Change In Resonant Frequency Research Articles

Wireless Passive Ceramic Sensor for Far-Field Temperature Measurement at High Temperatures.

A passive wireless high-temperature sensor for far-field applications was developed for stable temperature sensing up to 1000 °C. The goal is to leverage the properties of electroceramic materials, including adequate electrical conductivity, high-temperature resilience, and chemical stability in harsh environments. Initial sensors were fabricated using Ag for operation to 600 °C to achieve a baseline understanding of temperature sensing principles using patch antenna designs. Fabrication then followed with higher temperature sensors made from (In, Sn) O2 (ITO) for evaluation up to 1000 °C. A patch antenna was modeled in ANSYS HFSS to operate in a high-frequency region (2.5-3.5 GHz) within a 50 × 50 mm2 confined geometric area using characteristic material properties. The sensor was fabricated on Al2O3 using screen printing methods and then sintered at 700 °C for Ag and 1200 °C for ITO in an ambient atmosphere. Sensors were evaluated at 600 °C for Ag and 1000 °C for ITO and analyzed at set interrogating distances up to 0.75 m using ultra-wideband slot antennas to collect scattering parameters. The sensitivity (average change in resonant frequency with respect to temperature) from 50 to 1000 °C was between 22 and 62 kHz/°C which decreased as interrogating distances reached 0.75 m.

Atomic layer self-transducing MoS2 vibrating channel transistors with 0.5 pm/Hz1/2 displacement sensitivity at room temperature

We report on the experimental demonstration of high-performance suspended channel transistors with single- and bilayer (1L and 2L) molybdenum disulfide (MoS2), and on operating them as vibrating channel transistors (VCTs) and exploiting their built-in dynamic electromechanical coupling to read out picoampere (pA) transconduction current directly at the vibrating tones, without frequency conversion or down-mixing, for picometer (pm)-scale motion detection at room temperature. The 1L- and 2L-MoS2 VCTs exhibit excellent n-type transistor behavior with high mobility [150 cm2/(V·s)] and small subthreshold swing (98 mV/dec). Their resonance motions are probed by directly measuring the small-signal drain-source currents (iD). Electromechanical characteristics of the devices are extracted from the measured iD, yielding resonances at f0 = 31.83 MHz with quality factor Q = 117 and f0 = 21.43 MHz with Q = 110 for 1L- and 2L-MoS2 VCTs, respectively. The 2L-MoS2 VCT demonstrates excellent current and displacement sensitivity (Si1/2 = 2 pA/Hz1/2 and Sx1/2 = 0.5 pm/Hz1/2). We demonstrate f0 tuning by controlling gate voltage VG and achieve frequency tunability Δf0/f0 ≈ 8% and resonance frequency change Δf0/ΔVG ≈ 0.53 kHz/mV. This study helps pave the way to realizing ultrasensitive self-transducing 2D nanoelectromechanical systems at room temperature, in all-electronic configurations, for on-chip applications.

Magnetic-field-induced spin reorientation in TmFeO<sub>3</sub> single crystals

TmFeO<sub>3</sub> exhibits rich physical properties such as magneto-optical effect, multiferroicity, and spin reorientation, making it possess significant research value in condensed matter physics and materials science. In this study, we utilize a time-domain terahertz magneto-optical spectroscopy system to investigate the changes in spin resonance frequency of TmFeO<sub>3</sub> single crystal at <i>T</i> = 1.6 K under external magnetic fields in a range of 0–7 T. The TmFeO<sub>3</sub> sample is grown in an optical floating zone furnace and its crystallographic orientation is determined by using back-reflection Laue X-ray photography with a tungsten target. The measurement setup is a self-built time-domain terahertz magneto-optical spectroscopy system, with magnetic fields in a range of 0–7 T, temperatures in a range of 1.6–300 K, and a spectral range of 0.2–2.0 THz. A pair of 1 mm-thick ZnTe nonlinear crystals is used to generate and detect terahertz signals through optical rectification and electro-optic sampling technique. The system variable temperature and magnetic field are controlled by a superconducting magnet. In experiments, a linearly polarized terahertz wave is vertically incident on the sample surface, and its magnetic component <i>H</i><sub>THz</sub> is parallel to the sample surface. By rotating the sample, the angle (<i>θ</i>) between macroscopic magnetic moment <i> <b>M</b> </i> and <i>H</i><sub>THz</sub> can be tuned, achieving selective excitations of the two modes, that is, <i>θ</i> = 0 for q-AFM mode and 90° for q-FM mode. Terahertz absorption spectrum results indicate that as the magnetic field increases, the quasi-ferromagnetic resonance (q-FM) of TmFeO<sub>3</sub> single crystal shifts towards high frequencies, and quasi-antiferromagnetic resonance (q-AFM) transits to q-FM under low critical magnetic fields (2.2–3.6 T). Through magnetic structure analysis and theoretical fitting, it is confirmed that the magnetic moment of the single crystal undergoes magnetic field induced spin reorientation. This study is helpful in better understanding of the regulation mechanism of the internal magnetic structure of rare earth ferrite under the combined action of external magnetic field and temperature field, and also in developing related spin electronic devices.

Subharmonic resonance of phospholipid coated ultrasound contrast agent microbubbles

Phospholipid encapsulated ultrasound contrast agents have proven to be a powerful addition in diagnostic imaging and show emerging applications in targeted therapy due to their resonant and nonlinear scattering. Microbubble response is affected by their intrinsic (e.g. bubble size, encapsulation physics) and extrinsic (e.g. boundaries) factors. One of the major intrinsic factors at play affecting microbubble vibration dynamics is the initial phospholipid packing of the lipid encapsulation. Here, we examine how the initial phospholipid packing affects the subharmonic response of either individual or a system of two closely-placed microbubbles. We employ a finite element model to investigate the change in subharmonic resonance under ‘small’ and ‘large’ radial excursions. For microbubbles ranging between 1.5 and 2.5 µm in diameter and in its elastic state (σ0 = 0.01 N/m), we demonstrate up to a 10 % shift towards lower frequencies in the peak subharmonic response as the radial excursion increases. However, for a bubble initially in its buckled state (σ0 = 0 N/m), we observe a maximum shift of 8 % towards higher frequencies as the radial excursion increases over the same range of bubble sizes – the opposite trend. We studied the same scenario for a system of two individual microbubbles for which we saw similar results. For microbubbles that are initially in their elastic state, in both cases of a) two identically sized bubbles and b) a bubble in proximity to a smaller bubble, we observed a 6 % and 9 % shift towards lower frequencies respectively; while in the case of a neighboring larger bubble no change in subharmonic resonance frequency was observed. Microbubbles that are initially in a buckled state exert no change, 5 % and 19 % shift towards higher frequencies, in two-bubble systems consisting of a) same-size, b) smaller, and c) larger neighboring bubble respectively. Furthermore, we examined the effect of two adjacent bubbles with non-equal initial phospholipid states. The results presented here have important implications in ultrasound contrast agent applications.

Non-Destructive Testing Using Transmission Line-Based Microwave Sensors

In this study, some types of antennas and metamaterial structures have been designed and produced with the aim of determining and detecting ionized chlorine of sea sand in concrete. The first structure has a Loop-like resonator with the sample, the second structure has a Bowtie-shaped resonator with the sample and the third structure has double loop resonators on both sides of concrete samples also non-destructive method is applied for all structures. Different samples of concrete are produced with different proportions of ionized sea sand. Electrical properties of concrete samples for all structures are investigated in the frequency range of 1-9 GHz. The structures are designed in the CST Microwave Studio program. Also, the simulation study of the designed structures shows that the most important resonance frequency changes, considering the dielectric constant of concrete samples, for the Loop-like structure occur in the 1-8 GHz, Bowtie-shaped structure in 1-4 GHz and double Loop structure in 1-9 GHz of frequency band. The important point in this study is the changes of the waveform at the resonance frequency. The output waveform (reflection coefficient S11/ transmission coefficient S12) should change in linear form by considering the dielectric coefficient. We have used copper for the resonators and also the material with ℇ value of 3 as the substrate layers of the structures. We have simulated three types of designed structures with CST Microwave Software and then achieve the results and evaluate them. Both numerical and experimental tests have given approximately same results and are in good agreement with each other. These proposed structures can be used in many applications where it is necessary to determine the rate of ionized sea sand in cement-based composites such as concrete.

Self-induced back-action for aperture trapping: Bethe-Rayleigh theory.

A dielectric (nano)particle can influence the local electromagnetic field and thereby alter its interaction with that field through the process of self-induced back-action. While this phenomenon is usually considered theoretically as a change in a cavity resonance frequency, such theoretical approaches are not as appropriate when considering systems away from resonance, such as with a subwavelength aperture in a metal film. Here we consider the interaction between an aperture, modelled with Bethe theory as a magnetic dipole, and a Rayleigh particle, modelled as an electric dipole. Using this magnetic dipole - electric dipole interaction, we quantify the self-induced back-action of the particle on the aperture transmission and the optical trapping potential. The model shows quantitative agreement with finite-difference time-domain simulations. This shows that the physics of self-induced back-action for an aperture and a nanoparticle can be understood in terms of dipole-dipole coupling.

Reconstructing Late Quaternary Paleovalley Systems of Italy Through mHVSR: A Tool for Seismic Hazard Assessment in Modern Coastal Lowlands

AbstractEffective site characterization in highly urbanized coastal lowlands requires accurate stratigraphic and geophysical investigations. In these regions, which typically host shallowly buried paleovalley systems formed in response to Quaternary glacio‐eustatic fluctuations, the marked lithologic contrast between soft sediment paleovalley fills and the adjacent, stiff substrate has the potential to modify earthquake motions, and assessment of critical parameters, such as shear wave velocities (VS) and resonance frequencies (f), should be coupled with detailed stratigraphic architecture. To evaluate the potential of the microtremor horizontal‐to‐vertical spectral ratio (mHVSR) for paleovalley recognition and mapping, we performed mHVSR measurements along the Adriatic coastal plain of Italy, where two paleovalley systems (Pescara and Manfredonia) have been recently identified. In both areas, we detected rapid lateral variations in resonance frequencies and highlighted laterally continuous impedance contrasts. Relying on a robust stratigraphic framework, we carefully evaluated the relation between geological and geophysical data and identified the stratigraphic surfaces responsible for the observed resonances. We derived VS models for the sediment fill, reconstructing the geometry of the two buried paleovalleys. We address the importance of evaluating the geological context when designing microzonation studies, for a reliable interpretation of changes in resonance frequencies.

Investigation and hybrid deep belief neural network-based validation of piezoelectric bimorph cantilever composites assisted with tip mass

This work fabricated the piezoelectrical material using PMMA (polymethyl methacrylate) and Ce-doped ZnO nano-powders. The study was conducted to validate the piezoelectric performance of the proposed material and its suitability for the cantilever structure. The PMMA/Ce-ZnO makes the cantilever structure more flexible and performs better. The frequency response is applied to the beam using an electrical circuit to analyze the power and voltage output. The acceleration is given to the cantilever beams to analyze their resonant frequencies. The change in resonant frequencies results in a high voltage and power output. The resistive loads are used in the circuit to find the electrical load. The frequency response is analyzed in three different inner (18 mm, 20 mm, 22 mm) and outer (23 mm, 25mm, 27 mm) active layer lengths of beams. As a result, the maximum voltage of 21.94 V with 13.67 mW power and 2.9 mA current is obtained at a resonant frequency of 51.06 Hz and 1 g acceleration amplitude, which are approximately 42%, 45% and 15% higher voltage, power and current obtained from the lowest performer of proposed piezoelectric cantilevers. The experiment results are validated using the hybrid DBN-SSO (Deep Belief Network based Salp Swarm Optimization) machine learning technique. The proposed DBN-SSO achieved 0.9998 and 0.9966 regression coefficients for voltage and power outputs, thus proving the fitness of predicted results with the experiments. As per findings, a 27 mm inner and 18 mm outer active layer based energy harvesting system is suggested as a suitable energy source where ever 10-12 mW power, 2.5-2.9 mA current and 20-21.94 V voltage are applicable.

Detection of quenching cracks in 100Cr6 bearing steel by the eddy current method


 The article describes the research results in the identification and location of hardening cracks in 100Cr6 bearing steel using a proprietary control and measurement device for non-destructive testing using the eddy current method, Wirotest M2, and the automatic AutoWir-S1 station. A contact head with a frequency of 861 kHz was used for testing. The system recorded changes in voltage amplitude and resonance frequency. A clear decrease in the values of both parameters indicated the presence of discontinuities. The edge effect caused an increase in the voltage amplitude and a decrease in frequency, but these changes did not affect the detection of cracks. The smallest crack detected had a maximum width of approximately 20 µm and was invisible to the naked eye. The obtained surface charts clearly illustrate the course and location of individual discontinuities.

Metal Microelectromechanical Resonator Exhibiting Fast Human Activity Detection.

This work presents a MEMS resonator used as an ultra-high resolution water vapor sensor (humidity sensing) to detect human activity through finger movement as a demonstrator example. This microelectromechanical resonator is designed as a clamped-clamped beam fabricated using the top metal layer of a commercial CMOS technology (0.35 μm CMOS-AMS) and monolithically integrated with conditioning and readout circuitry. Sensing is performed through the resonance frequency change due to the addition of water onto the clamped-clamped beam coming from the moisture created by the evaporation of water in the human body. The sensitivity and high-speed response to the addition of water onto the metal bridge, as well as the quick dewetting of the surface, make it suitable for low-power human activity sensing.

Coevolution of Rock Slope Instability Damage and Resonance Frequencies From Distinct‐Element Modeling

AbstractAmbient vibration measurements can detect resonance frequency changes related to rock slope instability damage or boundary condition changes during progressive failure. However, the impact of slope kinematics on resonance changes and the expected form and sensitivity of frequency evolution during destabilization require clarification to improve the implementation of this technique across diverse settings. Since instrumented rock slope failures are rare, numerical modeling is needed to study the anticipated spectral response from in situ monitoring. We used 2D distinct‐element modeling to evaluate the sensitivity and evolution of rock slope resonance behavior for slab toppling, flexural toppling, and planar sliding instabilities during progressive failure. Model simulations revealed that fundamental resonance frequency decreases between 20% and 60% with changes correlated with increasing length of open joints. Changes to higher‐order frequencies associated with landslide sub‐volumes were also detectable for cases with multiple fracture networks. Resonance behavior was most pronounced for failures dominated by steeply dipping open tension cracks, that is, flexural and slab toppling. Additionally, amplification patterns across the slope varied for the flexural toppling and sliding cases, providing potential new information with which to characterize landslide failure mechanisms using ambient vibration array measurements. Our results demonstrate landslide characteristics well‐suited for in situ ambient resonance monitoring and provide new data describing the anticipated changes in resonance frequencies during progressive rock slope failure.

Solvent-Free Nuclear Magnetic Resonance Spectroscopy of Charged Molecules.

Nuclear magnetic resonance (NMR) spectroscopy of small molecules protonated in a solvent-free environment was successfully demonstrated. The method is referred to as solvent-free protonation NMR (SoF-NMR). Leveraging matrix-assisted ionization (MAI), we generated protonated species of aniline, 4-chloroaniline, 4-aminobiphenyl, and benzocaine for NMR analysis under mild pressure and temperature conditions. The SoF-NMR spectra were compared to traditional solution NMR spectra, and the shift changes in nuclear spin resonance frequencies verify that these small molecules are protonated by 3-nitrobenzonitrile (3-NBN). As the sample pressure decreased, new spectral features appeared, indicating the presence of differently charged species. Several advantages of SoF-NMR are highlighted, such as the elimination of H/D exchange in labile protons, resulting in the precise observation of protons that are otherwise transient in solution. Notably, the data on benzocaine show evidence of neutral, N-protonated, and O-protonated species all in the same spectrum. SoF-NMR eliminates the solvent effects and interactions that can hinder important spectral features. Optimizing SoF-NMR will result in more cost-effective and efficient NMR experimentation to monitor high-temperature, solvent-free reactions. SoF-NMR has a viable future application for studying exchangeable protons, intermediates, and products in gas-phase chemistry.

The influence of photothermal effect on the resonance frequency of fused silica micro hemispherical resonator

Micro-electro mechanical system resonant gyroscope plays a more and more important role in inertial navigation. As a core sensing component of micro resonant gyroscope, fused silica micro hemispherical resonator (FS-MHR) is widely concerned because of its great performance potential. The resonance frequency is one of the important characteristic parameters of micro resonators, and laser vibration measurement technology is often used for high-precision measurement of this parameter. During the measurement process, it is inevitably affected by the interference of some light sources. To explore how light affects the resonance characteristics of FS-MHR, this paper establishes a relevant theoretical model; and verifies and analyzes the influence of the photothermal effect on the resonance characteristics of FS-MHR through simulation and experiment. Revealed the trend of temperature and resonance frequency changes over time under the same lighting conditions for uncoated and metal-coated films. The measured data shows that the resonance frequency of FS-MHR coated with the metal film is more susceptible to the influence of the photothermal effect. After 60 s of illumination, the resonance frequency will increase by 6.13 Hz, and frequency splitting will also cause a deviation fluctuation of 2.35 Hz under continuous illumination. This will introduce certain errors in the measurement results, and corresponding measures need to be taken to avoid interference from the light source.

Expansivity of Fused Quartz Glass Measured with 6 x 10-10/K

Thermal expansion sometimes dominates uncertainty in a precision measurement. A cell-based refractometer has been designed at NIST which targets 10−6 relative uncertainty in the measurement of helium refractivity; in terms of absolute refractive index at ambient conditions, the accuracy goal is 3 × 10−11. To achieve this level of accuracy, the length of a 0.5 m gas cell would need to be known within 100 nm. This is achievable when cell length is measured by coordinate-measuring machine at 20 °C. However, the refractometer will operate at the thermodynamically known fixed-points of water and gallium, near 0 °C and 30 °C, respectively. The cell is made from fused quartz glass, which has a nominal thermal expansion coefficient of 0.4 (μm/m)/K. Therefore, to scale the accuracy of the dimensional metrology across 20 °C to the triple-point of water requires that the thermal expansion coefficient of fused quartz glass is known within 10 (nm/m)/K, or 2.5 %. A method is described to measure the thermal expansion coefficient of fused quartz glass. The measurement principle is to monitor the change in resonance frequency of a Fabry–Perot cavity as its temperature changes; the Fabry–Perot cavity is made from fused quartz glass. The standard uncertainty in the measurement was less than 0.6 (nm/m)/K, or 0.15 %. The limit on performance is arguably uncertainty in the reflection phase-shift temperature dependence, because neither thermooptic nor thermal expansion coefficients of thinfilm coatings are reliably known. However, several other uncertainty contributors are at the same level of magnitude, and so any improvement in performance would entail significant effort. Furthermore, measurements of three different samples revealed that material inhomogeneity leads to differences in the effective thermal expansion coefficient of fused quartz; inhomogeneity in thermal expansion among samples is 24 times larger than the measurement uncertainty in a single sample.

Analysis of HepG2 cell response to a wide concentration range of mitomycin C using a multichannel quartz crystal microbalance system with a microscope

The morphological response of HepG2 cells to mitomycin C was analyzed using a multichannel quartz crystal microbalance system equipped with a home-built movable microscope that enables the simultaneous acquisition of cell images and measurements of eight-channel quartz crystal microbalance. After 24 h of cell seeding, mitomycin C was injected into the culture medium. During the attachment process, the resonant frequency decreased, and the curves fitted well with the first-order lag response. Analysis of the response to mitomycin C revealed that the resonant frequency response curves varied with mitomycin C concentration. When the mitomycin C concentration was <10 μmol L−1, the delay time was observed before the increase in resonant frequency. When the mitomycin C concentration was extremely low, an additional decrease in resonant frequency was observed in the middle of the delay time that fitted well with the cumulative log-normal distribution curve. The resonant frequency response curves after the delay time fitted well with the cumulative log-normal distribution curves. The delay time and mean cumulative log-normal distribution time for the increase in resonant frequency correlated with the mitomycin C concentration; however, the mean time for the additional decrease in the resonant frequency did not show a statistically significant difference as a function of mitomycin C concentration. For mitomycin C concentrations of >20 μmol L−1, the response to the change in resonant frequency was rapid, and the response curves fitted well with the first-order lag response. The first-order lag response indicates that the response occurred simultaneously for all cells. The results showed that the time constant was independent of the tested mitomycin C concentration between 20 and 100 μmol L−1. These results suggested that different cell death processes occurred by mitomycin C. The findings of this study suggest that the system can be used to investigate cell death in adherent cells.

Modeling, design, and optimization of a dielectric elastomer acoustic liner

The modeling, design, and optimization of an embedded dielectric elastomer (DE) membrane acoustic liner is considered. The acoustic impedance of the liner is modified when the DE is subjected to voltage, resulting in a reduction of the in-plane stress. A lumped element model of an embedded dielectric elastomer acoustic liner is derived and validated in a normal incidence impedance tube and is subsequently used to optimize its performance. The optimization cost functions include (1) maximization of the average absorption coefficient over a targeted frequency range, 400 – 1600 Hz and (2) maximization of the change in the liner fundamental resonance frequency when the membrane is activated. Good agreement between measured and predicted absorption is observed. Tuning of the resonant frequency requires a numerical solution for resonance using the imaginary part of the impedance, since a simple analytical expression for resonance cannot be derived due to the complex coupling between the acoustics of the liner and the electro-mechanics of the DE membrane. Nonetheless, resonant frequency shifts predicted with the lumped element model compare favorably to those measured with the activated liner sample, with a shift of 213 Hz.

Electrodeposition of Silver in Cyanide-Free Solution Containing Pyrimidine Derivative as a Complexing Agent

Pyrimidine derivatives, for example, 2,4-pyrimidinedione (uracil), 1-methyluracil and 5-methyluracil (thymine) can bind with metal ions in alkaline solution. 5-methyluracil (thymine) as complexing agent in electroplating solution has not been investigated due to low solubility in water. The aims of this study were to determine the potential of 5-methyluracil (thymine) as complexing agent for cyanide-free silver electroplating solution. The influence of complexing agent and polyethyleneimine on the silver electrodeposition reaction were studied. Several methods which are electrochemical quartz crystal microbalance (EQCM) and electrochemical impedance spectroscopy (EIS) have been used to study the electrochemical behavior of cyanide-free silver electroplating solution. The surface morphology and brightness of silver deposits obtained from each cyanide-free silver electroplating solution were evaluated. A semi-bright deposit was obtained from thymine and uracil-complexing silver solution while matte deposit from 5,5-dimethylhydantoin-complexing silver solution. A bright silver deposit could be obtained in the presence of polyethyleneimine. The reduction current value decreases as the amount of polyethyleneimine added increases due to inhibition effect on the silver electrodeposition reaction. The results of electrochemical quartz crystal microbalance measurement showed that the addition of polyethyleneimine in thymine-complexing silver solution does not significantly affect the resonance frequency change.

Oxygen Partial Pressure Induced Mass Changes in Praseodymia Ceria (PCO) Thin Films Studied by Resonant Nanogravimetry

Oxygen non-stoichiometry, δ, is a well-known phenomenon occurring in metal oxides (e.g., in MO2– δ) that varies with the oxygen partial pressure, p O2, in the material’s surrounding atmosphere. Various properties e.g., the electrical conductivity, changes correspondingly with δ, as utilized in gas sensing applications. However, changes in δ can also be driven electrochemically by pumping oxygen ions into the material of interest through a solid electrolyte such as yttria stabilized zirconia (YSZ). Although the associated mass changes may be low, the associated mechanical strains induced may induce cracks in the brittle oxides or other forms of degradations. The precise knowledge of the correlation of mass change with induced strain is crucial for the development of fuel and electrolysis cells, sensors and other metal oxide based electronic devices. While classical thermogravimetric analysis (TGA) is the obvious choice for bulk samples, its resolution is insufficient for the analysis of mass changes induced in thin films by variations in δ.In this work, a direct characterization method based on resonant nanobalances is utilized for the detection of small mass changes in ceramic thin films due to changes in p O2. These nanobalances consist of piezoelectric high-temperature stable single crystal blanks of the langasite family (langasite, La3Ga5SiO14, LGS or catangasite, Ca3TaGa3Si2O14, CTGS) coated with Pt90Rh10 electrodes and the oxide of interest. In this study, the authors focus on thin-film praseodymia ceria solid solution (PrxCe1–xO2– δ, PCO) as a model system. Thin films of up to 1 µm thickness, and corresponding mass of a few 100 µg, are deposited by pulsed laser deposition on the nanobalance and simultaneously on high-resistivity sapphire substrates equipped with interdigitated Pt electrodes (digit and gap width 100 µm each). The latter serve for the detection of conductivity changes. The expected total mass changes in the PCO films are in the range of several hundred nanograms, well within the sensitivity limits of the nanobalance, that exhibits resolutions on the order of few ten nanograms or a Δδ of approximately 0.01.The resonance frequency of the nanobalances is both mass load and temperature dependent. As the films in this work are characterized at different temperatures in the range from 300 °C to 700 °C, the change of the serial resonance frequency f R can be directly converted to mass changes Δm using the Sauerbrey relation [1,2]:Δm = (A eff / Sm ) Δf R Here, A eff and Sm are the temperature dependent effective resonator area and mass sensitivity of the resonator. At high temperatures, the equilibration times are sufficiently fast to determine the mass change at single p O2 steps after equilibration of the thin PCO films. The kinetics slow down substantially towards lower temperatures. The oxygen exchange rate decreases by slightly one-to-two decades per 100 K [3,4]. Slower kinetics result in correspondingly longer time constants for reaching equilibrium, so that external disturbances during equilibration contribute to diminished resolution.At temperatures below 600 °C, the nanobalance is used in dynamic mode where the oxygen activity within the film is not in equilibrium with the external p O2. The p O2 in the furnace is altered over orders of magnitude from oxygen rich atmosphere to low p O2 atmosphere by mass flow controllers, within several tens of minutes. The attached figure shows an example where the atmosphere is changed from 25 % O2/Ar (p O2 = 0.25 bar) to pure Ar (purity: 99.9999 %; p O2 approximately 10–5 bar) within 15 min. The oxygen non-stoichiometry changes by Δδ = 0.095. The process is reversible as illustrated. During these changes, the resonance frequency change of the nanobalance and the conductivity change of the film are monitored simultaneously. To follow the dynamics of this process, single frequency conductivity relaxation, instead of complete electrochemical impedance spectra, are monitored. As the conductivity dependence on δ for PCO is well known, these data can be used to correlate the dynamic mass change with the effective oxygen activity in the PCO thin films.[1] Sauerbrey: Zeitschrift für Physik, 155, 206–222 (1959) [2] Fritze: Measurement Science and Technology, 22, 012002–012030 (2011) [3] Schaube et al.: Journal of Materials Chemistry A, 7, 21854-21866 (2019) [4] Nicollet et al.: Nature Catalysis, 3, 913–920 (2020) Figure 1

P-Tau Dephosphorylation Measurement on the Basis of Biomimetic Electrochemical-Polymerized Thin Film Modified Eqcm

Alzheimer’s disease (AD) is characterized by the abnormal protein deposit in the brain, as a most general neurodegenerative disorder in senior. Microtubule-associated tau protein was regarded as a critical biomarker for AD in recent years due to its post-translational modification, especially hyper-phosphorylated tau protein, which would render the protein aggregation and result in neuron degeneration and paired helical filaments (PHF) formation [1]. Unbalanced activities between kinase and phosphatase are the main reason of tau protein hyper-phosphorylation, including overexpression of kinase. Research has recorded that kinases inhibitor would reverse the hyper-phosphorylation induced pathology, showing the possible therapeutic strategy with adjusting the amount of phosphorylated sites. However, this indirect method is insufficient to reverse the neurofibrillary tangle and PHF aggregation [2]. A highly effective method of reversing hyper-phosphorylation need to be investigated. Furthermore, to control the phosphorylation of tau protein, a material with good interaction with biomolecules is required.In this study, polyaniline (PANI), as one of organic conducting polymers [3], was selected due to its fascinating properties and unparalleled multifunction, including good interaction with proteins, controllable electrical conductivity, ideal stability during electrochemical reactions, and changeable nanostructures, could meet above demands and offer further more bio-applications [4]. Through the electrochemical reaction-driven exchange of ions during oxidation and reduction, PANI mimics change in functional biological organs [5] and plays a key role to create a state-of-the-art biomimetic hippocampus.A new in vitro experimental architecture was developed based on electrical quartz crystal microbalance (EQCM). First, tau protein was adsorbed on PANI-modified electrodes by electrostatic interaction to mimic captured process on the hippocampus. Then, both the constant-potential method (current-time curve) and Cyclic Voltammetry (CV) were introduced to investigate the electrochemically-driven dephosphorylation-related process and mechanism following the found optimal potential and stimulation time.As the result, the feasibility of electrochemically-driven dephosphorylation was confirmed. By establishing the relationship between resonant frequency and mass change, this hippocampus-inspired biomimetic polymeric EQCM electrode could detect a trace amount of phosphate and whole protein adsorbed and desorbed to explore the possibility of a non-invasive therapeutic strategy for AD.[1]Alonso, A. D. C., Grundke-Iqbal, I., & Iqbal, K. "Alzheimer's disease hyperphosphorylated tau sequesters normal tau into tangles of filaments and disassembles microtubules," Nature medicine, 2(7), 783-787. (1996).[2]Engel, T., Goñi‐Oliver, P., Lucas, J. J., Avila, J., & Hernández, F., "Chronic lithium administration to FTDP-17 tau and GSK‐3β overexpressing mice prevents tau hyperphosphorylation and neurofibrillary tangle formation, but pre-formed neurofibrillary tangles do not revert," Journal of neurochemistry, 99(6), 1445-1455. (2006).[3]Higgins, M. J., Molino, P. J., Yue, Z., & Wallace, G. G. (2012). Organic conducting polymer–protein interactions. Chemistry of Materials, 24(5), 828-839.[4]Huang, L., Hu, J., Lang, L., Wang, X., Zhang, P., Jing, X., ... & Wei, Y. (2007). Synthesis and characterization of electroactive and biodegradable ABA block copolymer of polylactide and aniline pentamer. Biomaterials, 28(10), 1741-1751.[5] Higgins, M. J., Molino, P. J., Yue, Z., & Wallace, G. G. (2012). Organic conducting polymer–protein interactions. Chemistry of Materials, 24(5), 828-839. Figure 1

Reconfigurable THz metamaterial based on microelectromechanical cantilever switches with a dimpled tip.

We numerically and experimentally proposed a reconfigurable THz metamaterial (MM) by employing microelectromechanical cantilevers into a ladder-shaped MM (LS-MM). A fixed-free cantilever array with a dimpled tip behaved as Ohmic switches to reshape the LS-MM so as to actively regular the transmission response of THz waves. The cantilever tip was designed to be a concave dimple to improve the operational life without sacrificing the mechanical resonant frequency (fmr), and a fmr of 635 kHz was demonstrated. The device actively achieved a 115-GHz change in transmittance resonant frequency and a 1.82-rad difference in transmission phase shift, which can practically benefit advancing THz applications such as fast THz imaging and 6 G communications.