Rheometer for rapidly measuring small quantity samples
First Claim
1. A miniature rheometer for analyzing a small quantity sample, comprising:
- a first plate and a second plate, forming a pair of plates having a known geometry for confining the sample between the plates, said sample having a volume of 200 microliters or less;
an adjusting device for adjusting the separation of the plates;
an actuating element mechanically coupled to the first plate, which produces a shear strain within the sample by generating a defined small-scale relative motion of the first and second plates;
a sensing element which outputs a position signal indicative for a displacement of at least one of the first and second plates; and
a feedback circuit for providing force rebalance of the force applied to the sample by the small-scale relative motion of the first and second plates on the basis of the position signal, wherein an amount of force rebalance is a measure for the shear stress within the sample.
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Accused Products
Abstract
The present invention relates to a miniature rheometer, a parallel rheometer, and improved force sensor elements which may advantageously be used in combination with the miniature rheometer and the parallel rheometer. The miniature rheometer is adapted to determine rheological characteristics of materials which are provided in the form of small quantity samples. The miniature rheometer comprises an actuating element, a sensing element and a feedback circuit to provide rebalance of the shear force applied by the sample to the sensing element, which insures an exceptional stiffness in determining the shear strain so as to allow measurements of high accuracy. The parallel rheometer of the present invention allows simultaneous measurements of a plurality of samples so as to allow of a plurality of samples within a short time period. The force sensor element according to the present invention allows simultaneous measurement of a shear force and a normal force applied to the sensor element. Moreover, a rheometer is provided which comprises a force sensor based on stress-optic material.
50 Citations
77 Claims
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1. A miniature rheometer for analyzing a small quantity sample, comprising:
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a first plate and a second plate, forming a pair of plates having a known geometry for confining the sample between the plates, said sample having a volume of 200 microliters or less;
an adjusting device for adjusting the separation of the plates;
an actuating element mechanically coupled to the first plate, which produces a shear strain within the sample by generating a defined small-scale relative motion of the first and second plates;
a sensing element which outputs a position signal indicative for a displacement of at least one of the first and second plates; and
a feedback circuit for providing force rebalance of the force applied to the sample by the small-scale relative motion of the first and second plates on the basis of the position signal, wherein an amount of force rebalance is a measure for the shear stress within the sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. A parallel rheometer for simultaneously analyzing material characteristics of two or more samples, comprising:
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first and second plates respectively having regions for receiving and confining said two or more samples, the first and second plates being moveable relatively to each other;
an actuator adapted to move the first and second plates relative to each other for producing a shear strain within each sample;
and at least one sensor associated with each region for simultaneously detecting shear stress within each sample. - View Dependent Claims (43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 61, 62, 63)
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- 59. The parallel rheometer of clam 42, wherein the actuator comprises an actuator element for each sample which is symmetrical with respect to an axis normal to a surface of the sample, wherein the actuator element is rotatable around said normal axis by a driving means.
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64. A rheometer, comprising:
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a pair of plates spaced apart from each other by a defined distance for receiving and confining a sample therebetween, an adjusting means which adjusts the distance between the plates, a driving means coupled to at least one of the plates, which generates a relative motion between the plates without changing the distance, and a shear stress sensor, the shear stress sensor comprising a stress-sensing material of a defined stress-optic coefficient indicating one of birefringence and retardation of linearly polarized light passing the stress-sensing material, as a function of applied stress/unit path length. - View Dependent Claims (65, 66, 67, 68, 69, 70)
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71. A sensor element for outputting a signal in response to a mechanical deformation applied to the sensor element, comprising:
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a sample plate arranged within an opening of a substrate;
at least two tethers, one end of each tether being attached to the sample plate, the other end of each tether being attached to the substrate so as to support the sample plate;
a piezo-resistive portion in each of the tethers; and
first and second electrically conductive lines formed on the tethers and the substrate, connecting each piezo-resistive portion with first and second contact pads formed on the substrate, wherein the piezo-resistive portion of one of said at least two tethers is adapted to generate a maximum change of its internal resistance when a shear force is applied to the sample plate, and wherein the piezo-resistive portion of the other one of said at least two tethers is adapted to generate a maximum change of its internal resistance when a force normal to the sample plate is applied. - View Dependent Claims (72, 73, 74, 75, 76, 77)
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Specification