Mechanical Microprobe Research Articles

Large Indentation Method to Measure Elasticity of Cell in Robot-Integrated Microfluidic Chip

Robot-integrated microfluidic chip is a promising tool to realize mechanical characterization of a single cell with high throughput and high accuracy. The microfluidic chip used in our system has a pair of mechanical microprobes to measure deformation and reaction force of cells. In our previous studies, we measured the elasticity of cells in this measurement system. However, there were some problems on the measurement method limited in small deformation regions of cell. To avoid these problems, we changed the measurement method to utilize large deformation regions of cell. First, we proposed a differential-type sampling moire method to extend the range of the force or displacement measurement. Second, the mechanical model of the cell was improved to express the deformation characteristics up to large deformation region. The deformation model was derived from high-molecular theory. Therefore, the measured elasticity was related to the intracellular filament network. As a result, we accomplished in measuring the elasticity of the cells using the experimental data in a large deformation region. This study provided us with a more practical and reliable method to measure cellular elasticity.

Nanosensitive Silicon Microprobes for Mechanical Detection and Measurements

Nanosensitive mechanical microprobes with CMOS transistors, inverters, inverters cascades and ring oscillators, integrated on the thin silicon cantilevers are presented. Mechanical stress shifts linear, steep switching fragment of the inverters’ electrical characteristics. Microprobes were fabricated with use of the standard CMOS technology (3.5 μm design rules, one level polysilicon gate and one level of the metal interconnections) and relief MEMS technique. Control of the silicon cantilever thickness was satisfactory in the range above the few micrometers. Several computer simulations were done to analyze and optimize transistors location on the cantilever, in respect to the mechanical stress distribution. Results of the microprobes electromechanical tests confirm high deflection sensitivity 1.2 - 1.8 mV/nm and force sensitivity 2.0 - 2.4 mV/nN, both in nano ranges. Microprobes, with the ring oscillators revealed sensitivities 5 - 8 Hz/nm. These microprobes seem to be appropriate for applications in precise chemical and biochemical sensing.

Interfacial properties of sapphire/epoxy composites: Comparison of fluorescence spectroscopy and fiber push-in techniques

Experiments and analyses leading to the assessment of interfacial sliding friction and residual stresses in sapphire filament reinforced epoxy matrix composite by two different techniques are described in this paper. The first technique was based on measurements of stresses in filaments bridging a steady-state matrix crack using a laser microprobe to stimulate fluorescence from the sapphire filaments. The measured stress variation was consistent with un-bonded, frictionally constrained filaments with a constant friction stress along the sliding zone length. The second technique involved measurements of load–displacement records in filament push-in tests using a mechanical microprobe. The sliding friction stress and the residual stress in the filaments assessed by the two techniques were essentially identical. Analyses of the experimental results with different theoretical models indicated that the assessed values of the sliding friction stress and the residual stresses were not affected significantly by accounting for the mismatch in the Poisson’s ratios of the filaments and the matrix and taking into account the elastic anisotropy of the filaments.

Elastoplastic Indentation on Heat‐Treated Carbons

A Vickers indenter, as an efficient mechanical microprobe, was applied to carbon materials heat‐treated at temperatures in the range 880°–2600°C. The plasticity of the carbon materials, which was enhanced by increasing the heat‐treatment temperature (HTT), was assessed from the relation between the indentation load, P, and the penetration depth, h. Using the concept of the true hardness, H, as a measure of plasticity and the experimental estimate of the H‐value, the plasticity of the carbon materials was examined as a function of their crystallographic parameters. The residual impression of the carbons at HTT > 1800°C was hardly visible on the indented surface after unloading, because of the nearly complete elastic recovery of the indented surface, yielding a very unique indentation P–h hysteresis in the loading/unloading cycle. The microscopic processes associated with this unique elastic recovery during unloading are discussed here in relation to the reversible slip of the dislocation‐network structures on the graphitic basal planes.

Microprobe-type measurement of Young's modulus and Poisson coefficient by means of depth sensing indentation and acoustic microscopy

Nano-indentation and hyper frequency scanning acoustic microscopy (SAM) are mechanical microprobe techniques allowing measurement of the near-surface elastic response. In the first case, the composite modulus E/(1−ν 2) can be assessed using the slope of the elastic unloading plot. The second technique allows measurement of Rayleigh wave velocity, which depends on Young's modulus, Poisson ratio and density, to be measured through material acoustic signature. In both cases only one of the elastic constants may be determined using a hypothesis on the other one (usually on the Poisson coefficient). In the present paper we show that by joining both techniques for the same specimens, E and ν can be deconvoluted. Effectiveness of this deconvolution method is first tested on two well-known materials. Results on fused silica ( E=72.9 GPa; ν=0.17) as well as bulk aluminium ( E=69.6 GPa; ν=0.33) are in very good agreement with values commonly found in the literature. The method is finally applied on AlCuFe alloys presenting similar compositions but with different phases (icosahedral, tetragonal and cubic). This study shows the importance of crystallographic structure on elastic behaviour, especially on the Poisson ratio which ranges from ν=0.39 for the icosahedral phase down to ν=0.12 for the tetragonal phase.

Structure and properties of ion-beam-modified (6H) silicon carbide

The ion-beam-induced crystalline-to-amorphous phase transition in single crystal ( 6 H) α -SiC has been studied as a function of irradiation temperature. The evolution of the amorphous state has been followed in situ by transmission electron microscopy in specimens irradiated with 0.8 MeV Ne + , 1.0 MeV Ar + , and 1.5 MeV Xe + ions over the temperature range from 20 to 475 K. The threshold displacement dose for complete amorphization in α -SiC at 20 K is 0.30 dpa (damage energy=15 eV atom −1 ). The dose for complete amorphization increases with temperature due to simultaneous recovery processes that can be adequately modeled in terms of a single-activated process. The critical temperature, above which amorphization does not occur, increases with particle mass and saturates at about 500 K. Single crystals of α -SiC with [0001] orientation have also been irradiated at 300 K with 360 keV Ar 2+ ions at an incident angle of 25° over fluences ranging from 1 to 8 Ar 2+ ions nm −2 . The damage accumulation in these samples has been characterized ex situ by Rutherford backscattering spectrometry–channeling (RBS/C) along the [0001] direction, Raman spectroscopy, cross-sectional transmission electron microscopy (XTEM), and mechanical microprobe measurements.

Investigation of the properties of [formula omitted] multilayers using a mechanical microprobe

The characterization of compositionally modulated NiP Sn multilayers was tempted using a mechanical microprobe. Indentation tests were carried out on different cross-sections through multilayers with varying sublayer thicknesses. The experimental hardness results are mixed ‘composite’ values with contributions from the different (sub)layers. A model is applied and modified to separate these contributions. The influences of both the sublayer thickness and the interface strength are incorporated in this model.

A feedback controlled silicon microprobe for quantitative mechanical stimulation of nerve and tissue

The ability to apply and control the force and force velocity of mechanical stimulation is essential for the study of mechanoelectric transduction and adaptation processes. Silicon micromachining technology was used to produce miniature (20–70 μm wide) mechanical microprobes. Passive polysilicon, piezoresistive, force sensing elements were deposited onto the boron-doped epitaxial silicon and the individual devices were chemically etched from the bulk wafer. These microprobes display a linear force versus output voltage relationship. Stimulation forces upto 2 mN can be generated with a measurement resolution of 1.5 μN. The probes were mounted onto circuit board holders and their output sent to a proportional-integral controller which drives an electromagnetic actuator. By using this force-feedback control circuit coupled to a PC it is possible to define any stimulus wave form pattern and independently control and measure the actual stimulus force and velocity. A computer controlled 3-axis stepper motor (0.025 μm step capability) manipulator is used to position the silicon microprobe-actuator assembly relative to the mechanoreceptive field. Sensor feedback control coupled to the 3-axis stepper motor manipulator allows automatic touchdown control and/or preloading of the probe prior to stimulation. Three-dimensional topographic manipulator feedback position control allows automated receptive field mapping.

Force-sensing microprobe for precise stimulation of mechanosensitive tissues.

Quantitative study of the transduction mechanisms in mechanically sensitive nerve terminals has been impeded by the lack of instrumentation with which to generate precisely controlled, physically localized mechanical stimuli. We have developed high-resolution force sensing mechanical microprobes for use in the characterization of such nerve terminals. This paper describes their design, fabrication, and testing. A microprobe is comprised of a 0.5- to 2-mm long silicon cantilever beam projecting from a larger supporting silicon substrate. Acting as the variable leg of a Wheatstone bridge circuit, a piezoresistive polysilicon element located at the base of the beam is used to measure the stimulation force applied at the tip. The microprobes exhibit a stable, linear relationship between the stimulation force and the resulting output voltage signal. Stimulation forces up to 3 mN have been generated with a measurement resolution of 10 microN. These microprobes have been used as the force sensing element of a closed loop feedback-controlled stimulation system capable of stimulating the mechanoreceptive nerve terminals of the rabbit corneal epithelium.

What part does interfacial energy play in the deformation and adhesion of metals?

Many surface-mechanical phenomena, like the bulk strength properties of crystals, are dominated by the behaviour of imperfections. However, recent work in various laboratories suggests that the study of fundamental thermodynamic properties can usefully contribute to our understanding of adhesion, deformation and friction.Although accurate values of surface and interfacial energies, and hence of the Dupré energy of adhesion y, can seldom be calculated from first principles, y for smooth elastomers in contact has been derived from experimental measurements of adherence (at equilibrium the stress intensity factor for the crack at the periphery of the contact area is proportional to y12). With hard solids the problem of how to determine the real area of contact may be attacked with the help of specially-designed ‘mechanical microprobes’. A sufficiently clean metal-metal interface is generally stronger under tension than at least one of the bulk metals, in which case the practical significance of y disappears except that plastic deformation can occur even at zero applied load, as an indirect consequence of surface forces. This process may decisively influence the very early stages of sintering, according to the balance between the surface, elastic, grain and twin boundary energies. For thin elastic films subjected to peeling or scratch tests, given the value of y it is possible to predict the mode of detachment.Although for unlubricated metals friction involves energy-dissipative shearing of adhesive micro-contacts, large values of the thermodynamic quantity y may be associated with an increase in real contact area and/or interfacial shear strength, as with polymer monofilaments and carbon fibres. For the elastic case, there is a transition from peeling to sliding at a critical value of stress intensity factor. The plastic case has yet to be analysed but for metals, y should become significant in friction when its value approaches the product of hardness and standard deviation of asperity heights.

Adhesion energies at a metal interface: the effects of surface treatments and ion implantation

Studies the effect of various surface treatments upon the nanometre-scale thermodynamic and plastic properties of titanium interfaces. A mechanical microprobe technique gives curves of electrical contact resistance versus applied load. The curve shape depends upon the state of the original titanium surfaces. A characteristically stable contact area approximately=10-14 m2, can often be achieved through a combination of surface forces and a high enough load, despite the initial microroughness of the surface. With the help of field emission measurements of contact geometry, surface cleanliness and extent of plastic deformation, values of gamma (Dupre adhesion energy) and H (nanometre-scale hardness of the softer of the two samples) are derived. Ion implantation can reduce the value of gamma by a factor of three, and low values may be associated with the improved wear resistance that such treatment can give.

Highspeed Oscillography Using an Sem for Circuit Diagnostics

The rapid development in the VLSI technology which is a combination of process complexity and smaller physical device structures, is making greater demands of characterisation and functional testing of internal circuit operations. The state-of-the-art device structures have become much smaller than the mechanical microprobes that are conventionally used to test internal nodes and as a consequence the use of such probes to measure internal signals for either functional or parametric testing is no more feasible. The submicron devices have also better transient responses and the parasitic reactance of the mechanical probes present significant loading in the circuit causing distortion of the measured signals at high frequencies.