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Some of the challenges of adapting high-voltage amplifier (HVA) designs and solutions for driving highly capacitive loads such as piezoelectric actuators (PEAs) fast include cost, implementation complexity, management of thermal load, and difficult customization. In this work, we develop an easy to implement HVA with 525 kHz small signal bandwidth, 6 A pp , and 110 V pp HVA using a low-cost high voltage operational amplifier (HV-OPA) and a self-biasing power amplifier (PA). At 100 kHz, the phase lag is about -24 ∘ and the HVA can be configured for use with or without the PA stage to prioritize input tracking and output noise reduction or output stability improvement. When used to drive our custom high-speed atomic force microscope (HS-AFM) Z-scanner during imaging, compared to a conventional commercial HVA, our custom HVA is able to track topographical features at faster scan speeds.

There is a huge interest in developing superrepellent surfaces for antifouling and heat-transfer applications. To characterize the wetting properties of such surfaces, the most common approach is to place a millimetric-sized droplet and measure its contact angles. The adhesion and friction forces can then be inferred indirectly using Furmidge’s relation. While easy to implement, contact angle measurements are semiquantitative and cannot resolve wetting variations on a surface. Here, we attach a micrometric-sized droplet to an atomic force microscope cantilever to directly measure adhesion and friction forces with nanonewton force resolutions. We spatially map the micrometer-scale wetting properties of superhydrophobic surfaces and observe the time-resolved pinning–depinning dynamics as the droplet detaches from or moves across the surface.

This review critically summarizes the recent advances of the microcantilever-based force sensors for atomic force microscope (AFM) applications. They are one the most common mechanical spring–mass systems and are extremely sensitive to changes in the resonant frequency, thus finding numerous applications especially for molecular sensing. Specifically, we comment on the latest progress in research on the deflection detection systems, fabrication, coating and functionalization of the microcantilevers and their application as bio- and chemical sensors. A trend on the recent breakthroughs on the study of biological samples using high-speed atomic force microscope is also reported in this review.

Probing the mechanical properties of cells is critical for understanding their deformation behaviors and biological functions. Although some methods have been proposed to characterize the elastic properties of cells, it is still difficult to measure their time-dependent properties. This paper investigates the use of atomic force microscope (AFM) to determine the reduced relaxation modulus of cells. In principle, AFM is hard to perform an indentation relaxation test that requires a constant indenter displacement during load relaxation, whereas the real AFM indenter displacement usually varies with time during relaxation due to the relatively small bending stiffness of its cantilever. We investigate this issue through a combined theoretical, computational, and experimental effort. A protocol relying on the choice of appropriate cantilever bending stiffness is proposed to perform an AFM-based indentation relaxation test of cells, which enables the measurement of reduced relaxation modulus with high accuracy. This protocol is first validated by performing nanoindentation relaxation tests on a soft material and by comparing the results with those from independent measurements. Then indentation tests of cartilage cells are conducted to demonstrate this method in determining time-dependent properties of living cells. Finally, the change in the viscoelasticity of MCF-7 cells under hyperthermia is investigated.

Tribological properties mapping is a new technique that extracts friction coefficient and adhesion maps obtained from lateral atomic force microscope (LAFM) images. By imaging the surface systematically as a function of load, a series of images can be tiled, and pixelwise fitted to a modified Amontons’ Law to obtain friction coefficient and adhesion maps. This removes the ambiguity of friction contrast in LAFM imaging which can be a function of the load used for imaging. In ambient laboratory, air and tetradecane, a sample of Vancron ® 40, commercial powder metallurgical tool alloy containing nitrogen, have been scanned using a standard silicon cantilever in order to obtain tribological data. The tribological properties mapping provides unique information regarding the heterogeneous alloy microstructure as well as shedding light on the tribological behavior of the alloy.

The mechanical properties of the vesicles incorporated with ectoine were studied using atomic force microscope (AFM). The vesicles were prepared with dipalmitoylphosphatidylcholine (DPPC) by changing only the ratio of the ectoine to DPPC. After the vesicles were adsorbed on the mica substrate and their morphology were characterized, the plot of an AFM tip displacement versus the tip deflection was acquired by monitoring the behavior of the tip into the vesicle. The breakthrough of the tip into the vesicle was observed to occur twice. Each breakthrough represented a penetration of the tip into the top and bottom portions of the vesicle, respectively. The force data between the pre-contact and the first breakthrough were comparable with the Hertzian model to estimate Young’s modulus and the bending modulus of the vesicles. Both moduli decreased proportionally with the increase in the ratio of ectoine to lipid up to 0.5. However, above 0.5, the moduli were slightly changed with the increase. These results of the mechanical properties appear to be due to the osmotic and volumetric effect on the headgroup packing disruption.Graphic Abstract

In this paper, we demonstrate the fabrication of S-shaped micron-sized constrictions on steel ( Fe 3 C II ) surface using the femtosecond laser ablation technique. The femtosecond laser used has a wavelength of 775 nm, a power range of 0–1000 mW, a pulse duration of 130 fs, and a pulse repetition rate of 1–2 kHz. The ultra-low-pulse duration of 130 fs enables ablation of material surfaces without excessive thermal heating of the material around the zone of ablation. This becomes useful when ablating materials that are thermally sensitive such as superconducting thin films. This practice run of ablating S-shaped micron-sized constrictions on steel surfaces shown in this paper will enable one to use the same technique in ablating micron- and nano-sized structures on superconducting thin films without thermally altering the superconductive film. In this paper, S-shaped micron-sized constrictions on steel were fabricated with a constriction width of 37.1 and 47.3 μm whose images were created using an optical microscope (OM) and S-shaped micron-sized constrictions with a constriction width of 30.8 and 35.2 μm whose images were created using an atomic force microscope (AFM). The reduction in the constriction widths was achieved by reducing the laser ablation width or laser ablation spot size and then bringing the laser ablation spots closer together in G-code program. The reduction of the laser ablation width is achieved by reducing the laser fluence applied closer to the ablation threshold of steel and by using laser beam shaping techniques such as beam collimation and beam focusing.

In grinding process, cutting fluids play an important role to control high grinding zone temperature. However, their use causes detrimental effect on the operator’s health and environment. On the other hand, dry grinding not only results in thermal damage to ground surface but also deteriorates the surface quality and dimensional accuracy of the ground component. The possible solution is to apply cutting fluids using minimum quantity lubrication (MQL) technique. The objective of present research work is to investigate and compare the effect of different grinding environments: dry, flood, MQL with deionized water (DIW), MQL with liquid paraffin oil (LP), and MQL with castor oil based on vegetable oil (VO) during grinding of hardened H13 hot die steel. Grinding performance was evaluated in terms of specific grinding force, specific grinding energy, grinding force ratio, surface roughness, and microhardness. Ground surface and debris morphology were also analyzed using scanning electron microscope, atomic force microscope, and energy-dispersive X-ray spectroscopy to validate the grinding performance. The results showed that MQL-VO grinding leads to minimum specific grinding force, specific grinding energy, and grinding force ratio. Further, surface roughness was considerably reduced under MQL-VO grinding, where R ɑ and R z were 0.245 μm and 1.846 μm, respectively. AFM analysis indicated that the surface roughness of MQL-VO grinding was nearly 29.88% less as compared to dry grinding. Smooth ground surface topography, as well as long, thin, and no wear track grinding debris, were observed under MQL-LP and MQL-VO conditions. Moreover, dry grinding resulted in lower microhardness in comparison to other grinding conditions.

Colchicine is a drug commonly used for the treatment of gout, however, patients may sometimes encounter side-effects induced by taking colchicine, such as nausea, vomiting, diarrhea and kidney failure. In this regard, it is imperative to investigate the mechanism effects of colchicine on biological cells. In this paper, we present a method for the detection of mechanical properties of nephrocytes (VERO cells), hepatocytes (HL-7702 cells) and hepatoma cells (SMCC-7721 cells) in culture by atomic force microscope (AFM) to analyze the 0.1 μg/mL colchicine-induced effects on the nanoscale for two, four and six hours. Compared to the corresponding control cells, the biomechanical properties of the VERO and SMCC-7721 cells changed significantly and the HL-7702 cells did not considerably change after the treatment when considering the same time period. Based on biomechanical property analyses, the colchicine solution made the VERO and SMCC-7721 cells harder. We conclude that it is possible to reduce the division rate of the VERO cells and inhibit the metastasis of the SMCC-7721 cells. The method described here can be applied to study biomechanics of many other types of cells with different drugs. Therefore, this work provides an accurate and rapid method for drug screening and mechanical analysis of cells in medical research.

Graphite as a positive electrode material of dual ion batteries (DIBs) has attracted tremendous attentions for its advantages including low lost, high working voltage and high energy density. However, very few literatures regarding to the real-time observation of anion intercalation behavior and surface evolution of graphite in DIBs have been reported. Herein, we use in situ atomic force microscope (AFM) to directly observe the intercalation/de-intercalation processes of PF 6 − in graphite in real time. First, by measuring the change in the distance between graphene layers during intercalation, we found that PF 6 − intercalates in one of every three graphite layers and the intercalation speed is measured to be 2 µm·min −1 . Second, graphite will wrinkle and suffer structural damages at high voltages, along with severe electrolyte decomposition on the surface. These findings provide useful information for further optimizing the capacity and the stability of graphite anode in DIBs.