Resonance Frequency Of Probe Research Articles

Spatial Correlation between Fluctuating and Static Fields over Metal and Dielectric Substrates.

We report spatially resolved measurements of static and fluctuating electric fields over conductive (Au) and nonconductive (SiO_{2}) surfaces. Using an ultrasensitive "nanoladder" cantilever probe to scan over these surfaces at distances of a few tens of nanometers, we record changes in the probe resonance frequency and damping that we associate with static and fluctuating fields, respectively. We find static and fluctuating fields to be spatially correlated. Furthermore, the fields are of similar magnitude for the two materials. We quantitatively describe the observed effects on the basis of trapped surface charges and dielectric fluctuations in an adsorbate layer. Our results are consistent with organic adsorbates significantly contributing to surface dissipation that affects nanomechanical sensors, trapped ions, superconducting resonators, and color centers in diamond.

Dynamic pressure probe response tests for robust measurements in periodic flows close to probe resonating frequency

A single-hole probe was designed to measure steady and periodic flows with high fluctuation amplitudes and with minimal flow intrusion. Because of its high aspect ratio, estimations showed that the probe resonates at a frequency two orders of magnitude lower than the fast response sensor cut-off frequencies. The high fluctuation amplitudes cause a non-linear behavior of the probe and available models are neither adequate for a quantitative estimation of the resonating frequencies nor for predicting the system damping. Instead, a non-linear data correction procedure based on individual transfer functions defined for each harmonic contribution is introduced for pneumatic probes that allows to extend their operating range beyond the resonating frequencies and linear dynamics. This data correction procedure was assessed on a miniature single-hole probe of 0.35 mm inner diameter which was designed to measure flow speed and direction. For the reliable use of such a probe in periodic flows, its frequency response was reproduced with a siren disk, which allows exciting the probe up to 10 kHz with peak-to-peak amplitudes ranging between 20%–170% of the absolute mean pressure. The effect of the probe interior design on the phase lag and amplitude distortion in periodic flow measurements was investigated on probes with similar inner diameters and different lengths or similar aspect ratios (L/D) and different total interior volumes. The results suggest that while the tube length consistently sets the resonance frequency, the internal total volume affects the non-linear dynamic response in terms of varying gain functions. A detailed analysis of the introduced calibration methodology shows that the goodness of the reconstructed data compared to the reference data is above 75% for fundamental frequencies up to twice the probe resonance frequency. The results clearly suggest that the introduced procedure is adequate to capture non-linear pneumatic probe dynamics and to reproduce time-resolved data far above probe resonant frequency.

Influence of laser propagating direction on electromagnetic induced transparency

The influence of laser propagating direction on electromagnetically induced transparency (EIT) in a ladder type three-level thermal atomic system is presented. It is found that when the coupling laser beam co-propagates with the probe one, the EIT window at probe resonant frequency will disappear due to Doppler effect. The broadened two peaks beside of the transparent window overlap together and form the maximum value at the resonant point. While as the two laser beams counter-propagate, the probe absorption presents an interesting property, especially when the two lasers are with the same wavelength, we can get a broadened Doppler absorptive profile and a narrowed EIT window. The width of the EIT window decreases with the increase of temperature. But if the wavelengths of the two lasers are different, the EIT window at resonant point will be instead by a broadened dip. This dip will disappear gradually with the increase of the wavelength difference. Thus at thermal environment, when we perform the investigation associated with EIT, we ought to not only let two laser beams counter-propagate, but also select an atomic system owns a cascade equal energy interval as far as possible.

Development of a Metallic Photonic Bandgap-Inspired Probe for Detection of Weak Basic Dissociation Constant Drug in Bio-Fluid

The detection of a drug having a weak basic dissociation constant (pKa) in bio-fluids requires a complex organic framework, time-consuming assay, and costly characterization techniques. To overcome this, a novel metallic photonic bandgap-inspired probe that as a sensor device is proposed for the microwave spectroscopy of gold nanoparticles. Minoxidil drug with dissociation constant 4.61 was detected using gold nanoparticles as a colorimetric probe and the sensor device as a microwave signal detection probe. In this method, the aggregation of gold nanoparticles is induced with the drug and then shift in the probe resonant frequency through in situ analysis was calibrated. The induced aggregation between gold nanoparticles and the drug was confirmed by dynamic light scattering and Fourier transform infrared measurements. This method was tested and validated in human urine samples, which provided an acceptable linear relationship between the resonant frequencies over 100–500 and 0.1– $10~\mu \text{M}$ concentration of the drug. The present analytical technique can be effectively used for detecting drugs having low pKa value in the real biological samples.

Approaches to designing micro‐solenoidal RF probes for 14 T MRI studies of millimeter‐range sized objects

AbstractFull‐wave electromagnetic simulations have been employed to analyze the design approaches that allow for solving the problems preventing inductive performance of micro‐solenoidal RF probes and formation of strong and homogeneous magnetic fields inside probes at the studies of millimeter‐range sized objects in 14 T MRI scanners. In particular, the effects of non‐uniform coil wrapping on field homogeneity inside extended coils and of partitioning the coils by dielectric separators on coil self‐resonances have been investigated. The possibility to utilize tunable C‐C matching circuits with the coils and to mitigate the effects of sample insertion on the probe resonance frequency has been demonstrated. Challenges of coil fabrication have been also addressed.

Apertureless scanning microscope probe as a detector of semiconductor laser emission

An operating semiconductor laser has been studied using a scanning probe microscope. A shift of the resonance frequency of probe that is due to its heating by laser radiation has been analyzed. The observed shift is proportional to the absorbed radiation and can be used to measure the laser near field or its output power. A periodical dependence of the measured signal has been observed as a function of distance between the probe and the surface of the laser due to the interference of the outgoing and cantilever-reflected waves. Due to the multiple reflections resulting in the interference, the light absorption by the probe cantilever is greatly enhanced compared with a single pass case. Interaction of infrared emission of a diode laser with different probes has been studied.

Bidirectional quantitative force gradient microscopy

Dynamic operation modes of scanning force microscopy based on probe resonance frequency detection are very successful methods to study force-related properties of surfaces with high spatial resolution. There are well-recognized approaches to measure vertical force components as well as setups sensitive to lateral force components. Here, we report on a concept of bidirectional force gradient microscopy that enables a direct, fast, and quantitative real space mapping of force component derivatives in both the perpendicular and a lateral direction. It relies solely on multiple-mode flexural cantilever oscillations related to vertical probe excitation and vertical deflection sensing. Exploring this concept we present a cantilever-based sensor setup and corresponding quantitative measurements employing magnetostatic interactions with emphasis on the calculation of mode-dependent spring constants that are the foundation of quantitative force gradient studies.

Release control of drug-encapsulated liposomes by piezoelectric ultrasonic probe

Liposomes as a drug delivery system have been an attracting interest to many researchers. This paper concerns with the study on how to control the release rate of the inner-substances from liposomes by the ultrasonic irradiation. Two kinds of ultrasonic control methods are tested for investigation of the efficiency of the release property of the liposomes. One control method is to increase the input power by fixing its frequency at a frequency near the probe resonant frequencies. Another method is to adjust the input frequency around the probe resonant frequencies but fixing the input power. In the experiments, three kinds of liposomes with different lipid ratio were prepared and calcein as an indicator was enclosed into the liposomes. The release effect was evaluated from the fluorescence intensity changes which was measured by a spectrofluorometer. The results showed that the efficient release property could be achieved both by control of the input power and the input frequency, but adjusting the input frequency around the probe resonant frequency can get higher efficient release performance than that controlled by the input power.

Quantitative model for near-field scanning microwave microscopy: Application to metrology of thin film dielectrics

We have experimentally verified a recently proposed theoretical model for near-field microwave microscopy of multilayer media. The model addresses a near-field microwave probe as an electrically small antenna with a Gaussian-like current distribution that has a single characteristic length scale on the order of the probe size. Electrodynamic response of an antenna is calculated using Green functions in the form of integral transforms for electric and magnetic fields (both quasistatic and propagating), which are generated by a pointlike dipole. Experimental data were obtained at 4 GHz using a near-field scanning microwave microscope with aperture size of approximately 5 microm for a set of six SiO(2) films with thickness ranging from 0.1 to 1.5 microm. For each sample the probe resonant frequency was both measured and simulated as a function of the tip-sample distance, and good agreement between the theory and experimental data was observed. It was found that the model is capable of determining thin film dielectric constant with accuracy of approximately 5%-7%.

An alternative tuning approach to enhance NMR signals

By using spin-noise type measurement we show that the resonance frequency of the reception circuit of classical NMR spectrometers does not match the Larmor frequency even if, in emission, the electronic circuit is perfectly tuned at the Larmor frequency and matches the amplifier impedance. We also show that this spin-noise method can be used to ensure a match between the Larmor frequency and the reception circuit resonance frequency. In these conditions, (i) the radiation damping field is in perfect quadrature to the magnetization and (ii) the NMR signal level and potentially the signal-to-noise ratio, are enhanced. This choice induces a change of the probe resonance frequency by several hundreds of kHz for 500 or 700 MHz spectrometer. We show that the resulting mismatch condition for emission can be removed by adding other tuning and matching degrees of freedom located on the excitation line (or by symmetry on the reception line) decoupled to the probe resonance circuit by the crossed diodes.

Determination of the glass transition temperature of latex films: Comparison of various methods

The glass transition temperature ( T g) for two latices with different styrene/butadiene compositions was determined by the thermal SPM probe resonance frequency method. The results were compared with the T g values obtained by differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), process rheometer (PR) and thermo-mechanical analyzer (TMA) measurements. The T g values detected by the thermal SPM method agreed well with the T g values obtained by DSC and calculated by the Fox–Flory equation. DMA, on the other hand, showed a significantly higher T g value for both latices than those obtained from theoretical calculations, the thermal SPM method and DSC. The T g obtained from the PR curve was slightly higher for the latex with a low styrene content, whereas good agreement was obtained with the thermal SPM data for the latex with a high styrene content. The glass transition temperature determined by TMA agreed fairly well with the thermal SPM data for the latex with the low styrene content, whilst the value of T g for the second latex was much less than those obtained by the other methods. The thermal SPM method detects changes in thermal behavior (thermal diffusivity, heat capacity) during heating of the latex films rather than changes in the mechanical properties. Information about the sample history could be seen in the thermal SPM curves, which was further associated with the degree of latex film formation, especially when the roughness of the films was taken into consideration.

Thermal analysis and topographical characterization of latex films by scanning probe microscopy

Scanning probe microscopy (SPM) was utilized to study the thermal behavior of latex films dried under different conditions. Using the SPM probe resonance frequency method, the resonance frequency (ω) of the oscillating probe above the sample surface was followed as a function of temperature (T). Two different approaches for detecting thermal transitions were used and compared. In the heating-by-the-sample approach, the SPM probe acts as a thermal sensor detecting the heat dissipated by the heated sample. In the heating-by-the-probe approach, the SPM probe is utilized simultaneously as an actuator and a sensor: the heated probe both dissipates heat and detects the heat reflected from the sample surface. Thermal transitions in the polymer films could be observed in the Δω-T curves. The results were consistent with those observed by differential scanning calorimetry, but also additional information about the characteristics of the transitions was obtained. The heating-by-the-probe method showed higher surface sensitivity and more localized effects than the other approach. Furthermore, the progress of the latex film formation and the effect of the different drying conditions on film topography were studied by SPM imaging and roughness analysis. Skewness and local surface curvature are demonstrated to serve as useful numerical measures with which to distinguish different levels of particle deformation and the formation of a continuous film. Preannealing of the samples at high temperature influenced not only the topography (roughness) but also the characteristics of the thermal transitions.

Resonator-based touch-sensitive probe

Abstract This paper presents a design of a simple low-cost resonator-based touch-sensitive probe. The design exploits the fact that when a stiff element (probe) oscillating near the resonance frequency comes into physical contact with the surface of another body (workpiece), the frequency of vibrational resonance of the probe changes depending on the latter's stiffness. This change can be detected by monitoring the variations in the phase shift between the probe driving force and the resulting strain, which consequently prompts the trigger signal. Standard phase-lock-loop oscillator circuitry is used to adjust the drive frequency to maintain a pre-set phase difference between the input and output signals, thus ensuring that the oscillator remains locked at the probe resonance frequency as contact takes place. A prototype probe has been designed and tested. The probe is excited to resonate at its fundamental frequency by employing piezoelectric drive and pick-up arrangements. The operating frequency of the probe is set at 25.179 kHz (second-mode frequency), which seems to be an adequate choice for excellent static and dynamic characteristics. The shift in the natural frequency as the contact force progresses follows a non-linear trend before it saturates. The maximum frequency shift measured is about 2 kHz, which corresponds to 140 mN contact force in the axial direction, whilst the minimum detectable trigger force is 3.8 mN.