UV-LIGA Technology Research Articles

Miniaturized Lens Antenna with Enhanced Gain and Dual-Focusing for Millimeter-Wave Radar System.

This paper presents a waveguide Lens antenna at the W-band adopting dual-focusing Lens to improve the performance. The Lens antenna consisted of a waveguide slotted structure and lenses processed using NOA73 meet the demands of miniaturization for current communication systems. The antenna radome fabricated using NOA73 not only protects the antenna structure but also improves the gain of the antenna by about 9.5 dBi via electromagnetic wave dual-focusing. A prototype is fabricated using novel UV-LIGA technology. Measured results are compared with simulated values. Measured results confirmed the fabricated antenna operated in the W-band with a 10 dB fractional bandwidth (FBW) of 6.5% from 97.5 to 104 GHz and a peak gain of 22 dBi at 100 GHz in the direction perpendicular to the plane of the feed waveguide. A good agreement between simulation and measurement is obtained, demonstrating efficient radiations in the operating band.

Application of Ni/SiCw Composite Material in MEMS Microspring.

The microspring is a typical type of device in MEMS devices, with a wide range of application scenarios and demands, among which a popular one is the microelectroformed nickel-based planar microspring prepared by the UV-LIGA technology based on the SU-8 adhesive. It is worth noting that the yield strength of the electrodeposited nickel microstructure is low, and the toughness of the structure is not high, which is unbeneficial for the enduring and stable operation of the spring. The paper mainly presents the methods of preparing high-aspect-ratio Ni/SiCw microstructures for MEMS devices based on UV-LIGA technology, developing Ni/SiCw-based microspring samples with a thickness of 300 μm, and applying a DMA tensile tester for mechanical property tests and characterization. In addition, the paper explores the influence of heat treatment at 300 °C and 600 °C on the tensile properties and microstructure of composite coatings. The results show that the W-form microspring prepared from Ni/SiCw composites not only has a wider linear range (about 1.2 times wider) than that of pure nickel material but also has a stronger resistance capacity to plastic deformation, which is competent for MEMS device applications in environments below 300 °C. The research provides a frame of reference and guidance for improving the stable cyclic operating life of such flat springs.

Investigation of the corrosion resistance of graphene-nickel composite micro-parts

Nickel-based microparts possess a short lifetime owing to their rapid dissolution in corrosive environments. To mitigate this phenomenon, composite microparts of graphene/Ni were prepared using UV-LIGA technology; their corrosion behavior was examined in acid, alkali, and salt solutions as well as after subjecting them to heat-treatment processes. The microstructures were investigated with scanning electron microscopy (SEM), x-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Corrosion resistances were characterized through various electrochemical tests and compared with those of pure Ni microparts. The results demonstrate that the surface oxidation layer (i.e.,the protective layer) of the microparts was readily destroyed in NaCl and H2SO4 solutions without the formation of a passivation film; however, a passivation film was formed in the NaOH solution. The corrosion rates of graphene/Ni in NaCl, NaOH, and H2SO4 corrosion solutions were reduced by 73%, 22%, and 84%, respectively, relative to those of pure Ni microparts. This can be primarily attributed to the homogeneous dispersion of graphene in the Ni matrix, which refined the grain size, and the impermeability and chemical stability of graphene, which lengthened the diffusion path of the corrosive medium. In addition, heat treatment of the graphene/Ni microparts at 200 °C increased the corrosion resistance by a factor of nearly one with little change in microhardness, which can be attributed to the removal of internal stress and the increased proportion of CSL grain boundares. Corrosion occurred at the interface between nickel and graphene, lengthening the corrosion path.

Terahertz Rectangular Waveguides by UV-LIGA with Megasonic Agitation.

This paper researches the fabrication of a WR2.8 terahertz rectangular waveguide operating at the frequency ranging from 260 GHz to 400 GHz via UV-LIGA technology (UV-lithography, electroplating, and molding). In the process, megasonic agitation is applied to improve the mechanical properties and internal surface roughness of the WR2.8 rectangular waveguide. The effects of process parameters on the properties of structures are discussed, and optimized parameters are obtained to achieve accurate geometry dimensions. In addition, the highly crosslinked SU-8 is reliably removed from structures without damage through a synthesis method. The accuracy of the height and width of the WR2.8 rectangular waveguide is 5 µm and 2 µm, respectively, and the measured internal surface roughness is 79.6 nm. Moreover, experimental measurements and numerical simulations of the waveguide are conducted, and the difference between the two is also highlighted.

UV-LIGA Based Discrete Fabrication Process for Terahertz Corrugated Feed Horn

Corrugated horn is a kind of key feed component of antenna system, which could be fabricated by electroforming method. However, the feed horn is becoming more difficult to electroform with the increase of frequency. In the terahertz band, which is now of great interest in military and social safety application, the widths of the corrugation teeth and gaps decrease to the micrometer scale, and their depth-width ratios are higher than 2:1. It is really a challenging, time-consuming work to directly machine a terahertz feed horn or make a metal mandrel for electroforming of that.To solve the difficulties in the normal process of terahertz feed horn, a novel discrete fabrication method based on UV-LIGA technology is put forward avoiding the need of mandrel machining. In this method, the manufacturing of a 3D corrugated horn is transformed into 2D slices forming, that is, the corrugation structure is separated into discrete slices according to the width of each tooth or gap. The slices are formed through UV-LIGA technology, in which electroforming is an essential process. Consequently, slices with micro hardness higher than 250HV(200g) and internal compress stress less than 20MPa were electroformed. After assembly and vacuum bonding of slices, typical nickel micro-structure of a conical corrugated horn operating at frequency 2.5THz was fabricated successfully. This layer-by-layer method breaks though the traditional solution of direct machining of metal feed horn or its mandrel by coupling UV-LIGA and vacuum hot bonding technology, which is feasible for vacuum electronic devices like rectangular folded waveguide and multilayer MEMS components moreover.

A 0.34-THz High-Power, Slow-Wave Structure: Designing and Microfabricating an H-Plane Ridge-Loaded Folded Waveguide

High-power microvacuum electronic devices are one of the key technologies for the study of terahertz radiation sources. The traveling-wave tube (TWT) based on the folded waveguide slow-wave structure is the most promising terahertz device. This article designs the structural parameters of an H-plane ridge-loaded folded waveguide to improve the maximum output power of TWTs in the atmospheric window at 0.34 THz. The results predicted by a theoretical model and by electromagnetic (EM) simulation indicate the interaction impedance of the slow-wave structure is significantly increased. The simulation results show that the design is capable of raising the maximum output power to more than 50 W at 0.34 THz, with sheet electron beam parameters of 16.8 kV and 50 mA. The power gain, the 3-dB bandwidth, and the electronic efficiency of the folded waveguide can reach 30.5 dB, 10 GHz, and 6%, respectively. Finally, the designed slow-wave structure is microfabricated using multistep UVLIGA technology.

Development of a novel mechanical micro-engraving method for the high-aspect-ratio microstructures of an advanced window system

A transparent polymer film with embedded micro mirrors is developed, and it can be attached to a window glass pane for daylighting, improving visual comfort and reducing cooling load in buildings by redirecting sunlight. Despite existing cutting-edge techniques, the fabrication of large-area, linear micro structured surfaces combining high aspect ratio, curve sidewalls and a controlled shape remains challenging. In order to solve the problem, a novel mechanical scanning engraving method using blades with micro-teeth of desired patterns on soft substrates is developed. The usage of a blade enables the combination of high aspect ratio with almost any closed profile. Such blades can be obtained in a large variety of shapes using UV-LIGA technology which combines photolithography and electroforming. Master molds were prepared and the following steps of micro UV-imprinting from the master molds are also introduced. The present work confirms the feasibility of the fabrication for parabolic sidewall microstructures of aspect ratio of 3.8 and 6.7 with good controlled shapes. With a scanning speed of 0.15m/min, the method is proven to be efficient and appropriate for large-area microstructured fabrication.

Continuous-wave Y-band planar BWO with wide tunable bandwidth

A high performance continuous-wave (CW) backward wave oscillator (BWO) with planar slow wave structure (SWS) and sheet electron beam in Y-band is presented in this paper. The mode selection is discussed by studying the dispersion curve of SWSs, distributions of the electric field, and particle-in-cell simulation results, showing that the designed BWO operates in the fundamental mode TM11. The planar SWSs are fabricated by using the UV-LIGA technology with the processing error less than 0.003 mm. The electron gun can provide the 2.5 mm × 0.14 mm sheet electron beam with maximum current density of 57 A/cm2 at the CW mode. Experimental results show that the developed BWO can operate in the fundamental mode TM11 and generate the state-of-art output power of 182 mW at the frequency of 0.3426 THz with a large frequency tuning range from 0.318 THz to 0.359 THz.

UV-LIGA技術の機械時計への応用(研究)

UV-LIGA技術の機械時計への応用(研究)

Design and Simulation of MEMS-based Z-Axis Capacitive Accelerometer

In this paper, a MEMS-based Z-axis capacitive accelerometer is designed and simulated. An out-of-plane Z-axis accelerometer designed for 8 µm UV-LIGA technology for an acceleration range of ±10g. The operating voltage is 5 V DC. Simulation results show good linear characteristics in the operating range of DC-400 Hz, which is the bandwidth of the accelerometer. The simulations of the device were carried out using CoventorWare ® . By using modal analysis in CoventorWare ® the resonating frequency of 3.1 kHz is obtained.

Design, fabrication and measurement of a novel 140 GHz folded waveguide based on SU-8 UV-LIGA technology

In an RF MEMS field, a folded waveguide is the core structure of a traveling wave tube as a slow-wave structure. 140 GHz is an important atmospheric working window. In this paper, the dispersion property and interaction impedance of a novel 140 GHz folded waveguide were analyzed and simulated using CST Microwave Studio. The beam–wave interaction in the folded waveguide was also simulated, using CST Particle Studio. The output power gain of the folded waveguide reached 24.5 dB at 140 GHz when the emission voltage was 12.7 kV and the emission current was 0.15 A. The simulation process provided structure parameters for further micromachining. Furthermore, to analyze the effect of structure fabrication errors, CST was used to simulate the dispersion and interaction impedance by adding tolerance to some important structure parameters. Finally, multi-step SU-8 UV-LIGA technology was adopted for micromachining the folded waveguide. To ensure adhesion between the SU-8 photoresist and substrate, a thin TiO2 film was formed on the surface of the Ti substrate. In the end, test results showed that the reflection coefficient S11 and transmission coefficient S21 were near −28.1 dB and −1.2 dB respectively. Moreover, the output power gain was close to 23 dB at 140 GHz. Good accordance between the simulation and experimental results indicated a reasonable design and high precision of microfabrication by SU-8 UV-LIGA technology.

Fabrication of Micro Electrode Array by UV-LIGA and its Application in Micro ECM

In this paper, a fabrication process of ultra-high metal micro electrode array by means of UV-LIGA technology and its application in micro Electrochemical Machining (ECM) was investigated, and a new aided method, which can completely remove the ultra-thick cross-linked SU-8 resist without leaving remnants of the resist or destroying the electroplated microstructures, was advanced. During the lithography process, 1mm thick SU-8 moulds of different patterns were fabricated on the substrate. Before the electroforming process, a through-mask electrochemical micromachining (through-mask EMM) procedure was carried out to process micro roots on the substrate, the processed micro roots could improve the adhesion of micro electrode array electroformed on the substrate. After the electroforming process, cross-linked SU-8 resist was removed by the hot remover PG (MicroChem). Under the optimal experiment conditions of this fabrication process, the electrode arrays up to 800μm high of different shapes were fabricated. Finally, the fabricated electrode arrays was used as cathode to machine micro hole arrays on stainless steel by micro ECM.

Manufacture of a 2D optical fiber array coupler with micrometer precision for laser radar applications

This article presents the manufacture of a 2D-fiber array coupler using UV-LIGA technology for the precise positioning of a two-dimensional (2D) optical fiber array. The precision of the alignment of the eight-by-eight fiber array was demonstrated to be less than 2 μm. The average concentricity error of the fibers to the positioning holes of the array coupler had a minimum and maximum error of 1.7 µm and 6.5 μm, respectively. The 2D fiber array coupler can fulfill the coupling and transmission requirements of 2D light spots for laser radar applications. The method developed here can easily be extended to the manufacture of larger arrays.

New design architecture of a 3-DOF vibratory gyroscope with robust drive operation mode and implementation

This paper presents new gyroscope design architecture with the complete 2-DOF drive and 1-DOF sense mode oscillators that enable the implementation of reduced drive bandwidth without significantly decreasing the sense-to-drive mass ratio of the device. The mechanical structure has an additional anchoring of the decoupling frame mass which allows for the specification of the drive mode resonances and the coupling between the masses independent of the sense mode frequency. This feature eliminates the requirement of an increased design space for realizing a high operational frequency device with robust operation. In addition to this, a reduction in the bandwidth enabled by the additional anchor, leads to the increase in drive mass amplitude, which in turn results in an increased mechanical gain. With this arrangement, the actuation voltage can be further reduced for the same drive displacement as of non-anchored structure. This device has been mathematically modelled considering decoupled frame anchoring effect, designed and then fabricated by using the economical UV-LIGA technology with nickel as a key structural layer of 8 µm thickness; with an overall reduced key structure size of 2.13 by 1.93 mm. Experimental characterization demonstrates the two drive resonances at 8.55 and 10.6 kHz with a bandwidth of 1.0 kHz and the sense mode resonance at 9.2 kHz.

Design, fabrication and measurement of a microchannel heat sink with a pin-fin array and optimal inlet position for alleviating the hot spot effect

A microchannel heat sink with an inlet near the midpoint of the diagonal and high aspect ratio micro pin-fin array was designed, fabricated and measured. The heat transfer performance of the microchannel heat sink was simulated by a computational fluid dynamics (CFD) method. The inlet near the midpoint of the diagonal was proposed to alleviate the hot spot effect. The maximum temperature of the chip was reduced by up to 26.7% at a dissipation power of 72 W compared with other reference inlet/outlet configurations. Other parameters of the micro pin fins, such as the height, the spacing distance and the edge length, were optimized for improving heat transfer capacity. The microchannel heat sink prototype sample was fabricated and tested through UV-LIGA technology and an infrared thermal imaging system, respectively. The convective heat transfer increased at high flow rates (40 ml min−1~90 ml min−1), which resulted in a gradually increasing deviation between simulation and experiment. The measurement results show that the maximum dissipation heat flux can reach 209 W cm−2 when the chip maximum temperature is under 85 °C at a flow rate of 90 ml min−1. It is shown that the optimization of inlet position and micro pin-fin geometrical topology give the microchannel heat sink the potential to remove high heat flux.

Fabrication of novel MEMS inertial switch with six layers on a metal substrate

MEMS inertial switches have great potential to be widely used in toys, accessories, automotive, military weapons and industrial applications in recent years. Combining with UV-LIGA technology, a new fabrication method of multilayer movable microstructures on metal substrates is presented in this paper, by which a kind of MEMS omnidirectional inertial switch with six layers has been fabricated on metal substrate directly. The method consists of double alignment marks etching process on the back of metal substrates, SU-8 thick photoresist with high aspect ratio lithography process, micro electroforming process, no back plate growing process and SU-8 photoresist sacrificial layer process. Some problems in the fabrication process, such as poor adhesion property among electroforming deposit layers, high stress in electroforming layers, difficulty of preparing the SU-8 mould with high aspect ratio, have been solved effectively. The smallest dimension of the switch is 15 μm, the highest aspect ratio achieves 6:1, the total height of the switch is 210 μm and the outline size is 2.8 × 2.8 mm. The fabrication method presented in this paper provides a new option for the development of multi-layers micro metal devices and is helpful for the fabrication of similar kinds of micro devices.

Segmented magnetic circuit simulation of the large displacement planar micro-coil actuator with enclosed magnetic yokes

This paper proposed the segmented magnetic circuit method to simulate the large displacement planar micro-coil (PMC) microactuator for micro-magnetic relay applications, which adopted enclosed miniaturized magnetic yokes. The segmented magnetic circuit model has been established to describe the magnetic flux variation and the redistribution effects of the magneto motive force (MMF) induced by the large air gap and large ratio between the radical and vertical size. Based on the optimized parameters, the PMC microactuator was fabricated through UV-LIGA technology and tested to verify the model under scrutiny. The large displacement was realized by using laminated photoresist sacrificial layer process. After comparing the measurement and simulation results, it is concluded that the modified model can describe the influence of key parameters over the output electromagnetic force. The proposed methodology is demonstrated to be efficient in the analysis and optimization of the magnetic MEMS devices of PMC structures with embedded magnetic yoke.

The Fabrication of Trans-Scale Micro-Fuze Safety Device

Fuze Micro-Electro-Mechanical System (MEMS) has become a popular subject in recent years. Studies have been done for the application of MEMS-based fuze safety and arm devices. The existing researches mainly focused on reducing the cost and volume of the fuze safety device. The reduction in volume allows more payloads and, thus, makes small-caliber rounds more effective and the weapon system more affordable. At present, MEMS-based fuze safety devices are fabricated mainly by using deep reactive ion etching (DRIE) or LIGA technology, and the fabrication process research on the fuze MEMS safety device is in the exploring stage. In this paper, a new trans-scale fabrication method of metal-based fuze MEMS safety device is presented based on UV-LIGA technology and the micro Wire-cut Electrical Discharge Machining (WEDM). The method consists of fabrication of micro-spring by UV-LIGA technology, the fabrication of mesoscale structure by WEDM, the micro assembly of micro spring and mesoscale structure. Because UV-LIGA technology and WEDM technology were introduced, the production cycle was shortened and the cost was reduced. The overall dimension of the micro-fuse safety device is 9.5×12.3×0.6 mm and the smallest dimension is 10μm. Besides, four problems in the fabrication process have been solved effectively, which is helpful for the fabrication of similar kinds of micro devices. The fabrication method presented in this paper provides a new option for the development of MEMS fuze.

A Novel Method to Fabricate High Aspect Ratio Microcoils

In this study, we developed a new method to fabricate microcoils with narrow and high aspect ratio coil lines using TSV and UV-LIGA technology in a SU-8 mold. The combination of SU-8 and TSV makes it possible to fabricate microstructures with high aspect ratio. TSV technology resolved the difficulties of electroplating with high aspect ratio. We designed and fabricated microcoils consisiting of coil lines with widths of 15μm and aspect ratio of 2.

A Novel of Biodegradable Implants Based on PLGA for Control Delivery of Cisplatin

A novel controlled drug delivery micro-device was successfully prepared with biodegradable implants based on PLGA by solvent evaporation method. The micro-chambers were fabricated using the UV-LIGA technology. The controlled release process resulted from the design of the micro-chambers and the characteristics of biodegradable polymers. Implant bioactivity was tested using in vitro and in vivo release. The implants kept good shape and cisplatin was homogeneous loaded in the PLGA implants. The precast implants appeared hexagon. With different proportion of PLA and PGA segment, the swelling behavior and the hydrolytic degradation rate of implants became lower due to the increase of PLA hydrophobic segment. In vitro and in vivo drug release behavior was studied using cisplatin as model drug, the implants could control the diffusion of cisplatin. The results demonstrated that this type of controlled drug delivery micro-device could be more potential application in tumor therapy.