Mechanical Sensors Research Articles

Searching for Ghost Particles with a Mechanical Sensor

Searching for Ghost Particles with a Mechanical Sensor

Design strategy for hierarchical structure of carbon black on microporous elastomer surface toward stretchable and compressive strain sensors

Flexible mechanical sensors capable of sensing both compressive and tensile strains with high sensitivity and linear piezoresistive response are of great significance for the development of wearable devices, flexible electronic skins, and robotics. However, it is still of challenge to develop simple 3-dimensional (3D) porous polymer/carbon nanomaterial composite strain sensors capable of sensing both tensile and compressive strains with reproducible electrical signals. Herein, we report a simple and scalable morphology-engineering strategy, i.e., selective location of carbon black (CB) in polyoxyethylene (PEO)/ethylene-α-octene random copolymer (ORC) blends via phase separation, to fabricate isotropic 3D continuous porous composite strain sensors. Such a composite consists of a continuous porous ORC matrix inlaid with preferable CB distribution on ORC surface after PEO removal, enabling distinguishable detection of both compressive and tensile strains with opposite resistance changes. Specifically, the as-fabricated strain sensors exhibit linear response with a sensitivity of 16 for 0–46% compressive strain, a detection limit of 0.3% strain with 16/16 ms response/recovery time. Besides, it has a large gauge factor for tensile strain of 0–300%, a detection limit strain of 0.06% with 16/47 ms response/recovery time, and low hysteresis degree. As such, it allows for full-range body motion monitoring and Morse code communication.

The Actin Network Interfacing Diverse Integrin-Mediated Adhesions.

The interface between the cellular actin network and diverse forms of integrin-mediated cell adhesions displays a unique capacity to serve as accurate chemical and mechanical sensors of the cell's microenvironment. Focal adhesion-like structures of diverse cell types, podosomes in osteoclasts, and invadopodia of invading cancer cells display distinct morphologies and apparent functions. Yet, all three share a similar composition and mode of coupling between a protrusive structure (the lamellipodium, the core actin bundle of the podosome, and the invadopodia protrusion, respectively), and a nearby adhesion site. Cytoskeletal or external forces, applied to the adhesion sites, trigger a cascade of unfolding and activation of key adhesome components (e.g., talin, vinculin, integrin), which in turn, trigger the assembly of adhesion sites and generation of adhesion-mediated signals that affect cell behavior and fate. The structural and molecular mechanisms underlying the dynamic crosstalk between the actin cytoskeleton and the adhesome network are discussed.

Self-powered triboelectric mechanical motion sensor for simultaneous monitoring of linear-rotary multi-motion

To realize the simultaneous monitoring of linear-rotary multi-motion, a linear and rotary coupled-motion triboelectric mechanical motion sensor (LRC-TMMS) with a gear-like engagement electrode (GE-electrode) is proposed. The displacement and velocity measurement of the linear and rotary motions can be realized by using GE-electrode, and the linear, rotary, and helical motions of the LRC-TMMS can be distinguished by the signal processing method of fundamental frequency separation. The results illustrate that the LRC-TMMS can achieve stable monitoring with a maximum linear stroke of 70 mm. And the linear fitting lines between the parameters of the output signal and that of the input motion are consistent with the theoretical reference results. In addition, the velocities monitored by the LRC-TMMS in different motions have good linearity, and most error rates are less than 3%. The practical monitoring performance of the LRC-TMMS in nine motion modes is verified using a commercial linear-rotary motor, which has potential application prospects in the fields of the intelligent manipulator and automated manufacturing.

An 11.6aF/kPa Mechanical Stress Sensor With 0.808% Temperature-Drift Oscillator for Flip-Chip Packaging

During the package processes, including chip attachment and encapsulation, the stress caused by the thermal and mechanical load is usually generated in integrated circuit chips. This brief developed a mechanical stress sensor in a standard 180nm CMOS process for runtime stress measurement. The contributions done in this brief are summarized as follows: 1) A temperature-compensation RC oscillator circuit converts the warpage of the die induced by the mechanical stress into the frequency output. It even can measure the thermally induced stresses with a wide temperature range. The oscillator has a frequency variation of −0.808% from temperature stability measurements from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 40^{\circ }\text{C}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$120^{\circ }\text{C}$ </tex-math></inline-formula> . 2) Rather than the complicated calibrations and advanced measurement equipment, the frequency can be easily measured with the chip area less than 0.569 mm2 and the power consumption less than 22.9 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> . 3) As for the sensing array, the sensitivity and stability of the metal-insulator-metal (MIM) and metal–oxide–metal (MOM) capacitors are verified. The measured average sensitivity of the test chip using a MIM capacitor with 0.1736 Hz/kPa is more sensitive than that using a MOM capacitor with 0.102 Hz/kPa. The linear fit curves of the output frequency have the coefficient of determination ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}^{2}$ </tex-math></inline-formula> ) of 0.9983 for MIM and 0.9959 for MOM, indicating an excellent linear response of the sensor circuit.

A Review of Position Sensorless Compound Control for PMSM Drives

As position sensorless control technology can avoid many disadvantages caused by mechanical position sensors, improve the reliability of the motor, reduce costs and other advantages, a large number of researchers have conducted research on compound control technology in order to achieve position sensorless control technology in a wide speed range. In this article, the position sensorless compound control technology of a permanent magnet synchronous motor is reviewed, and the compound control technology of a permanent magnet synchronous motor without a position sensor is elaborated. Finally, the existing problems and development trend of sensorless compound control technology are summarized and prospected.

Numerical Investigation of the Effect of Symmetry on Evaporation Triggered Elastocapillary Top-Gathering of High Aspect Ratio Micropillars

High-aspect-ratio (HAR) micropillar arrays offer a wide range of applications in micro-contact printing, switchable transparent optical windows, superhydrophobic surfaces, mechanical sensors, and actuators, due to their properties such as large surface area and excellent mechanical compliance. However, owing to their high aspect ratio, these microstructures are prone to lateral deflection by elastocapillary forces in liquid environments, which is known as top-gathering, limiting their manufacturing processes and applications. Here, the impact of symmetry on evaporation triggered top-gathering of micropillars was studied numerically. The initiation of the micropillar deflection due to capillary forces under varying force distributions was simulated using a COMSOL Multiphysics simulation package. The simulation was carried out for the configurations of two, four, and an array of micropillars. For the four micropillar configuration, a new equation was suggested for calculating the micropillar deflection due to elastocapillary forces, using force distributions around the micropillars. The suggested equation was verified by comparison with the experimental observations. The effect of droplet evaporation on deflection/top-gathering of micropillars was also investigated. It was found that initiation of deflection is due to asymmetry at the rim of the droplet, generating domino-like deflection of the other micropillars. This study provides a new equation/criterion for estimating deflection of the micropillars, suggesting array designs that are resistant to such deflections when interacting with liquids.

The Properties of a Ship's Compass in the Context of Ship Manoeuvrability.

In evaluating the accuracy of most navigation measuring systems, it is accepted, as a rule, that measurement errors are characterised by a normal distribution. With reference to the compass, the approach of most producers is similar. However, in the case of this measuring device, the dynamics of the ship should also be taken into account. The problem is that any changes in the ship's heading can be measured exclusively with the use of a compass. Until quite recently, this device was built based on mechanical elements, so it possessed its own dynamic properties. This means the appearance of specific, positive feedback (self-reinforcing feedback) because if the compass did not point to the correct heading, it could lead the ship to stray from the correct heading. On the other hand, it could mean an incorrect compass setup, even though the ship had the correct heading. Any incorrect indications of the compass were then interpreted as a ship's departure from the correct heading. This problem was not essential in the era of magnetic compasses because the errors in these compasses are relatively constant, unlike the errors in gyrocompasses, which have an oscillatory and random character and, thus, it is not possible to describe them accurately with mathematical relations. This issue was already perceived before WWII, when the Anschutz Company proposed, among other solutions, using the so-called Schuler period in the construction of gyrocompasses. Fibre optic gyrocompasses do not possess mechanical sensors, so the variability of their indications is of a different character. However, computational processes, as well as applied inertial sensors, also cause certain errors of an oscillatory nature. This raises the following questions: what is the spectrum of the error frequency of such compasses, and what is the influence of the ship's movement on them? The authors attempted to evaluate this phenomenon by performing measurements made on board three hydrographic platforms and comparing them with the headings indicated by other compasses.

Design of an Automatically Controlled Multi-Axis Stretching Device for Mechanical Evaluations of the Anterior Eye Segment

The young eye has an accommodative ability involving lens shape changes to focus over different distances. This function gradually decreases with age, resulting in presbyopia. Greater insights into the mechanical properties of anterior eye structures can improve understanding of the causes of presbyopia. The present study aims to develop a multi-axis stretching device for evaluating the mechanical properties of the intact eye lens. A stretching device integrating the mechanical stretcher, motor, torque sensor and data transmission mechanism was designed and developed by 3D printing. The mechanical stretcher can convert rotation into radial movement, both at constant speeds, according to the spiral of Archimedes. The loading unit equipped with eight jaws can hold the eye sample tightly. The developed device was validated with a spring of known constant and was further tested with anterior porcine eye segments. The validation experiment using the spring resulted in stiffness values close to the theoretical spring constant. Findings from measurements with porcine eye samples indicated that the measured forces are within the ranges reported in the literature. The developed multi-axis stretching device has good repeatability during experiments with similar settings and can be reliably used for mechanical evaluations of the intact eye lens.

Modeling and development of an auxetic foam-based multimodal capacitive strain gauge

Auxetics are mechanical metamaterials with the unique properties of expanding their transversal section upon longitudinal positive strain, decoupling the deformations in normal and transversal directions. Such property can be exploited to develop soft sensors that can provide feedback to different mechanical stimuli, e.g. pressure and shear force. In this work, we propose for the first time a mathematical model to analytically simulate and design the auxetic behavior in a capacitive strain gauge, and show that, for a polyurethane (PU) auxetic foam, Poisson Ratio’s values can satisfy the negative gauge factor (GF) condition. We develop an innovative thermo-compressive process to obtain anisotropic auxetic PU sponges both in normal and normal/radial directions, and their mechanical properties are in agreement with the theoretical calculations validating our model. Then, we develop a capacitive strain gauge by integrating a normal auxetic PU foam with polydimethylsiloxane /carbon nanotubes electrodes. Results show that the capacitive change caused by an external force, is proportional to the induced deformation, but importantly it is also dependent on the direction of the applied force. A negative GF of GF = −2.8 is obtained for a longitudinal strain range up to 10%. This auxetic foam structure guarantees flexibility and paves the way for an improved design freedom for multimodal mechanical soft sensors providing new opportunities towards smart wearables and perceptive soft robots.

Fusion of two stable elastic structures resulting in an unstable system

It is shown that a compound elastic structure, which displays a dynamic instability, may be designed as the union (or ‘fusion’) of two structures which are stable when separately analysed. The compound elastic structure has two degrees of freedom and is made up of a rigid rod connected with two springs to a smooth support, which evidences a jump in the curvature at the equilibrium configuration. Instability is proven in a linearized context and is related to the application of a non-conservative load of the follower type so that the instability disappears under dead loads. In the fully nonlinear range, the instability is also confirmed through numerical simulations. The obtained results may be useful in the design of new mechanical sensors, devices for energy harvesting, or architected materials. In addition, our findings have conceptual implications on piecewise-linear theories of mechanics such as for instance plasticity or frictional contact.

From Piezoelectric Nanogenerator to Non-Invasive Medical Sensor: A Review.

Piezoelectric nanogenerators (PENGs) not only are able to harvest mechanical energy from the ambient environment or body and convert mechanical signals into electricity but can also inform us about pathophysiological changes and communicate this information using electrical signals, thus acting as medical sensors to provide personalized medical solutions to patients. In this review, we aim to present the latest advances in PENG-based non-invasive sensors for clinical diagnosis and medical treatment. While we begin with the basic principles of PENGs and their applications in energy harvesting, this review focuses on the medical sensing applications of PENGs, including detection mechanisms, material selection, and adaptive design, which are oriented toward disease diagnosis. Considering the non-invasive in vitro application scenario, discussions about the individualized designs that are intended to balance a high performance, durability, comfortability, and skin-friendliness are mainly divided into two types: mechanical sensors and biosensors, according to the key role of piezoelectric effects in disease diagnosis. The shortcomings, challenges, and possible corresponding solutions of PENG-based medical sensing devices are also highlighted, promoting the development of robust, reliable, scalable, and cost-effective medical systems that are helpful for the public.

Topological magnons on the triangular kagome lattice

We present the topology of magnons on the triangular kagome lattice (TKL) by calculating its Berry curvature, Chern number, and edge states. In addition to the ferromagnetic state, the TKL hosts ferrimagnetic ground state as its two sublattices can couple with each other either ferromagnetically or antiferromagnetically. Using Holstein-Primakoff (HP) boson theory and Green's function approach, we find that the TKL has a rich topological band structure with added high Chern numbers compared with the kagome and honeycomb lattices. The magnon edge current allows a convenient calculation of thermal Hall coefficients and the orbital angular momentum gives correlation to the Einstein--de Haas effect. We apply the calculations to the TKL and derive the topological gyromagnetic ratio showing a nonzero Einstein--de Haas effect in the zero-temperature limit. Our results render the TKL as a potential platform for quantum magnonics applications including high-precision mechanical sensors and information transmission.

A sensorless control system of permanent magnet synchronous motor for electric locomotive based on improved high-frequency rotating injection method

The mechanical sensor of electric locomotive is easy to lose, leading to position measurement error, which deteriorates the performance of permanent magnet synchronous motor (PMSM) drive system. Therefore, a limp-home mode based on high-frequency injection sensorless strategy is proposed. The signal processing of conventional high-frequency rotating injection needs several filters, and the delay has an impact on estimated position, which is phase-based demodulation. In this paper, an amplitude-based demodulation strategy is proposed, which needs only one low-pass filter, meanwhile the digital control delay can be canceled automatically. Accordingly, the position estimation precision and robustness can be enhanced with the aid of proposed method. The feasibility and effectiveness of theoretical analysis is verified on an 18-kW PMSM drive system experimental platform.

High-frequency torsional motion transduction using optomechanical coupled oscillators

Using light to measure an object’s motion is central to operating mechanical sensors that probe forces and fields. Cavity optomechanical systems embed mechanical resonators inside optical resonators. This enhances the sensitivity of optomechanical measurements, but only if the mechanical resonator does not spoil the properties of the optical cavity. For example, cavity optomechanical detection of resonators made from optically absorbing materials, or whose geometry does not possess suitable spatial symmetry, is challenging. Here we demonstrate a system that overcomes challenges in measuring high-frequency twisting motion of a nanodisk by converting them to vibrations of a photonic crystal cavity. Optomechanical readout of the cavity then enables measurement of the nanodisk’s torsional resonances with sensitivity 5.1 × 10 − 21 − 1.2 × 10 − 19 N m / H z for a mechanical frequency range of 5–800 MHz. The nanodisk can be outfitted with magnetic nanostructures or metasurfaces without affecting the optical properties of the cavity, making the system suitable for torque magnetometry and structured light sensing.

Predictive Current Control of Sensorless Linear Permanent Magnet Synchronous Motor

In the vector control system of a tubular oscillating permanent magnet synchronous linear motor, it is difficult to obtain accurate feedback information from the conventional mechanical sensors under bad and complex working conditions. This paper presents a new predictive current control designed to estimate the speed of the tubular oscillation permanent magnet synchronous linear motor. It implements two control techniques: The first technique is using the sliding-mode observer’s speed observer for speed estimation. The second is to design a deadbeat predictive current control to replace the PI regulator in the conventional current loop; it solves the difficulties of global optimization and PI parameter setting. The simulation and experimental results show that this method gives a good dynamic performance.

Liquid Metal-Based Electronics for On-Skin Healthcare.

Wearable devices are receiving growing interest in modern technologies for realizing multiple on-skin purposes, including flexible display, flexible e-textiles, and, most importantly, flexible epidermal healthcare. A 'BEER' requirement, i.e., biocompatibility, electrical elasticity, and robustness, is first proposed here for all the on-skin healthcare electronics for epidermal applications. This requirement would guide the designing of the next-generation on-skin healthcare electronics. For conventional stretchable electronics, the rigid conductive materials, e.g., gold nanoparticles and silver nanofibers, would suffer from an easy-to-fail interface with elastic substrates due to a Young's modulus mismatch. Liquid metal (LM) with high conductivity and stretchability has emerged as a promising solution for robust stretchable epidermal electronics. In addition, the fundamental physical, chemical, and biocompatible properties of LM are illustrated. Furthermore, the fabrication strategies of LM are outlined for pure LM, LM composites, and LM circuits based on the surface tension control. Five dominant epidermal healthcare applications of LM are illustrated, including electrodes, interconnectors, mechanical sensors, thermal management, and biomedical and sustainable applications. Finally, the key challenges and perspectives of LM are identified for the future research vision.

Nitric oxide synthase phosphorylation in fetoplacental endothelium is enhanced by agonism of Piezo1 mechanosensor in small for gestational age babies.

Friction caused by blood flowing across cells that line blood vessels (endothelial cells) activates sensors of mechanical force. This produces nitric oxide (NO) which widens placental blood vessels, enabling more blood flow to the baby. This study sought to determine whether the mechanical sensor, Piezo1, is important for NO production in fetoplacental endothelial cells (FpECs) and whether the steps in this pathway are different in small for gestational age (SGA) babies, where placental blood flow is often altered. We showed that in healthy FpECs, blood flow increased NO signalling. We suggest that in SGA babies, FpECs have an increase in baseline levels of NO signalling, suggestive of a compensatory drive. Treating healthy and SGA cells with a Piezo1 chemical activator, Yoda1, upregulated NO signalling. This shows that Piezo1 is linked to NO and that in SGA, FpECs have the capacity to further increase NO. Further research will establish whether Piezo1 enhancement leads to increased blood flow in the placenta. If so, Piezo1 could be a new target for developing treatments to prevent poor growth of babies in the womb.

Hybrid sensorless control of PMSM in full speed range using HFI and back-EMF

The permanent magnet synchronous motors (PMSM) are more and more used because of their high performance compared with other AC motors. The present paper proposes a hybrid controller which consists of a high frequency injection estimator and a back-electromotive-force observer in full speed range for the sensorless control of PMSM. The aim objective of the study to prevent speed overshot in startup time of the motor and provides a better dynamic response in transient and permanent states using this structure. A hybrid algorithm is applied to realize a smooth transition from low to high speed. At standstill and very low speed region, HF injection technique is used to detect the rotor initial position. In this first step study, the position estimation is derived from a HF current injection by using only one filter. When the rotor speed goes up to a certain value where back-EMF can provide adequate information, a back-EMF observer will dominate. Thanks to this structure, the mechanical sensor can be engaged using the best estimates and the developed control method is fast, simple, and flexible. The effectiveness, superiority, and performance of the proposed control method and extensive simulation results are provided on a 1 kW permanent magnet synchronous motor drive, demonstrating the expected performances.

Integrating physicomechanical and biological strategies for BTE: biomaterials-induced osteogenic differentiation of MSCs.

Large bone defects are a major global health concern. Bone tissue engineering (BTE) is the most promising alternative to avoid the drawbacks of autograft and allograft bone. Nevertheless, how to precisely control stem cell osteogenic differentiation has been a long-standing puzzle. Compared with biochemical cues, physicomechanical stimuli have been widely studied for their biosafety and stability. The mechanical properties of various biomaterials (polymers, bioceramics, metal and alloys) become the main source of physicomechanical stimuli. By altering the stiffness, viscoelasticity, and topography of materials, mechanical stimuli with different strengths transmit into precise signals that mediate osteogenic differentiation. In addition, externally mechanical forces also play a critical role in promoting osteogenesis, such as compression stress, tensile stress, fluid shear stress and vibration, etc. When exposed to mechanical forces, mesenchymal stem cells (MSCs) differentiate into osteogenic lineages by sensing mechanical stimuli through mechanical sensors, including integrin and focal adhesions (FAs), cytoskeleton, primary cilium, ions channels, gap junction, and activating osteogenic-related mechanotransduction pathways, such as yes associated proteins (YAP)/TAZ, MAPK, Rho-GTPases, Wnt/β-catenin, TGFβ superfamily, Notch signaling. This review summarizes various biomaterials that transmit mechanical signals, physicomechanical stimuli that directly regulate MSCs differentiation, and the mechanical transduction mechanisms of MSCs. This review provides a deep and broad understanding of mechanical transduction mechanisms and discusses the challenges that remained in clinical translocation as well as the outlook for the future improvements.