A plastic solar concentrating optical film with horizontal cylinder micro-lens array (HCMA) is presented in this study. The solar concentrator (SC) is in the form of optical film with HCMA and it is attached on the surface of a solar cell. This film is a polymethylmethacrylate (PMMA)-based optical layer. Compared with a plain solar collecting optical film without HCMA, the solar collecting optical film with HCMA can reduce the opportunity of reflection as light arrives at the surface and therefore can increase the refraction coefficient. As a result, the gain of photovoltaic power can be improved with the SC. Light is efficiently refracted by the HCMA and absorbed by the solar cell without the need of a solar tracking mechanism. Optimization of geometrical parameters of HCMA such as contact angle and gap (interspace) between each horizontal cylinder micro-lens is designed by simulation. The procedures of fabrication include reflow process, nickel cobalt (Ni-Co) electroplating, and molding process. The measurement equipment of NEWPORT Oriel 91160+ MODEL 6285 is utilized to measure the paramders such as open-circuit voltage V-oc, short-circuit current I-sc, and fill factor F.F., relating to the efficiency of the complete system. The experimental results show that a gain of photovoltaic power of about 3.30% is obtained with a contact angle of 62 degrees and a gap of 15 mu m. (C) 2011 Elsevier Ltd. All rights reserved.

Nano-scratch tests using nanoindenter with a Berkovich probe are applied to examine the scratch resistance of Mg-based bulk metallic glass (BMG). To realize nano-scratch behavior, a theoretical model of abrasive wear-resistant action on Berkovich is developed to determine the wear behavior. The experimental results of friction force are carried with the application of extensive normal forces. First, a low normal force (5mN) is applied on Berkovich at different scratch velocities to observe its effect on Mg-based BMGs. The experimental result shows that the dominating wear phenomenon is the rubbing and/or ploughing mode when a slightly normal load is applied. Second, varied normal forces (5–400mN) are applied on Berkovich at a constant scratch velocity. The experimental result shows that wear mode changes to cutting mode when the applied normal force rises. The indented depth increases when the applied normal force increases. Residual chips appear during the scratch test when the indented depth is about 1300μm under the normal force of 200mN. In this study, theoretical models of the forces such as tangential, friction and normal forces are analyzed.

Compared with single-step exposure of X-ray light source of high-power synchrotron radiation, lithographic process using multi-step exposures with a conformal mask has some advantages such as a thinner absorption layer, better heat dissipation, and shorter developing time. In this study, a conformal mask with an aurum (Au) absorber is fabricated using traditional ultraviolet (UV) lithography and Au electroplating process. For X-ray exposure, an analytical model of the absorption dosage (exposure dosage) along the exposed depth of x is developed. It can estimate accurately the time and dosage required for exposure. Based on the calculated dosage, 2-mm-thick PMMA (Polymethylmethacrylate) template with high-aspect ratio of 20 is fabricated by this multi-step exposures and developing process. With this template, nickel-cobalt (Ni–Co) alloy electroplating process is applied to fabricate a metallic mold with high hardness. For high-aspect-ratio microstructures, hardness and internal stress of the metallic mold by electroplating is a key factor to the quality. Experimentally, it is found that changing the ratio of Ni sulfamate to Co sulfamate can affect hardness and internal stress of the deposit. Though the hardness of the electroplated alloy is improved due to Co sulfamate, internal stress is induced at the same time. Thus, it is necessary to add a stress reducer to reduce internal stress. The currently result shows that the hardness of the mold of about 550 Hv with about 25wt.% of Co and zero internal stress can be made successfully after adding a stress reducer. With this electroplating technique, the 2-mm-thick and 100-μm-wide microstructure with high hardness is fabricated.

The mechanical properties of amorphous bulk metallic glassy (BMG) alloy, Mg58Cu31Y11, are examined using nano-indentation scratching test. This study investigates the influences of different scratching conditions on the mechanical properties such as the friction force and the friction coefficient (μ) to understand the abrasive behavior of the BMG. The scratching conditions include applied normal load, depth of scratch, scratching velocity, and scratching temperature. The experimental results of the friction force, friction coefficient, hardness, and scratching morphology of BMG are characterized. The result shows that the friction force is nearly proportional to the normal load; and the friction force exhibits a slightly dependent on the scratching temperature. Then, regression analysis method is utilized to establish a formula to fit the scratching condition of BMGs. The regression analysis can be applied to model the mathematical relationship between the scratching parameters. The regression result shows a good agreement with experimental one.

Mg–Cu–Y-based metallic glasses have exhibited superior glass-forming ability, and can be cast into bulk metallic glasses (BMGs). At temperatures above the glass transition temperature, the BMGs become supercooled viscous materials that can be formed into complicated shapes or patterns on micro- or even nano-scales. This paper presents the simulated forming evolution, using a finite element simulation software DEFORM 3D, and the experimental observations for the micro-imprinting of the Mg58Cu31Y11 BMGs for making hexagonal micro-lens arrays. The results demonstrate that the imprinting is feasible and promising.

A simple stacking process to fabricate microstructures with a high aspect ratio of 30 is presented in this study. For the x-ray absorption of a substance, an analytical model of the absorption dosage (exposure dosage) along a depth of x is developed. It can accurately estimate the time and dosage required for exposure. Based on the calculated result, 1 mm thick PMMA (polymethylmethacrylate) photoresist with a separate gold (Au)/graphite mask is exposed using x-rays followed by a developing process. Then a stacking process is applied for these 1 mm thick PMMA microstructures to form a microstructure with a high aspect ratio. With this stacking method, a PMMA microstructure with a height of 3 mm has been fabricated. In addition, a nickel–cobalt (Ni–Co) alloy electroplating process is applied to fabricate a metallic mold with high hardness. The hardness of the mold by electroforming is the key factor to the quality of the micro-punch process. As an integrated micro-punch head for IC leadframes, the hardness should be higher than 500 Vickers hardness (Hv). In addition, it was found experimentally that changing the ratio of Ni sulfamate to Co sulfamate can affect the deposit hardness and internal stress. The deposit internal stress varies with Co content. Thus, it is necessary to add a stress reducer to improve the hardness and reduce internal stress. A hardness of the mold of 550–560 Hv with 26–28 wt.% of Co and zero internal stress have been made successfully after adding a stress reducer. With this electroplating technique, a micro-punching head with high hardness and high aspect ratio can be fabricated by LIGA technology.

This study presents the hot embossing micro-forming of the V-groove and micro-lens array on the Au-based bulk metallic glasses (BMGs). The thermal and thermomechanical properties were firstly investigated by using thermomechanical analysis (TMA). Based on the results, the temperature of the hot embossing experiment was set at 177oC. The formability of the Au-based BMGs were evaluated under different embossing pressures and time durations, and the results showed the increasing trend of the forming quality with increasing forming pressure and time. The Au-based BMGs are considered to be promising for micro-electro-mechanical system applications.

The aim of this study is to investigate how the exposure dosage and developing temperature affect the developing rate for microstructures, with and without ultrasonic stirring, when the photoresist is exposed to X-ray radiation. Two experiments, “thick photoresist with low aspect ratio microstructure” (TPLARM) and “thick photoresist with high aspect ratio microstructure” (TPHARM) were conducted in this study. The TPLARM experiment was performed in order to investigate the relationship between exposure dosage and developing rate under ultrasonic agitation during the developing process. X-rays with an incident dose of 3500 mAmin/cm passed through the beryllium (Be) window and fell directly onto three graphite membranes of different thicknesses to expose a 3-mm thick PMMA substrate. PMMAs exposed to the X-rays were then placed into beakers filled with GG developer in two separate 28 and 36 °C isothermal baths for developing for 400 min. The TPHARM experiment was performed in order to study the effects of a high aspect ratio on developing rate using a Au microstructure as the absorber (15 μm in thickness; gap of 10 μm). This absorber was transferred onto a 3-mm thick PMMA substrate to form a conformal mask. The incident X-ray, at a dose of 800 mAmin/cm, passed through the Be window and directly exposed the PMMA substrate; the PMMA exposed to the X-ray was then immersed in a beaker filled with GG developer in a 28 °C isothermal bath for developing. The relationship between developing depth and time was then measured without the use of ultrasonic agitation stirring.

This study presents a new process to fabricate micro-lens array. The process of Micro-Electro-Mechanical Systems (MEMS) includes photoresist reflow technique, and nickel–cobalt (Ni–Co) electroplating to fabricate a first mold. Then, this first mold is applied to hot emboss on Mg–Cu–Y amorphous alloy to form a secondary mold. The secondary mold is a bulk metallic glass (BMG) material, whose thermal properties such as the glass transition temperature (Tg), the onset temperature for viscous flow (Tonset), the steady-state viscous flow temperature (Tvs), and the finish temperature for the viscous flow (Tfinish) are investigated using differential scanning calorimetry (DSC) and thermomechanical analyzer (TMA). The glass transition temperature of BMG is around 140°C (413K). Therefore, the temperature of the hot embossing experiment is set at 423K. This hot embossing process on BMG material makes molding process faster and more diverse applications. Next, the secondary mold is used to emboss on polymethylmethacrylate (PMMA) sheets. BMG is not only a good material for hot embossing process to fabricate micro-structure directly, but also fast-molding material for hot embossing process. Molding process using BMG material as a secondary mold can be more cost-effective and time-saving than the traditional MEMS process does.

The thermoplastic forming process of a bulk metallic glass (BMG) is simulated using commercial software DEFORM 3D and verified by hot-embossing experiment in this study. The fabrication process of micro-electro-mechanical systems (MEMS) includes a photoresist reflow technique, and Nickle-Cobalt (Ni-Co) electroplating to fabricate a first mold. Then, this mold is applied to hot emboss on an Mg-Cu-Y amorphous alloy to form a secondary mold. The thermal properties of the BMG material such as the glass transition temperature (Tg) and the onset temperature (Tonset) for the viscous flow are investigated using a differential scanning calorimetry (DSC) and a thermomechanical analyzer (TMA). The Tg of BMG is around 413 K (140 degrees C). The hot-embossing temperature is set at 423 K (150 degrees C). The supercooled liquid region Delta T between the T-g and the crystallization temperature (T-x) is the working temperature for the microforming study. This embossing process shows that the thermoplastic forming ability of the BMG material is better than polymethylmethacrylate ( PMMA) which requires high hot-embossing pressure and temperature. BMG is not only a good material for the hot-embossing process to fabricate micro-structure directly, but also a fast-forming material for mold ( or die) fabrication.

This study presents the development of an in-plane rotary electromagnetic microgenerator, which consists mainly of a multilayer planar copper (Cu) microcoil and a multipolar hard magnet made of NdFeB, the whole volume of which is approximately 5 × 5 × 2 mm3. The study focuses on the design and manufacturing required to obtain a high power generation output, and an analytical model is developed to predict the power output for different designs of microgenerators. The geometric pattern design of the Cu planar microcoil is manufactured using the filament winding method. Both the linewidth and spacing of the microcoil are 30 µm. The multipolar hard NdFeB magnet is molded and sintered, and a specially designed piece of equipment (a yoke) is used to magnetize the NdFeB magnet to produce an external magnetic field. After magnetization, an anisotropic residual induction (Br) of 1.44 tesla is produced. The theoretical model of this power microgenerator is evaluated and compared with experimental results, and it is found that the analytical simulation shows a good agreement with the experimental results. The induced electromotive force (EMF) is 111.2 mV and a maximum power output of 0.412 mW at a frequency of 149.3 Hz is obtained.

This study presents a high power rotary-type electromagnetic microgenerator with multilayer planar copper (Cu) microcoil and multipolar hard magnet of Nd/Fe/B. The size of this microgenerator is smaller than 1cm3 in volume. It can achieve the goal of compact integrated system. The induced voltage is simulated by FEMLAB and MATLAB software to solve the coupling problem, which involves in kinetic and electric issues. The multilayer microcoil is fabricated by MEMS process (micro-electro mechanical system), and the multipolar magnet is fabricated using sintering process. The sintered Nd/Fe/B exhibits an excellent hard magnet with Br of 1.44T and Hc of 975kA/m. Next, the multipolar magnet rotates relative to planar microcoil to induce electric current. The preliminary result shows that maximum induced voltage of 111.2mV and maximum power of 386.42μW can be achieved. Besides, the experimental result is compared with simulated one.

The development of coating optics to lower the reflected light and thereby to increase the optical efficiency of an optical system has been a very important issue for many years. Conventional solutions to this, such as multilayered alternation of high and low refractive index layers, often lead to an expensive coating process. Recently, the use of antireflection structured (ARS) surface, which is called “moth-eye structure”, has been proposed as an applicable option based on both the theoretical and experimental studies. In the current study, the experimental results of the reflectance and transmittance of two different thicknesses of silver films deposited on the moth-eye structure were carried out. The moth-eye structure arrays were fabricated by holographic exposure and photolithographic processes on the polymer film. The structure arrays were consisted of periodic length of about 300 nm, with the diameter of about 250 nm and the height of 150 nm. Compared with the silver coating film on the flat PET substrate, the optical property of the silver coating film on the moth-eye structure showed a better result for the anti-reflection application. The 25 nm-thick silver film on the moth-eye structure is suggested to be applied for the car window glass of antireflective films to obtain the high performance of heat insulation with acceptable transparency in the visible range.

This article reports a novel approach of applying silver nano-powders to the fabrication of ionic polymer-metal composites (IPMC) actuator with good adhesion between the metal electrodes and polymer membrane without surface roughening pretreatment at low cost, high repeatability and short processing time. Micro-fabrication technologies are used for this IPMC actuator fabrication including the dissolving and casting of silver nano-particles (35nm) in Nafion® diluted solution, followed embossing, nontoxic electroless plating of silver, and microelectroforming of nickel. This IPMC actuator exhibits large deformation of bending curvature angle of more than 90° at lower driving voltage of 3V. The frequency response of displacement with applied AC voltage of 2V at 1Hz results in a regular periodic deformations of the IPMC actuator. The elasticity modulus of the IPMC actuator can be reduced using an Ag–Nafion electrode for larger deformation than a pure Ag metal electrode. The electronic active polymer, IPMC, could be potentially used as the actuator of the active guide-wire, effective biomimetic sensor and artificial muscles.

Stresses normal to interfaces, i.e., interfacial peeling stresses and interfacial shear stresses, exist locally at edges of multilayers because of both the thermal mismatch between layers and the free‐edge effect. These peeling and shear stresses can result in modes I and II edge delamination, respectively. However, because of the complexity of the problem, exact closed‐form solutions for these stresses are very difficult if not impossible to derive even for bilayered systems. Hence, instead of the detailed stress field at edges, both the interfacial peeling moment resulting from the localized peeling stresses and the interfacial shear force resulting from the localized shear stresses are analyzed here. Exact closed‐form solutions for the peeling moment and the shear force at each interface in elastic multilayered systems are derived. To illustrate the application of present closed‐form solutions, specific results are calculated for five‐layered thermal barrier coating systems, and a finite‐element analysis is also performed to confirm the analytical results.

A mechanism of hydrostatic stress-induced mass flow is proposed to describe a medium under an action of ultra low load indentation at elevated temperatures. Two types of indenters of conical and spherical shapes and two loading conditions of constant indentation speed and constant load were used in the investigation. For both shapes of indenters, the maximum hydrostatic stress is located in the vicinity of the indentation tip. The maximum hydrostatic stress is proportional to the indentation speed and applied load, but inversely proportional to the atomic mobility. Comparing the loading conditions, the maximum hydrostatic stress is linearly proportional to the indentation area at constant indentation speed, but inversely proportional to the indentation area at constant applied load.