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A low-cost method of fabrication of high aspect ratio nano-channels by thermal nano-imprinting and Parylene deposition is proposed. SU-8 photoresist nano-channels were first manufactured by thermal nano-imprinting, and Parylene deposition was carried out to reduce the width of the nano-channels and increase the aspect ratio. During the process, the side walls of the SU-8 nano-channels were covered with the Parylene film, reducing the width of the nano-channels, and the depth of the channels increased due to the thickness of the Parylene film deposited on the surface of the SU-8 nano-channels, more so than that at the bottom. The influence of Parylene mass on the size of nano-channels was studied by theoretical analysis and experiments, and the deposition pressure of Parylene was optimized. The final high aspect ratio nano-channels are 46 nm in width and 746 nm in depth, of which the aspect ratio is 16. This simple and efficient method paves the way for the production of high aspect ratio nano-channels. [ABSTRACT FROM AUTHOR]

For a structure to show radiative cooling property, it must have first, high reflectivity of above 90% in the wavelength range of 0.3 to 3 μm, and second, high emissivity for the wavelengths ranging from 8 to 13 μm, namely atmospheric transparency window. Being inspired by the architecture of microwave absorbers used extensively for antenna measurements, we proposed a novel microstructure with near unity emissivity that can be further developed for radiative cooling. To this end, we designed and analyzed a V-grooved multilayer periodic microstructure capable of perfectly emitting in the aforementioned wavelength range. Further, SU-8 is selected as the material of the proposed microstructure. SU-8 is the commonly used material in photolithographic based microfabrication and it is shown, for the first time, that its bulk optical properties are appropriate for radiative cooling purposes. The numerical simulations of the emissivity were performed through a semi-analytical computational technique known as Transmission-Line Formulation (TLF) which enables us to accurately and efficiently calculate electromagnetic radiations reflected from or transmitted through a multilayer structures composed of periodic layers of absorbing materials. It was demonstrated through the simulations that the average emissivity of the proposed microstructure can even exceed 99% in the wavelength range desired for radiative cooling.

To solve the problem of shaping nonspecialized polymers, new generation micro- and nanoelectronic technologies are used, for example, nanoimprint lithography. A special case of nanoimprint lithography is soft lithography, which involves the formation of a topology using a soft master mold fabricated by a hard mold imprint. Therefore, the study of hard molds self-manufacturing possibility is an urgent task to fabricate a new generation printed circuit boards with optoelectronic buses made of nonspecialized polymer materials. In order to rationalize the cost of purchasing an expensive soft lithography hard mold, an original technological process for hard mold fabrication based on an SU-8 photoresist is developed and implemented. During the development of the proposed technological process, the reason for the formation of a negative slope (T-topping) of the walls of the soft lithography hard mold is determined. In order to eliminate the negative slope, a series of UV cutoff filters for optical radiation wavelengths less than 350 nm is developed and manufactured. According to the experimental measurements data of the i-line mercury lamp UV radiation intensity of the EVG620 NIL automated alignment and exposure unit, the dependences of the UV radiation intensity attenuation on the developed UV light filter functional layer thickness are plotted for 365 and 400 nm optical wavelengths. The effectiveness of the use of the developed UV filters is proved by eliminating the negative slope during the technological process of manufacturing a test topology of the soft lithography hard mold. Soft lithography will make it possible in the future to create printed circuit boards with a built-in optoelectronic data bus in the form of an array of polymer planar optical waveguides and optical input-output elements. [ABSTRACT FROM AUTHOR]

• Introduce a novel fabrication method to design optical cavity with SU-8 photoresist. • The optical cavity can localize wave around 1269.3 nm, and the Q factor in the cavity is comparatively higher. • The smaller thickness of SU-8, the higher quality factor Q value can be obtained. • Experiment showed that a high quality factor of Q = 8200 could be obtained. How to control electromagnetic wave effectively is the key to the realization of applicable filters in many optics technologies. In our work, a SU-8 photoresist micro-disk is written onto a photonic crystal waveguide to control electromagnetic wave. Corresponding simulation and experiment shows that, the quality Q increases as the thickness of SU-8 smaller. When the thickness exceeds 400 nm, the change of thickness has little influence on electromagnetic waves. Besides, the increase of the radius of disc-shaped SU-8 can also increase the Q value. By optimizing the simulation and experimental data, we can successfully create a SU-8 photoresist micro-disk cavity with the thickness of 5 µm and height of 20 nm, the quality factor of Q can reach 8200. However, longer exposure time and more stable experimental equipment is needed if we want to get a larger radius. The method in our work by using SU-8 photoresist micro-disk on photonic crystals to control electromagnetic wave is more practical and flexible, which can provide new significance for research into optical filter. [ABSTRACT FROM AUTHOR]

This paper investigates the fabrication accuracy of the W-band SU-8 photoresist micromachined 4th order waveguide bandpass filters (BPF). The designed filter based on cylindrical resonators is excited in TM010 mode. It is ideally suitable for the layered SU-8 micromachining process as the height of the resonator is much smaller than one wavelength, the electromagnetic fields remain unchanged in the thickness direction. The filter is composed of three silver-coated SU-8 layers based on a double-layer overlay process. Excellent manufacturing tolerances can be controlled within 4 μm in the thickness direction, around 10 μm in double-layer stacking accuracy, and an average of 1° in vertical angle deviation. Various challenges encountered in the SU-8 process are investigated while corresponding general solutions are proposed for machining high-precision devices. The measured results show a return loss of 12.4 dB and a minimum insertion loss of 0.8 dB, which are in agreement with the simulated one. Stress and deformation analysis are also conducted to confirm the maximum pressure that the filter can withstand and maintain good transmission performance. [ABSTRACT FROM AUTHOR]

A low-cost method of fabrication of high aspect ratio nano-channels by thermal nano-imprinting and Parylene deposition is proposed. SU-8 photoresist nano-channels were first manufactured by thermal nano-imprinting, and Parylene deposition was carried out to reduce the width of the nano-channels and increase the aspect ratio. During the process, the side walls of the SU-8 nano-channels were covered with the Parylene film, reducing the width of the nano-channels, and the depth of the channels increased due to the thickness of the Parylene film deposited on the surface of the SU-8 nano-channels, more so than that at the bottom. The influence of Parylene mass on the size of nano-channels was studied by theoretical analysis and experiments, and the deposition pressure of Parylene was optimized. The final high aspect ratio nano-channels are 46 nm in width and 746 nm in depth, of which the aspect ratio is 16. This simple and efficient method paves the way for the production of high aspect ratio nano-channels.

A novel approach to the design and fabrication of field-emission tips with self-aligned gates intended for electric propulsion micro-thruster applications is presented. Their micro-electromechanical systems fabrication process is derived from the recent proliferation of research toward developing field emitter arrays, which are used primarily for field-emission flat-panel display applications. An array of micronsized tips for electric field enhancement via wet isotropic etching of silicon, using silicon nitride as a hard mask is fabricated. The wet etching is accomplished using a combination of hydrofluoric, nitric, and acetic acids. The tips were then coated with a metal layer to enhance wetting by indium, the proposed propellant. Next, a layer of SU-8 photoresist was applied by spin coating and patterned to serve as a dielectric spacer. A second layer of metal was then applied to serve as a gate electrode. In addition, the results of electrostatic simulations of the prototype is described.

The stiffness and the topography of the substrate at the cell–substrate interface are two key properties influencing cell behavior. In this paper, atomic force acoustic microscopy (AFAM) is used to investigate the influence of substrate stiffness and substrate topography on the responses of L929 fibroblasts. This combined nondestructive technique is able to characterize materials at high lateral resolution. To produce substrates of tunable stiffness and topography, we imprint nanostripe patterns on undeveloped and developed SU-8 photoresist films using electron-beam lithography (EBL). Elastic deformations of the substrate surfaces and the cells are revealed by AFAM. Our results show that AFAM is capable of imaging surface elastic deformations. By immunofluorescence experiments, we find that the L929 cells significantly elongate on the patterned stiffness substrate, whereas the elasticity of the pattern has only little effect on the spreading of the L929 cells. The influence of the topography pattern on the cell alignment and morphology is even more pronounced leading to an arrangement of the cells along the nanostripe pattern. Our method is useful for the quantitative characterization of cell–substrate interactions and provides guidance for the tissue regeneration therapy in biomedicine.

This paper investigates the fabrication accuracy of the W-band SU-8 photoresist micromachined 4th order waveguide bandpass filters (BPF). The designed filter based on cylindrical resonators is excited in TM010 mode. It is ideally suitable for the layered SU-8 micromachining process as the height of the resonator is much smaller than one wavelength, the electromagnetic fields remain unchanged in the thickness direction. The filter is composed of three silver-coated SU-8 layers based on a double-layer overlay process. Excellent manufacturing tolerances can be controlled within 4 μm in the thickness direction, around 10 μm in double-layer stacking accuracy, and an average of 1° in vertical angle deviation. Various challenges encountered in the SU-8 process are investigated while corresponding general solutions are proposed for machining high-precision devices. The measured results show a return loss of 12.4 dB and a minimum insertion loss of 0.8 dB, which are in agreement with the simulated one. Stress and deformation analysis are also conducted to confirm the maximum pressure that the filter can withstand and maintain good transmission performance.

We propose a photonic crystal dual-resonant microcavity and waveguide-coupled temperature sensor structure. The resonant characteristics of photonic crystal microcavities are simulated by finite-difference time-domain method. Due to the positive thermo-optic effect of silicon and the negative thermo-optic effect of SU-8 photoresist, a resonant wavelength shift is detected for temperature sensing in the opposite direction, which significantly improves the sensitivity of the sensor. Simulation results highlight that the sensitivity of the temperature sensor is 124.69 pm/°C, the temperature measuring range is ~150°C, and the limitation of the temperature sensing area is reduced. The sensor can be integrated to lab-on-chip and system-on-chip to achieve real-time temperature measurement in different microregions. [ABSTRACT FROM AUTHOR]

A novel conical nozzle fabrication method for piezoelectric inkjet printhead is proposed based on the microelectromechanical system technology. By optimizing the exposure gap, exposure dose, postexposure bake (PEB), and development time, the SU-8 conical nozzle was fabricated. After thermal bonding with an open chamber, the piezoelectric inkjet printhead chamber was formed. The results show that the optimum SU-8 conical nozzle can be fabricated by applying exposure dose of 105 mJ/cm2, exposure gap of 50 µm, PEB temperature of 65°C, PEB time of 10 min, and development time of 210 s. The final size of optimum conical nozzle is the large aperture of 30.46 ± 1.17 µm, small aperture of 20.34 ± 1.42 µm, and nozzle height of 45.38 ± 1.02 µm. [ABSTRACT FROM AUTHOR]

This paper presents a low-cost non-invasive millimeter-wave surface-height measurement sensor of dielectric and polymer films on glass and quartz substrates. The surface-height profiler utilizes near-field resonance measurement technique operating at 96 GHz implemented by using a single complementary split-ring resonator (CSRR) integrated with a tailor-made WR10 rectangular waveguide. By placing a glass or quartz substrate uniformly coated with SU-8 photoresist on top of the CSRR, the thickness of the SU-8 polymer can be extracted based on the reflected and transmitted electromagnetic-wave energy interacting at the electrical boundary between the substrate and polymer film. Uniform single layers of SU-8 polymer with thicknesses from 3 to 13~\mu \textm coated on top of the glass substrate are measured and characterized. The extracted polymer-film thicknesses from the sensor in this paper show an agreement of higher than 95% as compared with the commercial surface profiler instrument, while offering various advantages, such as non-invasion, ease of measurement setup, low-cost, and miniaturization. [ABSTRACT FROM PUBLISHER]

This paper describes the effect of the modification of microchip microchannels with two different cationic surfactants on the electrochemical behavior of ferrocene carboxylic acid (FCA), common redoxprobe in bioanalysis. Cetyltrimethylammonium bromide (CTAB), a single-chain surfactant, and didecyldimethylammonium bromide (DDAB), double-chained, were evaluated. The purpose was to obtain a reversal of the electroosmotic flow for allowing precise determination of FCA, an anionic probe that is employed in electrochemical bioassays. Although this was possible in both cases, modification of the microchannel with a high concentration of CTAB produced a differentiation between the free CTAB fraction and the CTAB-combined FCA. DDAB is presented as a good alternative for this modification because this double-chained cationic surfactant forms a more stable quasi-permanent coating on the microchannel surface, avoiding these surfactant-probe interactions. Linear relationship was found between the analytical signal and the concentration of FCA (evaluated between 10 and 150 μM) for a modification with 0.1 mM of DDAB. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel vertical SU-8 waveguide for evanescent analyte sensing. The waveguide is designed to possess a vertical and narrow structure to generate evanescent waves on both sides of the waveguide’s surface, aimed at increasing the sensitivity by enlarging the sensing areas. We performed simulations to monitor the influence of different parameters on the waveguide’s performance, including its height and width. E-beam lithography was used to fabricate the structure, as this one-step direct writing process enables easy, fast, and high-resolution fabrication. Furthermore, it reduces the sidewall roughness and decreases the induced scattering loss, which is a major source of waveguide loss. Couplers were added to improve the coupling efficiency and alignment tolerance, and will contribute to the feasibility of a plug-and-play optical system. Optical measurements show that the transmission loss is 1.03 ± 0.19 dB/cm. The absorption sensitivity was measured to be 4.8 dB per refractive index unit (dB/RIU) for saline solutions with various concentrations.

We proposed herein a facile, fast and low cost metal-free photochemical method for preparing reduced graphene oxide (rGO) by ultraviolet (UV) irradiation of a solution containing mixture of a photoinitiator such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (GR-XBPO) and a triethylamine (TEA) in ethanol. Free radicals are generated via photoinitiator decomposition under UV irradiation. In this process, graphene oxide (GO) rapidly reduced to graphene via extensively removal of oxygen-containing functional groups (OFGs) by free radicals in the presence of anti-oxide inhibitor such as TEA exists. Furthermore, we prepared flexible conductive micropatterns over rGO/SU-8 composites deposited on several substrates (e.g., glass, polyethylene terephthalate (PET), aluminum, and silicon) by dispersing rGO into a photocurable SU-8 resin by means of a photolithography technique. The incorporation of rGO changed the properties of the composites. Thus, the behavior of SU-8 resin shifted from insulating to conductive/antistatic upon incorporation of rGO nanocomposites. This preliminary study provides us with the opportunity to not only develop an efficient metal-free photochemical reduction route towards GO but also obtain a processable conductive micropattern by optimizing the overall processing parameters, and maximizing the advantages of them for future carbon-based nanocomposites at large scale. [ABSTRACT FROM AUTHOR]

A binder-free carbon nanofibres web over stainless-steel wafer current collector was fabricated by controlled pyrolysis of electrospun SU-8 photoresist nanofibres. Electrochemical performance of the as-prepared carbon nanofibres webwas investigated by performing charge–discharge experiments at different current densities. At lowcurrent density (37.2 mA g−1,0.1C), SU-8-derived carbon nanofabric showed a large initial discharge capacity (1417 mAh g−1) with sufficiently higher initial coulombic efficiency (∼55%). More importantly, this carbon nanofibres web also exhibited excellent rate performance with considerably higher specific capacities at higher current densities (358 mAh g−1 at 1C). This superior electrochemical performance, in particular at high current rates, can be attributed to small lithium ion diffusion length and resilience in entangled carbon nanofibres to accommodate volume changes during charging and discharging. [ABSTRACT FROM AUTHOR]

This paper presents the design and a new low-cost process for fabrication of a second-order micromechanical filter using UV-LIGA technology. The micromechanical filter consists of two identical bulk-mode ring resonators, mechanically coupled by a flexural-mode beam. A new lumped modeling approach is presented for the bulk-mode ring resonators and filter. The validity of the analytical derivation is investigated using the finite element method by ANSYS software. The new low-cost fabrication process is used to achieve a high aspect ratio of 16 with 3 μm gap spacing. The rigid graphite serves as a low-cost primary substrate and plating base of nickel as structural material. The fabrication process needs only three UV-lithography steps with Mylar masks to fabricate the main structure and pattern the printed circuit board as a secondary substrate. The frequency response of the fabricated filter is characterized as a function of the DC-bias voltage using a fully differential drive and sense interface circuit. The experimental results demonstrates micromechanical filter with center frequency in the vicinity of 10.31 MHz and percent bandwidth less than 0.3% using a DC-bias voltage of 60 V. The detailed fabrication process can be applied as an appropriate low-cost alternative to X-ray LIGA and silicon-based micromechanical filters.

Thick SU-8 photoresist has been a popular photoresist material to fabricate various mechanical, biological, and chemical devices for many years. The accuracy and precision of the ultraviolet (UV) lithography process of thick SU-8 depend on key parameters in the set-up, the material properties of the SU-8 resist, and the thickness of the resist structure. As feature sizes get smaller and pattern complexity increases, accurate control and efficient optimization of the lithography process are significantly expected. Numerical simulations can be employed to improve understanding and process design of the SU-8 lithography, thereby allowing rapid related product and process development. A typical comprehensive lithography of UV lithography of thick SU-8 includes aerial image simulation, exposure simulation, post-exposure bake (PEB) simulation, and development simulation, and this article presents an overview of the essential aspects in the comprehensive simulation. At first, models for the lithography process of the SU-8 are discussed. Then, main algorithms for etching surface evolvement, including the string, ray tracing, cellular automaton, and fast marching algorithms, are introduced and compared with each other in terms of performance. After that, some simulation results of the UV lithography process of the SU-8 are presented, demonstrating the promising potential and efficiency of the simulation technology. Finally, a prospect is discussed for some open questions in three-dimensional (3D) comprehensive simulation of the UV lithography of the SU-8.

In this paper, we present a periodic hollowed-out pyramid microstructure with excellent superhydrophobicity. In our approach, T-topping pillars and capillary-induced self-assembly methods were combined with the photolithography process to fabricate a hollowed-out pyramid structure. First, a wideband ultraviolet source without a filter was used to fabricate the T-topping pillars during the exposure process; then, the evaporation-induced assembly collapsed the pillars and formed the hollowed-out pyramid structure. Scanning electron microscopy images showed the microstructures of the prepared surface. The contact angle of the surface was 154°. The surface showed excellent high temperature and ultraviolet irradiation tolerance, and the contact angle of the surface barely changed when the temperature dropped. This excellent environmental durability of our superhydrophobic surface has potential applications for self-cleaning and friction drag reduction under water.

Tissues are complex three-dimensional structures in which cell behaviour is frequently guided by chemotactic signals. Although starvation and nutrient restriction induce many different chemotactic processes, the recreation of such conditions in vitro remains difficult when using standard cell culture equipment. Recently, microfluidic techniques have arisen as powerful tools to mimic such physiological conditions. In this context, microfluidic three-dimensional cell culture systems require precise control of cell/hydrogel location because samples need to be placed within a microchamber without obstruction of surrounding elements. In this article, SU-8 is studied as structural material for the fabrication of complex cell culture devices due to its good mechanical properties, low gas permeability and sensor integration capacity. In particular, this manuscript presents a SU-8 based microdevice designed to create self-induced medium starvation, based on the combination of nutrient restriction and natural cell metabolism. Results show a natural migratory response towards nutrient source, showing how cells adapt to their own microenvironment modifications. The presented results demonstrate the SU-8 potential for microdevice fabrication applied to cell culture.

Photo sensitive polymer SU-8, owing to its excellent mechanical properties and dielectric properties on polymerization, is widely used in MEMS device fabrications. However, the removing, stripping or re-patterning of the cross-linked SU-8 is a difficult issue. In this paper, CF4/O2 gas mixture provided by a plasma asher equipment was used for the patterning of cross-linked SU-8 material. The RF power, the temperature of the substrate holder, chamber pressure and gas concentration were optimized for the cross-linked SU-8 etching process. When the CF4/O2 mixture contains about 5%CF4 by volume, the etching rate can be reached at 5.2 μm/min. [ABSTRACT FROM AUTHOR]

In order to produce disposable microneedles for blood-collection devices in smart homecare monitoring systems, we have developed a simple low-cost scalable process for mass fabrication of sharp-tipped microneedle arrays. The key feature in this process is a design of computer numerical control-machined aluminum sample (CAS). The inclined sidewalls on the CAS enable microfabricated traditional-shaped microneedles (TMNs) to be produced in the desired shape. This process provides significant advantages over other methods that use inclined lithography or anisotropic wet etching. TMNs with a length of 1510 \mu \textm , a hollow diameter of 120 \mu \textm , and the tip radius of 16 \mu \textm were successfully fabricated. Theoretical study and practical measurements of fracture force verified the improved mechanical strength of TMNs for safe skin insertion. In addition, the penetration tests on cadaver pork skin demonstrated that the TMNs could pierce the pork skin without breaking, and create the transport conduits through microneedle lumens. [2014-0361] [ABSTRACT FROM PUBLISHER]

A micro-injection mold cavity is designed and manufactured. By the method of no back plate growing technology, the micro-injection mold cavity with micro-array structure, micro-injection gate, micro-exhaust passage, exhaust vent and polymer melt flow channel is directly manufactured on an alloy steel substrate applying overlay UV-LIGA technology and mask etching technology. The optical lithography parameter of SU-8 thick photoresist is optimized and the proposed fabrication process for 350 μm SU-8 photoresist is given as follows:scraping photoresist by fixing the thickness of frame, prebaking by gradient heating-up and temperature rising every 5 °C from 65 °C to 85 °C,at 85 °C for 5.5-6.0 h, UV contacting exposure with dose of 630 mJ/cm2,post-baking at 85 °C for 15 min and development for 20 min. The causes for generating nodules in the process of Ni micro-electroforming are analyzed, and the process parameter is improved by controlling current density and pH respectively under 3 A/dm2 and 3.8-4.4.As a result, the micro-injection mold cavity of good quality is gained successfully. [ABSTRACT FROM AUTHOR]

Arrays of 11.2-16.6 μm holes were patterned on 50 μm thick SU-8 photoresist layers by using synchrotron X-ray lithography. After the resist development, the chemically stable and mechanically hardened SU-8 templates with varying hole sizes were used as substrates for RF sputtering of 1.5 μm-thick cobalt (Co). By comparing hysteresis loops from inplane and out-of-plane magnetisation, the Co film on patterned substrate with average hole size of 16.6 μm was more isotropic than in the case of 15.3 and 11.2 μm. Both magnetic squareness and coercive field were at the minimum when the holes were smallest. After the removal of Co on SU-8 surfaces, the remaining Co deposits in the holes exhibited smaller squareness and anisotropy. On the other hand, the enhanced coercive field was increased with a reduction in diameter of patterned holes. [ABSTRACT FROM AUTHOR]

We demonstrate GaAs thermophotovoltaic (TPV) devices with a patterned dielectric back contact (PDBC) architecture, featuring a dielectric spacer between the semiconductor and back metal contact over most of the back surface for high reflectance, and metal point contacts over a smaller area for electrical conduction. In the TPV application, high sub-bandgap reflectance is needed to reflect unused sub-bandgap photons to the thermal emitter to minimize energy losses in this portion of the thermal spectrum. We explore different PDBC fabrication processes with SU-8 and SiO 2 dielectric spacer layers to maximize sub-bandgap reflectance while minimizing series resistance to increase TPV conversion efficiency. We successfully demonstrate GaAs SU-8 PDBC TPV devices with 2200 °C blackbody-weighted sub-bandgap reflectance of 94.9% and 96.5% with and without a front metal grid, respectively. This is 0.7% and 2.3% (absolute) higher than the mean sub-bandgap reflectance of 94.2% for GaAs baseline TPV devices with 100% Au back contact with front metal grid. Lower sub-bandgap reflectance in TPV devices with front grids indicates the front grid induces light scattering leading to additional parasitic absorption in the TPV device. We also show that for higher contact coverage fractions, the PDBC reflectance cannot in general be treated by a linear interpolation using simple 1D transfer matrix method modeling and should be treated instead as a diffraction grating by solving Maxwell's equations in 3D. • We explore different patterned dielectric back contact (PDBC) fabrication processes with SU-8 and SiO 2 for TPV cells. • Sub-bandgap reflectance over 96% demonstrated using dielectric-metal point contact rear mirror structure, a gain of >1%. • PDBC structures should be modeled as a 3-dimensional diffraction grating by solving Maxwell's equations. • Front grids increase diffuse reflectance thus increasing absorption in the device. [ABSTRACT FROM AUTHOR]

Two four‐order dual‐mode rectangular waveguide filters centred at 100 GHZ with return loss all better than −19 dB are presented. The filters consist of two cascade resonant cavities suppose TE102/TE301 degenerate modes and three pairs of round corner inductive irises symmetrical with waveguide. Since the introduction of round corner irises and dual‐mode cavities, the filter structures have lower aspect ratio and less resonant cavities, thus the difficulty of fabrication sharply reduced. Single zero exists at the one side of pass‐band because of the same width of two resonant cavities. All the other parameters constant except for the widths of two cavities slightly unequal, two distinct transmission zeros can generate at the same side of pass‐band. UV lithography technology with SU‐8 photo‐resist is used for the fabrication of filters. On the whole, results from measurement are in good agreement with simulation, which fully confirm the validity of design and fabrication methods. [ABSTRACT FROM AUTHOR]

In this study, we present a novel optical fiber magnetic sensor based on electroforming long-period optical fiber grating (ELPFG) with a periodic polymer-metal (SU-8 photoresist and nickel) structure that is fabricated via a LIGA-like process. We measure the magnetic field through the nickel grating on the optical fiber, and an ELPFG magnetic sensor calibration experiment is also described. The coil produces a magnetic field to modulate the ELPFG, and we use an optical spectrum analyzer to analyze the resonant wavelength and changes in transmission loss. It is discovered from the experimental results that the optimal sensitivity of the ELPFG is -0.465 dB/mT, the linearity is 0.965, and the transmission loss will gradually increase following magnetic field enhancement. We infer that this phenomenon is due to the magnetostriction materials of nickel, which cause the nickel structure to impose a slight stretching strain on the ELPFG with the applied magnetic field. [ABSTRACT FROM PUBLISHER]

Micro-abrasive jet machining (AJM), also called micro-blasting, is a mainstream machining process that uses abrasive particles for difficult-to-cut workpieces such as glass, carbides, and ceramics. During the micro-blasting process, non-machined areas are covered by a protective mask. Today, either mask fabrication practice or micro-blasting process is well suited and optimized for producing micro-features on planar workpieces. However, the demand for micro-features on three-dimensional (3-D) freeform substrates in micro electro-mechanical systems (MEMS) and lab-on-a-chip devices requires more refined non-planar micro-manufacturing techniques. We focused on devising an appropriate photoresist mask required by micro-AJM processes on the surface of a 3-D freeform workpiece. Fundamental erosion mechanisms based on SU-8 mask properties (hardness, surface roughness, and thickness) were investigated. The optimal conditions were found at an ultraviolet (UV) energy of 12.0752 μJ/μm, focus ratio of 4.8341, and hard baking time of 8.4974 min. Under these settings, the mask hardness and surface roughness were 25.04 HV and 1.14 μm, respectively. The reliability of the fabricated mask was verified through a micro-AJM process. With existing plant conditions, the engraved microfeature dimensions on the surface of a 3-D freeform workpiece were 535.3 μm (width) and 11.6 μm (depth). [ABSTRACT FROM AUTHOR]