneedles is a minimally invasive procedure causing little or no pain, and is a potentially attractive alternative to intramuscular and subdermal drug delivery methods. This paper demonstrates the fabrication of a hollow microneedle array using a polymer-based process combining UV photolithography and replica molding techniques. The key characteristic of the proposed fabrication process is to define a hollow lumen for microfluidic access via photopatterning, allowing a batch process as well as high throughput. A hollow SU-8 microneedle array, consisting of 825 mum tall and 400 mum wide microneedles with 15-25 mum tip diameters and 120 mum diameter hollow lumens was designed, fabricated and characterized.
One-Shot Fabrication of Polymeric Hollow Microneedles by Standard Photolithography
Polymers, 2021
Microneedles (MNs) are an emerging technology in pharmaceutics and biomedicine, and are ready to be commercialized in the world market. However, solid microneedles only allow small doses and time-limited administration rates. Moreover, some well-known and already approved drugs need to be re-formulated when supplied by MNs. Instead, hollow microneedles (HMNs) allow for rapid, painless self-administrable microinjection of drugs in their standard formulation. Furthermore, body fluids can be easily extracted for analysis by a reverse use of HMNs, thus making them perfect for sensing issues and theranostics applications. The fabrication of HMNs usually requires several many-step processes, increasing the costs and consequently decreasing the commercial interest. Photolithography is a well-known fabrication technique in microelectronics and microfluidics that fabricates MNs. In this paper, authors show a proof of concept of a patented, easy and one-shot fabrication of two kinds of HMNs: ...
A review Recent Advanced of Fabrication Techniques and Application of Micro-Needle
Asian journal of pharmaceutical research and development, 2023
Micro-needles are micron-scaled medical devices used to administer vaccines, drugs, and other therapeutic agents. Micro-needles typically measure 0.1-1 mm in length. A variety of materials such as silicon, ceramic, stainless steel and polymers have been used for fabrication. Micro-needles devices are compatible with the delivery of both Small and macromolecular therapeutics. Microneedles (MNs) are currently being utilized to enhance transdermal delivery of small and large molecules. With the emergence of micro fabrication manufacturing technology over the past several decades, (MNs) have been developed by academic laboratories and pharmaceutical companies. Micro-needle has useful in application in diseases such as type 2 Diabetes, cancer treatment, Glaucoma, and also useful application in cosmetic, vaccine therapy. The present article provides an overview of micro-needle, fabrication technique, general properties, Material and methods of fabrication techniques, application and advantages and disadvantages of micro-needle drug delivery system. Micro-needles (MNs) are currently being utilized to enhance trans-dermal delivery of small and large molecules. With the emergence of micro fabrication manufacturing technology over the past several decades, have been developed by academic laboratories and pharmaceutical companies.
Microfabricated Polysilicon Microneedles for Minimally Invasive Biomedical Devices
2000
A two-wafer polysilicon micromolding process has been developed for the fabrication of hollow tubes useful for micro¯uidic applications. These small tubes can be fabricated with a pointed end, resulting in a micro hypodermic injection needle. Microneedles are desired because they reduce both insertion pain and tissue damage in the patient. Such microneedles may be used for low¯ow rate, continuous drug delivery, such as the continuous delivery of insulin to a diabetic patient. The needles would be integrated into a short term drug delivery device capable of delivering therapeutics intradermally for about 24 hours. In addition, microneedles can be used for sample collection for biological analysis, delivery of cell or cellular extract based vaccines, and sample handling providing interconnection between the microscopic and macroscopic world. The strength of microneedles was examined analytically, experimentally and by ®nite element analysis. Metal coatings provide signi®cant increases in the achievable bending moments before failure in the needles. For example, a 10 lm platinum coating increased the median bending moment of a 160 lm wide, 110 lm high microneedle with a 20 lm wall from 0.25 to 0.43 mNm. In addition,¯uid¯ow in microneedles was studied experimentally. Microneedles 192 lm wide, 110 lm high and 7 mm long have¯ow rates of 0.7 ml/sec under a 138 kPa inlet pressure. This¯ow capacity exceeds previous microneedle capacities by an order of magnitude.
Sharpening of hollow silicon microneedles to reduce skin penetration force
Journal of Micromechanics and Microengineering, 2010
In this research, hollow silicon microneedles with sharpened tips have been fabricated without any reduction to the needle shaft diameter. By sharpening the needles only at the tip and not over the entire length of the needle, their mechanical strength is maintained, while reducing the insertion force into skin. The process achieves this geometry by novel use photoresist depletion during DRIE. Microneedles of varying levels of tip sharpness were tested on human cadaver skin to measure their force of penetration. The results show a marked decrease of insertion force with progressive sharpening of microneedle tips, reducing more than 75 times in magnitude for extremely sharp tips. The toughness of human skin was derived to be approximately 24.28 kJ m −2 .