Electromagnetic energy harvesting from vibrations induced by Kármán vortex street

A new electromagnetic energy harvester for harnessing energy from vibration induced by Kármán vortex street is proposed. It converts flow energy into electrical energy by fluid flow, vortex shedding from a bluff body and electromagnetic induction. An analytical design method for the energy harvester is developed. A prototype of the energy harvester is fabricated and tested. The prototype has a volume of 37.9 cm³. Experimental results show that an output peak-to-peak voltage of nearly 20 mV in average is generated when the excitation pressure oscillates with an amplitude of 0.3 kPa and a frequency of about 62 Hz. By detecting the voltage drop across a matched load, the instantaneous power is determined as 1.77 μW under a pressure fluctuation frequency of 62 Hz and a pressure amplitude of 0.3 kPa in the Kármán vortex street.     

Electromagnetic energy harvesting from flow induced vibration

A new electromagnetic energy harvester for harnessing energy from flow induced vibration is developed. It converts flow energy into electrical energy by fluid flow and electromagnetic induction. A finite element model for estimation of the generated voltage of the energy harvester is developed. A prototype of the energy harvester is fabricated and tested. Experimental results show that an output voltage of 10.2 mV_pp is generated when the excitation pressure oscillates with an amplitude of 254 Pa and a frequency of about 30 Hz. The values of the generated voltage based on the finite element computations agree well with the experiments. By detecting the voltage drop across a matched load, the instantaneous power is determined as 0.4 μW under an excitation frequency of 30 Hz and a pressure amplitude of 254 Pa in the pressure chamber.     

Low power flexible organic thin film transistors with amorphous Ba0.7Sr0.3TiO3 gate dielectric grown by pulsed laser deposition at low temperature

We deposited amorphous Ba_0.7Sr_0.3TiO₃ (BST) on silicon and plastic substrate under 110 °C by pulsed laser deposition (PLD) and use it as the dielectric of the organic transistor. Depends on the thickness of BST layer, the highest mobility of the devices can achieve 1.24 cm² V^?1 s^?1 and 1.01 cm² V^?1 s^?1 on the silicon and polyethylene naphthalate (PEN) substrate, respectively. We also studied the upward and downward bending tests on the transistors and the dielectric thin films. We found that the BST dielectric pentacene transistor can maintain the mobility at 0.5 cm² V^?1 s^?1 or higher while the bending radius is around 3 mm in both upward and downward bending. Our finding demonstrates the potential application of PLD growth high-k dielectric in the large area organic electronics devices.     

Temperature-independent accelerometer using a fiber Bragg grating incorporating a biconical taper

An intensity-modulated optical fiber accelerometer is proposed and experimentally demonstrated by using a fiber Bragg grating (FBG) incorporating a biconical fiber taper. Acceleration-induced microbending of the fiber taper region introduces various attenuation to the light, so that acceleration can be measured from changes of the optical power of the reflected light from the FBG. This power detection method reduces the cost and complexity of the sensor setup since only photodetector is required for the signal detection. In the static measurement, a relatively large range of 5g (g is gravity, equals to 9.8 m/s²) with sensitivity of 4.85 nW/g is achieved. Vibration measurements have also been carried out with a frequency up to 20 Hz. The proposed accelerometer is nearly independent of temperature because the reflected optical power of the FBG is insensitive to temperature.     

Morphology,optical and AC electrical properties of nanostructure thin film of bromo indium phthalocyanine

Sandwich devices of bromo indium phthalocyanine (BrlnPc) thin films with aluminium electrodes were deposited on polyborosilicate substrate, using electron beam gun evaporation technique at room temperature. The AC electrical properties of nanostructure thin films (Al/BrInPc/Al) were examined in the temperature range of 303–393 K and frequency (f) between 10² and 10⁵ Hz. Structural and optical behaviour of samples were investigated by scanning electron microscope (SEM) images, X-ray diffraction (XRD) micrograph and optical absorption. Capacitance increase with increasing temperature for frequencies <10³ Hz and is almost independent of temperature for the range of frequencies >10³ Hz. Dissipation factor decrease with increasing frequency to a minimum value and increased noticeably thereafter. The AC electrical properties of nanostructured thin films of our materials are in agreement with the model of Goswami and Goswami. The band theory and hopping mechanism are applicable in explaining the conduction process for the frequency range of f<10³ Hz and f>10³ Hz, respectively.     

Study on new structure uncooled a-Si microbolometer for infrared detection

A new structure uncooled amorphous silicon (a-Si) microbolometer for infrared (IR) detection has been fabricated and characterized. New type of thermal isolation and IR absorption structures based on polyimide (PI) and bottom metal reflective layer are presented. The fabrication process is described in this paper. The as-prepared microbolometer has the advantage of low cost, high yield and moderate performance. The dependence of resistance with different aspect ratio on operating temperature has been investigated and the temperature coefficient of resistance (TCR) is achieved. Based on the measured responsivity and noise characteristics, the influence of detectivity on chopping frequency is discussed. According to the measurements and calculations results, the maximal TCR is −2.8% and at a bias voltage of 5 V, the maximum detectivity of 1.7×10⁸ cm Hz^1/2 W⁻¹ is achieved at chopping frequency of 30 Hz.     

A high-bandwidth,high-precision,two-axis steering mirror with moving iron actuator

This paper focuses on the design, fabrication, assembly, and testing of high bandwidth two-axis mirror positioners for precision optical platforms, which we refer to as the Advanced Fast Steering Mirror (AFSM) and the small Advanced Fast Steering Mirror (sAFSM). These novel positioners consist of a mirror platform driven in two rotational axes by flux-steering electromagnetic actuators, and controlled via position feedback loops. The devices are designed for beam stabilization tasks in lithography, laser communication, lidar, and similar optical applications. We have experimentally demonstrated small-signal system bandwidth of 10 kHz using optical quad-cell feedback and a two-channel analog control architecture. The AFSM has a travel range of ±3.5 mrad, and a measured angular acceleration of 1 × 10⁵ rad/s².     

A new wideband planar antenna with band-notch functionality at GPS,Bluetooth and WiFi bands for integration in portable wireless systems

Empirical results are presented for a novel miniature planar antenna that operates over a wide bandwidth (500 MHz to 3.05G Hz). The antenna consists of dual-square radiating patches separated by two narrow vertical stubs to reject interferences from GPS, Bluetooth and WiFi bands. Radiating patches and stubs are surrounded by a ground-plane conductor, and the antenna is fed through a common coplanar waveguide transmission line (CPW-TL). The two vertical stubs generate pass-band resonances enabling wideband operation across the following communications standards: cellular, APMS, JCDMA, GSM, DCS, PCS, KPCS, IMT-2000, WCDMA, UMTS and WiMAX. Embedded in the ground-plane conductor is an H-shaped dielectric slit, which has been rotated by 90°, whose function is to reject interferences from GPS, Bluetooth and WiFi bands. Measurements results confirm the antenna exhibits notched characteristics at frequency bands of GPS (1574.4–1576.4 MHz), Bluetooth (2402–2480 MHz) and WiFi (2412–2483.5 MHz). The impedance bandwidth of the antenna is 2.55G Hz for VSWR < 2, which corresponds to a fractional bandwidth of 143.66%. Measured results also confirm that the antenna radiates omnidirectionally in the E-plane with appreciable gain performance over its operating frequency range. The antenna has dimensions of 15 × 15 × 0.8 mm³.     

Large-area organic solar cells by accelerated blade coating

Large-area photovoltaic devices have been fabricated using the blade coating technique. In this study, the use of accelerated blade motion in this technique significantly improved the thickness uniformity of blade-coated layers of polymer solar cells on an A4 glass substrate. Two types of active layers, P3HT:PC₆₁BM and POD2T-DTBT:PC₇₁BM, were studied. For the P3HT:PC₆₁BM film, a thickness of 221 ± 14 nm was realised in a 12 × 15 cm² active region with a coating blade acceleration of 8 mm/s². For the POD2T-DTBT:PC₇₁BM film, a thickness of 98 ± 6 nm was realised with a coating blade acceleration of 10 mm/s². Ten cells, each measuring 0.9 cm × 12 cm and monolithically fabricated, were connected in series, yielding a total active area of 108 cm². The power conversion efficiency of the resulting 10-cell module was 2.66% and 3.64% for P3HT:PC₆₁BM and POD2T-DTBT:PC₇₁BM, respectively. The blade coating technique involving the accelerated blade motion is therefore useful for fabricating low-cost large-area organic solar cells, and it may be a promising alternative for the commercialisation of organic solar cells.     

High-resolution wide-band LC-VCO for reliable operation in phase-locked loops

This paper presents a novel sizing scheme to implement the array of switches in the capacitor bank of LC-VCOs for oscillation frequency coarse control. The proposed scheme allows increasing the number of elements in the capacitor bank beyond the values typically achieved by binary scaling, endowing the resulting LC-VCO with a wider tuning range and high frequency resolution, which is beneficial for the implementation of reliable phase-locked loops. Two different gigahertz LC-VCOs have been designed to validate the proposed scheme. The prototypes, fabricated in a cost-effective 0.18 μm CMOS process, cover a 700 MHz frequency range from 1.35 GHz to 2.05 GHz and from 2.05 GHz to 2.75 GHz, respectively, with a phase noise figure of − 122 dBc/Hz and − 119.5 dBc/Hz at 1 MHz from the mid-range carriers, and a power consumption of 18 mW. These figures result in a respective FOM_T of − 186.4 dBc/Hz and − 183.8 dBc/Hz. The performance of the fabricated LC-VCOs is achieved in each case with a dense coarse tuning range of 128 levels, which allows, respectively, a fine tuning gain smaller than 40 MHz V^− 1.     

Nanostructured nickel oxide ultrafine nanoparticles: Synthesis,characterization, and supercapacitive behavior

Well-dispersed NiO nanoparticles were prepared via cathodic electrodeposition followed by a heat-treatment method. The supercapacitive performance of the prepared nanoparticles was analyzed by means of cyclic voltammetry (CV) and galvanostatic charge–discharge tests at −0.2–0.5 V potential windows in 1 M KOH. The nanoparticles exhibited high specific capacitance (1623.1 F g⁻¹ at the scan rate of 5 mV s⁻¹) and good long-term cycling stability (9.6% capacity decay after 1000 cycling at the current density of 2 A g⁻¹).     

Design,fabrication and measurement of triple band frequency reconfigurable antennas for portable wireless communications

In this paper two triple-band monopole antennas are proposed for portable wireless applications such as WiFi, WiMAX and WLAN. Two different geometrical structures are used for the radiating elements of these antennas, each printed on a low cost FR-4 substrate. Truncated metallic copper ground is used to attain optimum radiation pattern and better radiation efficiency. The frequency of the antennas is reconfigured using a lumped-element switch. The proposed antennas covers three frequency bands 2.45, 3.50 and 5.20 GHz depending upon the switching conditions. Both antennas works with an optimum gain (1.7–3.4 dB), bandwidth (6–35%), VSWR (<1.5) and radiation efficiency (85–90%). Due to its affordable size (1.6 × 35 × 53 mm³), the antennas can be used in modern and portable communication devices such as laptops, iPads and mobile phones. The prototype of the antennas are fabricated and the measurements and simulations are found in close agreement.     

Effects of RTA temperatures on conductivity and micro-structures of boron-doped silicon nanocrystals in Si-rich oxide thin films

In this work, the B-doped Si rich oxide (SRO) thin films were deposited and then annealed using rapid thermal annealing (RTA) to form SiO₂-matrix silicon nanocrystals (Si NCs). The effects of the RTA temperatures on the structural properties, conduction mechanisms and electrical properties of B-doped SRO thin films (BSF) were investigated systematically using Hall measurements, Fourier transform infrared spectroscopy and Raman spectroscopy. Results showed that the crystalline fraction of annealed BSF increased from 41.3% to 62.8%, the conductivity was increased from 4.48×10⁻³ S/cm to 0.16 s/cm, the carrier concentration was increased from 8.74×10¹⁷ cm⁻³ to 4.9×10¹⁸ cm⁻³ and the carrier mobility was increased from 0.032 cm² V⁻¹ s⁻¹ to 0.2 cm² V⁻¹ s⁻¹ when the RTA temperatures increased from 1050 °C to 1150 °C. In addition, the fluctuation induced tunneling (FIT) theory was applicable to the conduction mechanisms of SiO₂-matrix boron-doped Si-NC thin films.     

Structural,electrical and optical properties of sintered SnO2 pellets

Tin dioxide (SnO₂) powder was prepared by the co-precipitation method using SnCl₂ solution as a precursor. The powder was then pelletized and sintered. Structural characterization of the samples with XRD confirmed that all the pellets were of SnO₂ having polycrystalline nature with the crystallite size of the order of 90 nm. SEM-EDAX was used to confirm the morphology and composition of the samples. The measurements of electrical properties were carried out in the frequency range of 100 Hz to 100 kHz at various fixed temperatures from 40 °C to 160 °C. The a.c. conductivity and the dielectric constant were found to be dependent on both frequency and temperature. The frequency and temperature dependent conduction properties of SnO₂ are found to be in accordance with correlated barrier hoping model. Infrared and visible spectroscopic studies show that a strong vibration band characteristic of the SnO₂ stretching mode was present at around 620 cm^?1 and the samples exhibited optical transmittance in the visible range.     

Optimal design of high precision XY-scanner with nanometer-level resolution and millimeter-level working range

This article presents the design and performance evaluation of a compact high precision XY-scanner providing nanometer-level resolution and a millimeter-level travel range. The proposed XY-scanner is composed of a voice coil motor (VCM) and double compound linear spring flexure guide mechanism. The challenge was to determine design variables properly while simultaneously satisfying the requirements of high resolution, long working range, high response speed, and compact size, because the relationships between the design variables and the system parameters are complex. Therefore, we developed a design that would provide the optimal tradeoff in terms of design variables. The objective was to maximize the first resonant frequencies of the XY-scanner to increase response speed while limiting the size of the scanner to 100 mm × 100 mm × 50 mm. The XY-scanner was fabricated with optimally-designed values, and its performance was evaluated. From the experimental results, the first resonant frequencies of XY-scanner were 26.68 Hz for the X-axis and 22.79 Hz for the Y-axis. The measured results of the 10 nm resolution and 2 mm working range confirmed that the designed scanner could be successfully used in precision fields requiring nanometer-level resolution and millimeter-level travel range.     

Synthesis and characterization of EuBa2Ca2Cu3O9−x: The influence of temperature on dielectric properties and charge transport mechanism

High dielectric constant materials have a crucial importance for various microelectronic applications such as memory devices, supercapacitors etc. Among other insulators, perovskite structured oxide materials attract great interest not only for their high dielectric constants but also their unique electrical and magnetic properties such as superconductivity etc. From this point of view, a new Europium based copper oxide layered material with perovskite structure (EuBa₂Ca₂Cu₃O_9−x coded as Eu-1223) has been synthesized by solid state reaction method in this work. The physical and chemical properties of Eu-1223 have been determined by FTIR, SEM, XRF, XRD, TGA and DTA techniques. The influence of temperature on impedance and dielectric properties of Eu-1223 has been investigated by impedance spectroscopy measurements performed within the frequency interval of 5 Hz–13 MHz between 298 K and 408 K temperatures. It has been found that the Eu-1223 material has high dielectric constants at each temperature operated. In addition, Eu-1223 sample behaves as a colossal dielectric material up to 300 kHz for 408 K due to observation of dielectric constant values which are greater than 10³. Furthermore, it has been revealed that Eu-1223 material can be used as thermally sensitive resistors in electronic circuits due to its decreasing resistance with increasing temperature. Moreover, it has been observed that the relaxation frequency of the system shifts from 46.5 kHz (low frequency radio wave band) to 1.57 MHz (mid frequency radio wave band) as the temperature increasing from 298 K to 408 K. According to dc conductivity investigations, the variation of dc conductivity with the inverse of temperature satisfies linear relationship that indicates a thermally activated nearest neighbor hopping conduction. On the other hand, it has been determined that ac conductivity has frequency dependent relation which obeys ω^s for the high frequency region. Furthermore, the frequency exponent, s, which takes values between 0.7 and 0.4, shows a decreasing behavior with increasing temperature. In conclusion, ac charge transport mechanism has been predicted as correlated barrier hoping for Eu-1223.     

Temperature dependent Young's modulus and quality factor of CMOS-MEMS resonator: Modelling and experimental approach

CMOS-MEMS resonators are the key parts of modern integrated systems. Most of these resonators are fabricated through CMOS composite layers that are sensitive to temperature. In this article, the effects of temperature on the collective Young's moduli and quality factor of CMOS composite layers based MEMS resonator are theoretically modelled and experimentally validated. A custom made environmental chamber is used to control the environmental effects and an external vibration shaker is used to actuate the fabricated CMOS-MEMS resonator at its resonance frequency in the presence of a permanent magnet. Variations with increasing temperature in the collective Young's moduli of the CMOS composite layers are determined through the measurement of change in resonance frequency of the resonator and found to be linear. A nonlinear behaviour of the quality factor is noticed in the temperature range of 25 °C to 80 °C, the quality factor is found to be increasing whereas from 60 ^∘ C to 80 ^∘ C, the quality factor is decreasing.     

Pseudo-V2 control with adaptive compensation for fast-transient current-mode buck converter

A type of pseudo-V² control, with on-chip adaptive compensation to achieve fast transient (FT) response for current mode DC–DC buck converter, has been proposed and simulated using 0.18 μm CMOS technology in this paper. Based on a new on-chip capacitor multiplier, adaptive compensation is achieved by making the compensation capacitance to track the load current. The proposed pseudo-V² control utilizes the output ripple to determine the duty cycle during load transient. Thus the overshoot/undershoot voltage and the transient recovery time are effectively reduced. Simulation results demonstrate the transient ripple is smaller than 50 mV and the transient recovery time is shorter than 10 μs for a 450 mA load current step. The maximum power conversion efficiency is 94.6% at 1 MHz switching frequency when input and output voltages are 5 V and 1.8 V, respectively.     

Strength determination of high-power LED die using point-load and line-load tests

The strength of high-power light emitting diode (LED) dies, cut from wafers with a laser, has to be determined for the need of design and quality control in order to assure the good reliability of packages in manufacturing and service. The objective of this study is to determine the strength of high-power LED die with a size of 1 × 1 × 0.1 mm³ by point-load test (PLT) and line-load test (LLT) associated with a plate-on-elastic-foundation configuration. ANSYS (one of commercial finite element codes) analysis is used to calculate the stress distributions of the die under both PLT and LLT. The ANSYS models of the PLT and LLT are validated by comparing with experimental force–displacement curves, and the results are further used to convert the die failure force from the tests into the die strength. The mechanism of tensile-stress dominated die strength has been discussed and validated in detail via these test results and analyses. The results of the PLT and LLT also indicate that for the die failure on chip surface, the average die strengths are about 1.44 GPa and 1.52 GPa from the PLTs with two different-radius pins, and about 1.2 GPa from the LLT. On the other hand, for failures on sapphire surface, the average die strengths are reasonably about 1.49 GPa and 1.26 GPa from the two PLTs, but the average one from the LLT is about 0.64 GPa (with less than 50% of the values from the PLT). The inconsistent data between two PLT and LLT for failure on sapphire surfaces were found to result from the edge chipping of the die specimen observed by scanning electron microscopy. It was also observed that the thin-layer GaN material has to be taken into account in the ANSYS analyses with a bi-material model of the LED die for precisely determining the die strength for failure on the chip surface. Otherwise, these strength data would be overestimated by a few tens of percent with a uni-material model of the LED die. All in all, this study has successfully demonstrated that the LED die strength can be determined by these feasible, easy-to-use and reliable test methods.     

An 8 bit, 100 kS/s,switch-capacitor DAC SAR ADC for RFID applications

An 8 bit switch-capacitor DAC successive approximation analog to digital converter (SAR-ADC) for sensor-RFID application is presented in this paper. To achieve minimum chip area, maximum simplicity is imposed on capacitive DAC; replacing capacitor bank with only a one switch-capacitor circuit. The regulated dynamic current mirror (RDCM) design is introduced to provide stabilized current. This invariable current from RDCM, charging or discharging the only capacitor in circuit is controlled by pulse width modulated signal to realize switch capacitor DAC. The switch control scheme is built using basic AND gates to generate the control signals for RDCM. Only one capacitor and reduced transistor count in digital part reduces the silicon area occupied by the ADC to only 0.0098 mm². The converter, designed in GPDK 90 nm CMOS, exhibits maximum sampling frequency of 100 kHz & consumes 6.75 µW at 1 V supply. Calculated signal to noise and distortion ratio (SNDR) at 1 V supply and 100 kS/s is 48.68 dB which relates to ENOB of 7.79 bits. The peak values of differential and integral nonlinearity are found to be +0.70/−0.89 LSB and +1.40/−0.10 LSB respectively. Evaluated figure of merit (FOM) is 3.87×10²⁰, which show that the proposed ADC acquires minimal silicon area and has sufficiently low power consumption compared to its counterparts in RFID applications.