-
U. Dammer,
D. Anselmetti,
M. Dreier,
J. Frommer,
J. Fünfschilling,
G. Gerth, H.‐J. Güntherodt,
H. Haefke,
H.‐R. Hidber,
L. Howald, [......],
E. Meyer,
A. Moser,
I. Parashikov,
P. Reimann,
T. Richmond,
M. Rüetschi,
H. Rudin,
U. D. Schwarz,
U. Staufer,
R. Sum
[show abstract]
[hide abstract]
ABSTRACT: Some examples are selected to demonstrate the variety of possible scanning probe microscopy application in industry. Magnetic and magneto-optical storage media can be investigated by magnetic force microscopy, whereas a conventional scanning force microscope is used to examine surface features of many different materials, such as technical glasses, photosensitive materials, new superconductors, and biomolecules. Some other examples include the modification as well as the observation of liquid crystal devices, and the impact that scanning probe microscopy has on other techniques such as high precision stepping motors and high quality electron beam sources.
Scanning 08/2011; 15(5):257 - 264. · 1.07 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The resonance frequency and the excitation amplitude of a silicon cantilever have been measured as a function of distance to a cleaved KBr(001) surface with a low-temperature scanning force microscope (SFM) in ultrahigh vacuum. We identify two regimes of tip-sample distances. Above a site-dependent critical tip-sample distance reproducible data with low noise and no interaction-induced energy dissipation are measured. In this regime reproducible SFM images can be recorded. At closer tip-sample distances, above two distinct atomic sites, the frequency values jump between two limiting curves on a timescale of tens of milliseconds. Furthermore, additional energy dissipation occurs wherever jumps are observed. We attribute both phenomena to rarely occurring changes in the tip apex configuration which are affected by short-range interactions with the sample. Their respective magnitudes are related to each other. A specific candidate two-level system is also proposed.
Nanotechnology 10/2007; 18(39):395503. · 3.98 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Scanning tunnelling microscopy (STM) is applied to investigate the surface structure of high-quality c-axis oriented laser-ablated thin YBa2Cu3O7-δ-films. The main features of the surface are steps of one-unit cell height documenting the two-dimensional growth process of the epitaxial film. For the first time atomic resolution with STM is achieved, indicating a 3.8 Å square lattice on YBa2Cu3O7-δ laser-ablated films, as expected from diffraction techniques. Screw dislocations and holes of different sizes are the most frequently observed types of lattice defects in these films.
EPL (Europhysics Letters) 07/2007; 15(6):667. · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Ultrasmall double-barrier junctions with capacitance 10-19-10-18 F were realized in a system consisting of a metallic substrate, an insulating thin organic film, an isolated metal particle, an adjustable tunnelling gap and the tip of a scanning tunnelling microscope (STM). These structures were characterized by STM topography and local current-voltage (I-V) measurements at room temperature. We found clear evidence of Coulomb blockade effects in the I-V characteristics which could readily be explained in terms of simulations based on the semi-classical theory of single-electron tunnelling. The charging energies and resistances derived from our experiments clearly exceed the theoretical limits of thermal energy and resistance quantum required for observing single-electron tunnelling. By varying the STM gap we also verified the dependences of the particle capacitance and of the double-barrier series resistance.
EPL (Europhysics Letters) 07/2007; 25(4):297. · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The availability of entire genome sequences has triggered the development of microarrays for clinical diagnostics that measure the expression levels of specific genes. Methods that involve labelling can achieve picomolar detection sensitivity, but they are costly, labour-intensive and time-consuming. Moreover, target amplification or biochemical labelling can influence the original signal. We have improved the biosensitivity of label-free cantilever-array sensors by orders of magnitude to detect mRNA biomarker candidates in total cellular RNA. Differential gene expression of the gene 1-8U, a potential marker for cancer progression or viral infections, has been observed in a complex background. The measurements provide results within minutes at the picomolar level without target amplification, and are sensitive to base mismatches. This qualifies the technology as a rapid method to validate biomarkers that reveal disease risk, disease progression or therapy response. We foresee cantilever arrays being used as a tool to evaluate treatment response efficacy for personalized medical diagnostics.
Nature Nanotechnology 12/2006; 1(3):214-20. · 27.27 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We studied the electronic structure of copper-octaethylporphyrin (CuEOP) adsorbed on three metal surfaces--Ag(001), Ag(111), and Cu(111)--by means of ultraviolet photoelectron spectroscopy (UPS). The adsorption-induced work function shifts saturate roughly beyond two monolayers. The saturation values are substrate dependent, negative, and range from -1.30 to -0.85 eV. This shift is larger than that for tetraphenylporphyrins. The two highest occupied molecular orbitals (HOMO and HOMO-1) of the organic are clearly resolved in the UPS spectra. The origin of the negative work function shift is discussed.
The Journal of Physical Chemistry B 01/2006; 109(49):23558-63. · 3.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Myomesin is the most prominent structural component of the sarcomeric M-Band that is expressed in mammalian heart and skeletal muscles. Like titin, this protein is an intracellular member of the Ig-fibronectin superfamily, which has a flexible filamentous structure and which is largely composed of two types of domain that are similar to immunoglobulin (Ig)-like and fibronectin type III (FNIII) domains. Several myomesin isoforms have been identified, and their expression patterns are highly regulated both spatially and temporally. Particularly, alternative splicing in the central part of the molecule gives rise to an isoform, EH (embryonic heart)-myomesin, containing a serine and proline-rich insertion with no well-defined secondary structure, the EH segment. EH-myomesin represents the major myomesin isoform at embryonic stages of mammalian heart and is rapidly down-regulated around birth, but it is re-expressed in the heart of patients suffering from dilated cardio-myopathy. Here, in order to facilitate a better understanding of the physiological, and possibly pathological, functions of myomesin proteins, we explore the mechanical stability, elasticity and force-driven structural changes of human myomesin's sub-molecular segments using single-molecule force spectroscopy and protein engineering. We find that human myomesin molecules are composed of modules (Ig and FNIII), that are designed to withstand force and we demonstrate that the human cardiac EH segment functions like an additional elastic stretch in the middle part of the EH-myomesin and behaves like a random coil. Consequently myomesin isoforms (proteins with or without the EH segment) have different elastic properties, the EH-myomesin being the more compliant one. These findings imply that the compliance of the M-band increases with the amount of EH-myomesin it contains. So, we provide the evidence that not only titin but also other sarcomeric proteins have complicated visco-elastic properties depending on the contractile parameters in different muscle types.
Journal of Molecular Biology 06/2005; 348(5):1127-37. · 4.00 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We propose and apply to the KBr(001) surface a new procedure for species recognition in scanning force microscopy (SFM) of ionic crystal surfaces which show a high symmetry of the charge arrangement. The method is based on a comparison between atomistic simulations and site-specific frequency versus distance measurements. First, by taking the difference of force-distance curves extracted at a few judiciously chosen surface sites we eliminate site-independent long-range forces. The obtained short-range force differences are then compared with calculated ones assuming plausible tip apex models. This procedure allows for the first time identification of the tip apex polarity and of the positive and negative sublattices in SFM images of the (001) cleavage surface of an ionic crystal with the rock salt structure.
Physical Review Letters 05/2004; 92(14):146103. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We report direct force measurements of the formation of a chemical bond. The experiments were performed using a low-temperature atomic force microscope, a silicon tip, and a silicon (111) 7x7 surface. The measured site-dependent attractive short-range force, which attains a maximum value of 2.1 nanonewtons, is in good agreement with first-principles calculations of an incipient covalent bond in an analogous model system. The resolution was sufficient to distinguish differences in the interaction potential between inequivalent adatoms, demonstrating the ability of atomic force microscopy to provide quantitative, atomic-scale information on surface chemical reactivity.
Science 04/2001; 291(5513):2580-3. · 31.20 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The interfacial stress of self-assembled monolayers on Au exposed to buffers of various pH values and ionic strengths is measured as a function of the liquid environment. The method uses two thiol-modified Au-covered silicon cantilevers and a differential method to compensate for thermal and refractive index changes of the liquid environment. Increasing pH and ionic strength leads to a bending, i.e., a compressive stress, of a mercaptohexadecanoic acid-covered cantilever compared to a hexadecanethiol-covered reference cantilever. In addition, the interfacial stress is found to be highly dependent on the surface density of the ionizeable mercaptohexadecanoic acid molecules when they are coadsorbed with hexadecanethiols on Au.
11/2000;
-
[show abstract]
[hide abstract]
ABSTRACT: Point mutants of three unrelated antifluorescein antibodies were constructed to obtain nine different single-chain Fv fragments, whose on-rates, off-rates, and equilibrium binding affinities were determined in solution. Additionally, activation energies for unbinding were estimated from the temperature dependence of the off-rate in solution. Loading rate-dependent unbinding forces were determined for single molecules by atomic force microscopy, which extrapolated at zero force to a value close to the off-rate measured in solution, without any indication for multiple transition states. The measured unbinding forces of all nine mutants correlated well with the off-rate in solution, but not with the temperature dependence of the reaction, indicating that the same transition state must be crossed in spontaneous and forced unbinding and that the unbinding path under load cannot be too different from the one at zero force. The distance of the transition state from the ground state along the unbinding pathway is directly proportional to the barrier height, regardless of the details of the binding site, which most likely reflects the elasticity of the protein in the unbinding process. Atomic force microscopy thus can be a valuable tool for the characterization of solution properties of protein-ligand systems at the single molecule level, predicting relative off-rates, potentially of great value for combinatorial chemistry and biology.
Proceedings of the National Academy of Sciences 09/2000; 97(18):9972-7. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A method is presented for the analysis of magnetic force microscopy (MFM) measurements that allows the quantitative determination of the sample stray field. It is shown how measurements on an easily obtainable calibration sample can be used to calibrate the MFM measurement as a function of the wavelength of the sample stray field at the tip apex. It is demonstrated that the thus obtained MFM calibration can be used to determine the stray field distribution of the tip. Furthermore, the effect of the tip on the MFM imaging mechanism is analyzed by comparing it to some simple tip models. From the analysis, it is shown that the point–monopole and dipole models do not accurately describe the MFM imaging mechanism. © 2000 American Institute of Physics.
Journal of Applied Physics 06/2000; 88(1):435-445. · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To explore the analytic relevance of unbinding force measurements between complementary DNA strands with an atomic force microscope, we measured the forces to mechanically separate a single DNA duplex under physiological conditions by pulling at the opposite 5'-ends as a function of the loading rate (dynamic force spectroscopy). We investigated DNA duplexes with 10, 20, and 30 base pairs with loading rates in the range of 16-4,000 pN/s. Depending on the loading rate and sequence length, the unbinding forces of single duplexes varied from 20 to 50 pN. These unbinding forces are found to scale with the logarithm of the loading rate, which is interpreted in terms of a single energy barrier along the mechanical separation path. The parameters describing the energy landscape, i.e. , the distance of the energy barrier to the minimum energy along the separation path and the logarithm of the thermal dissociation rate, are found to be proportional to the number of base pairs of the DNA duplex. These single molecule results allow a quantitative comparison with data from thermodynamic ensemble measurements and a discussion of the analytic applications of unbinding force measurements for DNA.
Proceedings of the National Academy of Sciences 10/1999; 96(20):11277-82. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The experimental limits of micromechanical calorimetry at ambient conditions are demonstrated. In the investigation of rotator phase transitions of n alkanes we have obtained a heat sensitivity of 500 pJ for a sample mass of about 7 pg with a time resolution of 0.5 ms. The time resolution is restricted by the thermal response of the bimetallic cantilever. A problem in the precise quantification of the transition enthalpies is heat transport through the atmospheric environment. A calibration of the apparatus constant is proposed to overcome this problem. © 1998 American Institute of Physics.
Applied Physics Letters 10/1998; 73(16):2296-2298. · 3.84 Impact Factor
-
Hans J. Hug,
B. Stiefel,
P. J. A. van Schendel,
A. Moser,
R. Hofer,
S. Martin, H.-J. Güntherodt,
Steffen Porthun,
Leon Abelmann,
J. C. Lodder,
Gabriel Bochi,
R. C. O’Handley
[show abstract]
[hide abstract]
ABSTRACT: We present a transfer-function approach to calculate the force on a magnetic force microscope tip and the stray field due to a perpendicularly magnetized medium having an arbitrary magnetization pattern. Under certain conditions, it is possible to calculate the magnetization pattern from the measured force data. We apply this transfer function theory to quantitatively simulate magnetic force microscopy data acquired on a CoNi/Pt multilayer and on an epitaxially grown Cu/Ni/Cu/Si(001) magnetic thin film. The method described here serves as an excellent basis for (i) the definition of the condition for achieving maximum resolution in a specific experiment, (ii) the differences of force and force z-derivative imaging, (iii) the artificial distinction between domain and domain wall contrast, and finally (iv) the influence of various tip shapes on image content. © 1998 American Institute of Physics.
Journal of Applied Physics 05/1998; 83(11):5609-5620. · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: N/ were achieved at room temperature, which is a considerable improvement over commercial cantilevers. Mechanisms which determine
Q-factors are discussed briefly. Quantitative understanding of MRFM is absolutely necessary. Calculations of the magnetic
field and field gradients for several types of permanent magnets are presented.
Applied Physics A 04/1998; 66:S341-S344. · 1.63 Impact Factor
-
H.P. Lang,
R. Berger,
F. Battiston,
J.-P. Ramseyer,
E. Meyer,
C. Andreoli,
J. Brugger,
P. Vettiger,
M. Despont,
T. Mezzacasa,
L. Scandella, H.-J. Güntherodt,
C. Gerber,
J.K. Gimzewski
[show abstract]
[hide abstract]
ABSTRACT: can be detected by its adsorption on aPt-coated sensor because achange in surface stress causes astatic bending of the
sensor. The diffusion of various alcohols into polymethylmethacrylate induces resonance frequency shifts in adynamic measuring
mode and bending in the static mode, which allows one to distinguish between the various alcohols.
Applied Physics A 04/1998; 66:S61-S64. · 1.63 Impact Factor
-
Applied Physics A 04/1998; 66:S55-S59. · 1.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A fast and extremely sensitive method for reversible thermal analysis of picoliter volumes of solid samples is presented. Using a micromechanical calorimeter based on the deflection of a bimetallic cantilever, enthalpy changes at phase transitions in n‐alkanes (paraffins) are determined. The key role of volume changes associated with phase transitions is discussed together with a method to separate thermal and volume‐induced stresses associated with these phase transitions. © 1996 American Institute of Physics.
Applied Physics Letters 06/1996; 69(1):40-42. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Molecular recognition between biotinylated bovine serum albumin and polyclonal, biotin-directed IG antibodies has been measured directly under various buffer conditions using an atomic force microscope (AFM). It was found that even highly structured molecules such as IgG antibodies preserve their specific affinity to their antigens when probed with an AFM in the force mode. We could measure the rupture force between individual antibody-antigen complexes. The potential and limitations of this new approach for the measurement of individual antigen/antibody interactions and some possible applications are discussed.
Biophysical Journal 06/1996; 70(5):2437-41. · 3.65 Impact Factor
