Evolution Of Resonance Frequency Research Articles

Multimodal real-time frequency tracking of cantilever arrays in liquid environment for biodetection: Comprehensive setup and performance analysis.

We present a nanomechanical platform for real-time quantitative label-free detection of target biomolecules in a liquid environment with mass sensitivity down to few pg. Newly fabricated arrays of up to 18 cantilevers are integrated in a micromachined fluidic chamber, connected to software-controlled fluidic pumps for automated sample injections. We discuss two functionalization approaches to independently sensitize the interface of different cantilevers. A custom piezo-stack actuator and optical readout system enable the measurement of resonance frequencies up to 2MHz. We implement a new measurement strategy based on a phase-locked loop (PLL), built via in-house developed software. The PLL allows us to track, within the same experiment, the evolution of resonance frequency over time of up to four modes for all the cantilevers in the array. With respect to the previous measurement technique, based on standard frequency sweep, the PLL enhances the estimated detection limit of the device by a factor of 7 (down to 2pg in 5min integration time) and the time resolution by more than threefold (below 15s), being on par with commercial gold-standard techniques. The detection limit and noise of the new setup are investigated via Allan deviation and standard deviation analysis, considering different resonance modes and interface chemistries. As a proof-of-concept, we show the immobilization and label-free in situ detection of live bacterial cells (E. coli), demonstrating qualitative and quantitative agreement in the mechanical response of three different resonance modes.

Annealing influence on the exchange stiffness constant of Permalloy films with stripe domains

An investigation of the annealing influence on the stripe domains structure in Permalloy films has been performed by comparing the static and dynamic magnetic properties. An increasing exchange stiffness constant Aex is found when the annealing temperature rises. The magnetic force microscopy images show that the width of stripe domain increases with the increase of annealing temperature, and the increasing exchange stiffness constant is considered to be the most prominent reason. A perpendicular standing spin-wave model is used to deduce the Aex from the evolution of resonance frequencies, and the Aex increases nearly twice from 7.2 × 10−7 ergs cm−1 for the as-deposited film to 12.9 × 10−7 ergs cm−1 for the film annealing at 400 °C. Micromagnetic calculation is also used to compute the magnetization configuration, and the results agree well with the experimental conclusions.

Formation of continuous metallic film on quartz studied by noncontact resonant ultrasound spectroscopy

Dynamics of continuous film formation of metallic films on quartz substrates is studied using an electrodeless resonance method. Bare quartz is used as a substrate, and a metallic film is deposited on it. We use antenna transmission technique to measure the evolution of resonance frequencies and internal friction of the substrate during and after deposition, and the morphological transition between discontinuous islands and a continuous film is detected. By comparison with atomic force microscopy images, we confirm that the frequency drop and the internal-friction peak that appear during deposition indicate this transition. We also find that Pt film shows unexpected morphology change after deposition.

Double-absorption ferromagnetic resonance in biphase magnetic microwires

We report a ferromagnetic resonance study of biphase magnetic microwires consisting of soft amorphous nucleus, intermediate nonmagnetic layers, and harder outer crystalline shell. Real and imaginary impedance components are investigated under increasing static axial magnetic field with a network analyzer in the microwave frequency range for selected microwires with different soft nuclei. Natural ferromagnetic resonance is even observed for particular microwires with strong axial anisotropy. The presence of a hard phase induces a second absorption peak at frequencies lower than those of the soft phase. Moreover, magnetic anisotropy of different soft phases is deduced from the evolution of resonance frequency with applied field.

Rapid multidimensional data acquisition in scanning probe microscopy applied to local polarization dynamics and voltage dependent contact mechanics

A rapid multidimensional spectroscopic imaging approach in scanning probe microscopy is developed and applied to piezoresponse force spectroscopy. Evolution of resonance frequency, dissipation, and piezoresponse signal at each point during acquisition of local hysteresis loops provides information on polarization dynamics and voltage dependent contact mechanics of ferroelectric surfaces. The measurements illustrate significant frequency shifts during piezoresponse force spectroscopy, necessitating the use of frequency-tracking methods. The method is universal and can be extended to other scanning probe microscopy techniques.

Elastometric sensing using higher flexural eigenmodes of microcantilevers

We present a method to detect with high sensitivity the viscoelastic property changes of sensor coatings on microcantilever arrays due to radiation, analyte binding, or adsorption. The method uses higher order flexural eigenmodes to identify the location and magnitude of the nonuniform elasticity changes in the microcantilever coating. We demonstrate the method by monitoring the time evolution of resonance frequencies and Q factors of different flexural eigenmodes of microcantilevers functionalized with a small drop of a photosensitive polymer as it is exposed to ultraviolet radiation. The method is particularly well suited for measuring quantitatively the time varying viscoelastic properties of thin films or biological materials attached to microcantilevers.

Direct measurement of permeability up to 3 GHz of Co-based alloys under tensile stress

The high frequency permeability of CoNbZr and CoZrMoNi prepared by magnetron sputtering, and of CoFeSiB deposited by ion beam sputtering was investigated. The layers were deposited on thin (8–12 μm) mylar films, and it was therefore possible to induce large tensile stress with moderate force. The permeability of the layers was measured along the stress direction, in a frequency range that allowed the observation of the rotational permeability and the gyromagnetic resonance. The resonance frequency of CoNbZr shifted from 1.4 to over 3 GHz under stress. A simple model assuming that the easy axis is constant over the whole film predicts the evolution of resonance frequency and initial permeability. This model is in good agreement with measurements on CoZrMoNi, and yields a satisfactory estimation of the magnetostriction coefficient. In the case of CoNbZr, a poorer agreement is attributed to the dispersion of local magnetization direction. For very large stress, cracks in the ferromagnetic films are expected to participate to the increase in the anisotropy field. It was observed that the linewidth of the resonance is slightly affected by the stress.