Development, Strength and Functional Evaluation of Plastic Microneedle Array Fabricated by Injection Molding

Yoshimura, Chisato; Ishikawa, Hiroyuki; Furuta, Shunsuke; Aoki, Hikoharu; Saito, Susumu

doi:10.1541/ieejsmas.124.387

Cited by 9 publications

(5 citation statements)

References 3 publications

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“…Although various authors had reported on the insertion or fracture forces of their fabricated micro-needles [7] or simulated results [8,9], few have actually shown the effect on the profile of the micro-needles after insertion. Typically, Davis [10] had shown that a micro-needle could fracture during insertion into the cadaver skin tested.…”

Section: Introductionmentioning

confidence: 99%

A systematic approach to fabricate high aspect ratio silicon micro-needles for transdermal drug delivery

Shearwood

2007

BioMEMS and Nanotechnology III

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The successful development of micro-needles can help transport drugs and vaccines both effectively and painlessly across the skin. However, not all micro-needles are strong enough to withstand the insertion forces and viscoelasticity of the skin. The work here focuses on the micro-fabrication of high aspect ratio needles with careful control of needleprofile using dry etching technologies. Silicon micro-needles, 150µm in length with base-diameters ranging from 90 to 240µm have been investigated in this study. A novel, multiple-sacrificial approach has been demonstrated as suited to the fabrication of long micro-needle bodies with positive profiles. The parameters that control the isotropic etching are adjusted to control the ratio of the needle-base diameter to needle length. By careful control of geometry, the needle profile can be engineered to give a suitable tip size for penetration, as well as a broad needle base to facilitate the creation of either single or multiple-through holes. This approach allows the mechanical properties of the otherwise brittle needles to be optimized. Finite element analysis indicates that the micro-needles will fracture prematurely due to buckling, with forces ranging from 10 to 30mN.

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Section: Introductionmentioning

confidence: 99%

A systematic approach to fabricate high aspect ratio silicon micro-needles for transdermal drug delivery

Shearwood

2007

BioMEMS and Nanotechnology III

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“…It mainly utilises a synchrotron radiation source of X-ray for lithography which is capable of achieving nano resolution due to its short wavelength [46]. However, to incorporate mass scale production techniques, the use of a LIGA mold is necessary and often results in a more blunt tip and shorter height of micro-needle [47] as shown in Table 2 [47] this defect could be due to the increase in resin viscosity during the filling process and also possible air trapped in the cavity.…”

Section: (B) Safetymentioning

confidence: 99%

“…proposed that micro-needles made from such biocompatible materials could also s fracture without any health hazards and needle tips could dissolve and break down in the blood stream [50]. However, the low tensile strength of polymeric materials may render them useless in drug delivery as well as the difficulty in attaining very sharp tips during mass molding techniques [47]. In addition, the equipment used for the master molds such as DEEP X-ray lithography is often expensive and requires special alignment techniques [46].…”

Section: V__>*umentioning

confidence: 99%

“…In particular, PMMA is the most common material being used for direct fabrication by deep X-ray lithography. A synchrotron radiation source is often being used with double or triple exposures adopting the PCT (plane pattern to cross section transfer) technique [40,47] or inclined X-ray exposure technique [20,86]. Although the fabricated micro-needles are very sharp and of controllable height, the alignment issues and expensive machine usage had lead to production of PMMA master molds instead for further mass production.…”

Section: Polymer Micro-needlesmentioning

confidence: 99%

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Fabrication of micro-needles for transdermal drug delivery

Ng¹

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Alternative means of delivering drugs such as insulin to patients sometimes include the usage of high voltage pulsing or electrical current. However, such systems are limited by their ability to push drugs across the stratum corneum at therapeutic rates. One promising solution could be the usage of a micron scale needle, to create micropores in the skin which can allow faster diffusion of drugs with greater molecular weight or polarity into the human body. In combination with a transdermal patch, an array of micro-needles can be created to enhance the intake of drugs as well. With rapid advancement in MEMS (Micro Electro Mechanical Systems), silicon micromachining had enabled the development of such devices and result in various micro-needle designs to date. In addition, micro-needles had been fabricated with the inclusion of a fluid channel along the structure to allow controlled diffusion rates. However, the steps in fabricating such structures are often complex which lowers the process reliability and repeatability. By further proposing certain fabrication protocols and improvising on the design of micro-needles, the process can be made simpler and result in more efficient manufacturing routes. An extensive study by researchers have revealed certain requirements of the microneedle during drug injection, various fabrication techniques for different kind of materials as well as the possibilities of mass manufacturing processes. These areas are widely investigated and a particular area of study uses the soft lithography techniques in fabricating polymeric micro-needles. This requires the fabrication of a master mold either from silicon or commonly nickel. The research focus in this report is devoted to fabricating an array of silicon micro-needles which can double as usages for direct drug applications or as master molds for soft molding. A novel, multiple-sacrificial approach has been demonstrated as suited to the fabrication of at least 150um long micro-needle bodies with positive profiles. By changing the mask design for base diameters from 90um to 240um, the needle profile can be engineered to give a suitable tip size for penetration, as well as a broad needle base to facilitate the creation of either single or multiple-through holes. This approach allows the mechanical properties of the otherwise brittle needles to be optimized up to buckling loads of 28mN. In i ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library comparison, silicon micro-needles had also been tested to be painless which is consistent with literature review and capable of skin penetration. Based on the experimental investigations and finite element simulations presented in this report, the objectives of creating and utilizing silicon microneedles had been met and various future work proposed. These include soft lithography on silicon microneedles, in vitro testing on humans, rats and porcine skin samples for feasibility of silicon micro-needles and finite element modeling of mi...

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“…To address this, polymers are increasingly being examined as an alternative material from which to manufacture these needles. In particular, molding techniques such as hot embossing [3], casting [4] and injection molding [5,6] show promise as viable techniques.…”

Section: Introductionmentioning

confidence: 99%

In-Plane, Hollow Microneedles Via Polymer Investment Molding

Lippmann

Pisano

19th IEEE International Conference on Micro Electro Mechanical Systems

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Investment molding is used to create hollow, in-plane, polymer microneedles. Sacrificial investment pieces (.32 µm-diameter aluminum bond wires) are bonded into silicon micromachined molds. Needles are formed by filling these molds with Cyclic Olefin Copolymer (Ticona Topas ® ) using an injection molding machine. These needles are immersed in etchant, dissolving the investment and leaving a hollow part. Two micromachining techniques are used to make molds, RIE and KOH. The RIE molds deliver microneedles 280 µm in length with rectangular (130 µm x 100 µm) crosssections and inner diameter of ~35 µm. The KOH molds are used to create 300 µm long microneedles with 150 µm wide triangular shafts with tapered tips.

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Development, Strength and Functional Evaluation of Plastic Microneedle Array Fabricated by Injection Molding

Cited by 9 publications

References 3 publications

A systematic approach to fabricate high aspect ratio silicon micro-needles for transdermal drug delivery

A systematic approach to fabricate high aspect ratio silicon micro-needles for transdermal drug delivery

Fabrication of micro-needles for transdermal drug delivery

In-Plane, Hollow Microneedles Via Polymer Investment Molding

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