Maximum Sensitivity Research Articles

Self-Powered and Self-Recovered Mechanoluminescent Electronic Skins for Detecting and Distinguishing Diverse External Stimuli.

The concept of simulating external mechanical stimuli to generate luminescence has been a long-standing aspiration in real-time dynamic visualization. However, creating self-power and self-restoring mechanoluminescent electronic skins for artificial sensors poses significant challenges. In this study, we introduce a cutting-edge triboelectric-mechanoluminescent electronic skin (TMES) that exhibits a remarkable response to multiple external stimuli. This advancement is achieved by integrating a mechanoluminescent intermediate layer within a triboelectric nanogenerator (TENG). When pressure is applied to TMES, the maximum detection voltage can reach hundreds of volts and the maximum correlation sensitivity is 11.76 V/N. Moreover, we incorporate luminescence materials into mechanoluminescence layer, and the maximum absolute sensitivity SR can reach 1.41%. The device can not only distinguish between external stimuli such as pressing and bending but also continuously track external mechanical stimuli. A 4 × 4 matrix and motion prediction of 8 different postures were established to further demonstrate the significant advantages of the developed device in spatial detection. The versatility and performance of the TMES hint at its vast potential in areas such as human-computer interaction and wearable electronics, paving the way for more intuitive and dynamic technological interfaces.

Impact of Palladium Decoration on the Performance of Co-SmFeO<sub>3</sub> Based Gas Sensor

The enhanced ammonia gas sensing properties of palladium decorated Co-SFO are demonstrated here. Pristine SmFeO3 thick films fabricated by screen printing technique were surface modified with Co by dipping method (dipping time 3 min) and identified as Co-SFO thick films. They showed maximum sensitivity to 50 ppm ammonia at 200 °C. In order to further increase its sensitivity, Co-SFO thick film was dipped into Palladium nitrate solution for 1 min, 2 min and 3 min. Surface morphology of as-prepared thick films was studied by FE-SEM. Formation of PdO phase and its uniform distribution over Co-SFO surface was confirmed from EDAX spectra. Gas sensing results revel that the sensitivity of Pd decorated Co-SFO thick films towards 50 ppm ammonia was increased. Moreover, decrease in operating temperature was also observed. Pd decorated Co-SFO thick film with dipping time 3 min has maximum sensitivity at lower operating temperature. The improved sensitivity at low temperature was attributed to the sensitization of palladium which was discussed in details. Keywords: Co-SFO, Chemical sensitization, Noble metal, Gas Response, Reducing gas.

Ultrasensitive refractive index and temperature sensor based on D-shaped photonic crystal fiber by group birefringence response in a Sagnac interferometer

In this paper, a D-shaped photonic crystal fiber (PCF) sensor based on a Sagnac interferometer is proposed, and it can achieve ultrahigh refractive index (RI) and temperature sensitivity when operating around the turning point of group birefringence (Bg). We undertake a theoretical analysis on Bg and a simulation calculation to study the sensing characteristics and obtain the optimized structure parameters of the D-shaped PCF sensor. The simulation results show that the maximum average RI sensitivities can reach 3253.33 and 15500 nm/RIU in the RI range of 1.33 to 1.35 and 1.40 to 1.42, respectively. When the temperature changes from -50 to 0 °C and 0 to 50 °C, the maximum average temperature sensitivities are up to 10.11 and 10.67 nm/°C, respectively. The proposed D-shaped PCF sensor can achieve dual-parameter sensing and has great potential for practical applications in biochemical and environmental science.

Photovoltaic, wireless wide‐field epiretinal prosthesis to treat retinitis pigmentosa

AbstractPurposeTo develop and evaluate a photovoltaic, wireless wide‐field epiretinal prosthesis for the treatment of retinitis pigmentosa.MethodsA mosaic array of thinned silicon‐based photodiodes with integrated thin‐film stimulation electrodes was fabricated with a flexible polyimide substrate film to form a film‐based miniaturized electronic system with wireless optical power and signal transmission and integrated electrostimulation. Manufactured implants were characterized with respect to their optoelectronic performance and biocompatibility following DIN EN ISO 10993.ResultsA 14 mm diameter prosthesis containing 1276 pixels with a maximum sensitivity at a near infrared wavelength of 905 nm and maximized stimulation current density 30–50 μm below the electrodes was developed for direct activation of retinal ganglion cells during epiretinal stimulation. Fabricated prostheses demonstrated mucosal tolerance and the preservation of both metabolic activity, proliferation and membrane integrity of human fibroblasts as well as the retinal functions of bovine retinas. Illumination of the prosthesis, which was placed epiretinally on an isolated perfused bovine retina, with infrared light resulted in electrophysiological recordings reminiscent of an a‐wave (hyperpolarization) and b‐wave (depolarization).ConclusionsA photovoltaic, wireless wide‐field epiretinal prosthesis for the treatment of retinitis pigmentosa using near infrared light for signal transmission was designed, manufactured and its biocompatibility and functionality demonstrated in vitro and ex vivo.

All-fiber light intensity sensor employing a three-core fiber taper integrated by magnetic fluids

An all-fiber optic light intensity sensor employing a three-core fiber (TCF) taper integrated by magnetic fluids (MFs) is proposed and fabricated. The three-beam interference and evanescent field characteristic of the TCF taper are combined with the laser-generated photothermal effect of the MFs for the first time. The effect of irradiation laser intensity on the interference spectrum of the proposed sensor is investigated experimentally. According to the experimental results, the interferential transmission spectrum is susceptible to the irradiation laser intensity. Under 473 nm laser irradiation, the maximum laser intensity sensitivity reaches −1.64425 nm/(mW/mm2). Moreover, the modal coupling processes of the TCF before and after tapering are investigated experimentally and by simulation. The proposed sensor is attractive because of its sensitive light response, simple structure, easy fabrication, and compact size. This work gives a significant reference for the manufacture and application of optically controlled microfluidic devices integrated by MFs.

Expanding the Toolbox for Industrial Luminescent Primary Thermometry: Er3+-doped SrMoO4

We herein demonstrate the feasibility of employing strontium molybdate as host matrix for trivalent erbium ions for the developing of an optical temperature sensor operating in a wide temperature range suitable for industrial applications. This class of metal molybdate, known for its chemical and thermal capabilities, works as primary luminescent thermometer, relying on the thermally coupled levels of Er3+ arising from downshifting processes, neglecting first, the requirement of calibration curve acquisition and second, the excitation induced heating on the sample typically observed in upconverting luminescent thermometers. The synthesised primary optical thermometer displays a maximum temperature relative sensitivity of 1.13 %. K−1 and minimum temperature uncertainty and 0.09 K. These values make the performance of the Er3+-doped strontium molybdate as optical temperature sensor competitive with the existing luminescent primary thermometers, including a wide operating temperature range up to 413 K and high accuracy as main features. Moreover, it can be easily scaled up and produced due to straightforwardness and cost-effectiveness of the ceramic synthesis method, matching the requirements for its usage in industrial environments.

Ultrasound Measurements of the Ulnar Nerve at the Medial Epicondyle Correlate With Electrodiagnostic Studies.

Cubital tunnel syndrome is the second most common compressive neuropathy in the upper extremity and is commonly evaluated with electrodiagnostic studies (EDS). Ultrasound (US) has emerged as a potentially more efficient alternative to EDS. The purpose of this study is to evaluate whether measurements of the cross-sectional area (CSA) of the ulnar nerve at the elbow correlate with EDS results. This study was a prospective analysis of patients who presented with signs and symptoms consistent of cubital tunnel syndrome, who received USs of the ulnar nerve at the elbow and nerve conduction tests. Pearson correlation coefficients were used to evaluate the correlation between ulnar nerve CSA and electrodiagnostic data. t Tests were used to evaluate statistical differences between the mean ulnar nerve CSA of patients with positive or negative nerve conduction study results. Youden Index was used to calculate the optimal cut-off point for US CSA based on maximal sensitivity and specificity. Statistical significance was based on a two-sided P less than .05. The association between increasing US CSA at the medial epicondyle with slowing of the conduction velocity of the ulnar motor nerve across the elbow was statistically significant (r = -0.35, P = .02). Patients with positive EDS tests had significantly larger nerve size than those with negative tests (all Ps < .03). A cut-off point of greater than or equal to 11 mm2 had a sensitivity of 70.83% and specificity of 66.67%. Larger ulnar nerve CSAs correlate with slowing of the conduction velocity on EDSs, and those with positive EDSs have larger nerve sizes than those with negative tests.

A novel fluorapatite-type deep-red CsSr3La(PO4)3F:Eu3+ phosphor with intense 5D0-7F4 transition for temperature sensors, plant growth lighting, and w-LEDs

The synthesis of CsSr3La(PO4)3F:xEu3+ phosphors (x = 1, 2, 5, 10, 20, 30, 40, and 50 mol%) with fluorapatite-type structure was successfully accomplished through a direct solid-state reaction in this work. A systematic characterization was carried out, encompassing the crystal structure, phase composition, morphology, optical properties, and diverse applications of the samples. The crystalline structure of CsSr3La(PO4)3F belongs to the hexagonal system with space group P63/m (176), displaying two polyhedral structures [AⅠO9] and [AⅡO6F]. The band gap (Eg) of the material CsSr3La(PO4)3F is 5.823 eV. At the excitation of 393 nm, CsSr3La(PO4)3F:30 mol%Eu3+ phosphor exhibits a primarily significant emission peak at 703 nm, referring to the 5D0→7F4 transition due to a highly polarizable chemical environment and a distorted coordination polyhedron around Eu3+ ions. The concentration quenching process is attributed to the quadrupole-quadrupole interaction between Eu3+ ions, with the maximum luminescence intensity achieved at a doping content of 30 mol%. At 420 K, the emission intensity of the CsSr3La(PO4)3F:30 mol%Eu3+ phosphor can still maintain 75.04 % of the emission intensity observed at 300 K. The value of activation energy is 0.18 eV. The maximum absolute and relative thermal sensitivities (Sa and Sr) for the temperature sensor can reach 5.25 × 10−4 K−1 and 7.71 % K−1, respectively. The made-up red LED is well-suited to meet the light requirements for the growth and development of plants. The fabricated white light-emitting diode (w-LED) has a relatively high color rendering index (Ra) of 89 and a suitable correlated color temperature (CCT) of 4392 K. The phosphors have applications in temperature sensors, plant growth lighting, and w-LEDs.

Community assembly influences plant trait economic spectra and functional trade-offs at ecosystem scales

Plant functional traits hold the potential to greatly improve the understanding and prediction of climate impacts on ecosystems and carbon cycle feedback to climate change. Traits are commonly used to place species along a global conservative-acquisitive trade-off, yet how and if functional traits and conservative-acquisitive trade-offs scale up to mediate community and ecosystem fluxes is largely unknown. Here, we combine functional trait datasets and multibiome datasets of forest water and carbon fluxes at the species, community, and ecosystem-levels to quantify the scaling of the tradeoff between maximum flux and sensitivity to vapor pressure deficit. We find a strong conservative-acquisitive trade-off at the species scale, which weakens modestly at the community scale and largely disappears at the ecosystem scale. Functional traits, particularly plant water transport (hydraulic) traits, are strongly associated with the key dimensions of the conservative-acquisitive trade-off at community and ecosystem scales, highlighting that trait composition appears to influence community and ecosystem flux dynamics. Our findings provide a foundation for improving carbon cycle models by revealing i) that plant hydraulic traits are most strongly associated with community- and ecosystem scale flux dynamics and ii) community assembly dynamics likely need to be considered explicitly, as they give rise to ecosystem-level flux dynamics that differ substantially from trade-offs identified at the species-level.

Optical Anapole Modes of the Hybrid Ring-Disk Nanoantenna for Electric Field Enhancement

A promising design combining low loss, high refractive index dielectric materials with metal nanoparticles, and local plasma resonance is described for ring-disk nanoantenna. A hybrid Au ring Si disk structure with chain gaps is constructed and the distributions of the electric field and near-field enhancement of the electric fields are analyzed by numerical simulation utilizing the multipole decomposition method. The electric field strength can be enhanced efficiently using metals to improve the anapole mode response of dielectric materials with large refractive indexes. Additional enhancement of the electric field is achieved by opening the chain gap to create high-intensity hot spots inside the disk. The chain comprises 14 normal octahedrons and a few tips are created by intersecting octahedrons. The electric field is greatly enhanced at the tips where there are high-intensity hot spots. The effectiveness of this structure as a refractive index sensor is assessed. The scattering cross-section (SCS) and wavelength shifts result in a maximum sensitivity of 210[Formula: see text]nm/RIU. The results validate the design concept and the hybrid structure boasting large electric field enhancement and excellent optical sensing properties have large potential in nonlinear photonics.

Laser patterned graphene pressure sensor with adjustable sensitivity in an ultrawide response range

Flexible pressure sensors have attracted wide attention because of their applications in wearable electronic, human-computer interface, and healthcare. However, it is still a challenge to design a pressure sensor with adjustable sensitivity in an ultrawide response range to satisfy the requirements of different application scenarios. Here, a laser patterned graphene pressure sensor (LPGPS) is proposed with adjustable sensitivity in an ultrawide response range based on the pre-stretched kirigami structure. Due to the out-of-plane deformation of the pre-stretched kirigami structure, the sensitivity can be easily tuned by simply modifying the pre-stretched level. As a result, it exhibits a maximum sensitivity of 0.243 kPa−1, an ultrawide range up to 1600 kPa, a low detection limit (6 Pa), a short response time (42 ms), and excellent stability with high pressure of 1200 kPa over 500 cycles. Benefiting from its high sensitivity and ultrawide response range, the proposed sensor can be applied to detect physiological and kinematic signals under different pressure intensities. Additionally, taking advantage of laser programmable patterning, it can be easily configured into an array to determine the pressure distribution. Therefore, LPGPS with adjustable sensitivity in an ultrawide response range has potential application in wearable electronic devices.

A Two-Axis Orthogonal Resonator for Variable Sensitivity Mode Localization Sensing.

This paper experimentally demonstrates a mode localization sensing approach using a single two-axis orthogonal resonator. The resonator consists of concentric multi-rings connected by elliptic springs that enable two orthogonal oscillation modes. By electrostatically tuning the anisotropic stiffness between the two axes, the effective coupling stiffness between the modes can be precisely controlled down to near-zero values. This allows the sensitivity of mode localization sensing to be tuned over a wide range. An order of magnitude enhancement in sensitivity is experimentally achieved by reducing the coupling stiffness towards zero. The resonator's simple single-mass structure offers advantages over conventional coupled resonator designs for compact, tunable mode localization sensors. Both positive and negative values of coupling stiffness are demonstrated, enabling maximum sensitivity at the point where coupling crosses through zero. A method for decomposing overlapping resonance peaks is introduced to accurately measure the amplitude ratios of the localized modes even at high sensitivities. The electrostatic tuning approach provides a new option for realizing variable sensitivity mode localization devices using a simplified resonator geometry.

Surface plasmon resonance photonic crystal fiber biosensor: Utilizing silver-phosphorene nanoribbons for Near-IR detection

In recent years, the utilization of two-dimensional materials in photonic crystal fiber structures has developed the capabilities of biosensors in biological and biochemical applications. A photonic crystal fiber biosensor based on surface plasmon resonance with silver and phosphorene layers is proposed in this paper. Phosphorene helps with the prevention of oxidation of the silver layer used as a plasmonic active metal. The sensor performance can be optimized by changing the structural parameters. The maximum wavelength sensitivity obtained was 1800 nm/RIU in the dynamic index range of 1.39–1.45, and the proposed sensor also showed the maximum amplitude sensitivity of 268 RIU−1 with an analyte refractive index of 1.40. The performance of the proposed sensor was analyzed using the finite element method. The results show that using phosphorene may open a new window for the study of online biomolecular interaction.

Study on trap sensitivity for single material gate and double material gate nano-ribbon FETs

In this work, the trap sensitivity of single material gate (SMG) and dual material gate (DMG) nano ribbon FETs (NRFETs) are reported using TCAD Sentaurus Device simulator. The trap sensitivity is extracted for Gaussian trap distribution of both acceptor and donor type traps. We have reported the trap sensitivity for the variation in trap concentration, energy peak position, work function of metal gate, and temperature for both the NRFETs. It is realized that trap sensitivity is greater and lesser than 100% for acceptor type trap in SMG and DMG NRFETs, respectively, whereas, such sensitivity is 147% and 123% for donor type trap concentration, respectively. Temperature also shows a significant variation in trap sensitivity for both the NRFETs. The increase in work function leads to the reduction in trap sensitivity for both NRFETs in existence of acceptor and donor trap charges. The maximum sensitivity in trap are 400% and 275% for SMG and DMG NRFETs, respectively, in presence of donor trap concentration. Moreover, the trap sensitivity is very insignificant at high gate bias for donor type trap concentration with wide variation in parameters.

A PCF-SPR sensor for dual-polarization and wide refractive index detection range

In this paper, we design a novel H-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor, which is composed of a dual-sided U-shaped groove and an Ag–MoS2 coating. The proposed sensor exhibits an asymmetrical structure with birefringence, which provides a possible way to detect the refractive index (RI) of analytes with dual-polarization. Based on the finite element method (FEM) simulations, the influences of the structural parameters on the sensing performances are discussed. For y-polarization, the proposed sensor detects the changes of RI from 1.37 to 1.41 with a maximum wavelength sensitivity of 11,700 nm/RIU, while for x-polarization, RI changes from 1.29 to 1.35 with a maximum sensitivity of 7800 nm/RIU. Thus, a PCF-SPR sensor with dual-polarization and wide RI detection range is achieved, which holds significant promise for applications in biology, medicine, and food safety.

Dual-mode microring resonator for humidity sensing with temperature compensation

On-chip refractive index (RI) sensors, which use resonant shifts of micro-cavities to detect environment change, have the advantages of high sensitivity, real-time detection, and compact footprints. However, the cross-sensitivity of the temperature variation severely interferes with sensing results. In this paper, we present a dual-mode microring resonator (MRR) with a cladding layer of polyhexamethylene biguanide hydrochloride (PHMB) for relative humidity (RH) sensing to overcome the limitation. Specifically, the influences of the RH-induced RI change of the PHMB cladding and temperature variations on the effective RIs of TE0 and TE1 modes can be decoupled based on the transmission spectral measurements. Using this method, we have demonstrated the temperature-compensated RH sensing which achieved a maximum sensitivity of −54.7 pm/%RH and a limit of detection of 0.8 %RH under the room temperature condition. Besides, a computational model based on the sensing response of the device was proposed and verified, which demonstrated that the structure can accurately measure changes in RH and temperature simultaneously. Our methodology has the potential to become a new reference for developing on-chip RI sensors with temperature compensation.

Promising lanthanide- NaYbF4:Er3+@NaYbF4:Tm3+ micro-phosphors for highly efficient upconversion luminescence and temperature sensing

In recent years, the fluorescence intensity ratio (FIR)-based technique for optical non-contact temperature measurement is of great interest to researchers due to its promising wide range of applications in high-voltage electricity fields, fires, corrosive environments, biological tissues, as well as other fields. Unfortunately, the FIR techniques based on thermally coupled energy levels (TCLs) often have the problem of low sensitivity as a result of the narrow energy gap. In contrast to FIR techniques with TCLs, the FIR technique with non-thermal coupled energy levels (NTCLs) is no longer restricted by the energy gap and is expected to achieve high signal resolution. In this study, we attempted to acquire a thermometric material that possesses high sensitivity as well as high signal resolution with the help of NTCLs. We successfully prepared NaYbF4:Er3+@NaYbF4:Tm3+ core-shell microcrystals by solvothermal technique using NaYbF4 as matrix and Er3+ and Tm3+ as luminescent centers and made necessary investigations on their crystal structures, microscopic morphologies, intrinsic mechanisms, and thermometric properties. The sample phosphors in a 980 nm laser show bright upconversion (UC) luminescence with emission peaks corresponding to the characteristic energy level jumps of Er3+ as well as Tm3+, respectively. The temperature sensing characteristic parameters have been investigated by FIR techniques with TCLs (2H11/2 → 4I15/2(Er3+)/4S3/2 → 4I15/2(Er3+)) & NTCLs (3H4→3H6(Tm3+)/1G4→3H6(Tm3+),3H4→3H6(Tm3+)/2H11/2 → 4I15/2(Er3+),3H4→3H6(Tm3+)/4S3/2 → 4I15/2(Er3+) and 3H4→3H6(Tm3+)/4F9/2 → 4I15/2(Er3+)), respectively. It is shown that the maximum absolute & relative sensitivities are 0.5677 K-1(495 K) as well as 1.20 % K−1(445 K) respectively with good thermal stability. In addition, the NTCLs have good separation of the emission bands, which enables the material to have excellent signal discrimination in temperature detection. These results indicate that the material is expected to be a potential candidate for optical thermometers.

High‐performance photonic crystal fibre biosensor for identifying Jurkat cells by refractive index analysis

AbstractJurkat cells are immortalised lines of human T lymphocyte cells widely used in research to study leukaemia, signalling of T cells, and immune responses. These cells can be used as models to define the mechanisms of leukaemia and to develop mechanism‐based therapies. Jurkat cells can be detected with remarkable accuracy using the recently created Photonic Crystal Fibre (PCF). The suggested design has a hybrid arrangement on its clad surface and a rectangular core. The recently released PCF analyser displays a maximum Relative Sensitivity are 95.81% for Jurkat (type I) and 94.93% for Jurkat (type II), respectively. The Effective Material Loss of 0.0070 cm−1, 0.0080 cm−1, and the Confinement Loss of 9.11 × 10−9 dB/m, 9.15 × 10−8 dB/m were also examined for the previously described units. Jurkat cells represent a model of leukaemia that is very malignant and proliferative, representative of aggressive T‐cell acute lymphoblastic leukaemia with the ability to progress rapidly and hence poor prognosis for patients. The benefit of applying a suggested PCF sensor to Jurkat cell detection lies in the high sensitivity to refractive index changes, allowing label‐free and real‐time monitoring of cell interaction. This PCF sensor can offer high light‐matter interaction, custom geometry, and biocompatibility for specific and reliable detection of deadly Jurkat cells in biomedical research and clinical diagnostics.

Experimental constitutive relationships for high-temperature deformation of as-cast Al–Si binary alloys

ABSTRACT As-cast binary Al–Si alloys containing ∼2 to 30 wt.% Si were deformed by differential strain rate and differential temperature test techniques at 600–840 K and strain rates 10−4–10−2 s−1 to find the parameters of the constitutive relationships for high-temperature deformation. The maximum strain rate sensitivity index (m) of flow stress was found to be 0.28 in the eutectic Al-12Si alloy. The Arrhenius plot for activation energy for deformation (Q) exhibits bilinear behaviour, with Q being greater at higher test temperatures than at lower temperatures. The magnitude of Q varies as a function of Si content: 95.7 ± 9.8 kJ/mol for Al-2Si to 311.4 ± 98.1 kJ/mol for Al-12Si alloy. Also, the constant initial strain rate tests performed at selected strain rates and temperatures revealed flow hardening at small strains followed by flow softening. Deformation of Al–Si alloys is suggested to be controlled by the dislocation climb mechanism through the participation of both the grain interior and grain boundaries by consideration of effective stress instead of applied stress.

A four-mode optical thermometer designed in double perovskite Ca2GdNbO6:Bi3+,Eu3+

High-sensitive multi-mode optical thermometry has become a superstar in the temperature sensing field and attracted great attention. Herein, a novel four-mode optical thermometer is designed in Eu3+ and Bi3+ co-doped double perovskite Ca2GdNbO6. The crystal structures of the host and the doped samples were characterized with X-ray diffraction patterns and Rietveld refinements. Under the excitation of 340 nm, the phosphors exhibit multiple emissions coming from Bi3+ and Eu3+. The energy transfer from Bi3+ to Eu3+ is proved in the perovskite and the transfer efficiency reaches as high as 92%. Benefiting from the different temperature-dependent photoluminescent properties of Bi3+ and Eu3+, a four-mode optical thermometer based on fluorescence intensity ratio, CIE coordinate, fluorescence lifetime, and excitation intensity ratio is realized in the Ca2GdNbO6:0.03Bi3+,0.01Eu3+ phosphor. The maximal relative sensitivities of the four modes are 1.90% K−1 at 460 K, 0.514% K−1 at 500 K, 2.69% K−1 at 437 K, and 1.43% K−1 at 310 K, respectively, most of which are higher than those of recently reported phosphors. These good thermometric performances suggest that Ca2GdNbO6:Bi3+,Eu3+ has a great potential application in temperature detection field.