This study reports the electrospinning of polyvinylidene fluoride (PVDF) piezoelectric nanofiber array on an interdigital (IDT) electrode to fabricate a flexible sensing device. This sensing device can convert the mechanical energies of low-frequency ambient vibrations and impacts into electrical signals. A mixed solution of PVDF and multi-wall carbon nanotube (MWCNT) was filled in a metallic needle injector that was connected with a high voltage of 1200 V. When the PVDF droplet in the needle tip was subjected to a high electric field, an extremely fine PVDF fiber can be spun out. The electrospun fibers were collected orderly using an X-Y stage. In the electrospinning process, the fiber was polarized and transformed into the piezoelectric beta-crystalline phase. PVDF/MWCNT crystallization as spherical composite structures can enhance the piezoelectric properties of PVDF fibers. Photolithography and etching processes were used to fabricate an IDT electrode with a gap of 100 mu m on a flexible polyimide (PI) substrate. The PVDF fiber array was packaged with epoxy/PI film. The packaged PVDF fiber array was repolarized in a high electric field of approximately 7V/mu m to increase d(33) mode conversion efficiency. The comparison of the analytical solution of the composite plate equation and the experimental results shows that the device can generate a peak voltage and current of 20.2 mV and 39 nA under 6 Hz vibration. In addition, at an impact testing at 15 Hz, the peak voltage of 24.4 mV with a current of 130 nA can be obtained. (C) 2014 Elsevier B.V. All rights reserved.

Small and efficient energy harvesters, as a renewable power supply, draw lots of attention in the last few years. This paper presents a planar rotary electromagnetic generator with copper coils fabricated by using printed circuit board (PCB) as inductance and Nd-Fe-B magnets as magnetic element. Coils are fabricated on PCB, which is presumably cost-effective and promising methods. 28-pole Nd-Fe-B magnets with outer diameter of 50 mm and thickness of 2 mm was sintered and magnetized, which can provide magnetic field of 1.44 Tesla. This harvester consists of planar multilayer with multi-pole coils and multi-pole permanent magnet, and the volume of this harvester is about 50x50x2.5 mm(3). Finite element analysis is used to design energy harvesting system, and simulation model of the energy harvester is established. In order to verify the simulation, experiment data are compared with simulation result. The PCB energy harvester prototype can generate induced voltage 0.61 V and 13.29mW output power at rotary speed of 4,000 rpm.

This study presents an analysis of an in-plane micro-generator with various microcoil shapes and multiple aspects of coupling, and reports the fabrication of a prototype micro-generator. It is important to establish analytical solutions for the micro-generator to predict the induced voltage. These analytical solutions can be used to estimate the micro-generator power to reduce the experimental time and the cost. Understanding the physical meanings of the variables can optimize the structure of the micro-electromagnetic generator. This model considers electromagnetism, kinematics, and geometry. The proposed in-plane rotary electromagnetic micro-generator was fabricated using low-temperature co-fired ceramic technology to co-fire the silver microcoils on the ceramic substrate with different shaped coils (e.g., square-shaped, circle-shaped and sector-shaped) both with the printing linewidth and 100 μm spacing of these microcoils. A planar permanent magnet with an outer diameter of 9 mm and a thickness of 700 μm was sintered by Nd/Fe/B. Its residual induction is 1.4 T. The experimental data in this study can be compared with analytical solutions. Analytical results show that the micro-generator with a sector-shaped microcoil generates a maximum effective value of 218.127 mV induced voltage at 1395.34 rad/s. Experimental measurements show a close agreement with these analytical solutions.

In this study, near-field electrospinning (NFES) was used to fabricate PVDF (Polyvinylidene fluoride) piezoelectric nano-fibers mixed with additional multiwalled-carbon nanotubes (MWCNT). Both mechanical strength and piezoelectric characteristics of a single nano-fiber were discussed. NFES technology can be used to fabricate PVDF piezoelectric fibers with an excellent piezoelectric property. By adjusting velocity of a x-y stage, DC voltage, and the distance between the needle and collector, the morphology and polarization intensity of piezoelectric fiber can be controlled. In addition, the optimal parameters of PVDF solution such as weight percentage of PVDF powder and MWCNT were also discussed. From the observation of XRD (X-ray diffraction), it reveals a high diffraction peak at 2θ=20.8° of piezoelectric crystal β-phase structure with PVDF/MWCNT spherical composite structures in fibers. Actuation property of fixed-fixed single PVDF fiber structure was tested using DC voltage supply, and the fiber has significant deflection in the experiment. The vertical deflection can be observed and compared with model solution.

This study focuses on the design and fabrication of a planar rotary electromagnetic energy harvester with a low rotary speed for bicycle dynamos. The primary components of a dynamo system include planar multilayer and multipole coils, a soft magnet (iron) used to enhance magnetic efficiency, and a multipole Nd/Fe/B (neodymium, iron, and boron) permanent magnet. Finite element analysis and the Taguchi method were used to design this dynamo system. The optimal parameters of the magnet, coil, and soft magnet were determined by using the Taguchi method. Low temperature co-fired ceramics (LTCC) technology was applied to fabricate silver planar multilayer coils with 10 and 20 layers, respectively. Nd/Fe/B was sintered to obtain the desired characteristics of a permanent magnet. A 28-pole magnet Nd/Fe/B with an outer diameter of 50 mm and a thickness of 2 mm was also sintered and magnetized, creating a magnetic field of 1.4T. Simulation results show that a harvester with 20-layer and 22 poles coils, a linewidth of 200 mu m, an interspace of 100 mu m, and a layer thickness of 40 mu m can generate voltages of 1.796V at a rotary speeds of 300 rpm. This harvester system was approximately 50 mm x 50 mm x 3 mm in volume (including 20-layer micro-coils + magnet + spacing between the coil and magnet surface). The experimentally induced voltages of 20-layer coils were 1.539 V. Measurements show a similar trend with finite element simulations. The power output was 0.788 mW with an external resistance load of 737 Omega. This harvester is capable of powering 200 LEDs (forward voltage (VF) <2.2 V and 20 mA) using a rotary speed of 250 rpm, and could be used for bicycle dynamo lighting. (C) 2012 Elsevier B.V. All rights reserved.

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.

This work presents a dual-band CMOS voltage controlled oscillator (VCO) design by using a pair of transformers as part of a switching resonator for band selection. The proposed design is characterized mainly by its ability to achieve two separate wide tuning bands. Additionally, the VCO phase noise is significantly diminished by applying the impedance locus method. Consequently, the dual-band VCO has a tuning range of 2.3 to 3.2 GHz for the low-band mode and 4.29 to 5.35 GHz for the high-band mode. The measured phase noises are -125 dBc/Hz and -123 dBc/Hz for the low-band and the high band, respectively, at the frequency offset of 1 MHz. This dual band VCO is implemented using 0.18 mu m CMOS technology with a supply voltage of 1.8 V.

This study focuses on the design, simulation, fabrication, and test of the in-plane microgenerator to obtain a high-power output. The microgenerator comprises multilayer planar silver (Ag) microcoil of low-temperature cofired ceramics (LTCC) and multipole hard magnet of Nd/Fe/B (neodymium, iron, and boron). The LTCC process is an approach that saves costs and time to fabricate the microcoil. The multipole hard magnet of Nd/Fe/B provides the large magnetic energy product to contribute to the power. Finite element simulations have been carried out using COMSOL Multiphysics (R) to observe electromagnetic information. The induced voltages of coils in different basic geometric shapes, including square-shaped coils, circle-shaped coils, and sector-shaped coils, are simulated separately in this study. A prototype of the microgenerator is <1 cm(3) in volume size. The simulated result can be compared to the experimental one. The results of simulation reveal that this microgenerator with a sector-shaped microcoil generates a maximum effective value of the induced voltage of 232.7 mV and the power of 2.5 mW. And the 1-mu m gap between the microcoil and the magnet achieved is the value that is mentioned above. Experimental measurement shows close agreement with finite element simulations. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3152363]

For the requirement of higher storage capacity of an optical disk, it is a good choice to shorten pit length and linewidth. However, the conventional laser beam mastering is difficult to fabricate smaller pit length and linewidth because of the optical diffraction limit. In order to solve this problem, optical disk mastering using electron beam lithography is presented. The process parameters of the electron beam mastering such as beam current, constant linear stage velocity, developing time, and focus distance are discussed in this research. In the experiments, it was found that the focus distance is an important parameter to fabricate nano-linewidth. The experimental results reveal that the 10 μm variance in focus distance causes about 12% variation in linewidth. The photoresist with nano-pattern defined by eletron beam was transferred into metal Ni–Co (Nickel–Cobalt) mold by electroplating process. The Ni–Co mold with hardness larger than Vicker Hardness (Hv) 650 was developed. Then, with the Ni–Co mold, LIGA (German: Lithographie GaVanoformung Abformung) process was applied to replicate high-density optical disk. The Ni–Co mold is served as a master for hot embossing process to transfer the nano-pattern onto PMMA sheet. Since the feature size is in nano-meter range, the study presents an innovative demolding mechanism to demold the master from the PMMA sheet without damaging the nano-meter structure. A spiral nano-groove with 112 nm in linewidth and 80 nm in depth has been successfully fabricated about 50 Gbytes storage capacity.

This study presents a new method of fabrication of in-plane rotary electromagnetic micro-generator. Low temperature co-fired ceramics (LTCC) technology is applied to fabricate micro-coil for the micro-generator. The process of the LTCC micro-coil provides more cost-effective and time-saving approaches than other process such as Lithographie Galvanoformung Abformung (LIGA), LIGA-like and filament-winding methods. This micro-generator consists of multilayer planar LTCC silver (Ag) micro-coil and multipolar hard magnets of Nd/Fe/B (neodymium, iron, and boron). This study focuses on the fabrication and test of the in-plane micro-generator to obtain a high power output. There are three different configurations of planar LTCC Ag micro-coils investigated in this study, which are sector-shaped, circle-shaped, and square-shaped micro-coils. Both the printing linewidth and spacing of these micro-coils are 100μm. The multipolar hard magnet Nd/Fe/B with outer diameter of 9mm and thickness of 700μm is molded and sintered. The self-designed measurement facility of the power output is established, which consists of a drive mechanism and data acquisition units. A prototype of the micro-generator is as small as 9mm×9mm×1mm in volume size. The experimental results show that the micro-generator with sector-shaped micro-coil has the highest power output of 1.89mW, and the effective value of the induced voltage of 205.7mV at 888.3Hz (about 13,325rpm) is achieved.