Ultrafast Sensor Research Articles

Highly sensitive and ultrafast film sensor based on polyethyleneimine-capped quantum dots for trinitrophenol visual detection.

Real-time detection of nitroaromatic explosives is a pressing problem for public security and environmental monitoring. Although many efforts have been devoted, sensing of explosives still suffers limitations of complicated and time-consuming sensing procedure. In this work, we develop a fluorescent film for rapid and visual detection of 2,4,6-trinitrophenol (TNP) by using polyethyleneimine-capped quantum dots (QDs-PEI) as fluorescent sensing probe and electrospun membrane as matrix. Fluorescent sensing is mainly based on effective reaction between amino groups of PEI and nitro groups, phenol hydroxyl groups of TNP. It also benefits from the rapid absorption of TNP in aqueous solution by PA6 nanofiber membranes with high hydrophilicity and porosity. As a result, visual sensing could be realized when TNP is >100ng·mL-1 by obvious fluorescent change with a thirty-second response time. We believe this fluorescent membrane sensor holds a promising prospect for real time and visual detection of TNP in environmental science and analytical fields.

Signal development for saturated ultrafast sensors with impact ionization gain

A closed-form approximate expression is presented for the short time-frame development of silicon diode sensor signals in the context of high frame-rate detection of incident X-ray fluxes, in the limit that the X-ray absorption profile generates a longitudinally-uniform distribution of electron-hole pairs in the detector bulk. The expression represents the immediate time development of signals from diode sensors both with (LGAD) and without (PIN) gain, and presents a temporal scale associated with the onset of gain. Principles limiting the detection frame rate in the presence of electronic readout noise are discussed. Making use of an elemental simulation, the relative advantage of LGAD vs. PIN diode sensors is explored as a function of the effective electronic collection time. It is found that for an idealized LGAD sensor with a gain of 30, the gain provided by impact ionization yields an advantage relative to PIN diode sensors for frame rates as high as 10 GHz.

Numerical and Theoretical Study of Tunable Plasmonically Induced Transparency Effect Based on Bright-Dark Mode Coupling in Graphene Metasurface.

In this paper, we numerically and theoretically study the tunable plasmonically induced transparency (PIT) effect based on the graphene metasurface structure consisting of a graphene cut wire (CW) resonator and double split-ring resonators (SRRs) in the middle infrared region (MIR). Both the theoretical calculations according to the coupled harmonic oscillator model and simulation results indicate that the realization of the PIT effect significantly depends on the coupling distance and the coupling strength between the CW resonator and SRRs. In addition, the geometrical parameters of the CW resonator and the number of the graphene layers can alter the optical response of the graphene structure. Particularly, compared with the metal-based metamaterial, the PIT effect realized in the proposed metasurface can be flexibly modulated without adding other actively controlled materials and reconstructing the structure by taking advantage of the tunable complex surface conductivity of the graphene. These results could find significant applications in ultrafast variable optical attenuators, sensors and slow light devices.

The role of anions and cations in the gas sensing mechanisms of graphene decorated with lead halide perovskite nanocrystals.

We report the effects of both anions and cations in lead halide perovskite-graphene hybrids applied to gas sensing. Ultra-fast sensors that can work at room temperature are developed and studied to elucidate the role in the gas sensing mechanisms of different ions in perovskite nanocrystals.

Ultrafast Photoinduced Strain in Super-Tetragonal PbTiO3 Ferroelectric Films

The ultrafast photoinduced strain in ferroelectric coupling of piezoelectric and photovoltaic effects have been focused in the last decade, making them extend numerous applications including ultrafast optical memories, sensors and actuators with strain engineering. The mechanism of screening of the depolarization field by photoinduced carriers is generally accepted for ultrafast photoinduced strain in ferroelectric, while the thermal component of the strain is usually diluted as the offset and have not been systematically confronted, leading to unnecessary confusion. Herein, both the positive and negative thermal expansion effect in composite ferroelectric epitaxial films have been investigated by use of high repetition rate ultrafast X-ray diffraction, along with the piezoelectric and photovoltaic effects. The coupling of the positive/negative thermal effects and the piezoelectric/photovoltaic effects in ultrafast strain have been evidenced and regulated. The opposite lattice response due to different thermal effect of the different axial ratio samples have been observed. The maximum ultrafast photoinduced strain is up to 0.24%, comparable to that of conventional ferroelectric. The interaction of thermal and ferroelectric effect in the induced strain could promote the diversified application with the coupling of light, heat and electricity.

Fast response and low temperature sensing of acetone and ethanol using Al-doped ZnO microrods

Abstract We report low temperature acetone and ethanol sensing properties of Al-doped ZnO microrods synthesized using hydrothermal technique. We observe the acetone detection at room temperature as well as ethanol and acetone detection at low temperature of 150 °C using Al-doped ZnO microrods. 3 wt% Al-doped ZnO microrods sensor exhibits the highest response of 231 toward 8100 parts per million (ppm) of ethanol at 150 °C. The response & recovery time are found to be ultrafast of 60 ms & 870 ms for ethanol and 110 ms & 330 ms for acetone of the Al-doped ZnO microrods at an operating temperature of 150 °C, respectively. In addition, sensing mechanism has explained to illuminate the improved sensing performances of Al-doped ZnO microrods. Thus it is revealed that Al-doped ZnO microrods are promising as an ultrafast gas sensor.

Ultrasensitive Anti-Interference Voice Recognition by Bio-Inspired Skin-Attachable Self-Cleaning Acoustic Sensors.

Human voice recognition systems (VRSs) are a prerequisite for voice-controlled human-machine interfaces (HMIs). In order to avoid interference from unexpected background noises, skin-attachable VRSs are proposed to directly detect physiological mechanoacoustic signals based on the vibrations of vocal cords. However, the sensitivity and response time of existing VRSs are bottlenecks for efficient HMIs. In addition, water-based contaminants in our daily lives, such as skin moisture and raindrops, normally result in performance degradation or even functional failure of VRSs. Herein, we present a skin-attachable self-cleaning ultrasensitive and ultrafast acoustic sensor based on a reduced graphene oxide/polydimethylsiloxane composite film with bioinspired microcracks and hierarchical surface textures. Benefitting from the synergetic effect of the spider-slit-organ-like multiscale jagged microcracks and the lotus-leaf-like hierarchical structures, our superhydrophobic VRS exhibits an ultrahigh sensitivity (gauge factor, GF = 8699), an ultralow detection limit (ε = 0.000 064%), an ultrafast response/recovery behavior, an excellent device durability (>10 000 cycles), and reliable detection of acoustic vibrations over the audible frequency range (20-20 000 Hz) with high signal-to-noise ratios. These superb performances endow our skin-attachable VRS with anti-interference perception of human voices with high precision even in noisy environments, which will expedite the voice-controlled HMIs.

Design and analysis of ultrafast and high-sensitivity microwave transduction humidity sensor based on belt-shaped MoO3 nanomaterial

In this study, an ultrafast and high-sensitivity humidity sensor is designed and analyzed based on microwave dual-band resonator functionalized with belt-shaped MoO3 nanomaterial. Two sensitive frequencies for water vapor were selected in the frequency band of 2–12 GHz using the developed interdigital capacitor. The proposed dual-band resonator structure was optimized to achieve higher response and improved quality factor (Q-factor) for sensitivity enhancement. To investigate the humidity sensing performance of the sensor, the sensing element deposited with sensitive material MoO3 was placed inside a humidity chamber with the humidity generator to yield five humidity levels at room temperature. Results indicate that the insertion loss linearly varies with the humidity level ranging from 10% to 90% relative humidity (RH) with sensitivity of 0.069 and 0.022 dB/% RH for 7.3 and 9.1 GHz, respectively. Moreover, the sensor exhibits sensitivity of 1.938 and 2.062 MHz/% RH for the two sensitive frequencies. The dynamic kinetics of response and recovery time was less than 5 s and the humidity hysteresis was about 0.25% RH. The humidity sensing mechanism was discussed from the perspective of sensitive material and microwave transduction. This study provides a facile approach for the implementation of microwave humidity sensors with high sensitivity and fast response speed.

Achieving exceedingly constructional characterization of magnesia-yttria (MgO-Y2O3) nanocomposite obtained via oxalate precursor strategy

Magnesium yttrium oxide (MgO-Y2O3) nanocomposites have been purposefully tailored using an oxalate precursor pathway. Commonly, MgO-Y2O3 nanocomposites possessed a significant technological challenge in electroceramics; particularly remarkable as the anode material for solid oxide fuel cells (SOFC). In this regard, different weight ratios, % of MgO and Y2O3 including (20:80), (50:50) and (80:20) were fabricated based on oxalic acid as a fuel in acidic medium. Indeed, the impact of the annealing temperature on the phase composition, crystallite size, morphology and optical properties was investigated using X-ray diffraction, field emission electron microscope (FESEM), TEM, FTIR and UV–VIS-NIR spectrophotometer. The FESEM results showed the nanocomposite had a cubic like structure with the fine grain sizes of 0–150 nm because of the rapid solidification. The band gap energy was found to be 4.83, 5.10 and 5.08 eV with increasing the ratio of Mg2+ ion from 20 to 50 and 80, respectively. Eventually, our currently studies consider to be an important achievement to investigate and recognize the features of the MgO-Y2O3 system for different applications involving microwave systems, advanced displays (field emission display, plasma display, electroluminescent display), ultra-fast sensors, durable, infrared windows and lasers.

Initial assessment of multilayer silicon detectors for hard X-ray imaging

Silicon detectors with lower material budget, ultrafast readout and radiation hardness are under developments. These unique features make pixelized silicon sensors a good option for hard X-ray imaging. To verify the performance of spatial resolution and energy sensitivity of silicon sensors to hard X-rays, a two layer setup of Pixelink PL-D725MU sensors has been tested at the Argonne National Laboratory Advanced Photon Source (APS) ID-10 sector with 29.2 keV high photon flux (4.5×10^8 to 4.5×10^(10) photons per second) X-rays. Better than 3 μm spatial resolution and clear energy characterization have been achieved by both layers. Commercial CMOS sensors with superior spatial resolution could be used for phase contrast imaging in current synchrotrons. These studies pave the path for future multilayer ultrafast silicon sensor development with ns to sub-ns readout speeds in hard X-ray imaging at synchrotrons and XFEL beamlines.

Temperature gradients in ultrafast thin-film nanocalorimetry

Temperature gradients can significantly affect the accuracy of ultrafast thin-film nanocalorimetry. In this regard, the problem of dynamic heat transfer for thin-film sensors of different geometry is solved analytically. Temperature distributions are analyzed in the direction perpendicular to the membrane of the calorimetric sensor, as well as in the lateral direction for the unloaded sensor and the sensor loaded with the sample. Different sensor designs are considered, including commercially available ultrafast sensor XEN-39472. Temperature gradients at different scanning rates up to 108 K/s were investigated. It was found that the temperature gradients in the membrane plane are significant even in quasi-static mode at scanning rates below 106 K/s and even in unloaded sensor. Possibility of improving the calorimetric sensors is studied. Based on the calculations of the analytical model, recommendations for modification of the sensor design are obtained.

Inside Front Cover: Widefield multifrequency fluorescence lifetime imaging using a two‐tap complementary metal‐oxide semiconductor camera with lateral electric field charge modulators (J. Biophotonics 5/2019)

A novel Widefield frequency‐domain fluorescence lifetime imaging system based on a ultrafast sCMOS sensor is reported. It can do parallel multi‐frequency FLIM up to 620MHz in one measurement with 64 phase images. With this system, measurement of FRET efficiency at multi‐frequencies is demonstrated in living cells. Meanwhile, the temperature change of living cells can be measured at each pixel based on FLIM of Rhodamine B at different frequencies.Further details can be found in the article by Hongtao Chen, Ning Ma, Keiichiro Kagawa, et al. (e201800223). image

Experimental characterization of a fast, pixelated CMOS sensor and design of a Recoil-Proton Telescope for neutron spectrometry

Abstract Neutrons are particles of interest in various domains such as fundamental physics, biology, elemental analysis or radio-protection. The measurement of the neutron energy is necessary in all these domains, but the required characteristics of the spectrometers can vary greatly from an application to another. The IPHC laboratory is currently developing a new CMOS pixel Recoil Protons Telescope (RPT). This compact detector allows a real-time reconstruction of the neutron spectrum up to very high flux. The pixelated ultra-fast CMOS sensors were characterized in two proton beam experiments. This experimental characterization was then used in a realistic Monte Carlo simulation of the full system to compute the expected performances. The simulated results exhibit very good spectrometric performances, with an energy resolution better than 4% over a 4 . 5 , 20 MeV energy range. These performances, combined with its compactness and ability to reconstruct the spectrum in real time, make it a very interesting device for various applications.

Single Synapse Indicators of Impaired Glutamate Clearance Derived from Fast iGlu u Imaging of Cortical Afferents in the Striatum of Normal and Huntington (Q175) Mice.

Changes in the balance between glutamate (Glu) release and uptake may stimulate synaptic reorganization and even synapse loss. In the case of neurodegeneration, a mismatch between astroglial Glu uptake and presynaptic Glu release could be detected if both parameters were assessed independently and at a single-synapse level. This has now become possible due to a new imaging assay with the genetically encoded ultrafast Glu sensor iGlu u We report findings from individual corticostriatal synapses in acute slices prepared from mice of either sex that were >1 year of age. Contrasting patterns of short-term plasticity and a size criterion identified two classes of terminals, presumably corresponding to the previously defined IT (intratelencephalic) and PT (pyramidal tract) synapses. The latter exhibited a higher degree of frequency potentiation/residual Glu accumulation and were selected for our first iGlu u single-synapse study in Q175 mice, a model of Huntington's disease (HD). In HD mice, the decay time constant of the perisynaptic Glu concentration (TauD), as an indicator of uptake, and the peak iGlu u amplitude, as an indicator of release, were prolonged and reduced, respectively. Treatment of WT preparations with the astrocytic Glu uptake blocker TFB-TBOA (100 nm) mimicked the TauD changes in homozygotes. Considering the largest TauD values encountered in WT, ∼40% of PT synapses tested in Q175 heterozygotes can be classified as dysfunctional. Moreover, HD but not WT synapses exhibited a positive correlation between TauD and the peak amplitude of iGlu u Finally, EAAT2 (excitatory amino acid transport protein 2) immunoreactivity was reduced next to corticostriatal terminals. Thus, astrocytic Glu transport remains a promising target for therapeutic intervention.SIGNIFICANCE STATEMENT Alterations in astrocytic Glu uptake can play a role in synaptic plasticity and neurodegeneration. Until now, the sensitivity of synaptic responses to pharmacological transport block and the resulting activation of NMDA receptors were regarded as reliable evidence for a mismatch between synaptic uptake and release. But the latter parameters are interdependent. Using a new genetically encoded sensor to monitor extracellular glutamate concentration ([Glu]) at individual corticostriatal synapses, we can now quantify the time constant of perisynaptic [Glu] decay (as an indicator of uptake) and the maximal [Glu] elevation next to the active zone (as an indicator of Glu release). The results provide a positive answer to the hitherto unresolved question of whether neurodegeneration (e.g., Huntington's disease) associates with a glutamate uptake deficit at tripartite excitatory synapses.

Spectral dynamics of shift current in ferroelectric semiconductor SbSI

Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.

Utilities roll out real-time grid controls: Synchrophasor tech enables rapid response to broken power lines and other emergencies - [News

Amidst what could be California's worst wildfire season on record, San Diego Gas & Electric is counting on technology to reduce dangerous sparking from its power lines. Last month, the utility completed the initial rollout of a home-grown automated control technology that taps ultrafast synchrophasor sensors to detect and turn off broken power lines before they hit the ground.

Ultrafast miniature fiber-tip Fabry-Perot humidity sensor with thin graphene oxide diaphragm.

We demonstrate here an ultrafast, miniature, and high-performance fiber-tip Fabry-Perot (F-P) humidity sensor with ∼300 nm-thick graphene oxide (GO) diaphragm suspended onto the end face of a capillary tube with an inner diameter of 50μm and a cavity length of ∼100 μm. The sensitivity to relative humidity (RH) spanning from ∼10%RH to ∼90%RH was examined based on the wavelength shift in the interference spectrum. Due to the intrinsic hydrophilicity of the porous GO membrane, the developed sensor exhibited an average wavelength variation of ∼0.2 nm/%RH, which indicated a relatively broad and readily detectable RH linear measurement range. More prominently, an ultrahigh response time of 60ms was achieved over other alternative F-P humidity sensors previously reported, to our knowledge.

Towards Low-Cost Yet High-Performance Sensor Networks by Deploying a Few Ultra-fast Charging Battery Powered Sensors.

The employment of mobile vehicles to charge sensors via wireless energy transfer is a promising technology to maintain the perpetual operation of wireless sensor networks (WSNs). Most existing studies assumed that sensors are powered with off-the-shelf batteries, e.g., Lithium batteries, which are cheap, but it takes some non-trivial time to fully charge such a battery (e.g., 30–80 min). The long charging time may incur long sensor dead durations, especially when there are many lifetime-critical sensors to be charged. On the other hand, other studies assumed that every sensor is powered with an ultra-fast charging battery, where it only takes some trivial time to replenish such a battery, e.g., 1 min, but the adoption of many ultra-fast sensors will bring about high purchasing cost. In this paper, we propose a novel heterogeneous sensor network model, in which there are only a few ultra-fast sensors and many low-cost off-the-shelf sensors. The deployment cost of the network in the model is low, as the number of ultra-fast sensors is limited. We also have an important observation that we can significantly shorten sensor dead durations by enabling the ultra-fast sensors to relay more data for lifetime-critical off-the-shelf sensors. We then propose a joint charging scheduling and routing allocation algorithm, such that the longest sensor dead duration is minimized. We finally evaluate the performance of the proposed algorithm through extensive simulation experiments. Experimental results show that the proposed algorithm is very promising and the longest sensor dead duration by it is only about 10% of those by existing algorithms.

Photography optics in the time dimension

Ultrafast sensors and depth cameras are key enablers for imaging through complex geometries, through scattering, and beyond the line of sight. However, despite accelerating advances in imaging electronics and imaging applications, the optics of such cameras have been inherited from conventional low-speed photography cameras. This has limited ultrafast cameras and their applications to the design constraints of conventional optics. Here, we exploit time as an extra dimension in the optical design and demonstrate that by folding large spaces in time using time-resolved cavities, one can enable new camera capabilities without losing the targeted information. We demonstrate lens tube compression by an order of magnitude, together with ultrafast multi-zoom imaging and ultrafast multispectral imaging by time-folding the optical path at different regions of the imaging optics. Considering the vast variety of designs that could emerge by time-folding conventional imaging optics, we expect this technique to have a broad impact on time-resolved imaging and depth-sensing optics.

Ultrafast glutamate sensors resolve high-frequency release at Schaffer collateral synapses

Glutamatergic synapses display a rich repertoire of plasticity mechanisms on many different time scales, involving dynamic changes in the efficacy of transmitter release as well as changes in the number and function of postsynaptic glutamate receptors. The genetically encoded glutamate sensor iGluSnFR enables visualization of glutamate release from presynaptic terminals at frequencies up to ∼10 Hz. However, to resolve glutamate dynamics during high-frequency bursts, faster indicators are required. Here, we report the development of fast (iGlu f ) and ultrafast (iGlu u ) variants with comparable brightness but increased Kd for glutamate (137 μM and 600 μM, respectively). Compared with iGluSnFR, iGlu u has a sixfold faster dissociation rate in vitro and fivefold faster kinetics in synapses. Fitting a three-state model to kinetic data, we identify the large conformational change after glutamate binding as the rate-limiting step. In rat hippocampal slice culture stimulated at 100 Hz, we find that iGlu u is sufficiently fast to resolve individual glutamate release events, revealing that glutamate is rapidly cleared from the synaptic cleft. Depression of iGlu u responses during 100-Hz trains correlates with depression of postsynaptic EPSPs, indicating that depression during high-frequency stimulation is purely presynaptic in origin. At individual boutons, the recovery from depression could be predicted from the amount of glutamate released on the second pulse (paired pulse facilitation/depression), demonstrating differential frequency-dependent filtering of spike trains at Schaffer collateral boutons.