Although microfluidic devices that integrate microfluidic chips with hollow out-of-plane microneedle arrays have many advantages in transdermal drug delivery applications, difficulties exist in their fabrication due to the special three-dimensional structures of hollow out-of-plane microneedles. A new, cost-effective process for the fabrication of a hollow out-of-plane Ni microneedle array is presented. The integration of PDMS microchips with the Ni hollow microneedle array and the properties of microfluidic devices are also presented. The integrated microfluidic devices provide a new approach for transdermal drug delivery.
Poly-L-Lactides(PLLA) is a biodegradable polymer material which is sensitive to X-ray as a resist and free of stress crack formation. The fabrication technique to generate the PLLA micro structures with the very smooth sidewall is demonstrated. The function of X-ray on PLLA polymer material is breaking the PLLA polymer main chain and generating intermediates which can be degraded further and finally dissolved by the solvent interaction. In this paper, we have illustrated PLLA polymer is a new resist material for x-ray lithography and can be developed in alkaline developers after x-ray exposure. Various polymer structures are fabricated using this novel X-ray lithography technique. The PLLA structure sidewall obtained by this process is very smooth compared with that of other micromachining methods. The result after 0.02Ahour X-ray exposure dosage and developed in NaOH (1N) developer for 1 hour at room temperature shows the smooth sidewall by consuming PLLA to generate lactic acid salts. The depth of the micro PLLA structure is about 150μm and the RMS value of the sidewall roughness was within 200nm. The data of exposure doses against the processed depth on the PLLA sheet is shown.
The microneedle for blood extraction and painless injection is a rapidly growing area of interest in bio-applications. Two new types of microneedle array are designed and developed for biomedical application. The one is hollow PMMA microneedle array with very shape tip fabricated by two times X-ray lithography (one time is with X-ray mask and one time is without X-ray mask). The other is PMMA microneedle array with tips and fluid channels fabricated by an X-ray lithography technique. The resist stage of the X-ray system driven by actuators is to realize movement lithography.
LIGA process technique is a three-dimensional micromachining technology which is applied to fabricate 3D micromechanical parts. Because the LIGA process requires LIGA mask for deep-etch X-ray lithography, the mask fabrication is a complex technique. The use of micro optical systems in commercial applications (as sensors or in telecommunication) is not only depending on the performance but also on the price of the system. It is highly dominated by fabrication and assembly costs. In order to solve this problem, many efforts have been made in the world. Direct laser patterning of absorber thin films of LIGA mask allows the possibility of rapid prototyping and low cost manufacture of X-ray lithography mask. Excimer laser mask projection techniques have been used in order to directly manufacture LIGA mask for X-ray lithography. The mask pattern with circles structures with 25µm pitch have been fabricated by sequential direct laser ablation of thin gold film using mask projection techniques.
This paper describes the X-ray mask design and fabrication processes in details. The fabricated LIGA mask is used as a pattern for x-ray exposure onto a polymethyl-methacrylate (PMMA) resist. A fine micro structures of PMMA in a low cost and a short fabrication period is obtained using the mask. It is confirmed that such LIGA mask is important for rapid prototyping in the areas of medical and biosensors.
In the microoptics field, precise alignment is very important to reduce the coupling losses in optical links. In this paper, a novel device of passive and fixed alignment of optical fiber is proposed. The rectangular V-groove formed by one sidewall of SU-8 resist and the substrate is used to position the optical fiber, and the leaf spring with flexure hinge clamps it. The spring is fabricated by the sacrificial layer technique. The clamping force provided by the spring acts on the upper semi-circle of the optical fiber's cross section, so that the device need not use the additional cover on the optical fiber to perform the vertical location and the final fixing. It has simple structure and process, and is convenient to assemble and integrate with other microparts. The coupling of two optical fibers using the devices in our experiment has less than 1.5dB insert loss.
A new LIGA-like microfabrication technique was developed by present authors. DEM (deepetching, electroforming and microreplication) is the abbreviation of three main process steps in this new microfabrication technique. In contrast to LIGA technique, DEM technique has the advantages of lower cost and shorter process period. Microfluidic systems like plastic capillary electrophoresis chips, micro flowmeters and three-dimensional DNA chips were developed using DEM technique. DEM technique offers a new way for fabrication of MEMS and MOEMS components.
Here we demonstrate two fine optical components fabricated by replica-molding from anisotropically etched Si molds. One component is microcavity in micro-scales and the other is grating computer with a pitch of 500 nanometer. We investigated the feasibility of two methods for the microfabrication of the SI molds: one method is for making hundreds of micrometer size Si molds by using conventional photolithography and reactive ion etching technique combined with post anisotropical crystalline etching; and the other is for fabrication of micro periodic structure in optical waveguide was presented. Periodicities in excess of 5000 lines/mm were successfully transferred from silicon mold to polymer layer. The yield, repeatability and efficiency of the original master are very good. This technique can also be used to fabricate other nanometer-scale structures.