Imaging microviscometer

Abstract

In one general aspect, a capillary viscometer is disclosed that includes a source of fluid pressure, and a first capillary tube having an inside volume that is hydraulically responsive to the source of fluid pressure. A two-dimensional array of optical detectors is positioned proximate the first capillary tube with a first plurality of its detectors optically responsive to the inside volume of the first capillary tube and including an image data output. An acquisition driver circuit is responsive to the image data output of the two-dimensional array to acquire a series of successive images of the inside volume of the first capillary tube. Viscosity computation logic is responsive to the acquisition driver circuit and operative to compute the viscosity of the fluid from the succession of images of the inside volume of the first capillary tube.

What is claimed is: 
     
         1 . A capillary viscometer, comprising:
 a source of fluid pressure,   a first capillary tube having an inside volume that is hydraulically responsive to the source of fluid pressure,   a two-dimensional array of optical detectors positioned proximate the first capillary tube with a first plurality of its detectors optically responsive to the inside volume of the first capillary tube and including an image data output,   an acquisition driver circuit responsive to the image data output of the two-dimensional array to acquire a series of successive images of the inside volume of the first capillary tube, and   viscosity computation logic responsive to the acquisition driver circuit and operative to compute the viscosity of the fluid from the succession of images of the inside volume of the first capillary tube.   
     
     
         2 . The apparatus of  claim 1 ,
 further including a second capillary tube having an inside volume responsive to the source of fluid pressure, wherein the inside volume of the first capillary tube is larger than the inside volume of the second capillary tube,   wherein the two-dimensional array of optical detectors is also positioned proximate the second capillary tube with a second plurality of its detectors optically responsive to the inside volume of the second capillary tube, and   further including shear rate computation logic responsive to the acquisition driver circuit and operative to compute the viscosity of the fluid from the succession of images of the inside volume of the first and second capillary tubes.   
     
     
         3 . The apparatus of  claim 1 ,
 further including further capillary tubes each having an inside volume responsive to the source of fluid pressure, wherein the inside volumes of the first capillary tube and the further tubes are all different from each other,   wherein the two-dimensional array of optical detectors is also positioned proximate the further capillary tubes with further pluralities of its detectors each being optically responsive to the inside volumes of one the further capillary tubes, and   further including shear rate computation logic responsive to the acquisition driver circuit and operative to compute a shear rate of the fluid from the succession of images of the inside volumes of the first capillary tube and the further capillary tubes.   
     
     
         4 . The apparatus of  claim 3  wherein the first and further capillary tubes are placed side-by-side where they are proximate the two-dimensional array of optical detectors, and are bundled at an open end. 
     
     
         5 . The apparatus of  claim 1  wherein the viscosity computation logic is operative to compute the viscosity based on detected movement of a meniscus in the first capillary tube. 
     
     
         6 . The apparatus of  claim 1  wherein the viscosity computation logic is operative to compute the viscosity based on a pixel size and frame rate. 
     
     
         7 . The apparatus of  claim 1  further including calibration storage for calibration information about a calibration run with a calibration standard, and wherein the viscosity computation logic is responsive to the calibration information stored in the calibration storage. 
     
     
         8 . The apparatus of  claim 1  further including at least one calibration tube having an inside volume that is hydraulically responsive to at least one source of a known fluid standard and wherein the two-dimensional array of optical detectors includes a plurality of its detectors that are optically responsive to the inside volume of the calibration tube. 
     
     
         9 . The apparatus of  claim 1  wherein the first capillary tube has a diameter below about 500 microns. 
     
     
         10 . The apparatus of  claim 1  wherein the two-dimensional array of optical detectors is a two-dimensional array of visible light detectors. 
     
     
         11 . The apparatus of  claim 1  wherein the two-dimensional array of optical detectors is a two-dimensional array of infrared light detectors. 
     
     
         12 . The apparatus of  claim 1  wherein the two-dimensional array of optical detectors is a two-dimensional array of ultraviolet light detectors. 
     
     
         13 . The apparatus of  claim 1  further including a filter positioned in an optical path between the first capillary tube and the two-dimensional array of optical detectors. 
     
     
         14 . The apparatus of  claim 13  wherein the filter is a variable filter, and further including spectrum derivation logic responsive to the two-dimensional array of optical detectors. 
     
     
         15 . The apparatus of  claim 13  wherein the filter is a bandpass filter. 
     
     
         16 . A capillary viscometry method, comprising:
 driving a fluid under test through an inside volume of a first capillary tube,   acquiring successive images of the fluid under test as it advances through the inside volume of the first capillary tube, and   deriving a viscosity of the fluid under test from the successive acquired images of the fluid under test as it advances through the inside volume of the first capillary tube.   
     
     
         17 . The method of  claim 16  further including the step of driving the fluid under test through an inside volume of one or more further capillary tubes,
 acquiring successive images of the fluid under test as it advances through the inside volume of the first capillary tube and the inside volumes of the further capillary tubes, and 
 deriving a shear rate of the fluid from the succession of images of the inside volumes of the first capillary tube and the further capillary tubes. 
 
     
     
         18 . The method of  claim 16  wherein the step of deriving a viscosity is operative to derive a viscosity of a sample of less than 10 microliters. 
     
     
         19 . The method of  claim 16  further including the step of recovering the fluid under test from the first capillary tube after the step of acquiring. 
     
     
         20 . The method of  claim 16  further including the following calibration steps performed before the step of driving a fluid under test through the inside volume of the first capillary tube:
 driving a fluid calibration standard through an inside volume of a the capillary tube, 
 acquiring successive images of the fluid calibration standard under test as it advances through the inside volume of the first capillary tube, and 
 deriving calibration information from the successive acquired images of the fluid calibration standard as it advances through the inside volume of the first capillary tube, and 
 wherein the step of deriving a viscosity of the fluid under test derives the viscosity of the fluid under test from calibration information and the successive acquired images of the fluid under test as it advances through the inside volume of the first capillary tube. 
 
     
     
         21 . The method of  claim 16  wherein the step of deriving a viscosity is operative to derive a viscosity of a sample of less than 10 microliters. 
     
     
         22 . The method of  claim 16  further including the step of introducing a dye in the fluid under test, and wherein the step of acquiring successive images of the fluid under test as it advances through the inside volume of the first capillary tube is sensitive to the dye. 
     
     
         23 . The method of  claim 16  further including the step of deriving a spectrum of the fluid under test as it advances through the inside volume of the first capillary tube. 
     
     
         24 . A capillary viscometer, comprising:
 means for driving a fluid under test through an inside volume of a first capillary tube,   means for acquiring successive images of the fluid under test as it advances through the inside volume of the first capillary tube, and   means for deriving a viscosity of the fluid under test from the successive acquired images of the fluid under test as it advances through the inside volume of the first capillary tube.