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Characterization of the weak absorption loss of optical materials requires highly sensitive photothermal detection. To address this requirement, the temperature field induced by a spatially modulated Gaussian heat source imposed on an optical glass is analyzed and compared with that induced by the same heat source modulated temporally. The theoretical analysis reveals that the temperature variation due to the spatial modulation (SM) of the heat source is much larger than that due to the temporal modulation (TM) because the irradiated site not only has a high temperature peak in the quasi-steady state of heating but also has a temperature valley as low as the ambient temperature. This distinct advantage allows for a stronger thermoelastic response of the material and accordingly highly sensitive photothermal detection. The results of the experiment on a fused silica glass verified that the photothermal image due to the SM shows up the weak absorptive defects that have not appeared in that due to the TM under the same experimental conditions. The improvement in the sensitivity is calculated to be 1.8, and the degradation of the sensitivity due to the inevitable experimental imperfections is finally discussed. [ABSTRACT FROM AUTHOR]

Vacuum pressure sensors play a significant role in industry and scientific research. However, there are still many challenges for further application of vacuum pressure sensors due to their complex fabrication and high cost. In this work, we have fabricated a graphene vacuum pressure sensor by one-step laser scribing within 25 min. The resistance of the sensor decreases with declining vacuum pressure. Four linear segments are obtained in the relationship between the resistance response and the vacuum pressure ranging from 7.5 × 10−4 Torr to 2.35 Torr at room temperature. Besides, the graphene sensor exhibits a high sensitivity of 1.2 × 10−2 Torr−1 and a rapid response time of 9 s, which are superior to previously reported sensors. The sensing mechanism of the graphene vacuum pressure sensor is investigated. Under the influence of van der Waals interactions between the stacked graphene multilayers, the void space among the neighboring graphene layers reduces with decreasing vacuum pressure, resulting in a decrease of the sheet resistance. The designed graphene vacuum pressure sensor with the distinguished features of high performance, small size, low cost, and simple fabrication shows great feasibility and tremendous potential for vacuum measurement applications. [ABSTRACT FROM AUTHOR]

The in painting of deliberately and randomly sub-sampled images offers a potential means to image specimens at a high resolution and under extremely low-dose conditions (≤1 e-/Å°²) using a scanning transmission electron microscope. We show that deliberate sub-sampling acquires images at least an order of magnitude faster than conventional low-dose methods for an equivalent electron dose. More importantly, when adaptive sub-sampling is implemented to acquire the images, there is a significant increase in the resolution and sensitivity which accompanies the increase in imaging speed. We demonstrate the potential of this method for beam sensitive materials and in-situ observations by experimentally imaging the node distribution in a metal-organic framework. [ABSTRACT FROM AUTHOR]

We report an ultra-compact surface-normal optofluidic refractometric sensor based on a twodimensional silicon photonic crystal on insulator. In contrast to the conventional symmetric Lorentzian resonance that is prevalently used in the label-free sensors, the asymmetric lineshape and steep peak-to-dip transition of a Fano resonance enable the enhanced detection sensitivity. The detection limit of 1.3×10-6 refractive index units is achieved, which is among the lowest reported experimentally in the defect-free photonic crystal sensors. [ABSTRACT FROM AUTHOR]

This paper presents surface plasmons (SPs) on ZnO: Ga layers using an asymmetric insulator-metalinsulator (IMI) geometry. The water-ZnO: Ga-cytop tri-layers comprising IMI structures showed narrower surface plasmon resonance spectra than insulator-metal structures with water-ZnO: Ga single layers. Measurements of bulk sensitivities based on refractive index changes revealed extended evanescent fields on the ZnO: Ga layer surfaces when using reduced layer thicknesses. Consequently, the asymmetric IMI geometry on ZnO: Ga provides enhanced sensitivity in the infrared range. This result is further discussed from theoretical analyses of SP field distributions. This IMI geometry provides structural concepts to assist with developments in the area of oxide-based sensing applications. [ABSTRACT FROM AUTHOR]

In this paper, we report a large lateral photovoltaic effect (LPE) with ultrafast relaxation time in SnSe/p-Si junctions. The LPE shows a linear dependence on the position of the laser spot, and the position sensitivity is as high as 250mV mm-1. The optical response time and the relaxation time of the LPE are about 100 ns and 2 μs, respectively. The current-voltage curve on the surface of the SnSe film indicates the formation of an inversion layer at the SnSe/p-Si interface. Our results clearly suggest that most of the excited-electrons diffuse laterally in the inversion layer at the SnSe/p-Si interface, which results in a large LPE with ultrafast relaxation time. The high positional sensitivity and ultrafast relaxation time of the LPE make the SnSe/p-Si junction a promising candidate for a wide range of optoelectronic applications. [ABSTRACT FROM AUTHOR]

In this contribution, we present a highly accurate approach for thickness measurements of multi-layered automotive paints using terahertz time domain spectroscopy in reflection geometry. The proposed method combines the benefits of a model-based material parameters extraction method to calibrate the paint coatings, a generalized Rouard's method to simulate the terahertz radiation behavior within arbitrary thin films, and the robustness of a powerful evolutionary optimization algorithm to increase the sensitivity of the minimum thickness measurement limit. Within the framework of this work, a self-calibration model is introduced, which takes into consideration the real industrial challenges such as the effect of wet-on-wet spray in the painting process. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate an approach for improved sensitivity in weak radio frequency (RF) electric-field strength measurements using Rydberg electromagnetically induced transparency (EIT) in an atomic vapor. This is accomplished by varying the RF frequency around a resonant atomic transition and extrapolating the weak on-resonant field strength from the resulting off-resonant Autler-Townes (AT) splittings. This measurement remains directly traceable to SI compared to previous techniques, precluding any knowledge of experimental parameters such as optical beam powers as is the case when using the curvature of the EIT line shape to measure weak fields. We use this approach to measure weak RF fields at 182 GHz and 208 GHz demonstrating improvement greater than a factor of 2 in the measurement sensitivity compared to on-resonant AT splitting RF electric field measurements. [ABSTRACT FROM AUTHOR]

Regeneration of a tissue fragment of freshwater polyp Hydra is accompanied by significant morphological fluctuations, suggesting the generation of active forces. In this study, we utilized a two fingered micro-robotic hand to gain insights into the mechanics of regenerating tissues. Taking advantage of a high force sensitivity (~1 nN) of our micro-hand, we non-invasively acquired the bulk elastic modulus of tissues by keeping the strain levels low (ϵ<0.15). Moreover, by keeping the strain at a constant level, we monitored the stress relaxation of the Hydra tissue and determined both viscous modulus and elastic modulus simultaneously, following a simple Maxwell model. We further investigated the correlation between the frequency of force fluctuation and that of morphological fluctuation by monitoring one "tweezed" tissue and the other "intact" tissue at the same time. The obtained results clearly indicated that the magnitude and periodicity of the changes in force and shape are directly correlated, confirming that our two fingered micro-hand can precisely quantify the mechanics of soft, dynamic tissue during the regeneration and development in a noninvasive manner. [ABSTRACT FROM AUTHOR]

In this research, we developed wireless, inductive, pressure sensors with high sensitivity and investigated the effects of the inner materials (copper or ferrite) on the performance of the sensors. The proposed sensor is comprised of two parts, i.e., the top and the bottom parts. The top part includes a micro coil and a capacitor for the wireless transfer of data, and the bottom part includes the inner materials and a thick or thin flexible membrane to induce changes in the inductance. An anchor is used to assemble the top and bottom parts. The behavior of the sensor with copper was based on the eddy current effect, and, as the pressure increased, its resonance frequency increased, while its phase depth decreased exponentially. The principle of the sensor with ferrite was related to the effective permeability between a ferrite and a coil, and its response was the opposite of that with copper, i.e., as the pressure increased, the resonance frequency decreased linearly, and the phase depth increased linearly. These different operational mechanisms can be explained by the changes in the equations of inductance presented in this paper. After characterizing four different types of inductive pressure sensors in ambient air, one type of inductive pressure sensor was used to monitor the intraocular pressure (IOP) of a rabbit's eye as a biomedical application. The results showed that, in the animal tests, the measured responsivity and sensitivity were 16.7 kHz/mmHg and 1340 ppm/mmHg, respectively. These data indicate that the proposed sensor is a good candidate for monitoring IOP. [ABSTRACT FROM AUTHOR]

We report on a preliminary laboratory based x-ray phase-contrast imaging system capable of achieving two-directional phase sensitivity, thanks to the use of L-shaped apertures. We show that in addition to apparent absorption, two-directional differential phase images of an object can be quantitatively retrieved by using only three input images. We also verify that knowledge of the phase derivatives along both directions allows for straightforward phase integration with no streak artefacts, a known problem common to all differential phase techniques. In addition, an analytical method for 2-directional dark field retrieval is proposed and experimentally demonstrated. [ABSTRACT FROM AUTHOR]

We show that simple radio-frequency (RF) interferometers can have slow-wave positive group delay (PGD) or negative group delay (NGD), as well as superluminal propagation (SP) regions, due to a destructive interference process. These properties are easily tunable, which makes RF interferometers unique among systems that have NGD and SP regimes. A two-stage interferometer arrangement, which includes a first stage interferometer in the material-under-test path of a second stage, has significantly improved sensitivity in comparison with a one-stage reference interferometer. With a power divider based first stage and at its maximum NGD frequency, the frequency sensitivity improvement is as high as 7 times. With a quadrature based first stage, the sensitivity is increased by as much as 20 times. Sensitivity improvements are also observed at PGD and SP frequency regions. [ABSTRACT FROM AUTHOR]

The detection of the intrinsic charge of biochemical molecules is a promising strategy for the fabrication of field-effect transistor (FET)-based sensors for direct, non-destructive detection of several biochemical reactions. Nevertheless, the high ionic concentration of standard environments for biochemical species represents a significant limitation to this sensing strategy. Here, an investigation on the physical mechanisms behind the ability of an organic FET-based sensor to detect DNA hybridization at high ionic strengths is proposed. The capability of the device to correctly detect single-stranded DNA oligonucleotides and their hybridization with a complementary target sequence has been analyzed in detail. In particular, the electrical response in solutions with different ionic strengths was investigated and put in relation with the nano-scale properties of DNA strands employed as receptors. Fluorescence analysis shows that it is possible to electrically modify their orientation and consequently improve the device sensitivity in conditions close to those occurring during in vivo hybridization. [ABSTRACT FROM AUTHOR]

A graphene-based electrical current sensor is proposed utilizing a microfiber coil resonator. Monolayer graphene sheet with a large sheet resistance is transferred onto the surface of a glass capillary rod. A microfiber is spirally wrapped around the graphene sheet to form a coil resonator. Heat generated from electrical current shifts the resonant wavelength because of the thermal effect in the microfiber resonator. The sensor exhibits a very good performance with a high sensitivity of 67.297 μm/A², which is two orders of magnitude higher than that reported earlier. Our results show that microfiber-graphene-integrated devices have great potential for miniature and highly sensitive fiber sensors for monitoring electrical current. [ABSTRACT FROM AUTHOR]

In this work, we theoretically and experimentally investigate the thermal response of whispering gallery mode microresonators operating in an aqueous glycerol medium. Thermal stabilisation of the resonance wavelength is realised by appropriate choice of the resonator radius and glycerol concentration, with a 60 fold reduction in thermal sensitivity demonstrated. Finally, we employ our stabilised system to determine the thermal dependence of the molecular polarisability of adsorbed bovine serum albumin molecules and the refractive index of dextran and poly(diallyldimethylammonium chloride) coatings. [ABSTRACT FROM AUTHOR]

A reconfigurable Mach-Zenhnder interferometer (MZI) based on a microfluidic cavity (MFC) constructed by embedding a microfiber between two segments of single-mode fibers with predesigned lateral offset has been proposed and experimentally demonstrated. The MFC serves as an interference arm with an eccentric annular cross section and allows convenient sample (gas or liquids) replacement procedure. The microfiber works as the other interference arm that provides the proposed device with ease of reconstruction and also enhances the force sensitivity. The reconfigurability and the ultra-wide tuning sensitivity range are demonstrated by immersing the MZI constructed with a 484 lm-long-MFC and a microfiber 44 lm in diameter in different droplets. Ultrahigh sensitivities of 34.65 nm/℃ (~88 380 nm/RIU) and -493.7 nm/N (~-590 pm/με) are experimentally achieved using a droplet with a refractive index of ~1.44. [ABSTRACT FROM AUTHOR]

Electron spin resonance (ESR) is a spectroscopic method that addresses electrons in paramagnetic materials directly through their spin properties. ESR has many applications, ranging from semiconductor characterization to structural biology and even quantum computing. Although it is very powerful and informative, ESR traditionally suffers from low sensitivity, requiring many millions of spins to get a measureable signal with commercial systems using the Faraday induction-detection principle. In view of this disadvantage, significant efforts were made recently to develop alternative detection schemes based, for example, on force, optical, or electrical detection of spins, all of which can reach single electron spin sensitivity. This sensitivity, however, comes at the price of limited applicability and usefulness with regard to real scientific and technological issues facing modern ESR which are currently dealt with conventional induction-detection ESR on a daily basis. Here, we present the most sensitive experimental induction-detection ESR setup and results ever recorded that can detect the signal from just a few tens of spins. They were achieved thanks to the development of an ultra-miniature micrometer-sized microwave resonator that was operated at ~34 GHz at cryogenic temperatures in conjunction with a unique cryogenically cooled low noise amplifier. The test sample used was isotopically enriched phosphorus-doped silicon, which is of significant relevance to spin-based quantum computing. The sensitivity was experimentally verified with the aid of a unique high-resolution ESR imaging approach. These results represent a paradigm shift with respect to the capabilities and possible applications of induction-detection-based ESR spectroscopy and imaging. [ABSTRACT FROM AUTHOR]

We demonstrate aqueous refractive index sensing with 15-30 µm diameter silicon nitride microdisk resonators to detect small concentrations of Li salt. A dimpled-tapered fiber is used to couple 780 nm visible light to the microdisks, in order to perform spectroscopy on their optical resonances. The dimpled fiber probe allows testing of multiple devices on a chip in a single experiment. This sensing system is versatile and easy to use, while remaining competitive with other refractometric sensors. For example, from a 20 µm diameter device we measure a sensitivity of 230620 nm/refractive index units (RIU) with a loaded quality factor of 1.5 X 104, and a limit of detection down to (1.3±.1) x 10-6 RIU. [ABSTRACT FROM AUTHOR]

The voltage dependence of sensitivity for Schottky-diode gas sensor is theoretically studied and experimentally verified in this work. The study is based on the forward current-voltage (I-V) characteristics of the device and benefits from its power exponent parameter α(V)=[d(ln I)]/[d(ln V)]. This proposed analytical method (1) provides an easier way to identify the current-flow mechanisms at different bias levels, (2) demonstrates the exponential relation between the device sensitivity and the voltage at low bias level, (3) allows easy and accurate calculation of the Schottky barrier-height change, and (4) lays the groundwork for investigating the maximum sensitivity and the corresponding bias voltage. This analytical method is verified by using a Pd/WO3/SiC diode under exposure to hydrogen gas with different concentrations at 150°C and 225°C. Based on the proposed method, the parameters (barrier-height change, maximum sensitivity and corresponding bias voltage) of the sensor can be easily extracted and show excellent consistence with those obtained by conventional method. [ABSTRACT FROM AUTHOR]

Wearable and sensitive photodetectors (PDs) have been demonstrated based on a blend film of PbS quantum dots (QDs) and QDs modified multiwalled carbon nanotubes (MWCNTs). Owing to the synergetic effect from high light sensitivity of PbS QDs and excellent conductive and mechanical properties of MWCNTs, the blend PDs show high sensitivity and flexibility performance: device responsivity and detectivity reach 583mA/W and 3.25 × 1012Jones, respectively, and could stand large number (at least 10000 cycles) and wide angle (up to 80°) bending. Furthermore, the wearable and sensitive PDs have been applied to measure the heart rate in both red and near infrared (NIR) ranges. The presented PDs are expected to work as sensor candidates in integrated electronic skin. [ABSTRACT FROM AUTHOR]

Resonating strings have shown promise in a variety of applications including micron-scale mass and temperature sensors. We present microchannel string resonators (MSRs) which have resonance frequency modulated by the internal gauge pressure of silicon nitride microchannels sitting atop the strings. We present an analytical model to predict the pressure sensitivity (Hz/kPa) of the first resonance frequency as well as experimental results for three identical MSRs. While the highest experimental sensitivity of one of the resonators is 5.19 Hz/kPa (0.5 Hz/mbar), the analytical model suggests sensitivity could increase by two orders of magnitude if the microchannels are fabricated at nanometer scale with a length of 10 μm, a channel width of 600 nm, and a channel thickness of 50 nm. The average pressure resolution of the sensors is 0.4 kPa. These results are for a calibrated range of pressure from 50 kPa to 100 kPa (500 mbar to 1000 mbar). However, the analytical model shows that resonance frequency is a linear function of pressure over a range of several MPa, suggesting that the microchannel resonators could have a pressure sensing range (dynamic range) suitable for many applications. [ABSTRACT FROM AUTHOR]

We report high performance flexible hybrid ultraviolet photodetector with solar-blind sensitivity using nanocomposite film of plasma polymerized aniline-titanium dioxide. A facile solvent-free plasma technique is used to synthesize superior quality hybrid material with high yield. The hybrid photodetector exhibited high photoconductive gain of the order of ~105 and fast speed with response and recovery time of 22.87 ms and 34.23 ms. This is an excellent result towards getting a balance in the response speed and photoconductive gain trade-off of the photodetectors reported so far. In addition, the device has the advantages of enhanced photosensitivity ((Ilight-Idark)/Idark) of the order of ~10² and high responsivity of ~104AW-1. All the merits substantiates that, to prepare hybrid material, plasma based method holds potential to be an easy way for realizing large scale nanostructured photodetectors for practical applications. [ABSTRACT FROM AUTHOR]

We analyze the contributions of quality factor, fill fraction, and group index of chip-integrated resonance microcavity devices, to the detection limit for bulk chemical sensing and the minimum detectable biomolecule concentration in biosensing. We analyze the contributions from analyte absorbance, as well as from temperature and spectral noise. Slow light in two-dimensional photonic crystals provide opportunities for significant reduction of the detection limit below 1×10-7 RIU (refractive index unit) which can enable highly sensitive sensors in diverse application areas. We demonstrate experimentally detected concentration of 1 fM (67 fg/ml) for the binding between biotin and avidin, the lowest reported till date. [ABSTRACT FROM AUTHOR]

ZnO nanowires (NWs) synthesized using the vapor-phase deposition method on an Au electrode substrate with and without Au nanoparticle (NP) modification are applied for glucose detection. A significant enhancement of glucose sensitivity is obtained with Au NP modification. The Au NPs/ZnO NWs/Au electrode has peak currents gradually increasing from 41.2 to 155.5 μA, and the ZnO NWs/Au electrode has peak currents increasing from 23.6 to 82.2 μA with glucose concentration (5, 10, 15, 20, and 25 mM) in cyclic voltammograms. Moreover, chronoamperometry results indicate that the response current of the Au NPs/ZnO NWs/Au electrode reached 140 μA in 18mM glucose in 0.1M NaOH, whereas that of the ZnO NWs/Au electrode was only around 74 μA in 31.5mM glucose. [ABSTRACT FROM AUTHOR]

Conventional microscale force sensors use moving parts to infer applied forces. Whenever physical deformations are involved, the sensor characteristics become a function of mechanical parameters, and there is an inevitable trade-off between the sensitivity and measurement range. We developed a microfabricated force sensor that uses feedback control to nullify any displacements within the device, directly transducing forces as high as 1.5mN with a 7.8 nN resolution. The range and sensitivity of the device no longer depend on mechanical parameters, which allow the same device to be used to test samples with a wide range of stiffnesses without loss of accuracy. [ABSTRACT FROM AUTHOR]

We investigate the angular dependence of asymmetric magnetoimpedance of NiFe/IrMn multilayers and explore the possibility of tuning the linear region of the magnetoimpedance curves by modifying the angle between the applied external magnetic field and exchange bias field, and probe current frequency. We quantify the sensitivity by calculating the ratio |ΔZ|=|ΔH| at low magnetic fields as a function of the frequency for samples cut with different orientations and show that considerable values in the linear region around zero field can be reached. The results extend the possibilities for application of exchange biased magnetoimpedance multilayers as probe element for the development and improvement of auto-biased linear magnetic field sensors. [ABSTRACT FROM AUTHOR]

We demonstrate a method for spin dependent recombination (SDR) in metal-oxide-semiconductor-field-effect-transistors which (i) greatly amplifies the spin dependent fraction of the investigated transistor current and (ii) concentrates the sensitivity of the measurement exclusively to the most technologically relevant defects, those at the semiconductor/oxide interface. We demonstrate a gain in sensitivity well in excess of an order of magnitude and a much better resolved spectrum. The boost in sensitivity reduces data acquisition time by orders of magnitude and significantly enhances the analytical power of SDR. The very large amplification effect may also be of interest for magnetic resonance controlled spintronic transistors. [ABSTRACT FROM AUTHOR]

Micropillar compression testing with repeated jumps in strain rate is used to circumvent inherent difficulties associated with nanoindentation and tensile testing of free-standing films. Application to sputtered 21 nm/21 nm Cu/Ni multilayer thin films with a cube-on-cube texture reveals an average strain rate sensitivity (m = 0.014) and activation volume (V = 17 b3), comparable to nanocrystalline face-centered cubic metals. Yet, m increases by ∼50% and V decreases by 70% with increasing strain, opposite to trends reported for nanotwinned Cu. The large, strain-dependent shifts in m and V are dependent on the underlying misfit dislocation structure of Cu/Ni interfaces. [ABSTRACT FROM AUTHOR]

Graphene is widely regarded as one of the most promising materials for sensor applications. Here, we demonstrate that a pristine graphene can detect gas molecules at extremely low concentrations with detection limits as low as 158 parts-per-quadrillion (ppq) for a range of gas molecules at room temperature. The unprecedented sensitivity was achieved by applying our recently developed concept of continuous in situ cleaning of the sensing material with ultraviolet light. The simplicity of the concept, together with graphene's flexibility to be used on various platforms, is expected to intrigue more investigations to develop ever more sensitive sensors. [ABSTRACT FROM AUTHOR]

In this work, nanowire field-effect transistors (NW-FETs) constructed from a top-down approach has been utilized for the detection of biomolecules. Here, we demonstrate that the sensitivity of NW-FET sensors can be greatly enhanced when the same dopant type is used for both channel region and source and drain. This type of FET, known as accumulation mode field-effect transistors (AM-FETs), functions under different operating principle compared with conventional inversion mode FETs. The improved sensitivity is attributed to the different conduction mechanism and current components of AM devices. The results have been verified through a direct comparison with a conventional FET. [ABSTRACT FROM AUTHOR]

The magnetic 1/f noise in miniature anisotropic magnetoresistive sensors has been studied quantitatively, and a linear correlation between sensitivity and magnetic 1/f noise parameter has been observed. The noise level can be effectively reduced by having an IrMn exchange bias layer adjacent to the permalloy layer, as sensing stripes of 2 lm width exhibit 16 times smaller magnetic 1/f noise parameter upon introduction of an IrMn layer. This simple method energetically stabilizes the magnetization fluctuation in permalloy, and lowers the 1/f noise without degrading the sensitivity. The geometry dependences of both noise and sensitivity have also been investigated to better guide future magnetoresistive sensor design. [ABSTRACT FROM AUTHOR]

Partial wetting has been recently proposed to facilitate the operation of microresonators with high quality factor in liquids. By applying this concept to a resonator operated in a shearing eigenmode, a further reduction of viscous damping is expected corresponding to theory. In this study, an excellent quality factor of 490 could be verified for suspended plate-microresonators operated in water combining these two approaches. As a proof of concept, the resonators were employed as mass sensors in water revealing a sensitivity of 80 Hz/pg. [ABSTRACT FROM AUTHOR]

An extraordinary magnetoresistance (EMR) device with a 3-contact geometry has been fabricated and characterized. A large enhancement of the output sensitivity at low magnetic fields compared to the conventional EMR device has been found, which can be attributed to an additional influence coming from the Hall effect. Output sensitivities of 0.19 mV/T at zero-field and 0.2 mV/T at 0.01 T have been measured in the device, which is equivalent to the ones of the conventional EMR sensors with a bias of ∼0.04 T. The exceptional performance of EMR sensors in the high field region is maintained in the 3-contact device. [ABSTRACT FROM AUTHOR]

We present a strain gauge that uses a carbon nanotube (CNT) forest, partially embedded in a Parylene-C membrane, as a piezoresistor. The device exhibits high sensitivity with a gauge factor of 4.52 or higher for strains up to ∼1.5%, offering much higher sensitivity in the strain range than those reported for other types of CNT-forest/polymer composite piezoresistors. The gauge also shows a linear response to bending strains generated by forces applied perpendicularly to the membrane with a 55-ppm/mN sensitivity. These findings suggest promising characteristics for a variety of sensing applications of the CNT-forest/Parylene film. [ABSTRACT FROM AUTHOR]

An integrated sensor based on a vertical hybrid coupler composed of a short-range surface plasmon polariton (SRSPP) waveguide and a SiNx dielectric waveguide has been realized. The output power of the sensor is observed to change drastically with the refractive index of the detection liquid, and the sensing region can be adjusted by varying the width of the SiNx waveguide. The resolution is estimated to be as high as 7.3 × 10-6 refractive index units. This sensor is expected to have significantly high effective sensitivity for detecting a hundred-nanometer-thick layer owing to the highly bounded field of the SRSPP mode. [ABSTRACT FROM AUTHOR]

We demonstrate a general concept of flow manipulation in microfluidic environments, based on controlling the shape and position of flow domains in order to force switching and sorting of microparticles without moving parts or changes in design geometry. Using microbubble acoustic streaming, we show that regulation of the relative strength of streaming and a superimposed Poiseuille flow allows for size-selective trapping and releasing of particles, with particle size sensitivity much greater than what is imposed by the length scales of microfabrication. A simple criterion allows for quantitative tuning of microfluidic devices for switching and sorting of particles of desired size. [ABSTRACT FROM AUTHOR]

We have proposed an optomechanical heterodyne method for measurements of carbon nanotube (CNT) cantilever vibrations and demonstrated the sustained mechanical self-oscillation of the CNT cantilever by the combination of the phase locked loop and the proposed method. Mass sensitivities less than 100 zg were easily achieved in vacuum for long term (∼100 s) deviation and even in air for short term (∼1 s) deviation. Furthermore, the CNT cantilever with the phase locked loop detection is achieved with the very high force sensitivity of a force gradient of ∼10-10 N/m, which is fifth orders magnitude higher than that for the conventional noncontact atomic force microscopy. [ABSTRACT FROM AUTHOR]

We describe a feedback-based dynamic cantilever magnetometry technique capable of achieving thermal limited magnetic moment sensitivity with low applied fields. Using this technique, we have observed periodic entry of vortices into mesoscopic Sr2RuO4 rings. The quantized jump in the magnetic moment of the particle produced by individual vortices was measured with a resolution of 7×10-16 emu with an applied field of 1 Oe. [ABSTRACT FROM AUTHOR]

Magnetic force microscopy (MFM) is able to image and quantify patterns of pinned uncompensated spins (UCS) in exchange-biased samples with high spatial resolution and submonolayer spin sensitivity. However, MFM can only detect magnetic moment distributions with spatial wavelengths within a certain range. Samples with large domains, homogeneous, or divergence-free magnetization fields are not accessible to MFM analysis. In this work we discuss the sample structure constraints placed by the requirement to measure UCS at high spatial resolution, and point out a method to engineer the size of the ferromagnetic domains accordingly. [ABSTRACT FROM AUTHOR]

We report nanotesla sensitivity in Metglas/piezoelectric/carbon fiber/piezoelectric laminates with active tip mass operating in the vicinity of second bending mode. The peak magnetoelectric response for the laminate with an active tip mass (1 g) in longitudinal-transversal mode under Hdc=8 Oe and Hac=1 Oe was found to be ∼1.08 V/cm Oe at 43 Hz (first bending mode) and ∼19 V/cm Oe at 511 Hz (second bending mode). At the standard 1 kHz frequency, the maximum resolution of 5 nT was measured under Hac=0.5 Oe. [ABSTRACT FROM AUTHOR]

A high-sensitivity setup for the observation of χ(2)-based, terahertz/optical, sum and difference frequency generation in liquids is presented. It relies on launching wavefront modulated terahertz radiation into a liquid traversed by an optical beam. Phase matching and polarization selection rules can be tuned to support three wave mixing via either chiral allowed electric dipole processes or higher order quadrupole/magnetic dipole processes. Under nonresonant excitation, hyperpolarizabilities from quadrupole/magnetic dipole processes are measured. Since this approach does not require terahertz transmission through macroscopic thicknesses of water, it has the potential to open a new window on the terahertz dynamics of water solvated molecules. [ABSTRACT FROM AUTHOR]

The sensitivity of conventional ion-sensitive field-effect transistors (ISFETs) is limited to 59 mV/pH, which is the maximum detectable change in electrochemical potential according to the Nernst equation. Here we demonstrate a transducer based on a ZnO dual-gate field-effect transistor that breaches this boundary. To enhance the response to the pH of the electrolyte, a self-assembled monolayer has been used as a top gate dielectric. The sensitivity scales linearly with the ratio between the top and bottom gate capacitances. The sensitivity of our ZnO ISFET of 22 mV/pH is enhanced by more than two orders of magnitude up to 2.25 V/pH. [ABSTRACT FROM AUTHOR]

Time-dependent second-harmonic generation (TD-SHG) is shown to be a sensitive, noncontact probe of dopant type and concentration at Si/SiO2 interfaces. TD-SHG signal magnitude increases for n-Si(111)/SiO2, while for p-Si(111)/SiO2 TD-SHG is nonmonotonic. This behavior is interpreted as a consequence of SHG sensitivity to electric fields induced by interfacial charge transfer and trapping. [ABSTRACT FROM AUTHOR]

Organic p-i-n solar cells having near infrared (NIR) sensitivity to 1050 nm were fabricated using a codeposited i-interlayer consisting of lead phthalocyanine (PbPc) and fullerene (C60). The external quantum efficiency and conversion efficiency for NIR light reached 43% (860 nm) and 2.3%, respectively. The codeposited i-interlayer was shown to have three separate nanostructural components each making a contribution to the operation of the cell. These were electron transport through amorphous C60, hole transport through the H-aggregates of PbPc, and carrier generation by NIR light at the J-aggregate sites of PbPc. [ABSTRACT FROM AUTHOR]

Hair cells in biological hearing organs transform mechanical stimuli into neuronal signals with great sensitivity, sharp frequency selectivity, and wide range of intensity. By combining principle of adaptation in hair cells with electronic engineering, we have produced a biomimetic force sensor under water showing all these features. For the nano-Newton force signal, the biomimetic sensor showed that more than an order of magnitude increases in sensitivity and frequency selectivity compared to the passive sensor. The nonlinear amplification mechanism in the hair cell is demonstrated by showing that the hair cell can precisely detect pulse signals weaker than noise. [ABSTRACT FROM AUTHOR]

A nanofield-effect transistor (nano-FET) is coupled to a massive piezoelectricity based electromechanical resonator integrated with a parametric amplifier. The mechanical parametric amplifier can enhance the resonator's displacement and the resulting electrical signal is further amplified by the nano-FET. This hybrid amplification scheme yields an increase in the mechanical displacement signal by 70 dB resulting in a force sensitivity of 200 aN Hz-1/2 at 3 K. The mechanical parametric amplifier can also squeeze the displacement noise in one oscillation phase by 5 dB enabling a factor of 4 reduction in the thermomechanical noise force level. [ABSTRACT FROM AUTHOR]

Biosensors with increasingly high sensitivity are crucial for probing small scale properties. The asynchronous magnetic bead rotation (AMBR) sensor is an emerging sensor platform, based on magnetically actuated rotation. Here the frequency dependence of the AMBR sensor's sensitivity is investigated. An asynchronous rotation frequency of 145 Hz is achieved. This increased frequency will allow for a calculated detection limit of as little as a 59 nm change in bead diameter, which is a dramatic improvement over previous AMBR sensors and further enables physical and biomedical applications. [ABSTRACT FROM AUTHOR]

The responses of the electrical and optical characteristics of an organic light-emitting device (OLED) with fac-tris(2-phenylpyridinato-N, C2′) iridium (III) [Ir(ppy)3] doped in a polymer matrix to compressive stresses were studied. The OLED converted stresses as low as 6.8 kPa into measurable and reversible changes in both current density and electroluminescence (EL) intensity. The current showed a nearly linear characteristic response with sensitivity up to 105 μA/kPa, whereas EL decreased by three orders of magnitude at 100 kPa. The latter was attributed to increased nonradiative back energy transfer between Ir(ppy)3 and neighboring host molecules. It is expected that similar OLEDs built on large curved surfaces may directly image stress distributions at a high-resolution and sense touch on a par with a human finger. [ABSTRACT FROM AUTHOR]

The terahertz detection by photoconductive antennas (PCAs) based on low-temperature grown (LTG) GaAs with 1.5 μm pulse excitation was revisited. We found that the detection efficiency can be improved by a factor of 10 (20 dB) by reducing the excitation spot size and the gap length of the PCA, maintaining the low noise feature of the PCA on LTG GaAs. As a result, the signal-to-noise ratio higher than 50 dB was obtained at a reasonable incident power of 9.5 mW, suggesting that the scheme is promising for the detection of terahertz waves in practical time domain systems. [ABSTRACT FROM AUTHOR]

We study ways to enhance the sensitivity and dynamic tuning range of the fundamental inductor-capacitor (LC) resonance in split ring resonators (SRRs) by controlling the aspect ratio of the SRRs and their substrate thickness. We conclude that both factors can significantly affect the LC resonance. We show that metafilms consisting of low height SRRs on a thin substrate are most sensitive to changes in their dielectric environment and thus show excellent potential for sensing applications. [ABSTRACT FROM AUTHOR]