This letter presents an enhanced design of interdigital electrodes that utilize fractal topology to achieve multidomain configurations, specifically incorporating a 12-fold pattern. The primary objective of this design is to generate rotationally symmetric electromagnetic fields at any sensing position. This characteristic effectively mitigates variations in sensing signals caused by random orientations of anisotropic analytes, such as long-chain polymers or proteins, particularly in scenarios involving low-concentration conditions or miniaturized device designs. Consequently, the proposed sensor not only offers the heightened sensitivity typically associated with conventional interdigital electrodes but also demonstrates the ability to avoid misjudgment of sensing signals influenced by the anisotropy and concentrations of the analyte simultaneously. To comprehensively evaluate the performance of the proposed sensor, a rigorous numerical analysis is conducted, comparing it with traditional interdigital structures. The results indicate that the proposed sensor outperforms its counterparts in terms of the limit of detection, electromagnetic compatibility, and measurement reproducibility. In addition, this research provides the MATLAB codes employed for generating the multidomain interdigital electrodes.
Electromechanical resonators are an essential component in many sensors. These systems are essentially mechanical resonators that are driven by harmonic electrostatic forces, and their response is often measured using capacitive sensing. There is some ambiguity in the literature with respect to the resonance response of mechanical resonators. Should resonance be associated with the peak amplitude of velocity or should it be associated with the peak amplitude of displacement? Another ambiguity relates to the definition of phase: Should phase relate velocity or displacement to the driving force? These two issues are addressed here, and it is shown why resonance should be associated with peak amplitude of velocity and not with peak amplitude of displacement.
This letter discusses and solves a relevant issue for Lissajous frequency modulated microelectromechanical system (MEMS) gyroscopes. Their working principle, under realistic control schemes, implies an undesired generation of spurious tones at twice the modulation frequency, which impairs system stability and bandwidth. A novel sensor design is proposed and coupled to an integrated circuit including an oscillator and a frequency to digital converter. The system is designed such that operation can occur at much smaller motion (down to 300 nm displacement amplitude) without, nevertheless, impairing significantly noise performance. In operation, the system shows a 51-fold reduction of the spurious harmonic while holding sub-10-mdps/√Hz input referred noise.
Flexible tactile sensors with superior sensitivity and linearity are in high demand for many applications, which require long-term and reliable detection. Low-pressure characterization is crucial in many applications. Surface microstructuring and compositional alterations have frequently been employed to improve the low-pressure performance of these sensors. In this letter, the nonlinear response of a polymer-based piezoresistive flexible tactile sensor is investigated by introducing changes in the mechanical properties of polydimethylsiloxane elastomer when altering the nature and thickness of the substrate. It is observed that there is significant nonlinearity in several sensor parameters within a low-pressure region of 0–1.5 kPa. When porosity is introduced, sensitivity rises by 27.7%. Furthermore, when the thickness is reduced in half, the sensitivity increases by 89.13%. When the applied pressure is increased, the overall sensitivity decreases by 83.7%. A similar trend is also seen in the resistive response output of the sensor, and the 2-mm thick-porous sensor, among others, has the lowest detection limit of 0.05 kPa.
Monitoring the health of civil engineering structures using implanted deformation, temperature, and corrosion sensors would further improve maintenance and extend the service life of those structures. However, sensor integration poses a number of problems due to the presence of cables and on-board electronics. Passive, wireless surface acoustic wave (SAW) sensors offer a very promising solution here. We used commercial SAW devices mounted on steel rebars to carry out an initial feasibility study. Without cables or embedded electronics, we were able to measure the deformation of a concrete beam subjected to bending load. We were also able to measure the temperature continuously over a three-week period.
Radio frequency (RF) signals can be converted to dc signals using an antenna and diode (which is so called rectenna). In a long-distance wireless transfer, weak RF signals cannot exceed the threshold voltage of the diodes in the rectenna, making RF-DC conversion very inefficient. This letter proposes resonator type GHz piezoelectric transformer based on c -axis zig-zag ScAlN films. Solidly mounted resonator (SMR) type transformer using an acoustic Bragg reflector enables a wider bandwidth operation than film/substrate type transformer we reported previously. As a result, zig-zag multilayers which was oriented 180° symmetrically on the acoustic Bragg reflector was fabricated by oblique RF magnetron sputtering. In addition, voltage gain of 2.7 and the fractional bandwidth of 3.2% which was 46 times wider than that of film/substrate type transformer were observed.
Magnetic interference from the spinning reaction wheels often used to control spacecraft orientation is a well-known issue for accurate sensing of geophysical measurements using sensitive magnetometers that capture the geophysical magnetic fields in the macroscale (order of 1 km or greater). Disentangling the reaction wheel interference from the background measurements has been an open challenge to geomagnetic signal analysis for several decades. In this letter, we address this challenge as a feature separation problem and leverage the informational redundancy and feature continuity across multiple spatial dimensions and dual sensors to calculate accurate spectral support estimates of the reaction wheel signature. Specifically, we exploit the feature continuity across multiple spectrograms to detect the multiharmonic reaction wheel signature across multiple spatial dimensions and inboard and outboard sensor measurements against the background geophysical magnetic field. A representative case study for the e-POP/Swarm-ECHO mission is presented.
The introduction of miniaturized piezoresistive sensing into Lissajous frequency modulated gyroscopes has an interesting potential to reduce noise. This letter presents the first design of such a system from both the electro-mechanical and electronics point of view and tests the system in operation. An angle random walk of 3 mdps/√hz is demonstrated, together with a full-scale range that exceeds 2000 dps for a 46 Hz split, thus corresponding to about 20 Hz system bandwidth. Experimental results also show the importance of tracking the mode-split in operation, as this largely correlates with the zero-rate output drift, leading to a stability improvement by almost a factor of 20, down to 1 °/hr.
The microelectro mechanical systems (MEMS) accelerometer has been implemented in various applications across industries. To expand its application to textiles, here, we propose a facile fabrication and packaging method for fiber-shaped flexible MEMS thermal accelerometer. The sensing structure was fabricated through a standard microfabrication process on a thin polyimide film substrate. The film was then cut into stick shape and packaged inside a flexible resin tube through a facile insertion process. A sensitivity improvement strategy by mitigating the thermal mass around the sensing structure was also introduced. Gravitational acceleration measurement using the proposed sensors was demonstrated using an inclination stage. Finally, measurement of human hand movement using the proposed sensors was demonstrated.
This letter presents an optical current sensor (OCS) for high-voltage dc networks. The proposed OCS combines electrical signal conditioning circuit and a low-voltage transducer (LVT) based on piezoelectric and photonic technologies. The characterization of the OCS individual components was performed in laboratory conditions, and the sensor operation was evaluated based on the current measurement range set by the IEC 61869-14 standard. The experimental results demonstrated that the device can be used under the input current range conditions specified in IEC 61869-14 and has the potential to provide current measuring functionality in challenging locations that impose limitation on conventional sensors.
In this letter, an attempt for rapid detection of biomarkers for SARs-CoV-2 virus is initiated for the first time, employing MoS 2= based dual-gate mosfet with embedded nanogap in the gate dielectric. Based on the spike, envelope, and DNA proteins of the virus, a deep analysis of the device performance in terms of transfer characteristics I on /I off ratio is performed using SILVACO ATLAS TCAD by considering the dielectric constant equivalent of the virus proteins as κ = 4,10,12 and with variation of DNA charge densities as −2 × 10 12 Ccm −2 to +2 × 10 12 Ccm −2 . The threshold voltage (V th ) is eventually extracted and is used as the detection metric to evaluate the sensing ability of the device exhibiting superior V th sensitivity as high as 100 mV as compared to some of the existing models. Results also reveal a high dependency of the sensitivity on the bioelement configuration within the nanogap and the channel material.
The development of biomarker-based diagnostic devices is undoub-tedly changing the healthcare sector and reshaping clinical trial designs for disease prediction and therapeutic guidance. Age-related macular degeneration (AMD) is a chronic eye disease for ageing adults, which severely affects their vision, and the damage is irreversible. The use of tears for noninvasive sampling to quickly diagnose ocular diseases has always been appealing. In this work, we aim to deliver a noninvasive complement component III (C3) biomarker-based electrochemical biosensor for early diagnosis of AMD using human tears. Here, indium zinc oxide (InZnO) nanofibers are used as a biotransducing element, where ZnO is an n-type semiconductor with a wide band gap of 3.35–3.37 eV, and the incorporation of a group III element, i.e., indium, is used to improve its free charge carrier concentration. The conduction mechanism in the InZnO nanofibers is investigated through a dielectric study, unveiling that conduction depends on both frequency and temperature. Furthermore, the electrochemical biosensor was constructed by immobilizing the monoclonal anti-C3 antibody on the InZnO nanofiber using a suitable linker. The biosensor was calibrated by spiking a wide range of C3 protein concentrations from 50 pg/mL to 5 μ g/mL in an artificial tears matrix and capturing the electrochemical response using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) techniques. The developed InZnO-based electrochemical biosensor response was also validated by testing the C3 protein in human tears from three healthy adults.
In this letter, we present a custom-designed and flexible readout circuitry for the characterization of flexible and planar electrolyte-gated carbon nanotube field-effect transistor-based biosensors for ammonium detection in sweat. We employed spray-deposited semiconducting carbon nanotubes as active material, and functionalized the devices with previously synthesized ion-selective membrane, based on the nonactin ionophore. In the design of the readout circuitry, we focused on enabling low-power operation with a single coin-cell battery with compact wireless data transmission. To maximize the bendability of the flexible PCB, particular attention was taken in layout routing as well as in selecting small-sized packages for the commercial integrated circuits and all-in-one systems such as programmable Bluetooth system-on-chip (i.e., ST microelectronics BlueNRG SoC). We recorded a high sensitivity of 4.516 μ A/decade for sweat ammonium level analysis between 0.1 and 100 mM, which fully covers the relevant range of interest in the context of sport monitoring. The characterization was carried out with the introduced front-end readout, and the results were benchmarked with a “gold standard” instrument, showing good and reliable performance of the developed fully flexible bioelectronic system.
Tactile information is usually important for object manipulation and grasping. Typically, soft hands and tactile sensors can deform passively and contribute to stable grasping. In particular, soft tactile sensors that use conductive materials as sensor elements can acquire contact information, including the contact position and pressure; however, this tactile information cannot be classified. This study attempts to classify tactile information based on conductive material arrangements. To this end, we develop a soft tactile sensor composed of a silicone rubber body with two channels filled with a conductive material. The two channels are arranged so that they are parallel from the top view and angled with different slopes from the side view. Our experimental data reveal that the contact position parallel to the channels can be determined based on the resistance changes in the two channels, whereas the pressure can be obtained through a model based on the estimated value of the contact position.
In this letter, we present a smart glove for Tactile Internet applications. The individual finger motions are measured via resistive strain sensors. The strain sensors are directly integrated with the textile glove and are produced in an automated process. The sensor glove is integrated with sensor conditioning, controller, wireless frontend, and battery. We investigate the measured sensor data for a variety of gestures, demonstrating the good quality of the data allowing for easy and low-energy gesture recognition.