High-speed imaging upgrade for a standard sample scanning atomic force microscope using small cantilevers

Adams, Jonathan D.; Nievergelt, Adrian P.; Erickson, Blake; Yang, Chen; Ðukić, Maja; Fantner, Georg E.

doi:10.1063/1.4895460

Cited by 40 publications

(37 citation statements)

References 34 publications

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“…The remaining liquid was immediately absorbed by aspirating to an absorbent filter paper held at the sample edge, and then the sample was dried under a gentle dry nitrogen flow. AFM measurements were made on a Multimode AFM (Bruker, Santa Barbara, CA) using either a custom fast scanning AFM head (Adams et al, ) in tapping mode or in ScanAsyst ™ mode. Fast‐Scan B probes (Bruker) were used for the former and PNP‐TRS probes (Nanoworld, Neuchatel, Switzerland) for the latter.…”

Section: Methodsmentioning

confidence: 99%

Histamine releasing factor and elongation factor 1 alpha secreted via malaria parasites extracellular vesicles promote immune evasion by inhibiting specific T cell responses

Demarta‐Gatsi

Rivkin

Bartolo

et al. 2019

Cellular Microbiology

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Protozoan pathogens secrete nanosized particles called extracellular vesicles (EVs) to facilitate their survival and chronic infection. Here, we show the inhibition by Plasmodium berghei NK65 blood stage‐derived EVs of the proliferative response of CD4+ T cells in response to antigen presentation. Importantly, these results were confirmed in vivo by the capacity of EVs to diminish the ovalbumin‐specific delayed type hypersensitivity response. We identified two proteins associated with EVs, the histamine releasing factor (HRF) and the elongation factor 1α (EF‐1α) that were found to have immunosuppressive activities. Interestingly, in contrast to WT parasites, EVs from genetically HRF‐ and EF‐1α‐deficient parasites failed to inhibit T cell responses in vitro and in vivo. At the level of T cells, we demonstrated that EVs from WT parasites dephosphorylate key molecules (PLCγ1, Akt, and ERK) of the T cell receptor signalling cascade. Remarkably, immunisation with EF‐1α alone or in combination with HRF conferred a long‐lasting antiparasite protection and immune memory. In conclusion, we identified a new mechanism by which P. berghei‐derived EVs exert their immunosuppressive functions by altering T cell responses. The identification of two highly conserved immune suppressive factors offers new conceptual strategies to overcome EV‐mediated immune suppression in malaria‐infected individuals.

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Section: Methodsmentioning

confidence: 99%

Histamine releasing factor and elongation factor 1 alpha secreted via malaria parasites extracellular vesicles promote immune evasion by inhibiting specific T cell responses

Demarta‐Gatsi

Rivkin

Bartolo

et al. 2019

Cellular Microbiology

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“…Imaging is performed using a home-built high-speed AFM head (see Adams et al (2014)) using a Bruker FastScan-C cantilever. As the controller runs on an FPGA, the computation time increases only linearly with the controller order, and is negligible in the shown example.…”

Section: Resultsmentioning

confidence: 99%

Data-Driven Controller Design for Atomic-Force Microscopy

Kammer¹,

Nievergelt

Fantner

et al. 2017

IFAC-PapersOnLine

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A novel method to design data-driven, fixed-structure controllers with H 2 and H ∞ performance objectives is presented. The control design problem is transformed into a convex optimization problem with linear matrix inequality constraints, which can be solved efficiently with standard solvers. The method is used to design a data-driven controller for an atomic-force microscope. The closed-loop performance of the calculated controller is validated on a real setup.

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“…To image the sanded mica sample, we used a modified NanoScope V controller and MultiMode 8 AFM system. The modifications to the system were as follows: a custom readout head for small cantilevers 31 , a custom scanner using combined tube and stack piezo actuators with an open-loop −3 dB z bandwidth of 95 kHz and a usable x-y scan range of ∼130 × 130 μm 2 and z scan range of ∼5 μm, and an online, system-identification-based compensation of the lateral scanner resonances 32,33 . We used a small SU-8 cantilever with f 0 = 1.37 MHz.…”

Section: Methodsmentioning

confidence: 99%

“…The amplitude of the drive was modulated with a square wave at a frequency of 20 Hz. To detect the deflection of the small SiN and SU-8 cantilevers, we used a custom-built AFM head 31 . The deflection signal was collected either with the NanoScope controller or with a Picoscope 5242A external oscilloscope at a sampling rate of at least 6 MHz.…”

Section: Methodsmentioning

confidence: 99%

Harnessing the damping properties of materials for high-speed atomic force microscopy

et al. 2015

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The success of high-speed atomic force microscopy in imaging molecular motors 1 , enzymes 2 and microbes 3 in liquid environments suggests that the technique could be of significant value in a variety of areas of nanotechnology. However, the majority of atomic force microscopy experiments are performed in air, and the tapping-mode detection speed of current highspeed cantilevers is an order of magnitude lower in air than in liquids. Traditional approaches to increasing the imaging rate of atomic force microscopy have involved reducing the size of the cantilever 4,5 , but further reductions in size will require a fundamental change in the detection method of the microscope [6][7][8] . Here, we show that high-speed imaging in air can instead be achieved by changing the cantilever material. We use cantilevers fabricated from polymers, which can mimic the high damping environment of liquids. With this approach, SU-8 polymer cantilevers are developed that have an imaging-in-air detection bandwidth that is 19 times faster than those of conventional cantilevers of similar size, resonance frequency and spring constant.A primary research goal in atomic force microscopy (AFM) is to increase the imaging speed, improve its ease of use and expand its potential range of applications 9 . In the most widely used AFM mode (a.c. mode or tapping mode) the detection speed (mechanical bandwidth, BW) of the AFM cantilever fundamentally limits the imaging speed. The bandwidth is a measure of the maximum rate of topography change the cantilever can accurately detect. It is related to the cantilever resonance as BW ∝ f 0 /Q, where the cantilever resonance frequency f 0 is primarily determined by the cantilever mass and elastic modulus, and the quality factor Q is determined by the cantilever damping 10 . When the oscillating cantilever experiences a change in boundary condition (that is, topography), it requires several cycles to reach a new steady-state amplitude (Fig. 1a). A cantilever with higher resonance frequency runs through the required number of cycles more quickly, thereby enabling faster imaging (Fig. 1b). The number of required oscillatory cycles is determined by the damping of the cantilever, characterized by Q. A cantilever with low resonance frequency and low Q can therefore be equally as fast as a cantilever with high resonance frequency and high Q (compare Fig. 1b and c). From a detection bandwidth perspective, the ideal combination is a high resonance frequency and low quality factor (Fig. 1d).The development of current high-speed AFM (HS-AFM) technology was enabled by the miniaturization of silicon and silicon nitride (SiN) cantilevers to x-y dimensions below 10 µm (the approach taken in Fig. 1b), resulting in cantilevers with megahertz resonance frequencies 4,5 . Modelling and an improved understanding of cantilever behaviour in fluids has greatly benefited this geometric optimization. For nearly all cantilevers, viscous damping in the surrounding medium determines Q (ref. 11). In liquid, viscous damping yields Q ≈ 2...

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High-speed imaging upgrade for a standard sample scanning atomic force microscope using small cantilevers

Cited by 40 publications

References 34 publications

Histamine releasing factor and elongation factor 1 alpha secreted via malaria parasites extracellular vesicles promote immune evasion by inhibiting specific T cell responses

Histamine releasing factor and elongation factor 1 alpha secreted via malaria parasites extracellular vesicles promote immune evasion by inhibiting specific T cell responses

Data-Driven Controller Design for Atomic-Force Microscopy

Harnessing the damping properties of materials for high-speed atomic force microscopy

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