Viscosity measuring using microcantilevers

Details Viscosity measuring using microcantilevers Viscosity measuring using microcantilevers

1999-09-23

2001-08-07

Williams, Hezron (Department: 2856)

Measuring and testing

Liquid analysis or analysis of the suspension of solids in a...

Viscosity

C073S023200, C073S024060, C073S054170

Reexamination Certificate

active

06269685

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods for measuring the viscosity of a fluid and related physical properties deriveable therefrom using a micromachined cantilever which may be optimized in geometry to the fluid being measured.
2. Prior Art
The atomic force microscope (AFM) was first demonstrated by Binnig and co-workers at IBM in Switzerland. In the AFM, the tip of a flexible cantilever stylus is rastered over the surface of a sample and the movement of the tip of the cantilever is monitored as a measure of minute forces characteristic of surfaces at the atomic level. Demonstration of this principle led to rapid development of microcantilevers [(Albrecht et al.,
J. Vac. Sci. Technol
, 8, 3386 (1990)] The concept of micromechanical and microelectromechanical detection devices has been developed for a number of analytical uses. Wachter et al., U.S. Pat. No. 5,445,008 describes the use of vibrated microcantilevers having a chemical coating as a detector for the presence of specific chemical entities. Thundat, et al. in Appliance Manufacturer, April 1997, 57 (1997) and
Microscale Thermophysical Engineering
1, 185 (1997) describe developments of the microelectromechanical sensors (MEMS) for the measurement of chemicals and physical phenomena including the use of sensors to determine concentrations of glycerol in water based on viscosity.
U.S. Pat. No. 5,719,342 to Thundat et al., addresses additional methods for analysis using MEMS devices particularly directed to induced stress in the microcantilever.
U.S. Pat. No. 5,130,257 to Bear et al., discloses a viscosity sensor fabricated using a surface transverse wave device for use in the measurement of viscosity.
Oden et al.,
Appl. Phys. Lett
., 68, 3814 (1996) discloses method for the measurement of viscosity using microfabricated cantilevers in a confined medium. The frequency of vibration of an isolated vibrating cantilever is measured in different solutions.
U.S. Pat. No. 5,494,639 to Grzegorzewski discloses a disposable biosensor which uses a vibrating member beneath a cell to accurately measure blood coagulation time as a function of viscosity.
The foregoing methods are attempts to find an alternative to the instruments most currently used to measure viscosity of both liquids and gases. These are instruments which perform the analysis by a comparison with a “control fluid.” For this reason, measurements are still routinely done using instruments such as the Redwood viscometer, the Couette or rotational concentric-cylinder viscometer (MacMichael or Stormer viscometer), the Rotating Sphere viscometer, the Sayboult Falling Body viscometer, the Vibrating String viscosity meter and the thickness-sheer mode resonators. All of these methods require comparatively large volumes and bulky equipment. The need remains for a small reliable and inexpensive instrument which can measure the viscosity or specific density of small amounts of a liquid or gas and which can be used in difficult-to-access locations.
BRIEF DESCRIPTION OF THE INVENTION
It is an object of this invention to accurately determine the viscosity of a fluid in a simple and reliable manner.
It is a further object of this invention to provide an apparatus and a method which may be optimized to determine the viscosity of fluids of a general type, e.g. gases, liquids and slurries.
These and other objects of this invention may be achieved by moving a microfabricated beam structure of an optimized shape through a fluid and determining the viscosity based upon the bending of the cantilever structure. The base of the cantilever structure may be rastered over a small distance at varying rates or frequencies to determine the approximate viscosity and optimal raster frequency to obtain optimal accuracy for the specific fluid of interest.


REFERENCES:
patent: 3411343 (1968-11-01), Baird, Jr.
patent: 3898871 (1975-08-01), Gerin
patent: 4437337 (1984-03-01), Fenrick
patent: 4464928 (1984-08-01), Dealy
patent: 4862735 (1989-09-01), Williams et al.
patent: 5130257 (1992-07-01), Baer et al.
patent: 5345816 (1994-09-01), Clabes et al.
patent: 5445008 (1995-08-01), Wachter et al.
patent: 5807758 (1998-09-01), Lee et al.
patent: 5892143 (1999-04-01), Namerikawa et al.
patent: 5955659 (1999-09-01), Gupta et al.
patent: 6016686 (2000-01-01), Thundat
patent: 6021665 (2000-02-01), Hayashi et al.
patent: 0 305 133 A2 (1988-08-01), None
patent: 1 476 935 (1977-06-01), None
patent: WO 97/26527 (1997-07-01), None
International Search Report for International Application No. PCT/US00/26104 (Nov. 24, 2000).
Nanofluid Handling by Micro-Flow-Sensor Based on Drag Force Measurements; V. Glass et al., pp. 167-172 (Feb. 7, 1993).
Oden, P. I. et al. Applied Physics Letters 68 (26) Jun. 24, 1996, pp. 3814-3816.*
Oden, Thomas et al. Appliance Manufacturer v45n4 Apr. 1997, pp. 57-58.

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