Use Of Arrays Research Articles

Baseband Feedback Frequency-Division Multiplexing with Low-Power dc-SQUIDs and Digital Electronics for TES X-Ray Microcalorimeters

We are developing frequency-division multiplexing (FDM) systems with baseband feedback for TES X-ray microcalorimeter arrays for use with the DIOS mission. To meet the requirement of limited cooling capacity at cryogenic temperatures, we developed low-power and FDM-optmized dc-SQUIDs. To make maximum use of the SQUIDs, we also developed digital electronics using FPGA evaluation boards and ADC/DAC FMC daughter cards, and evaluated signal-to-noise ratios and gain-bandwidth products.

Electrophysiological method to examine muscle fiber architecture in the upper lip in cleft-lip patients

The upper lip's musculature comprises several muscle fiber groups with different spatial orientations for various lip movements. In the past, it has not been possible to describe these various groups and their motor units in detail with traditional methods of electromyography (EMG). The purpose of this investigation was to create a viable method for studying the architecture of upper-lip muscle fibers in patients with surgically closed cleft lip by refining the design of a flexible electrode array for multichannel EMG. Calibrated perioral photographs of 36 adult subjects were used to determine the basic geometry of an electrode array for use on different facial shapes. A total of 256 chloride silver electrodes, 1 mm in diameter, were distributed over this geometry to form a grid with interelectrode distances of 2.5 mm. Technical implementation of the electrode array was based on a modified technique used for flexible printed circuit boards. A double-sided adhesive tape with perforations was used to apply the array to the skin in the upper-lip area. Surface EMG signals were recorded while the subjects were performing various lip movements and exerting specific lip forces. The latter were recorded with a specially developed transducer. Despite an extremely dense grid of electrodes associated with downsized contacts, the electrode array could be precisely applied to the perforated adhesive tape. The electrode array remained firmly attached to the skin even during extensive lip movements. The recorded EMG signals offered high baseline stability and a strong signal-to-noise ratio, thus, allowing us to extract individual motor unit action potentials (MUAPs). Spatiotemporal tracking of MUAPs succeeded in demonstrating the course of muscle fibers belonging to individual motor units. Pilot measurements taken on subjects with surgically closed unilateral cleft lip revealed an asymmetric distribution of muscle activity surrounding the closed cleft-lip segments. Our refined noninvasive electrophysiological method is capable of providing detailed information about muscle fiber architecture and the position, size, and organization of motor units in the lip area. It is thus feasible to conduct further studies to analyze differences in muscle morphology and motor control between surgically treated cleft-lip patients and noncleft individuals.

A Novel Open-source Master-slave Heliostat Array for Use as an Experimental Platform and Solar Power Applications

In this work we outline the basic design of a new heliostat array made with easily accessible components (used bicycle, automotive, plumbing hardware, and open-source electronics.) The system forms the base apparatus for scientific experiments in solar energy such as high-temperature solar ovens, industrial solar hot water heaters, concentrating PV power, to name a few. The system uses a novel mechanical design, a home built solid state relay, and a simple but accurate hybrid (active-absolute) solar tracking system. This system also has potential commercial use in mini-micro businesses.

Self-Assembly of Nanoparticle Arrays for Use as Mirrors, Sensors, and Antennas

The self-assembly of nanoparticles (NPs) at liquid-liquid interfaces (LLIs) has recently emerged as a promising platform for tunable optical devices, sensors, and catalysis. There are numerous advantages for such platforms when compared to more conventional solid-state counterparts. For example, they do not need engineering, self-assemble if proper conditions are provided, are self-healing, are practically nondegrading, and are easily renewable. Furthermore, they have the added benefit of being able to facilitate the interactions of analytes dissolved in often-inaccessible environments. In this Perspective, we highlight some important recent developments in understanding the mechanisms and applications of self-assembly of NPs at LLIs for use as mirrors and sensors. Finally, we explore future directions in this field, focusing on NP arrays with electrotunable properties assembled at a LLI, which has been one of the driving forces for developing such technologies.

Fabrication of a flexible penetrating microelectrode array for use on curved surfaces of neural tissues

Conventionally, invasive neural microelectrodes for recording neuronal signals or stimulating the nervous system have been fabricated based on silicon substrate mainly due to well-established manufacturing processes. However, these silicon-based microelectrode devices have an issue of mechanical stability caused by the absence of flexibility when implanted onto curved surfaces of tissues. In this paper, a flexible and penetrating microelectrode array, a hybrid structure composed of silicon and elastomer, was devised and fabricated by bulk micromachining technologies. The structure uses individual silicon needles as independent electrodes in a square array and polydimethysiloxane (PDMS) as a base to support the needles. The dimensions of the electrode array and the needles are adjustable, depending on the number of needles, the pitch between the needles and the targeted penetration depth of the neural tissue. For mechanical characterization, the adhesion between PDMS and silicon was evaluated and the flexibility and integrity of the fabricated structure were investigated through flexural test and insertion test. Also, the electrochemical impedance spectroscopy of the electrodes was measured. The results suggest that the proposed microelectrode array is promising for use in neuronal recording and stimulation over curved surfaces such as cortical surface and peripheral nerves with larger curvatures.

Preparation of large diameter and low density ZnS microtube arrays via a sacrificial template method

The uniform low density ZnS microtube arrays with a large diameter of up to 1um are prepared for the first time via a three-step approach. ZnO microrod arrays are first hydrothermally grown on fluorinated tin oxide glass as a sacrificial template, which are converted to ZnO/ZnS core/shell structures subsequently through a sulfidation process, ZnS microtube arrays are then obtained by selectively etching of ZnO cores. The unique properties of this large diameter and low density ZnS tube array are demonstrated by comparing it with those of small diameter and high density ZnS tube array for use in the hybrid film photoelectrode of dye-sensitized solar cells.

High-order harmonic generation from a dual-gas, multi-jet array with individual gas jet control

We present a gas jet array for use in high-order harmonic generation experiments. Precise control of the pressure in each individual gas jet has allowed a thorough investigation into mechanisms contributing to the selective enhancement observed in the harmonic spectra produced by dual-gas, multi-jet arrays. Our results reveal that in our case, the dominant enhancement mechanism is the result of a compression of the harmonic-producing gas jet due to the presence of other gas jets in the array. The individual control of the gas jets in the array also provides a promising method for enhancing the harmonic yield by precise tailoring of the length and pressure gradient of the interaction region.

Light Extraction Enhancement in AlGaInP-Based Vertical Light Emitting Diodes by Using Circular Micro-Contact Array

We have demonstrated that light output power of vertical AlGaInP-based light emitting diodes (LEDs) can be enhanced through use of a circular n+-GaAs/Ni/Ge/Au micro-contact array and an ITO current-spreading layer. We designed three different circular micro-contact arrays with different total areas and diameters for use as n-type electrodes in vertical AlGaInP LEDs. For comparison, LEDs with a normal linear-patterned n-type electrode were also fabricated. The results show that the circular micro-contact array for use an n-electrode in the vertical AlGaInP-based LEDs, greatly improved the uniformity of light output intensity, followed by increase in light output power. In addition, we also found that the total area of a circular micro-contact array and the thickness of the ITO current-spreading layer were important parameters for enhancing the light output power of the AlGaInP-based LEDs, due to a reduced light absorption in the circular micro-contact array and in the ITO layer.

High-Efficiency, High-Gain, Broadband Quasi-Yagi Antenna and Its Array for 60-GHz Wireless Communications

This paper introduces a high-efficiency, high-gain, broadband quasi-Yagi antenna, and its four-element array for use in 60-GHz wireless communications. The antenna was fed by a microstrip-to-slotline transition consisting of a curved microstripline and a circular slot to allow broadband characteristics. A corrugated ground plane was employed as a reflector to improve the gains in the low-frequency region of the operation bandwidth, and consequently, to reduce variation. The single antenna yielded an impedance bandwidth of 49 to 69 GHz for |S11| 12.0 dBi while the array exhibited a bandwidth of 52 to 68 GHz and a gain greater than 15.0 dBi. Both proposed designs had small gain variations (±0.5 dBi) and high radiation efficiency (>95%) in the 60-GHz bands. The features of the proposed antenna were validated by designing, fabricating, and testing a scaled-up configuration of the single antenna at the 15-GHz band. The measurements resulted in an impedance bandwidth of 13.0 to 17.5 GHz for |S11|< 10 dB, a gain of 10.1 to 13.2 dBi, and radiation efficiency in excess of 88% within this bandwidth. Additionally, the 15-GHz antenna yielded quite symmetric radiation profiles in both E- and H-planes, with a high front-to-back ratio.

TiO&lt;sub&gt;2&lt;/sub&gt; Thin Layer Coated Ag Nanoarrays Complex for Surface-Enhanced Raman Scattering Substrate

A novel method to prepare TiO2-coated Ag nanowire arrays for use as surface enhanced Raman scattering (SERS) active substrate is studied. First, Ag nanowires with an average diameter of 60 nm and length of several μm were synthesized in an anodic aluminum oxide (AAO) template by direct electrodeposition into the template. Then TiO2thin layers with a 20 nm thickness were coated on Ag nanoarrays in large scale by a hydrolysis approach of tetrabutyl titanate. The SERS substrates prepared by this strategy have been proved as excellent candidates for the detection of organic pollutants by enhancing the SERS signals of these target species. The detection limit of methyl-parathion (MP) can be reduced to 10-6M.

Improved event positioning in a gamma ray detector using an iterative position-weighted centre-of-gravity algorithm

An iterative position-weighted centre-of-gravity algorithm was developed and tested for positioning events in a silicon photomultiplier (SiPM)-based scintillation detector for positron emission tomography. The algorithm used a Gaussian-based weighting function centred at the current estimate of the event location. The algorithm was applied to the signals from a 4 × 4 array of SiPM detectors that used individual channel readout and a LYSO:Ce scintillator array. Three scintillator array configurations were tested: single layer with 3.17 mm crystal pitch, matched to the SiPM size; single layer with 1.5 mm crystal pitch; and dual layer with 1.67 mm crystal pitch and a ½ crystal offset in the X and Y directions between the two layers. The flood histograms generated by this algorithm were shown to be superior to those generated by the standard centre of gravity. The width of the Gaussian weighting function of the algorithm was optimized for different scintillator array setups. The optimal width of the Gaussian curve was found to depend on the amount of light spread. The algorithm required less than 20 iterations to calculate the position of an event. The rapid convergence of this algorithm will readily allow for implementation on a front-end detector processing field programmable gate array for use in improved real-time event positioning and identification.

A Low-Power DCVSL-Like GIDL-Free Voltage Driver for Low-Cost RFID Nonvolatile Memory

The realization of a low-cost passive radio frequency identification (RFID) tag requires the ability to fabricate the system in a bulk CMOS process without any additional process steps. A recently presented single-poly C-Flash memory bitcell provides an ultralow-power option for implementation of a nonvolatile memory array for use in an RFID system, using only core masks. This cell requires the application of a 10-V potential difference between the cell's control lines for program and erase operations. Providing the required voltages, while using only standard devices results in several design challenges for the voltage drivers, such as the elimination of gate-induced drain leakage (GIDL) currents. In this paper, we present a pair of voltage driver architectures that utilize novel techniques to overcome these challenges. In addition, for the first time, we present an in-depth analysis of the dynamic behavior of standard level shifters. This analysis is applied to our proposed GIDL-free level shifters to provide a sizing methodology for optimization of the area, energy-per-operation, and delay of these circuits. The drivers were designed and fabricated in a TowerJazz 0.18- μm bulk CMOS technology, providing the required functionality with a low static-power figure of 47-49 pW and 0.03-0.36 pJ energy-per-operation.

Application of statistical reduced isometry property to design of line arrays for compressive beamforming

The Statistical Reduced Isometry Property (StRIP) and Statistical Null Space Property (SNSP) are presented and reduced to numerical algorithms. These properties are used to predict the utility of a specific subsampled array for use in compressive sensing. Three examples of subsampling an equally spaced array are presented: random, Golomb and Wichmann. The Golomb array uses a Golomb ruler that has no repeated sensor element spacings. The Wichmann array includes at least one of every possible interval of sensor element spacings. The SNSP is shown to be insensitive to subsampling in the type of cases shown. The Golomb array is predicted to have superior performance to the Wichmann for comparable subsampling. The use of these two subsamplings for beamforming using at-sea data from the Five Octave Research Array (FORA) is shown. [Research funded by the Office of Naval Research.]

Highly Doped Nanowire Array for Use in Hybrid Silicon/Polymer Junction Solar Cells

not Available.

Metamaterials with angle selective emissivity in the near-infrared

Metamaterials have been previously studied for their ability to tailor the dispersive IR emissivity of a surface. Here, we investigate two metamaterial structures based on an electromagnetic band-gap surface and a dielectric resonator array for use as near-IR emitters with custom angle selectivity. A genetic algorithm is successfully employed to optimize the metamaterial structures to have minimum emissivity in the normal direction and high emissivity at custom off-normal angles specified by the designer. Two symmetry conditions are utilized to achieve emissivity patterns that are azimuthally stable or distinct in the two orthogonal plane cuts.

Influence of Morphology on the Optical Properties of Self-Grown Nanowire Arrays

Nanostructured materials such as nanowire arrays often absorb light more strongly than thin films, so they can be used to improve the performance of solar cells. In this study, a series of self-grown Cu2S nanowire arrays with different diameters, lengths, and morphologies is prepared by solid–gas reaction between Cu foil and a mixture of H2S and O2. The structure of the arrays is characterized by XRD, TEM, XPS, and Raman. Their light absorption performance is investigated systematically by diffuse reflectance and photoluminescence spectroscopy. The nanowire arrays are single-crystal Cu2S semiconductors, and their band gap can be adjusted by changing the morphology, diameter, and length of nanowires in the arrays. The light-absorption ability is enhanced from 70% for a planar Cu2S film to 93.5% for a Cu2S nanowire arrays and is less sensitive to both the wavelength and incident angle of light because of the morphology and distribution of the nanowires. The light absorption is high (about 92–95%) over a wide range of wavelengths (240–670 nm) and only decreases by 3% as the incident angle increases from 10 to 40°. This research shows the potential of Cu2S nanowire arrays for use in solar energy applications.

Investigation of 1D Siliver Nanoparticle Arrays for Use as Molecule Concentration‐Specific SERS Substrates

One‐dimensional arrays of silver nanoparticles with a particle size of 10.5 nm and interparticle spacing of 8.5 nm were fabricated by depositing nanoparticles in gas phase on block copolymer self‐assembled templates. The substrate showed a surface‐enhanced Raman scattering (SERS) enhancement factor as high as 1 × 107 with good reproducibility and stability. The dependence of the average enhancement factor and the SERS intensity on the packing density of the analyte molecules were investigated. For a tiny amount of analytes in the range of 1 × 10−14 to 3 × 10−13 mol/mm2, the SERS signal showed a linear dependence on the molecule packing density on a logarithmic scale, with a slope of about 1.25. The substrates are promising for quantitative detection of trace level molecules.

Stimuli-responsive opals: colloidal crystals and colloidal amorphous arrays for use in functional structurally colored materials

Two distinct types of colloidal particle aggregated states exist in opal, namely, the colloidal crystal and the colloidal amorphous array. Today, these aggregates can be artificially prepared and are now studied as non-fading structurally colored materials as a result of our better understanding of their optical properties. Additionally, by applying the aggregates as stimuli-responsive materials, we can fabricate stimuli-responsive structurally colored systems that change their hue and saturation in response to external stimuli. In this review, the conditions necessary for fabricating stimuli-responsive structurally colored systems using the two types of aggregates present in opal are explained.

Self-organized InGaAs/GaAs quantum dot arrays for use in high-efficiency intermediate-band solar cells

We have investigated the material properties of multi-layer stacked InGaAs/GaAs quantum dots (QDs) grown on GaAs (3 1 1)B substrates. Symmetrical lens-shaped QDs were observed along [0 1 -1], while their shape was asymmetric along the [-2 3 3] azimuth surrounded by two different dominant facets. Further, QDs were vertically aligned in the [3 1 1] direction when viewed along [0 1 -1], while the alignment was inclined with respect to the growth direction when viewed along [-2 3 3]. The inclination angle of vertical alignment QDs became monotonically smaller from 22° to 2° with decreasing spacer layer thickness from 40 to 20 nm. Time-resolved photoluminescence measurements showed that multi-stacked QDs with thinner spacer layers resulted in increased PL decay times. We believe that an electronically coupled QD state or an intermediate band was formed, if the spacer layer thickness was reduced below 20 nm in this material system. For an InGaAs/GaAs QD solar cell grown on a GaAs (3 1 1)B substrate, the external quantum efficiency showed a clear increase in the longer wavelength range due to an additive contribution from the QD layers. Furthermore, photocurrent production due to two-step absorption of sub-bandgap photons, which is a key element that is necessary to be demonstrated for an increase in the efficiency of a single-junction solar cell beyond the Shockley–Queisser, was observed at room temperature under one sun condition. This photocurrent production increased under a forward-bias regime as the QDs were partially filled with carriers under the bias.

SU-E-T-125: High-Resolution Linear Diode Array for Use in Stereotactic Beam Commissioning.

Task Group 106 discusses detector arrays and their usefulness in "soft-wedge" profile measurements. This study verifies an extension of their use; where a high-resolution linear diode array is used to measure profile scans for use in commissioning stereotactic beam. Small-field data is acquired with the LDA-99sc (IBA Dosimetry America, Memphis, TN), an array of 99 two-mm-diameter Hi-pSi diodes. These data are compared to data collected during serial scanning with an IBA SFD stereotactic diode. Field measurements were taken at varying depths using an LDA-99sc in 1×1 cm2 , 2×2cm2 , and 3×3cm2 fields of a Trilogy accelerator (Varian Medical Systems, Palo Alto, CA). These scans were duplicated in resolution and sample rate with an SFD scanning diode. Both techniques acquired point data in 1.0mm increments. In identical conditions, the LDA-99sc provided readings with significantly less signal fluctuation than with traditional diode scanning; which is attributed to the reduction of water motion associated with detector travel during traditional scanning. This smoother data precluded the use of smoothing and filtration algorithms; allowing the beam to be modeled using raw data. The LDA-99sc measured an average penumbra of 0.1 mm wider than that which was measured with the diode. The LDA-99sc also measured an average field size of 0.3mm wider than that which was measured with the diode. With respect to time, a single profile scan (30cm-depth, 3×3cm2 field) using the LDA-99sc took 31 seconds, while a diode scan took 229 seconds. The LDA99 provided accurate commissioning-grade small-field beam profile data, as verified by comparison with diode scans, with a reduction of uncertainty in readings and a substantial reduction in time. Variation in penumbra and beam widths were deemed acceptable and can be attributed to the LDA-99sc data being raw, while the diode data was processed. Research supported in-part by IBA Dosimetry America.