Shear Force Feedback Research Articles

Quantitative comparison of excitation modes of tuning forks for shear force in probe microscopy

This article provides a careful comparison between the electric and mechanical excitation of a tuning fork for shear force feedback in scanning probe microscopy, an analysis not found in present literature. A setup is designed and demonstrated for robust signal and noise measurements at comparable levels of physical movement of the probe. Two different signal amplification methods, combined with two excitation ways provide three possible configurations. For each method a quantitative analysis, supported by analytical elaboration and numerical simulations, is provided. Finally, it is shown that in practical circumstances electric excitation followed by detection with a transimpedance amplifier provides the best result.

Design and Experimental Evaluation of a Sensorimotor-inspired Grasping Strategy for Dexterous Prosthetic Hands.

Stable grasping without slips or crushing is a major challenge for amputees who lose the natural sensorimotor system in dynamically changing daily life environments. Amputees rely largely on visual cues to control the prosthetic hand to complete daily living activities due to a lack of haptic feedback. The human tactile sense can simultaneously feel normal and shear forces. When grasping objects based on the anticipated load conditions, the human hand adjusts the grasping force in real time based on shear force feedback. Here, a sensorimotor-inspired grasping strategy for a dexterous prosthetic hand is proposed to improve grasping performance. The proposed grasping strategy allows the amputee to intuitively control the prosthetic hand. The dexterous prosthetic hand can adaptively adjust the grasp force based on tactile sensory feedback to simultaneously prevent the slipping of objects with unknown shapes, weight, roughness, and softness. Experiments show that the myoelectrical prosthetic hand has grasping force adaptive adjustment and slip prevention ability and provides improved grasping compared to prosthetics with traditional open-loop control.

Passive dual-probe near-field microscopy.

Accurate and simultaneous multiposition near-field measurements are essential to study the time-dependent local dynamics, including heat and carrier transfer. The existing passive long-wavelength infrared (LWIR) scattering-type scanning near-field optical microscopy (s-SNOM) systems with a single probe cannot perform precise near-field measurements of the heat or carrier transporting process at the nanoscale level. Therefore, in this study, we developed a passive LWIR s-SNOM system with two probes. To test the effectiveness of the proposed passive LWIR dual-probe s-SNOM system, each probe was precisely controlled using a shear-force feedback system, and the mechanical interference between the probes was used to monitor the distance between the probes. We achieved simultaneous near-field measurements at two different positions 500nm apart using the proposed passive LWIR dual-probe s-SNOM system. The simultaneously detected near-field signals from two different points were extracted individually, making this technique an effective nanoscale analysis tool for local carrier dynamics.

Scanning Gel Electrochemical Microscopy (SGECM): Lateral Physical Resolution by Current and Shear Force Feedback.

Scanning gel electrochemical microscopy (SGECM) is a novel technique measuring local electrochemistry based on a gel probe. The gel probe, which is fabricated by electrodeposition of hydrogel on a microdisk electrode, immobilizes the electrolyte, and constitutes a two-electrode system upon contact with the sample. The contact area determines the lateral physical resolution of the measurement, and considering the soft nature of the gel it is essential to be well analyzed. In this work, the lateral physical resolution of SGECM is quantitatively studied from two aspects: (1) marking single sampling points by locally oxidizing Ag to AgCl and measuring their size; (2) line scan over reference samples with periodic topography and composition. The gel probe is approached to the sample by either current or shear force feedback, and the physical resolution of them is compared. For the optimal gel probe based on 25 μm diameter Pt disk electrode of Rg ≈ 2, the lateral physical resolution of SGECM at contact position is ca. 50 μm for current feedback and ca. 63 μm for shear force feedback. More importantly, the lateral physical resolution of SGECM can be flexibly tuned in the range of 14-78 μm by pulling or pressing the gel probe after touching the sample. In general, current feedback is more sensitive to gel-sample contact than shear force feedback. But the latter is more versatile, which is also applicable to nonconductive samples.

Scanning gel electrochemical microscopy (SGECM): The potentiometric measurements

SGECM potentiometric measurements are developed with a novel Ag/AgCl-gel micro-reference electrode. The electrode is prepared by electrodeposition of chitosan on Ag micro-disk electrode followed by anodic chlorination of Ag. It is approached to the sample by shear force feedback, and the potential between the electrode and the sample is recorded with a highly sensitive voltammeter. Based on this, simultaneous mapping of topography and electrochemical potential is achieved, with the sample exposed in air. Tests of model samples indicate that the electrode is reliable and stable for potentiometry, and two different metals (Al and Cu) are clearly identified from the topography and potential maps.

Scanning Gel Electrochemical Microscopy for Topography and Electrochemical Imaging.

Scanning electrochemical probe techniques have been widely applied for analyzing the local electrochemical activity of surfaces and interfaces. In this work, we develop a new concept of carrying out local electrochemical measurements by localizing both the electrode and the electrolyte. This is achieved through a gel probe, which is prepared by electrodepositing chitosan-gelatin gel on a microdisk electrode. It is positioned in contact with the sample surface by shear force feedback. The preliminary results indicate that the topography of the sample can be mapped by tapping the probe and recording the coordinates at a given normalized shear force signal, while the local electrochemical activity can be retrieved from local measurements with the probe touching the sample surface. The technique is denoted as scanning gel electrochemical microscopy. As compared with existing techniques, it has a major advantage of operating in air with the electrolyte immobilized in gel. This would prevent the spreading and leakage of solution on the sample surface and may lead to field applications.

A structural model of ultra-microelectrodes for shear-force based scanning electrochemical microscopy

The incorporation of a shear-force (SF) feedback in scanning electrochemical microscopy (SECM) hardware has enabled topographically resolved electrochemical imaging of electroactive substrates. Despite the versatility of SECM-SF imaging, structural response of the ultra-microelectrode (UME) to various excitation inputs is poorly understood and predictive mathematical models for characterizing dynamic behavior, particularly at high operating frequencies (>100 kHz), are absent. In this article, we present a finite element model to characterize SF behavior by modeling the UME as a rigid cantilever with two distributed piezoelectric wafers (dither and receiver) and demonstrate the model’s ability to predict experimentally observed SF behavior. The obtained SF response under different dither-to-receiver distances for various UME geometries and loading conditions provides insight to the optimum placement of piezoelectric wafers on the UME for achieving a high SF amplitude at SF-sensitive frequencies. In addition, the variations in SF response under different dither-to-receiver orientations indicate the existence of a system transfer function that is dependent on the operating modes of the receiver. The agreement between simulated and experimental results suggests that the finite element model along with the experimental methodology can be extended to automated SF imaging using SECM hardware.

Two-photon luminescence contrast by tip-sample coupling in femtosecond near-field optical microscopy

We investigate the role of tip-sample interaction in nonlinear optical scanning near-field microscopy. The experiment was performed by tightly focusing femtosecond laser pulses onto a sharp gold tip that was positioned in close proximity to the surface of a sample with gold nanostructures on a Si-substrate by shear force feedback. The nonlinear optical signal consists of two-photon photoluminescence and second harmonic signal from the gold tip and the gold nanostructures. These signals can be used to characterize different coupling parameters such as geometry, material and width of the tip-sample gap and enable to reveal the mechanism responsible for the image contrast. Under the excitation with 776-nm and 110-fs laser pulses nonlinear imaging is almost background free and yields super resolution showing features with dimensions significantly below the diffraction limit with a signal intensity following quadratic excitation power law.

Nanoscale polypyrrole sensors for near-field electrochemical measurements

Scanning electrochemical microscopy (SECM) is an electrochemical technique that is used to measure redox activity local to the surface of a sample. The incorporation of shear force (SF) feedback into SECM enables the concurrent acquisition of topographical data. Contemporary SECM measurements require a redox mediator (such as ferrocene methanol (FcMeOH)) for electrochemical measurements; however, redox mediators are detrimental to chemically sensitive materials such as biological cells. In this article, nanoscale polypyrrole membranes doped with dodecylbenzene sulfonate (PPy(DBS)) are deposited at the tip of highly sensitive ultra-microelectrodes (UME) to demonstrate a novel modification of the contemporary SECM–SF imaging technique that operates in the absence of a redox mediator. This technique leverages the redox activity of a PPy(DBS) membrane to locally detect changes in cation concentration. In conjunction with SF imaging, the PPy(DBS) membrane can (i) detect changes in distance from the surface by measuring changes in ion concentration of the diffusion shell, or (ii) detect local cation flux due to cell function when kept at a constant distance from the cell surface through SF-imaging techniques. Therefore, we predict this technique to enable high resolution mapping of surface cation concentrations and impact the field of biological imaging.

Development of a scanning nanopipette probe microscope for fine processing using atmospheric pressure plasma jet

We developed a novel technique for fine material processing based on a localized atmospheric-pressure plasma jet (APPJ) using a scanning probe microscope equipped with a nanopipette. Using a nanopipette — a tapered glass capillary with an aperture of sub-micrometer diameter — as a nozzle makes it possible to localize the discharge area of the APPJ for fine surface processing. The nanopipette can also be used as a probe for a scanning probe microscope operated with shear-force feedback control, which is capable of positioning the pipette edge in the vicinity of material surfaces for APPJ processing and imaging of the processed surface. Sub-micrometer holes and line patterns were successfully processed on a photoresist film. It was possible to control the size of the processed patterns by varying the applied pulse voltage and the distance between the pipette and the surface.

Determination of the local corrosion rate of magnesium alloys using a shear force mounted scanning microcapillary method.

The successful development of scanning probe techniques to characterize corrosion in situ using multifunctional probes is intrinsically tied to surface topography signal decoupling from the measured electrochemical fluxes. One viable strategy is the shear force controlled scanning microcapillary method. Using this method, pulled quartz micropipettes with an aperture of 500 nm diameter were used to resolve small and large variations in topography in order to quantify the local corrosion rate of microgalvanically and galvanically corroded Mg alloys. To achieve topography monitoring of corroded surfaces, shear force feedback was employed to position the micropipette at a reproducible working height above the substrate. We present proof of concept measurements over a galvanic couple of a magnesium alloy (AE44) and mild steel along with a microgalvanically corroded ZEK100 Mg alloy, which illustrates the ability of shear force to track small (1.4 μm) and large (700 μm) topographic variations from high aspect ratio features. Furthermore, we demonstrate the robustness of the technique by acquiring topographic data for 4 mm along the magnesium-steel galvanic couple sample and a 250 × 30 μm topography map over the ZEK100 Mg alloy. All topography results were benchmarked using standard optical microscopies (profilometry and confocal laser scanning microscopy).

Combined electrochemical-topographical imaging: a critical review

This review critically analyses the state-of-the-art in correlative electrochemical-topographical imaging, focusing on AFM, shear-force, ion conductance, and electrochemical positional feedback.

Adaptive Sliding Mode Control for Prosthetic Hands to Simultaneously Prevent Slip and Minimize Deformation of Grasped Objects

Adaptive sliding mode and integral sliding mode grasped object slip prevention controllers are implemented for a prosthetic hand and compared to a proportional derivative shear force feedback slip prevention controller as well as a sliding mode controller without slip prevention capabilities. Slip of grasped objects is detected by band-pass filtering the shear force derivative to amplify high frequency vibrations that occur as the grasped object slides relative to the fingers. The integral sliding mode slip prevention controller provides a robust design framework for slip prevention while addressing the issue of reducing the amount of deformation that the grasped object experiences to prevent slip. Averaged results from bench top experiments show that the integral sliding mode slip prevention controller produces the least amount of deformation to the grasped object while simultaneously preventing the object from being dropped.

SECM detection of single boron doped diamond nanodes and nanoelectrode arrays using phase-operated shear force technique

Boron doped diamond (BDD) is a promising electrode material for electrochemical biosensor applications due to its low bio-fouling, chemical stability, and large potential window. For the first time, BDD nanoelectrode arrays (NEA) were studied using Scanning Electrochemical Microscopy (SECM) measurements. Using the phase-operated shear force technique and feedback mode, it was possible to scan a platinum (Pt) nanode with an active radius of 167nm over a diamond array at a constant distance of 45nm and to detect the electrochemical activity of single BDD nanodes in the 100nm range.

Large scale scanning probe microscope: Making the shear-force scanning visible

We describe a demonstration of a scanning probe microscope with shear-force tuning fork feedback. The tuning fork is several centimeters long, and the rigid fiber is replaced by a toothpick. By scaling this demonstration to visible dimensions the accessibility of shear-force scanning and tuning fork feedback is increased.

Transfected Single-Cell Imaging by Scanning Electrochemical Optical Microscopy with Shear Force Feedback Regulation

Gene-transfected single HeLa cells were characterized using a scanning electrochemical/optical microscope (SECM/OM) system with shear-force-based probe-sample distance regulation to simultaneously capture electrochemical, fluorescent, and topographic images. The outer and inner states of single living cells were obtained as electrochemical and fluorescent signals, respectively, by using an optical fiber-nanoelectrode probe. A focused ion beam (FIB) was used to mill the optical aperture and the ring electrode at the probe apex (the inner and outer radii of the ring electrode were 37 and 112 nm, respectively). To apply an appropriate shear force between the probe tip and the living cell surface, we optimized the amplitude of oscillation of the tuning fork to which the probe was attached. Field-programmable gate arrays (FPGA) were adopted to drastically increase the feedback speed of the tip-sample distance regulation, shorten the scanning time for imaging, and enhance the accuracy and quality of the living cell images. In employing these improvements, we simultaneously measured the cellular expression activity of both secreted alkaline phosphatase outside and GFP inside by using the SECM/OM with shear force distance regulation.

Hybrid shear force feedback/scanning quantitative phase microscopy applied to subsurface imaging

Quantitative phase microscopy allows for the study of the surface morphology and dynamics of transparent biological specimens. Although phase data often contains coupled subsurface information, decoupling the surface and subsurface components is often very difficult or impossible. We hereby present a simple procedure which exploits simultaneous obtained quantitative phase and shear-force feedback topography data to extract subsurface sample information. Our results reveal subsurface features in fabricated samples and fish erythrocytes.

2A1-G08 マスタスレーブマニピュレータによる柔軟物搬送の操作支援制御(フレキシブルロボット・メカニズム)

This paper presents an assist control method for flexible parts transportation using a master slave manipulator. The proposed assist control consists of notch filters in the master side and shear force feedback in the slave side. The resonance frequency components of a flexible part are removed from operating force signal by the notch filters, by which the excitation of the vibration of the flexible part is reduced. The vibration of the flexible part is suppressed by the shear force feedback. The shear force of the flexible part is measured with the force sensor attached at the end-effector. The effectiveness of the proposed method is verified from standpoints of maneuverability and operator's feeling. The former is based on the evaluation of the time responses and the success time of the task. The latter is based on the subjective evaluation of an operator using Semantic Differential Method and Principal Component Analysis.

Evaluation of new materials for plasmonic imaging lithography at 476nm using near field scanning optical microscopy

A new resist formulation was successfully patterned using near field optical microscopy in order to simulate the conditions prevailing in silver based plasmonic imaging tools. Radiation at 476nm was transmitted through a near field scanning optical microscopy fiber probe tip to cross-link a film of poly(4-methacrylmethyl styrene) via polymerization of pendant methacryloyl groups using camphorquinone and dimethyl aniline as an initiating system. Patterns were generated by scanning at several speeds in order to moderate the dose while maintaining a constant probe height of about 5nm above the sample through shear force feedback. After development, lines corresponding to the exposed regions were observed. At a scanning speed of 4μm∕s, the observed pattern has a full width at half maximum of 275nm and a height of ∼25nm.

Sample heating in near-field scanning optical microscopy

Heating near the aperture of aluminum coated, fiber optic near-field scanning optical microscopy probes was studied as a function of input and output powers. Using the shear-force feedback method, near-field probes were positioned nanometers above a thermochromic polymer and spectra were recorded as the input power was varied. Excitation at 405 nm of a thin polymer film incorporating perylene and N-allyl-N-methylaniline leads to dual emission peaks in the spectra. The relative peak intensity is temperature sensitive leading to a ratiometric measurement, which avoids complications based solely on intensity. Using this method, we find that the proximal end of typical near-field probes modestly increase in temperature to 40–45 °C at output powers of a few nanowatts (input power of ∼0.15mW). This increases to 55–65 °C at higher output powers of 50 nW or greater (input power of ∼2–4mW). Thermal heating of the probe at higher powers leads to probe elongation, which limits the heating experienced by the sample.