WO2009064164A2 - Method for fabricating microneedles and microneedle fabricated from the same - Google Patents

Abstract

This invention relates to a method of fabricating microneedles using dry etching methods on a silicon based material and more particularly a method of fabricating hollow out-of-plane microneedles which are arranged in a single row of at least two microneedles. The fabrication process comprises of multiple steps involving reactive ion etching (RJE) isotropic and deep reactive ion etching (DRIE) anisotropic processes. The process involved only dry etching and the isotropic process step particularly, includes Plasma Etch.

Description

METHOD FOR FABEICATING MICRONEEDLES AND MICRONEEDLE FABRICATED FROM THE SAME

1. TECHNICAL FIELD OF THE INYENTION

The present invention relates generally to a method of fabricating microneedles, and more particularly to a method of fabricating microneedles via isotropic and anisotropic etching process. The present application also relates to microneedles fabricated from the same.

2. BACKGROUND OF THE INVENTION

Much research has been directed towards the development of microneedles formed on chips or wafers by use of mioro-macbining techniques.

This approach promises the possibility of producing numerous, very small needles which are sufficient to form small perforations in the dermal barrier- thereby overcoming the molecular size limitations of conventional transdermal patches, while being safe for use by for example unqualified personnel.

Targeted drug delivery or the application of a high concentration of one or more drugs to a specific target area within the body has become of paramount importance to the fight against tumors, restentosis and similar life threatening medical conditions. Generally, these target areas are reachable through the walls of the blood vessels of the body. Present systems use a catheter with an imaging device to locate the target area. Once located, a specific drug or drugs are delivered to the targeted vessel wall area. But, this process may have serious problems.

fe One approach provides a drug inside a perforated balloon at the end of the catheter. When the balloon reaches the target area, it is inflated causing the drug to be released through the perforations of the balloon locally around the targeted walls of the vessel. This perfusion of the drag at the surface of the vessel walls relies heavily on the drug being absorbed quickly and efficiently by the vessel walls at the target area.

However, in some cases the drug may not be absorbed by the vessel walls very effectively. In these cases, the drug may be caused to move downstream with the blood stream which may cause adverse medical effects to portions of the body not intended to receive the drugs, especially at such high concentrations. The drugs may also be diluted in this delivery process and lose their effectiveness. In any event, these relatively expensive drugs may not be achieving their intended purpose.

What is needed for effective drug delivery is an array of microneedles of sufficient length which may be deployed to the target site within the body and adequately penetrate the vessel walls thereat to permit the drug to effectively act on the target area at the high concentrations intended. Such an array structure may also be used transdermally for drug delivery as well.

Generally in pattern transfer technologies to characterize tapered or isotropic profile, the best method known is wet etch, however it is the difficult to control especially the uniformity and profile of etch product. Furthermore current technologies require miniature device applications and it is challenging in wet etch process.

The conventional method of venepuncture using hypodermic needle and syringe created several physical consequences such as insertion pain, skin irritation and damage to the needle because of penetration of vast needle sizes. Therefore, new interface device between human skin and microsystem has to be developed to control or at least able to eliminate the physical impairment and increasing the efficiency of blood extraction system. Microneedles could be one of the possible solutions. 3. SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a method of fabricating microneedles using dry etching of silicon to solve the above- mentioned problems.

It is another object of the present invention to provide a method a miniature hypodermic needle which harmless to human body.

It is another object of the present invention to provide a microneedles having, high efficiency of blood extraction from human body.

These and other objects of the present invention are achieved by,

A method of fabricating hollow out-of-plane microneedles, said method comprises the step of:-

preparing a silicon substrate (1) with an etch resistant mask layer (2), said etch resistant mask layer ^"(2) is formed on a first side of said silicon substrate

(D;

performing deep reactive ion etching (DRIB) anisotropic process on said first side to form microneedle hollow (3);

forming a second etch resistant mask layer (4) on the adjacent side of said silicon substrate (1);

performing deep reactive ion etching (DRIE) anisotropic process on said adjacent side of said silicon substrate (1) to form micorneedle shaft (5);

forming a third etch resistant mask layer (6) on said adjacent side of said silicon substrate (1) having said microneedle shaft (5); performing reactive ion etching (RIE) isotropic process on said adjacent side of said silicon substrate (1) to form tapered profile of said microneedle shaft (5); and

wafer bonding a silicon substrate (7) on the first side of said silicon substrate (1) to provide microneedle shaft base (8) thus forming an array of formed microneedles;

characterized in that,

said formed microneedles are arranged in single row of at least two microneedles.

Preferably, said microneedle hollow (3) and microneedle shaft (5) are formed through the process of anisotropic directional dry etching process.

4. BRIEF DESCRIPTION OF THE DRAWINGS

Other aspect of the present invention and their advantages will be discerned after studying the Detailed Description in conjunction with the accompanying drawings in which :

FIG. 1 shows FESEM cross-section image of tapered etch profile using Plasma Etch.

FIG. 2 shows FESEM cross-section image of isotropic etch profile using Plasma Etch.

FIG. 3 shows fabrication process flow of an aligned of hollow out-of-plane microneedles according to the present invention.

FIG. 4 shows cross-section view of a hollow out-of-plane microneedle. D. DETAIL DESCRIPTION OE THE DRAWINGS

In recent years, technology in medical applications has encouragingly progressed which- have been benefited, which includes artificial limbs, surgical instrumentations, drug delivery, pacemakers, circumcision devices and many more. Microelectromechanical systems (MEMS) is the technology of the very small, and merges at the nano-scale into nanoelectromechanical systems (NEMS) and Nanotecbnology. MEMS are also referred to as micro machines, or Micro Systems Technology (MST). MEMS structures and system are miniature devices that enable the operation of complex system. They exist today in many environments especially automotive, medical, consumer, industrial and aerospace. Microneedles for medical application could be one of these MEMS devices.

In the present invention, a method for fabricating a microneedle using dry etching such as Plasma Etch, -Reactive Ion Etching (RIB) and Deep Reactive Ion Etching (DRIE) has been developed. The development of this method can be an alternative to the conventional method which uses wet etch in pattern transfer technologies.

In its application, the fabricated microneedles could be used to assure enhancement of the conventional blood extraction system by concentrating on the physical consequerj.ce in medical field and increasing the efficiency of the blood extraction system. A new blood extraction system that minimally invasive, able to control physical consequences such as pain, skin irritation and trauma has been developed using dry etching process mentioned above.

Now referring to the figures. As depicted in Figure 1 and Figure 2, microneedles generally include a hollow shaft with tapered sharp tip and their dimensions could be in micrometer range. Ia this respect, Figure 1 shows

FESEM cross-section image of tapered etch profile using Plasma Etch and Figure 2 shows FESEM cross-section image of isotropic etch profile using Plasma Etch.

The fabrication methods of an aligned three needles preferably hollow σut-of-plane microneedles is shown in Figure 3. Silicon is the material used to create most integrated circuits used in consumer electronics and such silicon is preferably used for the present invention. A silicon substrate (1) is first prepared having an etch resistant mask layer (2) on one side of the silicon substrate (1). Microneedle hollow shaft (3) is created by pejforming deep reactive ion etching (DRIE) anisotropic process on the first side of the silicon substrate (1).

A second etch resistant mask layer (4) is formed on the adjacent side of the silicon substrate (1). Then to form microneedle shaft (5), deep reactive ion etching (DREE) anisotropic process is performed on the adjacent side of the silicon substrate (1). The microneedle hollow (3) and microneedle shaft (5) are formed through the process of anisotropic directional dry etching process.

A third etch resistant mask layer (6) is formed on the adjacent side of the silicon substrate (1) that disposed thereon the microneedle shaft (5). By performing reactive ion etching (RIE) isotropic process on the adjacent side of the silicon substrate (I)₃ a tapered profile is formed on the microneedle shaft (5) thus creating the sharp tip of the microneedles. The reactive ion etching (RIE) process is preferablydone by using plasma etching.

A silicon substrate (T) is wafer bonded on the first side of the silicon substrate (1) to create microneedle shaft base (8), thus forming an array of microneedles. The fabricated microneedle maybe advantageously used for medical application as previously mentioned.

While a particular form of the present invention has been illustrated and described, it will be apparent that many varying embodiments with various modifications can be made -without departing from the scope of the invention. Therefore, it is understood that the detail herein are to be interpreted as illustrative and not in a limiting sense.

Claims

CLAIMWhat is claim is

1. A method of fabricating Jhollow out-of-plane microneedles, said method comprises the step of:-

preparing a silicon substrate (1) with an etch resistant mask layer (2), said etch resistant mask layer (2) is formed on a first side of said silicon substrate

(i);

performing deep reactive ion etching (DRDE) anisotropic process on said first side to form microneedle hollow (3);

forming a second etch resistant mask layer (4) on the adjacent side of said silicon substrate (1);

performing deep reactive ion etching (DRIE) anisotropic process on said adjacent side of said silicon substrate (1) to form micorneedle shaft (5);

forming a third etch resistant mask layer (6) on said adjacent side of said silicon substrate (1) having said microneedle shaft (5);

performing reactive ion etching (EUE) isotropic process on said adjacent side of said silicon substrate (1) to form tapered profile of said microneedle shaft (5); and

wafer bonding a silicon substrate (7) on the first side of said silicon substrate (1) to provide microneedle shaft base (8) thus forming an array of formed microneedles; characterized in that,

said formed microneedles are arranged in single row of at least two microneedles.

2. A method of fabricating hollow out-of-plane microneedles as claimed in Claim 1. further characterized in that said microneedle hollow (3) and microneedle shaft (5) are formed through the process of anisotropic directional dry etching process.

3. A method of fabricating hollow out-of-plane microneedles as claimed in Claim 1, further characterized in that said reactive ion etching (RIE) isotropic process forming the sharp tip of said microneedles.

4. A method of fabricating hollow out-of-plane microneedles as claimed in Claim 3, further characterized in that said reactive ion etching (RJE) isotropic process is executed using plasma etching.

5. An out-of-plane hollow microneedles, said out-of-plane hollow microneedles are fabricated through the steps of:-

preparing a silicon substrate (1) with an etch resistant mask layer (2), said etch resistant mask layer (2) is formed on a first side of said silicon substrate

(D;

performing deep reactive ion etching (DRIE) anisotropic process on said first side to form microneedle hollow (3);

forming a second etch resistant mask layer (4) on the adjacent side of said silicon substrate (1); performing deep reactive ion etching (DRIE) anisotropic process on said adjacent side of said silicon substrate (1) to form micorneedle shaft (5);

forming a third etch resistant mask layer (6) on said adjacent side of said silicon substrate (1) having said microneedle shaft (5);

performing reactive ion etching (RIE) isotropic process on said adjacent side of said silicon substrate (1) to form tapered profile of said microneedle shaft (5); and

wafer bonding a silicon substrate (T) on the first side of said silicon substrate (1) to provide microneedle shaft base (8) thus forming an array of formed microneedles;

characterized in that,

said formed microneedles are arranged in single row of at least two microneedles.