Biomedical subjects

U Staufer

Publications and source records attributed to U Staufer.

5 recordsLinked to original sources

PubMed2003

Atomic force bio-analytics.

The atomic force microscope (AFM) allows biomolecules to be observed and manipulated under native conditions. It operates in buffer solution, produces molecular images with outstanding signal-to-noise ratio, and addresses single molecules. Progress in sample preparation and instrumentation has led to topographs that reveal sub-nanometer details and surface dynamics of biomolecules. Antibodies or oligonucleotides immobilized on cantilevers induce bending upon binding of the cognate biomolecule, allowing sub-picomolar concentrations to be measured. Biomolecules tethered between support and retracting AFM-tip produce force extension curves that reflect the mechanical stability of secondary structure elements. Furthermore, multifunctional tips may activate single molecules to observe them at work. In all cases, the cantilever is critical: its mechanical properties dictate the force-sensitivity and the scanning speed.

Microscopy, Atomic Force↗

PubMed2003

Characterization and fabrication of fully metal-coated scanning near-field optical microscopy SiO2 tips.

The fabrication of silicon cantilever-based scanning near-field optical microscope probes with fully aluminium-coated quartz tips was optimized to increase production yield. Different cantilever designs for dynamic- and contact-mode force feedback were implemented. Light transmission through the tips was investigated experimentally in terms of the metal coating and the tip cone-angle. We found that transmittance varies with the skin depth of the metal coating and is inverse to the cone angle, meaning that slender tips showed higher transmission. Near-field optical images of individual fluorescing molecules showed a resolution < 100 nm. Scanning electron microscopy images of tips before and after scanning near-field optical microscope imaging, and transmission electron microscopy analysis of tips before and after illumination, together with measurements performed with a miniaturized thermocouple showed no evidence of mechanical defect or orifice formation by thermal effects.

Aluminum↗

PubMed2001

Near-field optical microscopy based on microfabricated probes.

We demonstrate high resolution imaging with microfabricated, cantilevered probes, consisting of solid quartz tips on silicon levers. The tips are covered by a 60-nm thick layer of aluminium, which appears to be closed at the apex when investigated by transmission electron microscopy. An instrument specifically built for cantilever probes was used to record images of latex bead projection patterns in transmission as well as single molecule fluorescence. All images were recorded in constant height mode and show optical resolutions down to 32 nm.

Journal Article↗

PubMed2000

Microfabrication of a combined AFM-SNOM sensor

The objective of this work is to fabricate a scanning probe sensor that combines the well-established method for atomic force microscopy, employing a micro-machined Si cantilever and integrated tip, with a probe for the optical near field. A photosensitive pn-junction is integrated into the tip for that purpose and an Al coating is applied to the tip. It comprises an aperture of 50-70 nm in diameter at the apex of the tip in order to spatially limit the interaction of the tip to the optical near field of the sample. Characterization of the tip and first results of simultaneously recorded force and photon images are presented.

Journal Article↗

PubMedDate not supplied

Towards better scanning near-field optical microscopy probes--progress and new developments.

Several approaches are described with the aim of producing near-field optical probes with improved properties. Focused ion beam milling allows the fabrication of small apertures in a controlled fashion, resulting in probes with excellent polarization properties and increased transmission. Microfabrication processes are described that allow the production of apertures of 30-50 nm, facilitating the mass-fabrication of apertured tip structures that can be used in a combined force/near-field optical microscope. Finally, possible future developments are outlined.

Journal Article↗