Micro-scale Probe Research Articles

G204 マイクロプローブL2Fによる噴霧の不均一構造の研究(GS-2 キャビテーション・マイクロバブル・数値計算1,一般セッション)

A laser 2-focus velocimeter (L2F) with a micro-scale probe was used for measurements of velocity, size, and vortex scale in diesel sprays. The focal diameter of the laser probe was about 3 μm, and the distance between two foci was 17 μm. The data sampling rate of the L2F system has been increased to 15 MHz. Investigated were diesel fuel sprays injected intermittently into the atmosphere from the injector with a nozzle orifice 0.113 mm in diameter. The injection pressure was set at 40 MPa by using a common rail system. Measurement position was located at 25 mm from the nozzle exit. It was found that the vortex scale estimated by the L2F was close to the one observed by image measurement.

An optical-fiber-scale electro-optic probe for minimally invasive high-frequency field sensing

A sub-millimeter-dimension electro-optic probe that provides enhanced scanning accessibility with significantly less intrusiveness than metal-based or even other dielectric probes during electromagnetic characterization of microwave devices is presented. The quantitative and qualitative relative invasiveness of the probe on the operation of an example antenna device-under-test is explored with respect to previously demonstrated fiber and wafer electro-optic sensors. We also demonstrate that the miniaturized probe, with a diameter of 125 microm, can be used to reconstruct the three orthogonal vector components of near-electric fields without the need for different probe crystals or multiple calibration procedures. Finally, the advantages of the reduced size and invasiveness of the new micro-scale probe are demonstrated through the enhanced resolution of detailed images extracted from planar antennas, as well as the capability of reaching into circuit locations heretofore inaccessible.

Measurement of droplet size distribution in core region of high-speed spray by micro-probe L2F

In order to investigate the distribution of droplet sizes in the core region of diesel fuel spray, instantaneous measurement of droplet sizes was conducted by an advanced laser 2-focus velocimeter (L2F). The micro-scale probe of the L2F is made up of two foci and the distance between them is 36 µm. The tested nozzle had a 0.2 mm diameter single-hole. The measurements of injection pressure, needle lift, and crank angle were synchronized with the measurement by the L2F at the position 10 mm downstream from the nozzle exit. It is clearly shown that the droplet near the spray axis is larger than that in the off-axis region under the needle full lift condition and that the spatial distribution of droplet sizes varies temporally. It is found that the probability density distribution of droplet sizes in the spray core region can be fitted to the Nukiyama-Tanasawa distribution in most injection periods.

In-situ electrical probing of zones of nanoindentation-induced phases of silicon

AbstractPhase transformed zones of silicon have been formed by nanoindentation both at the micro- and nanoscale and electrically probed using an in-situ measurement system. Zones composed of the high pressure crystalline phases (Si-III/Si-XII) have higher conductivity than those of amorphous silicon (a-Si). At the microscale probing laterally across the surface shows that the conductivity varies within the zones composed of the high pressure phases. The sensitivity to the different conductivities of the two phases allows mapping within the zones. Finally, at the nanoscale the conductivity of the high pressure phase zones can be correlated with the position of the pop-out associated with the formation of the phases. The zones have higher conductivity when the pop-out occurs earlier on unloading and we suggest that this is due to the reduction in trace volumes of a-Si formed during the early portion of the unloading cycle.

High-throughput diffusion multiples

A diffusion multiple is an assembly of three or more different metal blocks, in intimate interfacial contact, subjected to high temperature to allow thermal interdiffusion to create solid-solution compositions and intermetallic compounds. Using microscale probes, composition-structure-phase-property relationships can be established with an efficiency orders of magnitude higher than conventional one-composition-at-a-time practice. For structural materials, such relationships include phase diagrams, diffusion coefficients, precipitation kinetics, solution strengthening effects, and precipitation strengthening effects. Many microscale probes can also be used to study several materials phenomena. For instance, microscale thermal conductivity measurements can be used to study order-disordering transformation, site preference in intermetallic compounds, solid-solution effect on conductivity, and compositional point defect propensity. This article will use a few examples to illustrate the capabilities and developmental needs of this approach.

Development of a virtual probe tip with an application to high aspect ratio microscale features

Nondestructive measurement of microscale features remains a challenging metrology problem. For example, to assess a high aspect ratio small hole it is currently common to cut a cross section and measure the features of interest using an atomic force microscope, scanning probe microscope, or scanning electron microscope. Typically, these metrology tools may be suitable for surface finish measurement but often lack the capability for dimensional metrology. The aim of this article is to discuss the development of a high aspect-ratio microscale probe for measurement of microscale features. A 700:1 high aspect ratio probe shank is fabricated with a 7μm diameter, and attached at one end to an oscillator. The oscillator produces a standing wave in the oscillating probe shank as opposed to conventional probes that use a microscale sphere on the end of a comparatively rigid shank. As a result of the standing wave formed in steady state vibration, the free end of the shank generates an amplitude of oscillation greater than the probe shank diameter. Thus, the probe does not require a spherical ball to serve as the contact point and simply uses the contact diameter of the free end of the vibrating shank. This methodology is referred to as a virtual probe tip. The virtual probe tip in conjunction with a nanopositioning scanner is used to measure surface profile measurements over traverse lengths of 130μm. In this article, results from profiles of a 500 nm step height and a ruby sphere of diameter 1 mm are presented. Experiments in this article indicate the ability to repeatedly resolve surface features of less than 5 nm while maintaining bandwidths greater than 1 kHz. Furthermore, adhesion problems often encountered with micrometer scaled probes were not observed during profile measurements with this virtual probe.

Advective velocity and energy dissipation rate in an oscillatory flow

Characterizing the transport processes at the sediment-water interface along sloping boundaries in lakes and reservoirs is of fundamental interest in lake and reservoir water quality management. The turbulent bottom boundary layer (TBBL) along a slope, induced by the breaking of internal waves in a linearly stratified fluid, was investigated through laboratory measurements. Fast response micro-scale conductivity and temperature probes in conjunction with laser-Doppler velocimetry were used to measure the time series of salinity, temperature, and velocity along a sloping boundary. Turbulent energy spectra were computed from the velocity data using a time-dependent advective velocity and Taylor's hypothesis. The energy spectra were used to estimate the energy dissipation rate at different positions in the TBBL. The advective velocity in this near-zero mean shear flow is based on an integral time scale (T(int)). The integral time scale is related to the average frequency of the spectral energy density of the flow velocity. The energy dissipation rate estimated from the variable advective velocity with an averaging time window equal to the integral time scale (T=T(int)) was 43% higher than the energy dissipation rate estimated from a constant advective velocity. The estimated dissipation rates with T=T(int) were comparable to values obtained by curve-fitting a theoretical Batchelor spectrum for the temperature gradient spectra. This study proposes the integral time scale to be used for the oscillatory flows as (a) a time-averaging window to estimate the advective velocity and associated energy dissipation level, and (b) a normalizing parameter in the energy spectrum.

Velocity and size of droplets in dense region of diesel fuel spray on transient needle opening condition

In order to investigate the effect of transient needle opening on early stage of spray behavior, simultaneous measurements of velocity and size of droplet were conducted by a newly developed laser 2-focus velocimeter (L2F). The micro-scale probe of the L2F was consisted of two foci with a distance of 36 µm. The tested nozzle had a single hole with a diameter of 0.2 mm. The measurements of injection pressure, needle lift, and crank angle were synchronized with the spray measurement by the L2F at the position 10 mm downstream from the nozzle exit. It has been clearly shown that the velocity and size of droplet increase with needle valve opening and that the probability density distribution of droplet size can be fitted to the Nukiyama-Tanasawa distribution under the transient needle opening condition.

Probing the Viscoelastic Behavior of Cultured Airway Smooth Muscle Cells with Atomic Force Microscopy: Stiffening Induced by Contractile Agonist

Complex rheology of airway smooth muscle cells and its dynamic response during contractile stimulation involves many molecular processes, foremost of which are actomyosin cross-bridge cycling and actin polymerization. With an atomic force microscope, we tracked the spatial and temporal variations of the viscoelastic properties of cultured airway smooth muscle cells. Elasticity mapping identified stiff structural elements of the cytoskeletal network. Using a precisely positioned microscale probe, picoNewton forces and nanometer level indentation modulations were applied to cell surfaces at frequencies ranging from 0.5 to 100 Hz. The resulting elastic storage modulus ( G′) and dissipative modulus ( G″) increased dramatically, with hysteresivity ( η = G″/ G′) showing a definitive decrease after stimulation with the contractile agonist 5-hydroxytryptamine. Frequency-dependent assays showed weak power-law structural damping behavior and universal scaling in support of the soft-glassy material description of cellular biophysics. Additionally, a high-frequency component of the loss modulus (attributed to cellular Newtonian viscosity) increased fourfold during the contractile process. The complex shear modulus showed a strong sensitivity to the degree of actin polymerization. Inhibitors of myosin light chain kinase activity had little effect on the stiffening response to contractile stimulation. Thus, our measurements appear to be particularly well suited for characterization of dynamic actin rheology during airway smooth muscle contraction.

Mixing phenomena through the heat and salt transports across a density interface in a stratified two-layer system

We have investigated the mixing phenomena in a stratified two-layer fluid system where a layer of fresh water is initially put on top of salty water. When this stabilized system by a salt gradient is heated from below, it becomes unstable by an onset of convection in the lower layer due to the thermal buoyancy effect. Thereafter the heat and salt is ready to diffuse into the upper layer through the adjacent diffusive interface. To examine quantitatively the merging process of the two layers as the destabilizing temperature gradient gets more dominant, we have measured many profiles of temperature and salinity in both layers by using accurate micro-scale measurement probes. Each run of experiment with several different initial concentrations of salt is followed until there appears a sudden overturning into a perfect mixing state. The order of thermal Rayleigh number has been kept as order of 107 around which we have observed uniform temperature and salt profiles in the upper layer without any external mixing force. Since the employed measuring probes shows good reproducibility and very fast response time to the variations of the temperature and salt concentration, the mixing phenomena with the double-diffusive convection has been pursued easily.