Noncontact Sensitivity and Compliance Calibration Method for Cantilever-Based Instruments

• US 20070062252A1
• Filed: 06/26/2006
• Published: 03/22/2007
• Est. Priority Date: 02/28/2001
• Status: Active Grant

• Current Assignee: Oxford Instruments Asylum Research Inc (Oxford Instruments PLC)
• Original Assignee: Asylum Research Corporation (Oxford Instruments PLC)
• Inventors: Proksch, Roger
• Granted Patent: US 7,434,445 B2
• Time in Patent Office: Days
• US Class Current: 73/1.790
• CPC Class Codes: G01B 5/28 for measuring roughness or irregularity of surfaces
• CPC Class Codes: G01F 1/00 Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow measuring a proportion of the volume flow G01F5/00
• CPC Class Codes: G01F 1/28 by drag-force, e.g. vane type or impact flowmeter
• CPC Class Codes: G01N 2203/0688 Time or frequency
• CPC Class Codes: G01N 3/00 Investigating strength properties of solid materials by application of mechanical stress
• CPC Class Codes: G01N 3/02 Details
• CPC Class Codes: G01N 3/06 Special adaptations of indicating or recording means
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups
• CPC Class Codes: G01Q 40/00 Calibration, e.g. of probes

Abstract

Apparatus for determining physical properties of micromachined cantilevers used in cantilever-based instruments, including atomic force microscopes, molecular force probe instruments and chemical or biological sensing probes. The properties that may be so determined include optical lever sensitivity, cantilever spring constant and cantilever sample separation. Cantilevers characterized with the method may be used to determine fluid flow rates. The apparatus measures cantilever deflection resulting from drag force as the cantilever is moved through fluid. Unlike other methods for determining such physical properties of cantilevers, the method described does not depend on cantilever contact with a well-defined rigid surface. Consequently, the apparatus may be employed in situations where such contact is undesirable or inconvenient. The apparatus may be used for applications such as molecular force measurements, atomic force microscopy and manipulation technology, chemical or biological sensing, nanometer scale surface profiling, and other aspects of nanotechnology.

Claims

1. An apparatus for determining cantilever parameters, comprising:

means for measuring a drag force acting on a cantilever by monitoring a deflection of the cantilever;

means for determining a power spectrum of the cantilever;

means for measuring motion of a base of the cantilever; and

means for determining one or more characteristics of the cantilever based on the motion of the base, the power spectrum, and the cantilever deflection.

2. The apparatus of claim 1, including means for directing a fluid flow over the cantilever;

wherein the means for determining characteristics includes means for determining a fluid flow rate of the fluid flow.

3. The apparatus of claim 1, including means for oscillating the cantilever;

wherein;

the means for monitoring the deflection is configured to monitor the deflection of the cantilever while oscillating; and

the means for determining characteristics includes a means for determining a spring constant based at least in part on the power spectrum associated with the cantilever.

4. The apparatus of claim 3, wherein the means for monitoring the deflection includes means for determining a hysteresis of deflection of the cantilever and for monitoring the hysteresis;

and

the means for determining characteristics is further configured to determine a distance between the cantilever tip and the surface based at least in part on the hysteresis.

5. The apparatus of claim 2, wherein the means for determining the fluid flow rate is configured to determine the fluid flow rate based at least in part on a spring constant and dampening constant of the cantilever.

6. The apparatus of claim 5, including means for oscillating the cantilever;

wherein;

the means for monitoring the deflection is configured to monitor the deflection of the cantilever while oscillating;

the means for determining characteristics is configured to determine a hysteresis of the deflection of the cantilever as a function of position of the base of the cantilever.

7. The apparatus of claim 1, wherein the means for monitoring the deflection is configured to determine a hysteresis of deflection of the cantilever and to monitor the hysteresis;

and

the means for determining characteristics is configured to determine a distance between the cantilever tip and the surface.

8. The apparatus of claim 1, wherein the means for monitoring the deflection is configured to determine a hysteresis of deflection of the cantilever and to monitor the hysteresis;

and

the means for determining characteristics is configured to determine dissipation between the cantilever tip and the surface in accordance with the hysteresis of deflection of the cantilever.