Shear Force Mode Research Articles

In-situ monitoring of signal transduction between skin cells induced by UVB irradiation using scanning electrochemical microscopy

Skin is the first barrier of the immune system, protecting the body from various damages of the external environment, the signal transduction between skin cells plays an important role in skin healing and injury. Scanning electrochemical microscopy (SECM) combined with a Transwell co-culture device has been proposed to in-situ investigate the signal transduction between skin cells with UVB irradiation, in which, keratinocyte HaCaT cells and fibroblast HFF cells were used as signaling cells and signal-receiving cells, respectively. Extracellular ROS and pH, cell membrane permeability and cell height were in-situ monitored by multi-potential step waveform in SECM (SECM-MPSW), potentiometric mode, shear force mode and the probe approach curve (PAC) combined with COMSOL simulation, respectively. The results revealed that UVB irradiation stimulated HaCaT cells to release excess H+, which diffused to HFF cells and increased the ROS release and membrane permeability with unchanged cell height. Therefore, this work provides an effective way to in-situ investigate intercellular signal transduction.

Effect of isothermal aging on the microstructure, shear behavior and hardness of the Sn58Bi/Sn3.0Ag0.5Cu/Cu solder joints

In order to decrease the hardness and brittleness of eutectic Sn58Bi (SnBi) solder joint, Sn3.0Ag0.5Cu (SAC) bulk was added into SnBi/Cu by a two-step soldering process to obtain solder joint with superposition structure. The microstructure, shear behavior and hardness of Sn58Bi/Sn3.0Ag0.5Cu/Cu (SnBi/SAC/Cu) during isothermal aging were investigated in comparison with SnBi/Cu and SAC/Cu solder joints. Experimental results indicated that the addition of SAC bulk affected the formation and growth of the β-Sn dendritic in the SnBi bulk in SnBi/SAC/Cu. The relative area and grain size of β-Sn in the SnBi bulk were enlarged due to the increasing concentration of Sn. The atomic diffusion during aging led to the volume reduction of SAC bulk in the SnBi/SAC/Cu joint. The addition of SAC bulk suppressed the brittleness of SnBi/Cu and transformed its failure mode from brittle failure to brittle-ductile failure after reflow. Such effect was weakened and the shear force and failure mode of SnBi/SAC/Cu joint were similar to those of SnBi/Cu, as the solder joints were aged for 600 h at 80 °C. Furthermore, the addition of SAC bulk significantly decreased the hardness of SnBi/Cu before and after aging.

True Tapping Mode Scanning Near-Field Optical Microscopy with Bent Glass Fiber Probes.

In scanning near-field optical microscopy, the most popular probes are made of sharpened glass fiber attached to a quartz tuning fork (TF) and exploiting the shear force-based feedback. The use of tapping mode feedback could be preferable. Such an approach can be realized, for example, using bent fiber probes. Detailed analysis of fiber vibration modes shows that realization of truly tapping mode of the probe dithering requires an extreme caution. In case of using the second resonance mode, probes vibrate mostly in shear force mode unless the bending radius is rather small (ca. 0.3 mm) and the probe's tip is short. Otherwise, the shear force character of the dithering persists. Probes having these characteristics were prepared by irradiation of a tapered etched glass fiber with a CW CO2 laser. These probes were attached to the TF in double resonance conditions which enables achieving significant quality factor (4000–6000) of the TF + probe system (Cherkun et al., 2006). We also show that, to achieve a truly tapping character, dithering, short, and not exceeding 3 mm lengths of a freestanding part of bent fiber probe beam should also be used in the case of nonresonant excitation.

Vacuum scanning capillary photoemission microscopy

We demonstrate the use of a conical capillary in a scanning probe microscopy for surface analysis. The probe can measure photoemission from a substrate by transmitting photoelectrons along the capillary as a function of probe position. The technique is demonstrated on a model substrate consisting of a gold reflecting layer on a compact disc which has been illuminated by an unfocused laser beam with a wavelength 400nm, from a femtosecond laser with a beam size of 4mm. A quartz capillary with a 2-µm aperture has been used in the experiments. The period of gold microstructure, shown to be 1.6µ, was measured by the conical probe operating in shear force mode. In shear force regime, the dielectric capillary has been used as a “classical” SPM tip, which provided images reflecting the surface topology. In a photoelectron regime photoelectrons passed through hollow tip and entered a detector. The spatial distribution of the recorded photoelectrons consisted of periodic mountain-valley strips, resembling the surface profile of the sample. Submicron spatial resolution has been achieved. This approach paves the way to study pulsed photodesorption of large organic molecular ions with high spatial and element resolution using the combination of a hollow-tip scanner with time-of-flight technique.

Magnetoelectric versus thermal actuation characteristics of shear force AFM probes with piezoresistive detection

In this paper the authors compare methods used for piezoresistive microcantilevers actuation for the atomic force microscopy (AFM) imaging in the dynamic shear force mode. The piezoresistive detection is an attractive technique comparing the optical beam detection of deflection. The principal advantage is that no external alignment of optical source and detector are needed. When the microcantilever is deflected, the stress is transferred into a change of resistivity of piezoresistors. The integration of piezoresistive read-out provides a promising solution in realizing a compact non-contact AFM.Resolution of piezoresistive read-out is limited by three main noise sources: Johnson, 1/f and thermomechanical noise. In the dynamic shear force mode measurement the method used for cantilever actuation will also affect the recorded noise in the piezoresistive detection circuit. This is the result of a crosstalk between an aluminium path (current loop used for actuation) and piezoresistors located near the base of the beam.In this paper authors described an elaborated in ITE (Institute of Electron Technology) technology of fabrication cantilevers with piezoresistive detection of deflection and compared efficiency of two methods used for cantilever actuation.

Hollow-tip scanning photoelectron microscopy

A new type of microscopy based on scanning in vacuum by a beam of charged particles transmitted through a hollow probe has been implemented. This approach provides controllable motion of spatially localized ion, electron, molecular (atomic), and soft X-ray beams and investigation of the surface in the shear force mode. In the photoelectron mode, in which electrons are transmitted through a 2-μm quartz capillary, a surface profile of gadolinium irradiated by 400-nm femtosecond laser pulses has been visualized with a subwave spatial resolution. The new method of microscopy opens an opportunity of investigations in the field of nanometer local photodesorption of molecular ions (one of the last ideas of V.S. Letokhov).

Piezoresistive cantilever working in a shear force mode for in situ characterization of exposed micro- and nanostructures

This paper presents a method of characterization micro- and nanostructures defined in a photolithography process. To implement this method a measurement system composed of an atomic force microscope (AFM) integrated with a system for maskless lithography was developed. This integration enables exposed patterns to be examined in situ, without any necessity for a developing process. The microscope works in a shear force mode, uses a cantilever with a piezoresistive method of detecting deflection and can be used for measuring surfaces with high aspect ratio by applying an appropriate technology of sharpening in a focused ion beam process. The cantilever fabrication process, its calibration and examination procedures are presented. Finally, the AFM images of structures scanned directly after exposure are shown.

Determination of Temperature Gradients with Micrometric Resolution by Local Open Circuit Potential Measurements at a Scanning Microelectrode

AbstractA method to determine localized temperature profiles using a scanning electrochemical microscopy (SECM) setup and potentiometry is presented. A Pt microelectrode was first calibrated to correlate the open circuit potential (OCP) with temperature in an electrolyte containing ferri/ferrocyanide. Using the calibration graph, the temperature at a given position and a time could be derived. For dynamic measurements, the thermal expansion of the surface was initially determined using shear force mode SECM. Following the OCP at the microelectrode static as well as dynamic temperature gradients above the heated surface were successfully probed and visualized with vertical micrometric resolution and with precision in temperature determination below 1 °C.

Calibration technique for scanning near-field optical microscopes for measuring the geometrical parameters of objects in the shear-force mode

The feasibility of using a diffraction grating manufactured by laser photoinduced etching of the (001) surface of single-crystal InP and monatomic steps on a highly-oriented (0001) surface of pyrolytic graphite as reference samples for calibration of scanning near-field microscopes operating in the shear-force (quasifriction) mode is demonstrated.

Sn-58Bi 솔더 페이스트와 ENIG 표면 처리된 기판 접합부의 계면 반응 및 접합강도

Sn-Bi eutectic alloy has been widely used as one of the key solder materials for step soldering at low temperature. The Sn-58Bi solder paste containing chloride flux was adopted to compare with that using the chloride-free flux. The paste was applied on the electroless nickel-immersion gold (ENIG) surface finish by stencil printing, and the reflow process was then performed at <TEX>$170^{\circ}C$</TEX> for 10 min. After reflow, the solder joints were aged at <TEX>$125^{\circ}C$</TEX> for 100, 200, 300, 500 and 1000 h in an oven. The interfacial microstructures were obtained by using scanning electron microscopy (SEM), and the composition of intermetallic compounds (IMCs) was analyzed using energy dispersive spectrometer (EDS). Two different IMC layers, consisting of <TEX>$Ni_3Sn_4$</TEX> and relatively very thin Sn-Bi-Ni-Au were formed at the solder/surface finish interface, and their thickness increased with increasing aging time. The wettability of solder joints was investigated by wetting balance test. The mechanical property of each aging solder joint was evaluated by the ball shear test in accordance with JEDEC standard (JESD22-B117A). The results show that the highest shear force was measured when the aging time was 100 h, and the fracture mode changed from ductile fracture to brittle fracture with increasing aging time. On the other hand, the chloride flux in the solder paste did not affect the shear force and fracture mode of the solder joints.

Application of Tuning Fork Sensors for In-situ Studies of Dynamic Force Interactions Inside Scanning and Transmission Electron Microscopes

Mechanical properties of nanoscale contacts have been probed in-situ by specially developed force sensor based on a quartz tuning fork resonator (TF). Additional control is provided by observation of process in scanning electron microscope (SEM) and transmission electron microscope (TEM). A piezoelectric manipulator allows precise positioning of atomic force microscope (AFM) probe in contact with another electrode and recording of the TF oscillation amplitude and phase while simultaneously visualizing the contact area in electron microscope. Electrostatic control of interaction between the electrodes is demonstrated during observation of the experiment in SEM. In the TEM system the TF sensor operated in shear force mode: Use of TEM allowed for direct control of separation between electrodes. New opportunities for in situ studies of nanomechanical systems using these instruments are discussed. DOI: http://dx.doi.org/10.5755/j01.ms.18.2.1927

Mechanical strength and fracture mode transition of Sn-58Bi epoxy solder joints under high-speed shear test

The shear force and failure behaviors of the Sn-58Bi epoxy solder joints with various surface finishes under the high-speed shear test were investigated. The relationships between the shear speed, shear force, and fracture mode are elucidated in this study. The shear force of the Sn-58Bi solder joints increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloys. Brittle interfacial fractures were more easily achieved at higher shear speed in the high-speed shear test. This result was discussed in terms of the relationship between the strain-rate of the solder alloy, the work-hardening effect, and the resulting stress concentration in the interfacial regions. The fracture mode changed from ductile solder fracture to brittle interfacial fracture with increasing shear speed. On the other hand, the different surface finish materials did not affect the shear force and fracture mode of the Sn-58Bi solder joints under high-speed shear loading.

PASSIVELY DETECTING THERMAL EVANESCENT WAVES FROM ROOM TEMPERATURE OBJECTS

We have developed a scattering-type scanning near-field optical microscope in long-wavelength infrared region (wavelength: λ ~ 14.5 μm) with a highly sensitive detector, named charge sensitive infrared phototransistor. A tungsten near-field probe was fabricated via electrochemical etching and the sample-probe distance was precisely controlled in shear-force mode. By vertically modulating the probe independently of lateral oscillation for shear-force mode, we successfully detected thermal evanescent waves from a 3 μm-pitch Au/GaAs grating without any external illumination. The spatial resolution was experimentally estimated to be better than 150 nm (λ/100) and the signal-to-noise ratio was around 4 with an averaging time of 300 ms. The strong near-field signal from Au was suggested to be ascribed to thermally excited surface plasmons generating evanescent waves at the surface.

A sensitive near-field microscope for thermal radiation

A scattering-type scanning near-field optical microscope in long-wavelength infrared (LWIR) region is developed by using an extremely sensitive detector, called the charge-sensitive infrared phototransistor. A tungsten probe attached to a quartz tuning fork is controlled in shear-force mode. Evanescent wave at a sample surface is periodically scattered by slowly (2 Hz) modulating the probe in the direction normal to the sample surface. Near-field microscopy of thermal LWIR radiation from room-temperature Au/GaAs gratings is demonstrated without using any external illumination or excitation. Achieved spatial resolution is better than 300 nm.

Parameters of tip–sample interactions in shear mode using a quartz tuning fork AFM with controllable Q-factor

A quartz tuning fork-based atomic force microscopy for investigating the tip–sample interactions at the nanoscale in the shear-force mode is described. Results of force interactions (damping and elastic forces) can be obtained from the amplitude-phase-distance spectroscopy measurements made with a tuning fork with a tungsten tip and a sample surface. The influence of the interaction between tip and sample using the quality factor as an indicator is investigated. Furthermore, a simple model shows that the extension of a tuning fork-based AFM can be applied to quantitative analysis of the properties of the sample surface.

Amplitude and frequency modulation torsional resonance mode atomic force microscopy of a mineral surface

Scanning probe imaging in a shear force mode allows for the characterization of in-plane surface properties. In a standard AFM, shear force imaging can be realized by the torsional resonance mode. In order to investigate the imaging conditions on mineral surfaces, a torsional resonance mode atomic force microscope was operated in amplitude (AM) and frequency modulation (FM) feedback. Freshly cleaved chlorite was investigated, which showed brucite-like and talc-like surface areas. In constant amplitude FM mode, a slight variation in energy dissipation was observed between both surfaces. Amplitude and frequency vs. distance curves revealed that the tip was in repulsive contact with the specimen during imaging.

Fabrication of gold tips suitable for tip-enhanced Raman spectroscopy

The authors report on a simple method of fabricating gold tips, suitable for use in a shear-force mode atomic force microscope for tip-enhanced Raman spectroscopy (TERS). The proposed electrochemical method is highly optimized and offers five advantages: produces a low-aspect ratio tip that can withstand the lateral force at the end of the tip during scanning, produces a sharp tip end to generate good Raman enhancements for TERS, a self-terminating process that makes the etching process easy, use of inexpensive electronic systems so that it can be adopted by any laboratory, and less time consuming (takes less than 20s to fabricate a single tip). This article demonstrates TERS imaging using such tips.

X-ray excited optical luminescence detection by scanning near-field optical microscope: A new tool for nanoscience

Investigations of complex nanostructured materials used in modern technologies require special experimental techniques able to provide information on the structure and electronic properties of materials with a spatial resolution down to the nanometer scale. We tried to address these needs through the combination of x-ray absorption spectroscopy (XAS) using synchrotron radiation microbeams with scanning near-field optical microscopy (SNOM) detection of the x-ray excited optical luminescence (XEOL) signal. This new instrumentation offers the possibility to carry out a selective structural analysis of the sample surface with the subwavelength spatial resolution determined by the SNOM probe aperture. In addition, the apex of the optical fiber plays the role of a topographic probe, and chemical and topographic mappings can be simultaneously recorded. Our working XAS-SNOM prototype is based on a quartz tuning-fork head mounted on a high stability nanopositioning system; a coated optical fiber tip, operating as a probe in shear-force mode; a detection system coupled with the microscope head control system; and a dedicated software/hardware setup for synchronization of the XEOL signal detection with the synchrotron beamline acquisition system. We illustrate the possibility to obtain an element-specific contrast and to perform nano-XAS experiments by detecting the Zn K and W L(3) absorption edges in luminescent ZnO and mixed ZnWO(4)-ZnO nanostructured thin films.

Crystal sensor for microscopy applications

We report a force sensor based on a quartz crystal that is used for measuring nanoscale topographic images. The crystal is a length-extensional mode oscillator with a resonant frequency of about 650 kHz. Compared to 33 kHz tuning forks, such crystal sensors have a much higher resonance frequency, which allows for high force sensitivity and a fast response time. The crystal sensor is operated in the shear-force mode, with the probes vibrating parallel to the sample surface. The tip-sample interaction during operation is estimated to be less than 300 pN.

Shear force distance control in a scanning near-field optical microscope: in resonance excitation of the fiber probe versus out of resonance excitation

The experimental results of the direct measurement of the absolute value of interaction force between the fiber probe of a scanning near-field optical microscope (SNOM) operated in shear force mode and a sample, which were performed using combined SNOM-atomic force microscope setup, are discussed for the out-of-resonance fiber probe excitation mode. We demonstrate that the value of the tapping component of the total force for this mode at typical dither amplitudes is of the order of 10 nN and thus is quite comparable with the value of this force for in resonance fiber probe excitation mode. It is also shown that for all modes this force component is essentially smaller than the usually neglected static attraction force, which is of the order of 200 nN. The true contact nature of the tip–sample interaction during the out of resonance mode is proven. From this, we conclude that such a detection mode is very promising for operation in liquids, where other modes encounter great difficulties.