Leland Stanford Junior University

Ozgur Sahin

Olav Solgaard

Calvin F Quate

Abdullah Atalar

Henrik Persson

Method and apparatus which uses harmonic cantilevers, such as used in atomic force microscopy, to detect variations in the attractive and repulsive forces on a solid surface as a result of macromolecular binding, for example, hybridization of a single stranded DNA molecule attached to the surface with another DNA molecule. The complexed macromolecule is less flexible than an uncomplexed molecule. It will typically have more negative charge due to amino acids or DNA monomers. Both stiffness of the surface and the attractive capillary forces will change after binding and may be detected. The present methods and materials enable ultraflat surfaces for the macromolecule deposition, and may include the use of a gold-coated mica substrate and a self-assembling monolayer.

Detection of macromolecular complexes on ultraflat surfaces with harmonic cantilevers

Method and apparatus which uses harmonic cantilevers, such as used in atomic force microscopy, to detect variations in the attractive and repulsive forces on a solid surface as a result of macromolecular binding, for example, hybridization of a single stranded DNA molecule attached to the surface with another DNA molecule. The complexed macromolecule is less flexible than an uncomplexed molecule. It will typically have more negative charge due to amino acids or DNA monomers. Both stiffness of the surface and the attractive capillary forces will change after binding and may be detected. By scanning the harmonic cantilever across a surface with macromolecules attached in tapping-mode and by recording the signals at the high frequency vibrations provided by harmonic cantilever, complexed molecules on a surface may be identified and quantified.

Detection of macromolecular complexes with harmonic cantilevers

A harmonic cantilever for use in an atomic force microscope includes a cantilever arm and a probe tip. The cantilever arm has a shape selected to tune the fundamental resonance frequency or a resonance frequency of a selected higher order mode so that the fundamental and higher-order resonance frequencies have an integer ratio or near integer ratio. In one embodiment, the cantilever arm can be shaped to tune the fundamental resonance frequency. Alternately, the cantilever arm can include a geometric feature for tuning the resonance frequency of the fundamental mode or the selected higher order mode. An imaging method using the harmonic cantilever is disclosed whereby signals at the higher harmonics are measured to determine the material properties of a sample. In other embodiment, a cantilever includes a probe tip positioned at a location of minimum displacement of unwanted harmonics for suppressing signals associated with the unwanted harmonics.

Harmonic cantilevers and imaging methods for atomic force microscopy

An atomic force microscope based apparatus for examining a sample includes a cantilever having a cantilever arm and a probe tip where the probe tip is offset laterally from a longitudinal axis of torsion of the cantilever arm, an oscillator that drives the cantilever into oscillation in a flexural mode to cause the probe tip to repeatedly interact with the sample where the tip-sample interaction of the laterally offset probe tip excites torsional motion of the cantilever, and a detection system that detects torsional motion of the cantilever in response to the tip-sample interaction.

Atomic force microscope using a torsional harmonic cantilever

A method for measuring high frequency force of interaction between a tip of a cantilever and a sample includes providing a cantilever having a cantilever arm and a probe tip formed on a free end of the cantilever arm where the cantilever arm has a first shape and an axis of torsion associated with the first shape and the probe tip is positioned in an offset displacement from the axis of torsion, vibrating the cantilever at or near the fundamental flexural resonance frequency with a predetermined oscillation amplitude, bringing the cantilever to the vicinity of the sample, tapping the surface of the sample repeatedly using the probe tip, and detecting changes in the amplitude or the phase of a high frequency vibration harmonic of the cantilever as the cantilever is deflected in response to features on the surface of the sample.

Torsional harmonic cantilevers for detection of high frequency force components in atomic force microscopy

A cantilever for the use in atomic force microscopy includes a cantilever arm having a fixed end being attached to a base member and a free end where the cantilever arm has a first shape and an axis of torsion associated with the first shape, and a probe tip projecting from the cantilever arm near the free end where the probe tip is positioned in an offset displacement from the axis of torsion. Alternately, the cantilever arm has a first shape selected to tune a torsional resonance frequency of a selected torsional mode or the fundamental flexural resonance frequency of the fundamental mode so that the torsional resonance frequency and the fundamental flexural resonance frequency has an integer ratio. In this manner, the torsional motion of the torsional harmonic cantilever at that harmonic frequency will be largely enhanced by the corresponding torsional resonance.

A harmonic cantilever for use in a tapping-mode atomic force microscope includes a cantilever arm and a probe tip. The cantilever arm has a shape selected to tune the fundamental resonance frequency or a resonance frequency of a selected higher order mode so that the fundamental and higher-order resonance frequencies have an integer ratio or near integer ratio. In one embodiment, the cantilever arm can be shaped to tune the fundamental resonance frequency. Alternately, the cantilever arm can include a geometric feature for tuning the resonance frequency of the fundamental mode or the selected higher order mode. An imaging method using the harmonic cantilever is disclosed whereby signals at the higher harmonics are measured to determine the material properties of a sample. In other embodiment, a cantilever includes a probe tip positioned at a location of minimum displacement of unwanted harmonics for suppressing signals associated with the unwanted harmonics.

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Stanford, CA, United States of America

Ozgur Sahin