UV-LIGA Technology Research Articles

Processing of PZT actuator and nickel plate in a multi-droplets microejector

The fabrication processes of components for a liquid microejector are described in the paper. The components of the microejector, the vibration plate and the nozzle nickel-made plate, were produced by multilevel electroforming of UV-LIGA technology. A shear-mode PZT actuator, manufactured by powder metallurgy, was devised to drive the microejector for generating tiny liquid droplets. This plate-shaped actuator poled with remnant polarization perpendicular to the actuating field induced a piezoelectric shear effect. The polarizing procedure of the PZT actuator was illustrated in detail. The components were bonded together by thermosetting adhesive. The temperature effect on the PZT actuating performance was further investigated since the bonding temperature can substantially affect the electromechanical properties of the PZT actuator. An appropriate bonding temperature for PZT actuator was suggested.

The Electrochemical Micro-Fabrication Method for Micro-Scale Flow Channels

Due to lack of desirable mechanical properties of silicon substrate; the current trend of micro-fabrication technology is towards metallic materials. In this study, the electrochemical micromachining (EMM) technology is developed to fabricate micro-scale flow channels on thin metallic 316L stainless steel plate. The cathode electrode, the tool, is the mirror image of flow channels. It was produced by the MEMS and UV-LIGA technology and the size is 200μm in width and 500μm in height for the intension to fabricate a serpentine flow channel of 200μm in both depth and width. Because of the electrode size, the process control parameters and geometrical features surpassed conventional and CMOS methods. The flow channels on 0.6mm thick SS 316L plates were fabricated by EMM process within 30 seconds with effective area of 625mm2. The dimensions of flow channel were varying from 1504m to 5004m in width and about 2004m in depth. The results demonstrate the EMM technology produces good quality metallic flow channels efficiently.

Design and fabrication of a bistable electromagnetic microactuator

An electromagnetic microactuator with two stable positions is presented. The actuator consists of a cantilever beam with two free ends, a torsional beam with two fixed ends, planar coils and permanent magnets. The cantilever beam has two stable positions due to the use of permanent magnets. With electromagnetic actuation arising from the planar coils, the cantilever beam will switch from one stable position to the other. Mechanical and magnetic analysis are carried out on the actuator, and the device with a size of 2.2 mm×2.5 mm is fabricated with the UV-LIGA technology. The test results show that a current pulse with an amplitude of 70 mA is needed for actuator’s switching between the two stable states, and the switching time is no more than 6 ms. Displacement of the end of cantilever is about 15 µm.

Study on structural optimum design of implantable drug delivery micro-system

In this paper, design, modeling, and simulation of a new type of controlled drug delivery system based on biodegradable polymers is report. The system consists of arrays of micro-chambers for drug storage to achieve linear release. The micro-chambers were fabricated with biodegradable polymer using the UV-LIGA technology and the controlled release process is the combined results of design of the micro-chambers and the biodegradable characteristics of the polymer. This type of drug delivery system has some unique advantages in controlled long-term drug delivery, such as improved efficiency, reduced side effect, on-spot delivery, and convenient therapy. Mathematical model has been developed for two kind of biodegradable polymer micro-system respectively, and numerical simulations were conducted to analyze the biodegradation and the controlled release process. The mathematical model can be used to optimize the structural design for controlled-release system with the desired release characteristics.

Multi-layer microstructure fabrication by combining bulk silicon micromachining and UV-LIGA technology

A novel method for fabrication of multi-layer microstructures of microelectro-mechanical system (MEMS) devices is described. This technique, which combines bulk silicon micromachining technique and UV-LIGA technique can overcome some shape limitations of single technique on complex microstructures. To demonstrate this combination, the SU-8 microstructure fabricated in the etched silicon grooves is presented. In this fabrication process, a SU-8 removal method by fuming sulfuric acid was introduced and a novel type of plastics PETG was tried in microhot embossing process. The proposed fabrication process can be applied to fabricating a high-aspect-ratio microstructure for a large displacement actuator and precision sensors. Moreover, this combined process enables the fabrication of more complex structures, which cannot be fabricated by bulk micromachining or UV-LIGA alone.

A fast switching bistable electromagnetic microactuator fabricated by UV-LIGA technology

A fast switching electromagnetic microactuator with two stable positions is presented. The actuator consists of a cantilever beam with two free ends, a torsional beam with two fixed ends, planar coils and permanent magnets. The cantilever beam has two stable positions due to the use of the permanent magnets. With electromagnetic actuation arising from the planar coils, the cantilever beam will switch from one stable position to the other. The behaviour of the microactuator is studied using a coupled electromagnetic-mechanical FEM-simulation with ANSYS software. The working mechanism for the bistability of the actuator is analysed. The device with a size of 2.0 mm × 2.2 mm is fabricated by UV-LIGA technology using sacrificial layer. The results of test show that a current pulse with an amplitude of 50 mA is needed for actuator’s switching between two stable states, and the switching time is approximately 20 μs. The displacement of the end of cantilever is about 17 μm.

Preparing of a high speed bistable electromagnetic RF MEMS switch

A radio-frequency micro-electro-mechanical systems (RF MEMS) switch with bistable states based on electromagnetic actuation is presented. The switch has two stable positions due to the adoption of the permanent magnets, which will lead to a lower power consumption of the device. With electromagnetic actuation arising from the planar coils, the cantilever beam can switch from one stable position to the other. The structure sizes of the switch are simulated by the finite element software of the ANSYS 7.0. The device with a size of 2.0 mm × 2.2 mm is fabricated by UV-LIGA technology. A current pulse with an amplitude of 50 mA is needed for the fabricated switches’ switching between two stable states that is in good agreement with the simulation, and the switching time is only approximately 20 μs. The insertion loss is −0.11 dB, and the isolation is −43 dB at 3 GHz.

Modeling and simulation of drug delivery from a new type of biodegradable polymer micro-device

In this paper, modeling and simulation of a new type of controlled drug delivery micro-device based on biodegradable polymers is reported. The micro-device consists of micro-chambers arrays for drug storage to achieve linear release. The micro-chambers are fabricated with polyanhydrides (CPP-SA) using the UV-LIGA technology and the controlled release process are the combined results of the design of the micro-chambers and the biodegradable characteristics of the polymer. This type of drug delivery system has some unique advantages in controlled long-term drug delivery, such as larger loading volume than the matrices release systems, easier control for the release rate, etc. It is necessary to optimize the structure for the long-term and zero-order drug release. Based on the Monte Carlo erosion model, the drug release model is founded for the drug delivery system and using the new model, the drug release profiles from the delivery systems with different structures are simulated. The simulated results indicate that the effect of the drug delivery is dependent on the micro-structure of the delivery system and the simulated drug profiles of coaxial rings micro-cavity shape equal to zero-order released model approximatively. The simulated results are very important to the application research of the new biodegradable polymer micro-device.

Design and UV-LIGA microfabrication of an electro-statically actuated power relay

A novel type of micro power relay has been designed and fabricated using UV-LIGA technology. The relay is based on electrostatic actuation and SU-8 was used as a functional material. The unique character of this novel power relay is that other than two SU-8 strips used both as electrical insulators mechanical connectors, all other components are made of metal or alloys. Because UV-LIGA technology has the advantages of broad material selection and the capability of making high aspect ratio microstructures, the technology is best suited for fabricating micro electro mechanical system power relays. A multi-step, multi-layer UV-LIGA process has been successfully developed and a prototype relay has been successfully fabricated.

A novel method to fabricate complex three-dimensional microstructures

Conventional three-dimensional (3D) microstructures such as arcs or spiralities are generally fabricated using some complicated methods like LIGA or two-photon lithography. In this paper, a new approach of fabricating 3D microstructures is provided. The process is based on UV-LIGA technology yet including a novel reformation method in the post bake procedure. The fabrication process started with coating SU-8 as thick as 500 microns on the silicon substrate, and then it was followed by an exposure with patterned mask under UV light. Subsequently, a force on the exposed SU-8 photo resist was applied in the post-bake process. By adjusting the amount of force, the way in which the force was placed and the exposure dose, we directly fabricated some complicated three-dimensional structures on the SU-8 photo resist after development of the SU-8. We call this microfabrication method as Force-LIGA (F-LIGA). Firstly, orthogonal experiment method conducted to optimize the hot-press process is presented, and then we give some experiment examples using F-LIGA approach and discuss the relationships among the exposure time, pressure and the profile of microstructures. The fabrication process can be used widely in making useful three-dimensional devices.

Fast switching bistable electromagnetic microactuator

A fast switching electromagnetic microactuator with two stable positions is presented. The actuator of size 2.0×2.2 mm is fabricated using UV-LIGA technology. Test results show that a current pulse with an amplitude of 50 mA is needed for the actuator's switching between two stable states, and the switching time is approximately 20 µs. The displacement of the actuator is about 17 µm.

Multilevel electroforming for the components of a microdroplet ejector by UV LIGA technology

A microdroplet ejector actuated by the shear mode PZT actuator is proposed. It consists of three electroforming components including a vibration plate, a chamber plate and a nozzle plate. The three components are fabricated by nickel electroforming technology and assembled by aligning apparatus using epoxy adhesive. The AZ-type thick positive photoresist is used as the electroforming mould, which is patterned by UV lithography. The repeat steps including the photoresist patterning and nickel electroforming make the component form a quasi 3D (or 2.5D) multilevel microstructure. The vibration plate has the feature of two different sized bulges piled on the diaphragm. Those nozzles in the nozzle plate are formed by the nickel lateral deposition when depositing over columnar photoresist moulds.

Microfabrication of an electromagnetic power relay using SU-8 based UV-LIGA technology

Most of the MEMS relays reported in the field now are based on silicon fabrication and cannot be used for power applications. In this paper, we report a research effort to microfabricate an electromagnetic relay for power applications using a multilayer UV-LIGA process. A mechanically wrapped coil was used and very simple design for the magnetic circuit was adopted to increase the design flexibility and performances. The broad material selection and the capability of making high aspect ratio microstructures of the UV-LIGA make the technology best suited for fabricating microelectromechanical relays for power applications. The prototype relay has a truly three-dimensional structure and very suitable for large power capacity applications.

Determination of Young’s modulus of electroplated nickel–iron (Ni/Fe) and micro-machined Si thin films by the balance method

This paper presents a simple method to measure Young’s moduli of thin films shaped into micro-cantilever beams (MCBs). Young’s moduli of electroplated Ni/Fe thin films and 〈1 1 0〉-oriented silicon have been determined in this paper based on this method. First, the principle of the balance method is introduced and the systematic error of this set-up is analyzed. Then, using photoresist AZ9620 as the electroplating molds, free-standing low stress Ni/Fe cantilever beams (CBs) with different Ni/Fe mole ratios were prepared by UV-LIGA technology. Micro silicon CBs also were fabricated by the standard wet-etching process. The experiment results show that the Young’s modulus of electroplated Ni/Fe films is associated with the process conditions. The measured Young’s moduli of Ni/Fe films change greatly, from 101 GN/m 2 (Ni 43 wt.%, Fe 57 wt.%) to 186 GN/m 2 (Ni 64 wt.%, Fe 36 wt.%). The average value for (1 1 0) silicon CBs is about 164 GN/m 2, which is in good agreement with previously published data. This method that has been developed is simple, non-destructive and universal and can be used for in situ measurement with all kinds of micro-machined components.

Micro- and Nano-Fabrication of Polymer Based Microfluidic Platforms for BioMEMS Applications

AbstractIn this paper, we review the approaches developed in our laboratory for polymer-based micro/nanofabrication. For fabrication of microscale features, UV-LIGA (UV-lithography, electroplating, and molding) technology was applied for low-cost mass production. For fabrication of sub-micron or nanoscale features, a novel nano-manufacturing protocol is being developed. The protocol applies a novel nano-lithography imprinting process on an ultra-precision motion-control station. It is capable of economically producing well-defined pores or channels at the nanometer scale on thin polymer layers. The formed thin layers can be used as nano-filters for chemical or bio-separation. They can also be integrated into miniaturized devices for cell immunoprotection or tissue growth. For bonding of polymer-based microfluidic platforms, a novel resin-gas injection-assisted technique has been developed that achieves both bonding and surface modification. This new approach can easily seal microfluidic devices with micron and sub-micron sized channels without blocking the flow path. It can also be used to modify the channel shape, size, and surface characteristics (e.g., hydrophilicity, degree of protein adsorption). By applying the masking technique, local modification of the channel surface can be achieved through cascade resin-gas injection.