Fabrication methods of polymer microstructures for μTAS, Lab-on-a-chip and BioMEMS developed so far are reviewed. Conventional plastic molds of hot embossing, injection molding and casting have been applied for fabrications of the microstructures with improvements of precise temperature control etc. New silicone like material, PDMS have been widely used in μTAS. Some UV photolithography methods have also been developed to realize 3D microstructures. Surface micromachining technologies using polymer as the structure and positive photoresist as the sacrificial layer are another potential fabrication methods in μTAS.

View full abstract

A new micro hot-embossing process which combines the high accuracy of silicon micromachining process and low cost production of forming process was reported. A movable cantilever-array structure with vertical mirrors were designed under the limitation of hot-embossing fabrication and material properties of polymer. The cantilever has non-uniform width optimized for electrostatic actuation and high-density array configuration. Two metal molds were transferred by electroplating from silicon structures which is micromachined by DRIE and anisotropic wet etching. The polymer optical switch array chip was produced by hot-embossing between the two molds and laser cutting. Finally, the operation of the assembled 8 × 8 optical switch system was demonstrated.

View full abstract

Three dimensional structures on SU-8 photoresist were fabricated by gray-scale lithography. A thin glass substrate was plastered over with SU-8 and UV light was irradiated through the glass substrate. SU-8 structures with maximum 400μm height and strong adhesion to the substrate were achieved by the lithography technique. The relation between gray-scale value and the resist height were evaluated and the maximum surface roughness of the structure was 0.98μm. Three dimensional structures such as micro capillaries were fabricated on PDMS from the SU-8 structures by molding.

View full abstract

PDMS microstructures whose whole inner surfaces are covered with perfluoro polymer are described. The major problems of PDMS microfluidic devices in Micro Total Analysis Systems (μTAS) applications are surface degradation with organic solvents and unexpected adsorption of chemical materials. In order to overcome these problems, perfluoro amorphous polymer is coated on the PDMS micro structures. This method is useful to realize chemical durability of the PDMS microfluidic devices. And novel method for fabricating metal electrodes on the perfluoro polymer is also proposed.

View full abstract

We have developed a sensor system for surface movement aircraft passage. The system is laid underground and can be used though out the whole airport area. It includes a GPS receiver, an accelerometer, an object detection part, and a kind distinction part. The object detection part monitors the decay of GPS signals, and detects passage of an object. Because GPS satellites are not stationary, the number of satellites which can receive the GPS signal is not fixed. Also the number of satellites which receive the GPS signal changes at the time of the object’s passage and the amount of change varies with the size of the passing object and its shape. We developed an algorithm which accurately detects the object by the change in GPS signal based on estimation of the change. The kind distinction part detects the vibration propagated from objects by using the accelerometer, and an index is calculated which shows the kind of object based on the vibration frequency characteristics when the object is detected. This detection distinguishes aircraft from vehicles.
We verified the efficiency of the aircraft sensor with the kind distinction function by field tests.

View full abstract

We present RF silicon passive devices fabricated by a newly developed dielectric-air-metal (DAM) cavity process. The demonstrated components are grounded coplanar waveguide (GCPW), lumped-element hybrid for Ku-band application, and thru/shunt-type MEMS switch, which were fabricated by front-surface-only processes on a silicon substrate. They consist of transmission lines on a silicon nitride membrane suspended above a metallized deep cavity. The demonstrated depths are 6 μm and 30 μm for GCPWs, 30 μm for hybrids, and 2 μm for switches. The DAM cavity process is adaptive to the RF MEMS modules, which have several kinds of components with different cavity depths to each other on the same surface of the substrate. Good agreement between the measured and simulated results validates the proposed structure utilizing the DAM cavity process. For instance, in the hybrid, we obtained 2.03 dB and 2.18 dB as the insertion losses and 21.63 dB as return loss at 12 GHz.

View full abstract

We have proposed and developed Electrostatic Micro Actuator with Distributed Ciliary Electrodes (E-Maccel). This actuator consists of two fixed electrodes having many oblique ciliary electrodes distributed on a plate, which like foxtail grass, and a moving electrode that is sandwiched by the fixed electrodes. When the voltage is applied between the fixed electrode and the moving electrode, the electrostatic force is generated at the gap between the moving electrode and the ciliary electrodes, and the moving electrode sticks to the ciliary electrodes and is attracted to the fixed electrode. The moving electrode moves parallel to the fixed electrode as well as perpendicularly to it. The E-Maccel was fabricated by micromachining. The ciliary electrodes were made of two-layer polyimide film. The 4382 ciliary electrodes, each of which was 3 μm thick, 300 μm long and 150 μm wide, were fabricated on a 20 mm x 20 mm Pyrex glass plate. The fabricated E-Maccel was driven, and the movement of 9.6 μm/cycle was observed at the driving voltage of 150 V.

View full abstract

We hereby fabricated the microneedle arrays whose dimensions of 300 μm in height, 100 and 150 μm in diagonal lengths of bottom surface and with densities of 900 and 4,400 needles/ cm² by injection molding. The resist patterns were pre-formed by three-dimensional fine manufacturing with movable resist during the exposure in LIGA process. Polylactic acid was used for microneedle arrays in consideration of the prospective medical use in transdermal methods and the like. Our study was to evaluate the material filling of the needle tips and dermal penetrability. The flexibility of the needle tips was also tested by the force added to the tips, and its result was compared with the analysis of flexibility by CAE; computer aided experiment. The resin filling did not reach to the deepest point of the Ni stamper, and the filling remained within the range of 12 to 17 μm in diameter. However, the penetration rate on pig skin with the density of 900 needles / cm² resulted in the range of 60 to 80%, and this result represented the satisfactory capability of dermal penetration in spite of the previously described needle tip dimensions of microneedle array. Closely resembling needle flexibility to its analysis proved that CAE analysis on the strength of microstructures was well effective.

View full abstract