# US 5,705,738 A · Precise shear-stress measurement apparatus

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- Number: US 5,705,738 A
- Document ID: US5705738A
- Status: Granted
- Kind: A
- Application number: 08/784,704
- Filed: 1997-01-16
- Granted: 1998-01-06
- Earliest claimed: 1997-01-16
- Assignees: Japan Science and Technology Corporation
- Inventors: Kazue Kurihara
- Web page: https://patentgrep.com/patent/US5705738A

## CPC

- G01N 19/02: Measuring coefficient of friction between materials {(testing of tyres G01M17/02; determinations of friction coefficient used in vehicle braking or traction control systems B60T8/172)}
- G01N 11/00: Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N 13/00: Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects (scanning-probe techniques or apparatus G01Q)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A precise shear-stress measurement apparatus includes a spring disposed perpendicularly to a sample surface, and a cylindrical piezoelectric element disposed perpendicularly to the sample surface and connected to the spring. The piezoelectric element is circumferentially divided into a plurality of pieces. The apparatus further includes a circuit for driving the piezoelectric element, a capacitance-type displacement gauge for detecting a horizontal displacement of the spring, and a battery for driving the displacement gauge. This reduces noise from an electric system, thereby making it possible to precisely measure even rheology motion in a very small space on the order of nanometers.

## Claims

### Claim 1

A precise shear-stress measurement apparatus comprising:
(a) a spring disposed perpendicularly to a sample surface;
(b) a cylindrical piezoelectric element disposed perpendicularly to said sample surface and connected to said spring, said piezoelectric element being circumferentially divided into a plurality of pieces;
(c) means for driving said piezoelectric element;
(d) a capacitance-type displacement gauge for detecting a horizontal displacement of said spring; and
(e) a battery for driving said displacement gauge.

### Claim 2 (depends on 1)

A precise shear-stress measurement apparatus according to claim 1, wherein said piezoelectric element has a four-segment structure having a common electrode and at least two drive electrodes, and first and second voltages each having a triangular waveform are supplied to said drive electrodes, the first and second voltages having a phase difference of 180.degree. therebetween.

### Claim 3 (depends on 1)

A precise shear-stress measurement apparatus according to claim 1, wherein a member that provides said sample surface has a lens-like shape and is replaceable, and said member is held by a pair of springs disposed perpendicular to said sample surface and is horizontally moved by said piezoelectric element at a constant speed.

### Claim 4 (depends on 3)

A precise shear-stress measurement apparatus according to claim 3, wherein said sample surface is a surface of a solid material such as glass or mica, or a chemically modified surface of the solid material.

### Claim 5 (depends on 1)

A precise shear-stress measurement apparatus according to claim 1, wherein said capacitance-type displacement gauge is provided with a lock-in amplifier.

### Claim 6

A precise shear-stress measurement apparatus comprising a spring disposed perpendicularly to a sample surface; a cylindrical piezoelectric element disposed perpendicularly to said sample surface and connected to said spring, said piezoelectric element being circumferentially divided into a plurality of pieces; means for driving said piezoelectric element; and a capacitance-type displacement gauge for detecting a horizontal displacement of said spring, wherein said measurement apparatus is assembled as an exchangeable unit.

### Claim 7 (depends on 6)

A precise shear-stress measurement apparatus according to claim 6, wherein said precise shear-stress measurement apparatus is immersed into a liquid within a sealed container.

### Claim 8 (depends on 6)

A precise shear-stress measurement apparatus according to claim 6, wherein said precise shear-stress measurement apparatus in the form of a unit is built into a surface-force measurement apparatus which comprises:
means for measuring the distance between a pair of sample surfaces; and
means for changing the distance between the pair of sample surfaces.

### Claim 9 (depends on 8)

A precise shear-stress measurement apparatus according to claim 8, wherein the distance between the pair of surfaces is determined through measurement of interference fringes using white light.