JPH02140643A - Measuring method for magnetic grain quantity in magnetic fluid - Google Patents

Abstract

PURPOSE:To measure the magnetic grain quantity of a general magnetic fluid containing a fluid of low concentration whose grain quantity is small, as well in a short time by providing a test piece and a magnet, and placing a polarizer on both sides of the test piece. CONSTITUTION:When a magnet 3 is allowed to work on both ends of a test piece 4, magnetic grains are arranged with directivity in the magnetic pole direction by an action of magnetic force, therefore, when a monochromatic light which is brought to plane polarization by a polarizer 2 is allowed to pass through therein, a double refraction is generated. Subsequently, when a polarizer 5 whose main axis is rotated at a right angle against a main axis of the polarizer 2 is placed behind the test piece 4, the test piece 4 is a non-polarization substance, when a magnetic field is not applied, and light is cut off by the polarizers 2, 5. However, when a magnetic field is applied to a magnetic fluid, an optical anisotropy is generated, a double refraction of light caused by magnetism occurs and the light is detected. Since magnitude of this double refraction is proportional to the quantity of the magnetic grains, the quantity of the magnetic grains can be known by photodetecting the intensity of light which passes through the polarizer 5 by a photodetecting part 7, and measuring it by an oscilloscope 8.

Description

[Detailed Description of the Invention] (Industrial Application Field) A liquid in which magnetic particles are dispersed in a colloidal form is called a magnetic fluid, and has recently attracted much attention in terms of measurement and control. Actuators are actively being developed. For example, magnetic bearings using magnetic fluid,
Magnetic seal, magnetic 'jK? Attempts have already been made to put things into practical use, such as magnets, magnetic dampers, and optical switches. In addition, in the field of medicine, research has recently been conducted on methods of attaching magnetic particles to cells, or incorporating magnetic particles into cells, and then extracting them along with blood for examination. The properties of the fluid containing magnetic particles (hereinafter collectively referred to as magnetic fluid) used in these applications are based on the properties of the magnetic particles originally mixed into the fluid, so depending on the amount of magnetic particles, the characteristics as a magnetic fluid can be significantly affected. different.

Therefore, a method for accurately measuring the amount of magnetic particles in a fluid is essential for the development of devices using magnetic fluids.

The present invention relates to a method for optically measuring the amount of magnetic particles in a magnetic fluid.

(Prior Art) In a high 1 degree magnetic fluid containing many magnetic particles, if the specific gravity of the magnetic particles and the solution is known, the amount of magnetic particles can be measured from the volume and the II amount. However, this method has the disadvantage that it requires a considerable amount of magnetic fluid as a sample, a measuring device to accurately measure volume and weight, and the specific gravity of the solution and magnetic particles must be determined in advance. Ta. Especially in low-concentration fluids where the amount of magnetic particles is small, the measurement error is large and the amount of magnetic particles in the fluid cannot be accurately measured. The objective is to obtain a measurement method that can measure the amount of magnetic particles in general magnetic fluids, including low-concentration fluids with a small amount of particles, in a short time and with a small amount of sample.

(Means for Solving the Problems) In order to achieve this object, the present invention includes a light-transmitting object (hereinafter referred to as a test piece) filled with a sample liquid and a magnet that applies magnetism in one direction to the object. , and is configured such that polarizers are arranged on both sides of the test piece so that their main axes are perpendicular to each other, and monochromatic light is passed through the polarizers to optically measure the amount of magnetic particles in the fluid. This provides a method for measuring the amount of magnetic particles.

The test piece is made by providing a gap in an object that allows light to pass through, and filling it with a magnetic fluid as a sample liquid.The material may be any material that allows light to pass through, but the structure is similar to that in the example. A plate-shaped object filled with sample liquid in a plane direction is convenient for aligning the optical axis. It is not necessary and may be block-shaped or beam-shaped.

The magnet may be a permanent magnet or an electromagnet, and inside the test piece,
That is, they are arranged so that magnetic flux passes in one direction through the magnetic fluid. On the other hand, when the axis of the magnet is orthogonal to the optical axis of the monochromatic light as in the embodiment, a large amount of light can be output, but measurement is possible even if the axis is crossed obliquely.

(Function) A simple method for measuring the amount of magnetic particles in a magnetic fluid containing a small amount of magnetic particles has not yet been established, which has hindered the development of devices using magnetic fluid. Since the amount of particles can be measured fairly accurately and easily with a small amount of sample liquid, it becomes possible to design precision equipment using magnetic fluids. In particular, the development of various sensors and actuators will be promoted.

(Example) In the zero-line measurement method, the configuration of an example of the present invention is shown in FIG.
Monochromatic light R1, polarizer 2, magnet 3, test piece 4, polarizer 5,
The principle of the present invention, which is composed of a filter 6, a light receiving part such as a photomultiplier tube 7, and a measuring part such as an oscilloscope 8, utilizes the birefringence of a test piece 40 filled with magnetic fluid. In other words, when magnetism (N-3)3 is applied to both ends of the test piece, the magnetic particles dispersed in the magnetic fluid are oriented in the direction of the magnetic poles due to the action of the magnetic force. When monochromatic light that has been plane-polarized by the polarizer 2 is passed through it, birefringence occurs. When a polarizer 6 whose main axis is rotated at right angles to the main axis of the polarizer 2 is placed behind the test piece 4, the test piece 4 is a non-polarizing material when no magnetic field is applied, and 2. 5
The light is blocked by the light. However, when a magnetic field is applied to a magnetic fluid, optical anisotropy occurs, causing birefringence of light due to magnetism, and the light is detected. The magnitude of this birefringence increases as the amount of magnetic particles increases, so the polarizer 6
The amount of magnetic particles can be determined by receiving the intensity of the light that has passed through the light receiving portion 7 and measuring it with an oscilloscope 8 or the like. Although the optical anisotropy of magnetic fluids is well known, the relationship between the amount of magnetic particles and the birefringence of light is not clear, and was clarified for the first time by the present invention.

A very specific example of the above configuration will be described below. The magnetic fluid used in the experiment had a specific gravity of 1.43 (256 C), a saturation magnetization of 310±20 Gauss, and an appearance of a black liquid. Water was used as a solvent, and the solute (magnetic particles) was magnetite particles of 20 to 50 nm. The length of the test piece 4 used in the measurement was 4.
0 rn In * Radius 10mm, Thickness 1.3mm
A polyvinyl chloride spacer (thickness: 0.1 mm) is sandwiched between two transparent glass plates, and the spacer is filled with magnetic fluid. On the other hand, the magnet 3 for providing magnetic anisotropy is an electromagnet designed to generate a negative magnetic field, and the monochromatic light source is a helium neon laser.

These were arranged in exactly the same manner as in FIG. 1, and the phase difference and the mixed concentration of the magnetic fluid were examined, and FIG. 2 shows the result.

In this example, a low-concentration magnetic fluid with few magnetic particles was shown, but of course high-concentration measurements can be made by narrowing the gap in which the sample liquid is filled in the test piece.

(Effect of the invention) Since this method is configured as described above, the following (1)
As is clear from FIG. 2, the phase increases with the particle concentration within the magnetic fluid. Therefore, the amount of magnetic particles in the magnetic fluid can be measured by this method.

(2) Capable of measuring the amount of particles in low-concentration magnetic fluids (Figure 2 1)
1N), it is possible to eliminate the disadvantage of the inability to measure low concentration fluids with respect to the conventional specific gravity measurement method.

(3) Measurement results can be obtained simply by filling a test piece with a sample of magnetic fluid and emitting salt with a laser beam, so measurements can be carried out in a short time with a sample of v& amount.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of a method for measuring magnetic particles in a magnetic fluid according to the present invention, and FIG. 2 is a graph showing the relationship between the magnetic particle concentration and phase of a magnetic fluid. Symbols in the figure: 1. Monochromatic light source, 2. Polarizer, 3.
・Magnet, 4. ・Test piece, 5. ・Polarizer, 6. Filter, 7. ・Photomultiplier tube. 8. A similar effect to the oscilloscope was obtained.

Claims (1)

[Claims] 1 A light-transmitting object (hereinafter referred to as a test piece) filled with a sample liquid and a magnet that applies magnetism in one direction, and polarizers are placed on both sides of the test piece so that their main axes are at right angles to each other. A method for measuring the amount of magnetic particles in a fluid, the method comprising: passing monochromatic light through the magnetic particles, and measuring the amount of magnetic particles optically.