Super Sensitivity Research Articles

Theory of Broadband Super Sensitivity Receiving With Closely Spaced Antenna Arrays

Theory of Broadband Super Sensitivity Receiving With Closely Spaced Antenna Arrays

Nanoengineering Ultrathin Flexible Pressure Sensors with Superior Sensitivity and Wide Range via Nanocomposite Structures.

Flexible pressure sensors have attracted great interest due to their bendable, stretchable, and lightweight characteristics compared to rigid pressure sensors. However, the contradictions among sensitivity, detection limit, thickness, and detection range restrict the performance of flexible pressure sensors and the scope of their applications, especially for scenarios requiring conformal fitting, such as rough surfaces such as the human skin. This paper proposes a novel flexible pressure sensor by combining the nanoengineering strategy and nanocomposite structures. The nanoengineering strategy utilizes the bending deformation of nanofilm instead of the compression of the active layer to achieve super high sensitivity and low detection limit; meanwhile, the nanocomposite structures introduce distributed microbumps that delay the adhesion of nanofilm to enlarge the detection range. As a result, this device not only ensures an ultrathin thickness of 1.6 μm and a high sensitivity of 84.29 kPa-1 but also offers a large detection range of 20 kPa and an ultralow detection limit of 0.07 Pa. Owing to the ultrathin thickness as well as high performance, this device promotes applications in detecting fingertip pressure, flexible mechanical gripping, and so on, and demonstrates significant potential in wearable electronics, human-machine interaction, health monitoring, and tactile perception. This device offers a strategy to resolve the conflicts among thickness, sensitivity, detection limit, and detection range; therefore, it will advance the development of flexible pressure sensors and contribute to the community and other related research fields.

Super efficiency and sensitivity analysis of the Indian hotels and restaurants

Super efficiency and sensitivity analysis of the Indian hotels and restaurants

Disposable Screen-Printed Microchip Based on Nanoparticles Sensitive Membrane for Potentiometric Determination of Lead

Realization of screen-printed disposable microchip based on organic membrane sensitive layer highly responsive to lead has been demonstrated for the first time. Fabrication, potentiometric characterization and analytical application of the novel microchip have been reported. A sensitive layer comprises TiO2 nanoparticles and multiwalled carbon nanotubes “MWCNTs” composite incorporated in PVC membrane has uploaded on the plastic screen-printed microelectrode substrate surface using novel protocol. The new chip provided a linear behavior for Pb2+ ions over the lead concentration range of 1 × 10−6–1 × 10−1 mole L−1 with super Nernstian sensitivity (49 mV), relatively long life span (>4 months), and a fast response time (10 s). The advantages showed by the microchip include simple fabrication, small size, mass production, cost effectiveness, and automation and integration feasibility. The realized new microchip has been successfully utilized in the quantification of some lead (II) samples with average recovery of 101.9% and the RDS was <3.

Quantum-enhanced super-sensitivity of Mach–Zehnder interferometer using squeezed Kerr state

We study the phase super–sensitivity of a Mach–Zehnder interferometer (MZI) with the squeezed Kerr state (SKS) and coherent state as the inputs. We discuss the lower bound in phase sensitivity by considering the quantum Fisher information and the corresponding quantum Cramér–Rao bound. With the help of single intensity detection, intensity difference detection, and homodyne detection schemes, we find that our scheme gives a better sensitivity under both lossless and lossy conditions as compared to the well–known results of the combinations of inputs, such as coherent plus vacuum, coherent plus squeezed vacuum, and double coherent states. Because of the possibility of the generation of SKS with the present available quantum optical techniques, we expect that SKS may be an alternative nonclassical resource for the improvement in the phase super–sensitivity of the MZI in realistic scenarios.

Confined-Enhanced Raman Spectroscopy.

In 1997, the discovery of single molecule-surface enhanced Raman spectroscopy (SM-SERS) rekindled broad interests owing to its ultrahigh enhancement factor up to the 1014-1015 level. However, regretfully, the advantage of SM-SERS with an ultralow detection limit has not yet been fully utilized in commercialized applications. Here, we report a strategy, which we name confined-enhanced Raman spectroscopy, in which the overall Raman properties can be remarkably improved with in situ-formed active nanoshell on the surface of silver or gold nanoparticles. The nanoshell can confine and anchor molecules onto the surface of plasmonic nanoparticles and avoid desorption from hot spots so that the "on and off" blinking effect can be eliminated. It is the first time the single-molecule detection of analytes with super sensitivity, high stability, and reproducibility based on gold nanoparticles has been realized. In addition, this strategy is suitable for SERS detection in diverse molecule systems, including biomedical diagnosis, catalytic reaction, etc.

A non-linear delayed resonator for mimicking the hearing haircells

The auditory system possesses remarkable characteristics: super sensitivity and frequency selectivity. However, these traits come at the cost of non-fidelity due to non-linear effects. The culprit behind this active behavior is likely the haircells, as suggested by some in vivo observations and theoretical studies. These haircells appear to operate as non-linear oscillators near a Hopf bifurcation. In this article, we experimentally design a single delayed Hopf resonator to examine its dynamic responses and uncover striking parallels with the human ear. After a systematic characterization of this resonator, we experimentally verify on this single resonator two non-linear phenomena that mimic hearing distortions. This provides further support for hearing models based on Hopf bifurcation.

Petal-like ZnO-based ultra-sensitive ethylene glycol sensors synthesized by solvent regulation

The ZnO-10, ZnO-20, ZnO-30, and ZnO-40 nanopetal-shaped samples were successfully synthesized by a hydrothermal method. The results of XRD, SEM, TEM, and BET indicate that the micro–nano petal-like samples have the advantages of high purity, good crystallinity, and large specific surface area. The ZnO-20 sample with the largest specific surface area and pore volume was prepared by adjusting the scheme without changing the sample morphology. The specific surface area and pore volume of the sample were 33.6914[Formula: see text]m2/g and 0.1561[Formula: see text]ml/g. The results of gas sensitivity test show that the sample has the highest response and super good gas sensitivity selectivity. At 250∘C, the responses to 5[Formula: see text]ppm and 50[Formula: see text]ppm ethylene glycol can reach 14.4 and 293, respectively. Because of the excellent gas performance of ZnO nanosheets, this work can provide a theoretical basis for the research and development of ultra-sensitive ethylene glycol gas sensors in the industry.

Oriented-aptamer encoded magnetic nanosensor with laser-induced fluorescence for ultrasensitive test of okadaic acid

Okadaic acid (OA) biotoxin acts a well-established inhibitor of protein phosphatase even a tumor promoter of human being, arouse great attention in safety monitoring. However, the powerful and convenient nanosensing technologies for addressing the demands such as rapidity, high sensitivity, and stability in the in-field test of OA shellfish toxin is still scarce. Herein, a high-performance magnetic biometric nanosensor (MBNS) integrating oriented aptamers and ultrasensitive laser-induced fluorescence (LIF) was firstly proposed for the in-field detection of trace OA in seafoods. High-density aptamers hybridized with FAM-labeled cDNA were tethered to the surface of AuNPs on magnetic MIL-101@Fe3O4, and then finely regulated by mercaptohexyl alcohol (MCH) to be orderly assembled, as was successfully utilized to engineer an active biological nanosensor for highly specific recognition of OA. Aptamers anchored on magnetic Fe3O4@MOF@AuNPs activate a biometric microreactor of OA, in which the superior LIF properties, conformation regulation of aptamer, and the specific recognition using aptamer genes were adopted. The magnetic nanosensor with an excellent specificity and super sensitivity for OA analysis was achieved within 20 min. Moreover, the content of captured OA could facilely be recorded by measuring the fluorescence intensity, and the limit of detection (LOD) and limit of quantitation of OA (LOQ) reached 0.015 and 0.050 ng/mL respectively, which was far better than most aptamer-based biometric sensing methods. The feasibility for accurate test of trace OA toxin in the fortified shellfish samples was validated with the recovery yields of 88.2–107.5% and RSD of 0.5–7.6%, respectively. The result demonstrated that the oriented-aptamer encoded MNS had significant practical values in rapid and ultrasensitive detection of OA biotoxin and the related safety applications.

A virtual-pinhole PET device for improving contrast recovery and enhancing lesion detectability of a one-meter-long PET scanner: a simulation study

This paper presents a simulation study to demonstrate that the contrast recovery coefficients (CRC) and detectability of small lesions of a one-meter-long positron emission tomography (PET) scanner can be further enhanced by the integration of high resolution virtual-pinhole (VP) PET devices. The scanner under investigation is a Siemens Biograph Vision Quadra which has an axial field-of-view (FOV) of 106 cm. The VP-PET devices contain two high-resolution flat panel detectors, each composed of 2 × 8 detector modules each of which consists of 32 × 64 lutetium-oxyorthosilicate crystals (1.0 × 1.0 × 10.0 mm3 each). Two configurations for the VP-PET device placement were evaluated: (1) place the two flat-panel detectors at the center of the scanner’s axial FOV below the patient bed; (2) place one flat-panel detector at the center of the first and the last quarter of the scanner’s axial FOV below the patient bed. Sensitivity profiles were measured by moving a point 22Na source stepwise across the scanner’s FOV axially at different locations. To assess the improvement in CRC and lesion detectability by the VP-PET devices, an elliptical torso phantom (31.6 × 22.8 × 106 cm3) was first imaged by the native scanner then subsequently by the two VP-PET geometry configurations. Spherical lesions (4 mm in diameter) having 5:1 lesion-to-background radioactivity concentration ratio were grouped and placed at nine regions in the phantom to analyze the dependence of the improvement in plane. Average CRCs and their standard deviations of the 7 tumors in each group were computed and the receiver operating characteristic (ROC) curves were drawn to evaluate the improvement in lesion detectability by the VP-PET device over the native long axial PET scanner. The fraction of coincidence events between the inserts and the scanner detectors was 13%–16% (out of the total number of coincidences) for VP-PET configuration 1 and 2, respectively. The VP-PET systems provide higher CRCs for lesions in all regions in the torso, with more significant enhancement at regions closer to the inserts, than the native scanner does. For any given false positive fraction, the VP-PET systems offer higher true positive fraction compared to the native scanner. This work provides a potential solution to further enhance the image resolution of a long axial FOV PET scanner to maximize its lesion detectability afforded by its super high effective sensitivity.

Enhanced Sensitivity of Binary/Ternary Locally Resonant Porous Phononic Crystal Sensors for Sulfuric Acid Detection: A New Class of Fluidic-Based Biosensors.

This research presented a comprehensive study of a one-dimensional (1D) porous silicon phononic crystal design as a novel fluidic sensor. The proposed sensor is designed to detect sulfuric acid (H2SO4) within a narrow concentration range of 0-15%. Sulfuric acid is a mineral acid extensively utilized in various physical, chemical, and industrial applications. Undoubtedly, its concentration, particularly at lower levels, plays a pivotal role in these applications. Hence, there is an urgent demand for a highly accurate and sensitive tool to monitor even the slightest changes in its concentration, which is crucial for researchers. Herein, we presented a novel study on the optimization of the phononic crystal (PnC) sensor. The optimization process involves a comparative strategy between binary and ternary PnCs, utilizing a multilayer stack comprising 1D porous silicon (PSi) layers. Additionally, a second comparison is conducted between conventional Bragg and local resonant PnCs to demonstrate the design with the highest sensitivity. Moreover, we determine the optimum values for the materials' thickness and number of periods. The results revealed that the ternary local resonant PnC design with the configuration of {silicone rubber/[PSi1/PSi2/PSi3]N/silicone rubber} is the optimal sensor design. The sensor provided a super sensitivity of 2.30 × 107 Hz for a concentration change of just 2%. This exceptional sensitivity is attributed to the presence of local resonant modes within the band gap of PnCs. The temperature effects on the local resonant modes and sensor performance have also been considered. Furthermore, additional sensor performance parameters such as quality factor, figure of merit, detection limit, and damping rate have been calculated to demonstrate the effectiveness of the proposed liquid sensor. The transfer matrix method was utilized to compute the transmission spectra of the PnC, and Hashin's expression was employed to manipulate the porous silicon media filled with sulfuric acid at various concentrations. Lastly, the proposed sensor can serve as an efficient tool for detecting acidic rain, contaminating freshwater, and assessing food and liquid quality, as well as monitoring other pharmaceutical products.

Resolution Enhanced Array ECT Probe for Small Defects Inspection.

It is a continual and challenging problem to detect small defects in metallic structures for array eddy current testing (ECT) probes, which require the probe to have ultra-high resolution and sensitivity. However, the spatial resolution of an ECT array probe is limited by the size of the induction coils. Even if it is possible to increase the spatial resolution by using smaller coils, the sensitivity of the sensor also decreases. To obtain finer spatial resolution without sacrificing sensitivity, this paper proposes a resolution enhanced ECT array probe with four rows of coils attached to a flexible printed circuit board (FPCB). The distance between each two adjacent coils in a row is 2 mm and the position of each row is offset by 0.5 mm along the horizontal direction related to its prior row. The outputs of the four rows are aligned and interpolated in a line, and in this way the image resolution of the probe is increased to 0.5 mm. The probe is configured to operate with the differential setting, namely two differential coils operate simultaneously at each time. The currents in the two coils can be controlled to have the same flowing direction or opposite flowing direction, resulting in different distributions of the induced eddy current and two sets of output images. A patch-image model and an image fusion method based on discrete wavelet transforms are employed to suppress the noise and highlight the defects' indications. Experimental results show that small defects with dimensions as small as length × width × depth = 1 mm × 0.1 mm × 0.3 mm on a 304 stainless-steel sample can be detected from the fused image, demonstrating that the probe has super sensitivity for small defects inspection.

Enhancement of NH3 gas sensing with Ag-Pt co-catalyst on SnO2 nanofilm towards medical diagnosis

Exhaled breath analysis is a noninvasive diagnostic method for fatal disease monitoring and screening, which is recently gained extensive interest of researchers worldwide emphasizing on the development of effective chemiresistive gas sensor for practical application. Here, the Ag-Pt bimetallic nanoparticles were used to decorate nanofilms of SnO2 making different gas sensors with high performance. We found that the bimetal alloy improved the sensor performance significantly with super sensitivity as compared with the separate Ag and Pt catalyst. The right ratio of the bimetal made the sensor very sensitive to NH3, so that it was able to quickly (12 s) detect 1 parts-per-million of NH3 with a response of 4.31 at a temperature of 250 °C. The sensor limit of detection for NH3 was less than 10 parts-per-billion. The response of the sensor was negligibly affected by humidity and interfering gases. The results showed that the tiny, robust, and inexpensive sensor developed in this work can be used in breath analysis for early diagnosis via NH3 monitoring.

Synthesis of uniformly dispersed Fe2TiO5 nanodisks: a sensitive photoelectrochemical sensor for glucose monitoring in human blood serum.

A novel photoelectrochemical (PEC) sensor was constructed, using Fe2TiO5 nanodisks under visible-light irradiation, for the determination of glucose in human blood serum. The uniformly dispersed Fe2TiO5 nanodisks were synthesized for the first time by an ion exchange method and subsequent heat treatment. As excellent catalysts, the Fe2TiO5 nanodisks can directly catalyze the oxidation of glucose to produce current in the absence of glucose oxidase. Compared with commercial TiO2, the Fe2TiO5 nanodisks exhibit better activity in the electrocatalytic oxidation of glucose and can generate a photocurrent as a signal for glucose detection. The PEC sensor shows a wide linear range (4 μM-10 mM), a low limit of detection (0.588 μM) and a super sensitivity of 2653 μA mM-1 cm-2, which are much better than similar configurations reported previously. This PEC sensor has been successfully used to monitor glucose in human blood serum. Moreover, this PEC glucose sensor based on Fe2TiO5 nanodisks possesses great potential for application in point-of-care clinical diagnosis.

Recent advances in nanotechnology-enhanced biosensors for α-fetoprotein detection.

α-Fetoprotein (AFP) is a kind of fetal protein that is related to tumor, the increasing concentration of which gives birth to a large variety of diseases, such as liver cancer. Therefore, the detection method with super sensitivity, high selectivity, and less time consumption under trace concentrations in early stage of diseases is becoming a necessity. In recent years, nanomaterials have been regarded as significant resources for the exploration of efficient biosensors with high sensitivity, selectivity, speed, as well as simple process, due to their excellent optical, electrical, and chemical properties. In this paper, we reviewed the research progress of AFP biosensors with enhanced sensitivity and selectivity by nanoparticles. Representative examples have also been displayed in this paper to expound the nanotechnologies utilized in the early detection of AFP. Furthermore, challenges of the clinical application of AFP biosensors based on nanotechnology have been elaborated, as well as the development opportunity in this field in the future. This review provides a comprehensive overview on the various nano-biosensor for AFP detection based on functional nanotechnology.

Conductive, self-healing, and antibacterial Ag/MXene-PVA hydrogel as wearable skin-like sensors.

The rapid development of flexible electronic technology has led to the in-depth study of flexible wearable sensors to achieve accurate sensing under different external stimuli. However, it is still a huge challenge to develop hydrogel-based wearable skin-like sensors with super ductility, high sensitivity, and self-healing properties. Herein, the Ti3C2 type of MXene was synthesized, and the Ag/MXene nanocomplexes were incorporated into polyvinyl alcohol-borax matrix to construct a novel composite hydrogel as the multifunctional nanofillers, which could bring both improved properties and novel functionalities. The Ag/MXene-Poly (vinyl alcohol) (PVA) hydrogel displayed integrated merits of highly strain sensitive (GF = 3.26), self-healing (within 10 min, 91% healing efficiency), and excellent antibacterial activity. The hydrogel could be assembled into a wearable skin-like sensor to monitor human movement, including large deformations (finger, elbow, wrist, and knee bending) and tiny deformations (mouth's movement and throat vocalization) in real time. Therefore, this work shed a new light on the development of flexible wearable skin-like sensors for the personalized healthcare monitoring, human-machine interfaces, and artificial intelligence.

Novel photoelectrochemical sensor for cholesterol based on CH3NH3PbBr3 perovskite /TiO2 inverse opal heterojunction coated with molecularly imprinted polymers

Developing cost-effective, ease-to-use and sensitive cholesterol sensors is of great importance. Photoelectrochemical (PEC) sensor has exhibited their potential with low cost, simple instrumentation, easy miniaturization, and high sensitivity. Organometal lead halide perovskites (MAPbX3) with exceptional opto-electronic properties have been appealing materials for optoelectronic devices. Whereas the extreme sensitivity of MAPbX3 towards even moisture has always restricted their application in biological use. Here we report a novel MAPbX3 photoelectrochemical cholesterol sensor with water stability. The titanium dioxide inverse opal (TiO2 IOPCs) and CH3NH3PbBr3 quantum dot heterojunction on ITO glass exhibited a remarkably increased photoelectric current density of approximately 40 μA/cm2. The further encapsulation within the imprinted polymer presented high selectivity towards cholesterol and significantly improved the stability of perovskites as well. Linear detection of cholesterol in buffer was achieved with the detection limit of 2.51 × 10-10 mol/L, lower than that of the reported cholesterol PEC sensor in aqueous buffer. Recovery rates in serum were also obtained with the cholesterol concentration lower than the reported imprinted polymer based (photo)electrochemical sensor. Additionally, the photocurrent intensity under continuous emission was maintained at 80% after immersing this sensor in an aqueous solution for 500 s. The storage stability was more than 20 days. Here we present the first MAPbX3 perovskite-based sensor applicable in aqueous samples with super sensitivity and selectivity, which promote the perovskite nanomaterial-mediated sensing of biologically important species.

MOF-based sensor platforms for rapid detection of pesticides to maintain food quality and safety

Pesticides are primarily used in agriculture to increase crop yield because of their highly lucrative, stable structure and agricultural benefits such as eliminating fungi, plant diseases, pests and insects to regulate the growth of crops. Apart from their rebel design and agricultural benefits, pesticides have severe toxicity to a variety of other living organisms. Therefore, developing effective pesticide detection systems is an ongoing challenge. Multiple technologies that for the rapid, easy, sensitive, and selective detection of these neurotoxic compounds are in demand. This paper reviews the recent advances in sensing assays based on the metal-organic framework (MOF) structure for pesticide detection. We have reviewed state-of-the-art optical biosensors for in-place sensing that have the advantages of a simple protocol, simple manipulation, super sensitivity, wide linear range, and cost-effectiveness. These biosensors use chemiluminescence with a short sensing time and a highly sensitive luminescence sensor that enables real-time detection by easy smartphone pairing. For profitable platforms, the obstacles related to sample preparation and equipment cost can be overcome by employing electrochemical sensors. The intensity, impedance, and potential difference measurement techniques used in these biosensors allow for low detection limits and observable durations in water, agricultural, and food samples containing high levels of pesticides.

Er-Based Luminescent Nanothermometer to Explore the Real-Time Temperature of Cells under External Stimuli.

Temperature as a typical parameter, which influences the status of living creatures, is essential to life activities and indicates the initial cellular activities. In recent years, the rapid development of nanotechnology provides a new tool for studying temperature variation at the micro- or nano-scales. In this study, an important phenomenon is observed at the cell level using luminescent probes to explore intracellular temperature changes, based on Yb-Er doping nanoparticles with special upconversion readout mode and intensity ratio signals (I525 and I545 ). Further optimization of this four-layer core-shell ratio nanothermometer endows it with remarkable characteristics: super photostability, sensitivity, and protection owing to the shell. Thus this kind of thermal probe has the property of anti-interference to the complex chemical environment, responding exclusively to temperature, when it is used in liquid and cells to reflect external temperature changes at the nanoscale. The intracellular temperature of living RAW and CAOV3 cells are observed to have a resistance mechanism to external stimuli and approach a more favorable temperature, especially for CAOV3 cells with good heat resistance, with the intracellular temperature 4.8 °C higher than incubated medium under 5 °C environment, and 4.4 °C lower than the medium under 60 °C environment.

Production of MFe2O4 (M = Zn, Ni, Cu, Co and Mn) multiple cavities microspheres with salt template to assemble a high-performance acetone gas sensor

In this study, a one-step chemical vapor deposition (CVD) method was used, utilizing template NaCl and dextrin as the porogen and structural support. The synthesized spinel MFe2O4 (M = Zn, Ni, Cu, Co and Mn) microspheres with multiple cavities structure were applied to the acetone gas sensor detection. Through the characterization of the sensitive materials, the average pore diameter of the microspheres was about 60 nm. Compare with other metal cations, when M = Zn or Ni, the MFe2O4 samples revealed the super gas sensitivity at working temperatures of 250 °C and 175 °C, and the response values to 100 ppm acetone were 25 and 24.3, respectively. In addition, they also exhibited excellent selectivity and long-term stability to acetone. The excellent gas sensitivity of ZnFe2O4 and NiFe2O4 could be attributed to the replacement of Fe with Zn and Ni ions to obtain a higher Fe3+/Fe2+ atomic ratio, thereby increasing the content of adsorbed oxygen. In summary, the gas sensing performance of spinel MFe2O4 oxide had been systematically studied by replacing Fe with other transition metals. The iron-containing spinel oxides are expected to be promising sensing material for gas sensors due to their rich elements and excellent activity.