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1.  High-frequency multimodal atomic force microscopy 
Multifrequency atomic force microscopy imaging has been recently demonstrated as a powerful technique for quickly obtaining information about the mechanical properties of a sample. Combining this development with recent gains in imaging speed through small cantilevers holds the promise of a convenient, high-speed method for obtaining nanoscale topography as well as mechanical properties. Nevertheless, instrument bandwidth limitations on cantilever excitation and readout have restricted the ability of multifrequency techniques to fully benefit from small cantilevers. We present an approach for cantilever excitation and deflection readout with a bandwidth of 20 MHz, enabling multifrequency techniques extended beyond 2 MHz for obtaining materials contrast in liquid and air, as well as soft imaging of delicate biological samples.
PMCID: PMC4311654
atomic force microscopy; multifrequency imaging; nanomechanical characterization; photothermal excitation; small cantilevers
3.  Kinetics of Antimicrobial Peptide Activity Measured on Individual Bacterial Cells Using High Speed AFM 
Nature nanotechnology  2010;5(4):280-285.
Observations of real time changes in living cells have contributed much to the field of cellular biology. Eluding the field thus far is the ability to image whole, living cells with nanometre resolution on a time scale that is relevant to dynamic cellular processes1,2. Here we investigate the kinetics of individual bacterial cell death using a novel high-speed atomic force microscope (AFM) optimized for imaging live cells in real time. The increased time resolution (13 seconds per image) allows the characterization of the initial stages of the action of the antimicrobial peptide (AmP) CM15 on individual Escherichia coli cells with nanometre resolution. Our results suggest that the killing process is a combination of a time-variable incubation phase (which takes seconds to minutes to complete) and a more rapid execution phase.
PMCID: PMC3905601  PMID: 20228787
4.  Increased imaging speed and force sensitivity for bio-applications with small cantilevers using a conventional AFM setup 
Micron (Oxford, England : 1993)  2012;43(12):1399-1407.
► Development of small cantilever. ► Speed increase by a factor of ten using small cantilevers on a commercial AFM. ► Force sensitivity increase by a factor of five using small cantilever prototypes for force spectroscopy measurements.
In this study, we demonstrate the increased performance in speed and sensitivity achieved by the use of small AFM cantilevers on a standard AFM system. For this, small rectangular silicon oxynitride cantilevers were utilized to arrive at faster atomic force microscopy (AFM) imaging times and more sensitive molecular recognition force spectroscopy (MRFS) experiments. The cantilevers we used had lengths between 13 and 46 μm, a width of about 11 μm, and a thickness between 150 and 600 nm. They were coated with chromium and gold on the backside for a better laser reflection. We characterized these small cantilevers through their frequency spectrum and with electron microscopy. Due to their small size and high resonance frequency we were able to increase the imaging speed by a factor of 10 without any loss in resolution for images from several μm scansize down to the nanometer scale. This was shown on bacterial surface layers (s-layer) with tapping mode under aqueous, near physiological conditions and on nuclear membranes in contact mode in ambient environment. In addition, we showed that single molecular forces can be measured with an up to 5 times higher force sensitivity in comparison to conventional cantilevers with similar spring constants.
PMCID: PMC3430863  PMID: 22721963
Small cantilever; High resolution imaging; Fast AFM imaging; Ultra-sensitive molecular recognition force spectroscopy
5.  Large-scale analysis of high-speed atomic force microscopy data sets using adaptive image processing 
Modern high-speed atomic force microscopes generate significant quantities of data in a short amount of time. Each image in the sequence has to be processed quickly and accurately in order to obtain a true representation of the sample and its changes over time. This paper presents an automated, adaptive algorithm for the required processing of AFM images. The algorithm adaptively corrects for both common one-dimensional distortions as well as the most common two-dimensional distortions. This method uses an iterative thresholded processing algorithm for rapid and accurate separation of background and surface topography. This separation prevents artificial bias from topographic features and ensures the best possible coherence between the different images in a sequence. This method is equally applicable to all channels of AFM data, and can process images in seconds.
PMCID: PMC3512124  PMID: 23213638
adaptive algorithm; artifact correction; atomic force microscopy; high-speed atomic force microscope; image processing
6.  Focused electron beam induced deposition: A perspective 
Background: Focused electron beam induced deposition (FEBID) is a direct-writing technique with nanometer resolution, which has received strongly increasing attention within the last decade. In FEBID a precursor previously adsorbed on a substrate surface is dissociated in the focus of an electron beam. After 20 years of continuous development FEBID has reached a stage at which this technique is now particularly attractive for several areas in both, basic and applied research. The present topical review addresses selected examples that highlight this development in the areas of charge-transport regimes in nanogranular metals close to an insulator-to-metal transition, the use of these materials for strain- and magnetic-field sensing, and the prospect of extending FEBID to multicomponent systems, such as binary alloys and intermetallic compounds with cooperative ground states.
Results: After a brief introduction to the technique, recent work concerning FEBID of Pt–Si alloys and (hard-magnetic) Co–Pt intermetallic compounds on the nanometer scale is reviewed. The growth process in the presence of two precursors, whose flux is independently controlled, is analyzed within a continuum model of FEBID that employs rate equations. Predictions are made for the tunability of the composition of the Co–Pt system by simply changing the dwell time of the electron beam during the writing process. The charge-transport regimes of nanogranular metals are reviewed next with a focus on recent theoretical advancements in the field. As a case study the transport properties of Pt–C nanogranular FEBID structures are discussed. It is shown that by means of a post-growth electron-irradiation treatment the electronic intergrain-coupling strength can be continuously tuned over a wide range. This provides unique access to the transport properties of this material close to the insulator-to-metal transition. In the last part of the review, recent developments in mechanical strain-sensing and the detection of small, inhomogeneous magnetic fields by employing nanogranular FEBID structures are highlighted.
Conclusion: FEBID has now reached a state of maturity that allows a shift of the focus towards the development of new application fields, be it in basic research or applied. This is shown for selected examples in the present review. At the same time, when seen from a broader perspective, FEBID still has to live up to the original idea of providing a tool for electron-controlled chemistry on the nanometer scale. This has to be understood in the sense that, by providing a suitable environment during the FEBID process, the outcome of the electron-induced reactions can be steered in a controlled way towards yielding the desired composition of the products. The development of a FEBID-specialized surface chemistry is mostly still in its infancy. Next to application development, it is this aspect that will likely be a guiding light for the future development of the field of focused electron beam induced deposition.
PMCID: PMC3458607  PMID: 23019557
atomic force microscopy; binary systems; electron beam induced deposition; granular metals; micro Hall magnetometry; radiation-induced nanostructures; strain sensing

Results 1-6 (6)