A novel fabrication method of micro-needle mold by using the micro-lens mask through contact printing

This study presents a novel and precision process for fabricating a microneedle mold. The process includes a microlens array mask with contact printing in ultraviolet lithography. This method can precisely control the geometric profile of a microneedle array without the use of an etching process. The micro tapered cone microneedle mold utilizes the microlens array mask with geometrical optics. The light passes through the microlens and a hole in a Cr film of a mask, and then radiates onto the photoresist film. The light transmitted through the microlens has an aligned focal point on the photoresist film. An optical system is set up to characterize the optical performance of the machined microneedle, and then compared with theoretical data. The results show that the length of the microneedle from the experiment is close to the derived results. Moreover, the length of the microneedle is significantly influenced by the height and diameter of the microlens. Therefore, this method could also simplify the process and reduce the time needed for the fabrication of the microneedle. The micro cone microneedle has have great potential in the area of the drug delivery applications.     

Concave microlens array mold fabrication in photoresist using UV proximity printing

This paper presents a simple and effective method for fabricating a polydimethyl-siloxane (PDMS) microlens array with a high fill factor. The proposed method utilizes the UV proximity printing and photoresist replication methods. A concave microlens array mold is made using a printing gap in a lithography process. Optical UV light diffraction of UV light is used to deflect light away from the aperture edges to produce a certain exposure in the photo-resist material outside the aperture edges. This method can precisely control the geometric profile of a concave microlens array. The experimental results show that a concave micro-lens array can be formed automatically in photo-resist when the printing gap ranges from 240 to 720 μm. A high fill factor microlens array can be produced when the control pitch distance between the adjacent apertures of the concave microlens array is decreased to the aperture size.     

Fabrication of microlens array with graduated sags using UV proximity printing method

A graduated microlens array is presented in this paper. The proposed device has the same aperture microlens with a gradually increasing sag in the substrate. The design produces gradual decrease in the focal length and intensity when the light passes through the graduated microlens array. This paper presents a new graduated microlens array fabrication method that uses a variable printing gap in the UV lithography process. This method can precisely control the geometric profile of each microlens array without using the thermal reflow process. The angles between the mask and photoresist were placed at 5°, 8°, 10°, 15°, and 20° using a fixture designed in this study. The mask patterns were ellipses with an isosceles triangle arrangement to compensate for the partial geometry.     

New high fill-factor dual-curvature microlens array fabrication using UV proximity printing

A new high fill-factor dual-curvature microlens array fabrication method using lithographic proximity printing process is reported. The proposed technology utilizes UV proximity printing by controlling a printing gap between the mask and substrate. The designed microlens array pattern with high density can produce a high fill-factor dual-curvature microlens array in photoresist. Because the UV light diffraction deflects away from the aperture edges and produces exposure in photoresist material outside the aperture edges, this method can precisely control the geometric profile of a high fill factor dual-curvature microlens array. The experimental results showed that the dual-curvature micro-lens array can be formed automatically in photoresist when the printing gap ranged from 360 to 600 μm. The gapless dual-curvature microlens array will be used to enhance the luminance uniformity for light-emitting diodes (LEDs).     

New high fill-factor triangular microlens array fabrication method using UV proximity printing

A simple and effective method for fabricating a high fill-factor triangular microlens array using the proximity printing in lithography process is reported. The technology utilizes the UV proximity printing by controlling the printing gap between the mask and substrate. The designed approximate triangle microlens array pattern can be fabricated in photoresist. This is because to the UV light diffraction deflects away from the aperture edges and produces a certain exposure in photoresist material outside the aperture edges. This method can precisely control the geometric profile of a high fill-factor triangular microlens array. The experimental results showed that the triangular photoresist microlens array could be formed automatically when the printing gap ranged from 240 to 840 μm. The gapless triangular microlens array will be used to increase the luminance for the backlight module of liquid crystal displays. An erratum to this article can be found at     

Fabrication of a polymeric tapered HARMs array utilizing a low-cost nickel electroplated mold insert

A simple low-cost technique has been developed to fabricate a mold insert for replicating polymeric tapered high aspect ratio microstructures. A backside exposure technique is used to first obtain a tapered sidewall structure as an electroplating mold in SU-8 photoresist on a glass wafer. Nickel electroplating is utilized to form the mold insert. The lowest average surface roughness of the nickel mold insert on the side that interfaces with the glass wafer during electroplating is measured to be 7.02 nm. A novel technique involving use of titanium putty is introduced here to reduce cost and effort required to fabricate the mold insert. Replication of tapered microstructures in polymeric materials utilizing the fabricated mold insert is demonstrated here in polydimethylsiloxane by a direct molding process and in polymethyl methacrylate by hot embossing. The fabrication details for the mold insert are described. Advantages and disadvantages of the use of titanium putty for achieving superior metal surface finish are given.     

Fabrication of polymer micro-tip by optical lensing technique

Fabrication of polymer micro-tips using SU-8 negative photoresist for bio-applications is reported. The SU-8 processing technology and isotropic glass etching process have been developed and utilized to fabricate micro-tips on glass substrate by applying optical lensing effect during photolithography. Experimentally, micro-tips of 25?μm base diameter, ~1?μm tip diameter, and ~250?μm height, have been demonstrated.     

Fabrication of grids and collimators using SU-8 as a mold

The fabrication process of ultradeep (aspect ratio greater than 25) microchannels in SU-8 photoresist using deep X-ray lithography is described. We have demonstrated that with single-layer coatings, 1-mm-deep trenches in continuous resist layer can be achieved reproducibly. Microchannels with vertical walls and with walls tilted up to 20° from vertical have been fabricated. Electroforming of the channels resulted in metal grids and collimators for various applications. A thickness enhancement method for fabrication of very tall structures is also described.We would like to thank Dr. Francesco De Carlo for support on the beamline, and Judi Yaeger and Ruben Khachatryan for the experimental assistance. The work was supported by NIH SBIR Grants: R44 CA76752 and R43 CA91762, and by the U.S. Department of Energy, under Contract No. W-31–109-ENG-38.     

Fabrication of a stainless steel shadow mask using batch mode micro-EDM

A metal shadow mask for organic thin-film transistors (OTFTs) has been fabricated by batch mode electro-discharge machining (EDM). Batch mode micro-electro-discharge machining method was applied for productivity improvement. Negative electrode with multiple holes (3 × 3 or 4 × 4) was fabricated using a single tool electrode. With the negative electrode, 3 × 3 and 4 × 4 tool electrode arrays are EDMed; 6 × 6 and 16 × 16 square hole array masks were batch mode EDMed with the fabricated multi-electrodes arrays. With 4 × 4 electrode array, the productivity is improved to five times of that in the case using a single electrode. Source and drain electrodes of OTFTs were successfully patterned on a pentacene active layer through the mask, and the fabricated pentacene TFTs had good output characteristics.     

New horizontal frustum optical waveguide fabrication using UV proximity printing

This paper presents a novel method for fabricating the horizontal frustum structure as a planar optical waveguide using the proximity printing technique. A horizontal frustum optical waveguide with both lateral and vertical taper structure was produced. The orthogonal and inclined masks with the diffraction effect were employed in the lithography process. This method can precisely control each horizontal frustum optical waveguide geometric profile in the fabrication process. The horizontal frustum optical waveguide and its array with the same inclined angle were generated. The beam propagation simulation software (BPM_CAD) was used to model the optical performance. The simulation results reveal that the mode profile matched into horizontal frustum optical waveguide and fiber from the laser diode. The optical loss of the horizontal hemi-frustum optical waveguide structure was less than 0.2 dB. The horizontal hemi-frustum waveguide will be used for fiber coupling on boards for future optical communication systems.     

Fabrication of a freestanding micro mechanical structure using electroplated thick metal with a HAR SU-8 mold

In this thesis, fabrication technology of a freestanding micro mechanical structure using electroplated thick metal with a high-aspect-ratio SU-8 mold was studied. A cost-effective fabrication process using electroplating with the SU-8 mold was developed without expensive equipment and materials such as deep reactive-ion etching (DRIE) or a silicon-on-insulator (SOI) wafer. The process factors and methods for the removal of SU-8 were studied as a key technique of the thick metal micro mechanical structure. A novel method that removes cross-linked SU-8 completely without leaving remnants of the resist or altering the electroplated microstructure was utilized. The experimental data pertaining to the relationship between the geometric features and the parameters of the removal process are summarized. Based on the established SU-8 removal process, an electroplated nickel comb structure with high-aspect-ratio SU-8 mold was fabricated in a cost-effective manner. In addition, a freestanding micro mechanical structure without a sacrificial layer was successfully realized. The in-plane free movements of the released freestanding structure are demonstrated by electromagnetic actuation. This research implies that various types of MEMS devices can be developed at a low-cost with design flexibility.     

Fabrication of electrochemical carbon-based microelectrodes using electrohydrodynamic jet printing technique

Microsystem Technologies - Due to unique advantages, carbon is widely used as electrode material for electrochemical sensors. In this paper, an efficient method of combining the electrohydrodynamic...     

Fabrication of high-aspect-ratio polymer nanochannels using a novel Si nanoimprint mold and solvent-assisted sealing

We present a low cost nanofabrication method to fabricate high-aspect-ratio (HAR) polymer nanochannels using a novel silicon nanoimprint mold fabrication technique and a solvent-assisted sealing method. These nanofluidic channels are being developed for single biomolecule detection. The silicon nanoimprint mold fabrication process is based on the combination of anisotropic etching of silicon by potassium hydroxide (KOH) solution and the local oxidation of silicon (LOCOS) process. The resulting high-aspect-ratio silicon mold has smooth sidewalls owing to the anisotropic KOH etching process along the silicon crystalline geometry as well as the LOCOS process. The nanostructures in the nanoimprint molds that form the nanochannels can be easily controlled by the initial micropattern sizes defined using conventional UV lithography and the oxidation time, making this technique a practical solution for low cost and high-throughput HAR silicon nanoimprint mold fabrication. Nanoimprint molds having aspect ratios of more than 1:5.5 (width: 200 nm, height: 1.1 μm, length: 1 cm) were successfully fabricated. Nanoimprinting technique was used to create poly(methyl methacrylate) (PMMA) nanotrenches out of this nanoimprint mold. A novel solvent-assisted sealing technique was developed in order to seal the HAR PMMA nanotrenches. This technique enables the generation of nanochannels with various nanoscale dimensions without the need for complicated and expensive nanolithography tools.     

Fabrication of LIGA mold inserts

 The present paper describes the fabrication sequence of a LIGA mold insert by electroforming after the patterning steps of the overall process. These tools are applied for large scale fabrication of microcomponents made by molding and embossing processes. The application of an intermediate layer system leads to optimized process performance and to a better surface quality of the mold insert. The plating processes are described and the materials properties, e.g. hardness, are used for the characterization of the recrystallization behavior of the electroformed nickel which yields the high temperature application limit of the tool. Received: 25 August 1997 /Accepted: 22 September 1997     

Fabrication of CNT field‐emitter array using a polymer insulator

Abstract— The fabrication process of a carbon‐nanotube (CNT) field‐emitter array (FEA) having a polymer insulator is reported. This polymer material is suitable for a large‐sized FEA because of its coating property and thermal stability. These features contribute to the display‐image uniformity, the tolerance to the thermal‐sealing process, etc. A new method of forming via holes on the insulator instead of gate holes has been developed. The method uses a spin‐wet‐etching (SWE) technique instead of the typical reactive‐ion‐etching (RIE) method. The RIE method damages and contaminates the CNT at the end of the etching process. However, the SWE technique ensures fine gate hole configurations with little under‐cut without any damage nor contamination. An FEA panel 1.5 in. on the diagonal was fabricated by using the method. The FEA showed good emission uniformity with proper surface treatment of the CNT.     

Fabrication of HARM structures by deep-X-ray lithography using graphite mask technology

The cost-effective fabrication process for high-aspect-ratio microstructures using X-rays depends largely on the availability and quality of X-ray masks. The fabrication of X-ray masks using commercially available graphite sheet stock, as a mask membrane is one approach that is designed to reduce cost and turnaround time. Rigid graphite offers unique properties, such as moderate X-ray transmission, fairly low cost, electrical conductivity, and the ability to be used with either subtractive or additive processes [1, 2]. This paper will demonstrate the potential of a cost-effective, rapid prototyping of high-aspect-ratio microstructures (HARMs) using graphite masks. The graphite wafer accommodates both the intermediate mask and the working mask. In order to allow a direct comparison of the graphite mask quality with other X-ray masks, the primary pattern was derived from a Ti X-ray mask using soft X-ray lithography (XRL). Received: 7 July 1999 / Accepted: 29 September 1999     

AGGLO-Hi clustering algorithm for gene expression micro array data using proximity measures

Gene selection is imperative to clustering in light of gene articulation information, as a result of high Clustering quality. Clustering gene articulation information is a vital research subject in bioinformatics on the grounds that knowing which genes act correspondingly can prompt the disclosure of vital natural data. Many clustering systems have been proposed to the examination of gene articulation information got from microarray innovation. Clustering is one of the major procedures of investigating gene articulation information, fundamentally by contrasting gene articulation profiles or test articulation profiles. The Proposed strategy is an Agglo-Hi clustering algorithm which is accounted for the fuse of vicinity similarity estimates like Euclidean Distance, Manhattan Distance Chebyshev Distance, and Cosine Similarity for their execution. The technique is quality articulation information in microarray which is extricated and quality can be chosen from the preprocessed information, at that point the Agglo-Hi Clustering algorithm is utilized for quality information. The grouped information get approved utilizing legitimacy file and the outcome is gotten in light of nearness measures. To refine quality articulation information onto enhanced bunch quality by accelerating Unsupervised Learning stage and the execution of Agglo-Hi algorithm figures the Clustering quality, exactness and time unpredictability.

     

Fabrication of microneedle array using LIGA and hot embossing process

We demonstrate a novel fabrication technology of the microneedle array applied to painless drug delivery and minimal invasive blood extraction. The fabrication technology consists of a vertical deep X-ray exposure and a successive inclined deep X-ray exposure with a deep X-ray mask whose pattern has a hollow triangular array. The vertical exposure makes triangular column array with a needle conduit. With the successive inclined exposure, the column array shapes into the microneedle array without deep X-ray mask alignment. Changing the inclined angle and the gap between the mask and PMMA (PolyMethylMetaAcrylic) substrate, different types of microneedle array are fabricated in 750–1000 m shafts length, 15^o–20^o tapered tips angle, and 190–300 m bases area. The masks are designed to 400–600 m triangles length, 70–100 m conduits diameter, 25–60EA/5 mm² arrays density, and various tip shapes such as triangular, rounded, or arrow-like features. In the medical application, the fabricated PMMA microneedle array fulfills the structural requirements such as three-dimensional sharp tapered tip, HAR (High-Aspect-Ratio) shafts, small invasive surface area, and out-of-plane structure. In the skin test, the microneedle array penetrates back of the hand skin with minimum pain and without tip break and blood is drawn after puncturing the skin. Hot embossing process and mold fabrication process are also investigated with silicon and PDMS mold. The processed tetrahedral PMMA structures are fabricated into the microneedle array by the additional deep X-ray exposure. With these processes, the microneedle array can be utilized as the mold base for electroplating process.The author thanks the staff in 9 C LIGA beamline, Pohang Light Source (PLS), Korea for their assistance on the fabrication process.     

Fabrication of X-rays mask with carbon membrane for diffraction gratings

We have produced diffraction gratings for obtaining high resolution X-ray phase imaging, such as X-ray Talbot interferometer. These diffraction gratings were required to have a fine, high accuracy, high aspect ratio structure. Therefore, we decided to use the X-rays lithography technique that used synchrotron radiation of the directivity for a manufacture process. The accuracy of the completed structure depends largely on the accuracy of the X-ray mask. In our group, a resin material is conventionally used for the membrane of large X-ray masks. However, X-ray masks comprising a resin membrane have the disadvantage that, after several cycles of X-ray exposure, they crease and sag due to X-ray-derived heat. As a substitute for the conventional resin membrane, we experimentally fabricated a new X-ray mask using a carbon wafer membrane. The newly fabricated X-ray mask was subjected to X-ray exposure experiment. We succeeded in making the structure body which was almost shape. And the experimental results verified that the new mask did not deteriorate even when used repeatedly, demonstrating that it was highly durable.     

Fabrication of wireless sensors on flexible film using screen printing and via filling

Wireless sensors are fabricated on flexible plastic films by means of screen printing and via-hole filling. The wireless sensors are battery free with data and power transmission functions. The sensors, fabricated on polyethylene terephtalate films, are designed based on RFID technology. Using an additive patterning process known as screen printing, metallization on polymer films is created. Both sides of a polymer film are printed with metallic patterns and connected with micro vias filled with conductive paste. One side of the film consists of printed electrical traces for discrete components like resistors and transistors that would be mounted onto it; the other side consists of a printed inductive coil used for wireless data and power transmission. The micro vias, which have a diameter of 120 μm, are formed by mechanical punching and filled with conductive silver paste. The size of one sensor unit is approximately 2 cm × 1.5 cm; an array of 4 × 7 sensor units are printed over an area of 15 cm × 15 cm on a PET film. Details of manufacturing processes, component assembly and functionality test are presented in this paper.