JP2002065866A - Compound electrode to be used for electric stimulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for compensating the spatial dispersion of the skin impedance. SOLUTION: An electrode for electric stimulation from a skin surface is a compound electrode formed of plural fine electrodes, and the current of the fine electrodes is controlled. The fine electrodes are used for a constant current source. Dimension of the fine electrode is decided on the basis of the density of sweat glands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode used for electrical stimulation, and more particularly to an electrode which can be used for general electrical stimulation from the skin surface. Electrical stimulation (used for rehabilitation, etc.), transdermal drug administration (some voltage may be applied)
And so on.

[0002]

2. Description of the Related Art Electrical stimulation of human skin for a certain purpose has been carried out in various fields for many years. However, when electricity is supplied from the skin surface, the following problems occur. . The contact area on the skin surface is keratin (Stratum Corn
Since the sweat glands (Sweat Duct) are distributed in the eum), the current path greatly changes depending on whether or not sweat exists in the sweat glands. In particular, when sweat is present, the sweat glands are turned on (FIG. 1 (a)), so that current is concentrated on the sweat glands, and the generated Joule heat causes pain.

[0003] On the other hand, there is known a method of alleviating this situation by sandwiching a conductive gel layer (Gel) (FIG. 1B). In this case, the gel acts as a resistance layer, thereby mitigating a change in conductance of a minute portion due to a sweat gland or the like. The gel layer must be high resistance and thin. This is because the high resistance corresponds to the change in conductance, and the thinness ensures anisotropic conductivity.

[0004] However, this involves (1) an increase in required voltage due to the interposition of the high resistance layer, and (2)
(3) When an array electrode is used, there is a problem in that a current flows between electrodes only through a gel. Therefore, the ideal gel (Smart Ge
l) The ability required for what should be called is deduced (Fig. 1
(C)). That is, there is a need for a device that actively changes the local impedance of the gel so as to compensate for minute and local changes in the impedance of the skin.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode which compensates for the spatial dispersion of skin impedance.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and is an electrode for performing electrical stimulation from the skin surface, wherein the electrode is a bundle of a plurality of microelectrodes. Wherein each of the microelectrodes is configured to control the current, and preferably, the microelectrodes are used as a constant current source.

The present invention relates to an electrode having a function of compensating for a change in conductance of a minute portion, and provides a system for equivalently controlling impedance by using a minute electrode and performing current control on each of the electrodes. (FIG. 1D). That is, a plurality of fine electrodes are bundled and used as a single composite electrode.

[0008] The size required for the microelectrode is determined from the density of sweat glands. In one preferred (but not limited to) embodiment, there is at most one sweat gland under one microelectrode. For example, there are 3 to 5 sweat glands per mm ² in the fingertip skin. Therefore, the diameter 0.3
With a fine electrode of mm, there is at most one sweat gland on each electrode. When the entire electrode covers several cm as in functional electrical stimulation, it may be possible to divide the electrode into about 3 to 20. In a preferred embodiment, the shape of the microelectrode is a circular shape in a plan view, but the shape of the microelectrode is not limited to this, and may be, for example, a fine linear shape.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows an electro-tactile display device, which performs analog multiplication of a one-channel high-speed pulse signal (1 MHz) and an eight-channel low-speed weighting signal to obtain a completely synchronized eight-channel stimulus signal. This is converted into a current by a VI converter, and the subject is energized. The subject places his finger on the electrode array and wears a grounded ring. By changing the weight of the electrode array, sensory nerves under the skin can be selectively stimulated, and various sensations can be generated. This is described in detail in Japanese Patent Application No. 11-332177.

In such an electro-tactile display, there is a problem that the skin impedance is locally dispersed. In particular, when a sweat gland exists under the electrode, current concentrates on the sweat gland, causing Joule heat to occur, which may cause sudden pain. In the present invention, the electrodes themselves are formed of a set of fine electrodes, and current control is performed on each of the electrodes to prevent local concentration of current.

FIG. 2 shows one embodiment of the composite electrode according to the present invention. Seven microelectrodes 1 having a diameter of 0.3 mm are bundled to form a composite electrode 2 having a diameter of 1 mm. More specifically, a composite electrode is formed by radially disposing six microelectrodes around one microelectrode. The microelectrode 1 is formed from a stainless steel 3 having a circular shape in a plan view, and an insulator 4 is coated therearound. Therefore, the plurality of microelectrodes 1 constituting one electrode 2 are adjacent to each other with the insulator 4 interposed therebetween.
Is filled with a filling 5. Each microelectrode 1 is used as a single electrode 2 by controlling the current,
It corresponds to the spatial dispersion of skin impedance. The arrangement of the plurality of microelectrodes is not limited to that of FIG. 2. For example, one electrode may be configured by arranging microelectrodes in a row.

In the embodiment, the array electrodes 6 are formed by further arranging the electrodes 2 composed of a plurality of microelectrodes 1 in an array. This means that, by changing the weighting of the array electrodes 6, the nerve axons are selectively stimulated in accordance with the direction in which the nerve axons extend, and the nerve axons having different depths with respect to the skin surface by changing the stimulation depth. Is selectively stimulated, and the selection of the weight of the array electrode 6 is performed by selecting the yin and yang of each electrode 2 constituting the array electrode 6 and selecting the arrangement of each electrode 2. A tactile display for selectively stimulating nerve axons is disclosed in Japanese Patent Application No. 11-332177 as described above.

As described above, there are 3 to 5 sweat glands per 1 mm ² in the fingertip skin. Therefore 0.3mm in diameter
With only one microelectrode, there is at most one sweat gland on each electrode. Therefore, local concentration of current can be prevented by controlling the current of each fine electrode.

[0014] By producing a large number of fine electrodes, there is a problem that a huge control circuit may be required. However, the individual fine electrodes constituting one electrode only need to output the same current, so that the electrode according to the present invention can be realized by adding a simple circuit.

FIG. 3 shows an example of an electrode circuit according to the present invention. A current mirror circuit is used to perform current control for the number of electrodes at the same time. As is clear from FIG.
Compared with the conventional single electrode, the number of transistors only increases by 2 × N (N is the number of fine electrodes), and there is little cost problem. The circuit constituting the electrode according to the present invention is not limited to the one shown in FIG. 3, and a transistor may be formed on an electrode substrate.

[0016]

According to the present invention, local concentration of current can be prevented by forming the electrode itself as a set of fine electrodes and controlling the current of each fine electrode. Compensation can be performed, thereby compensating for a change in conductance of a minute portion due to sweat glands or the like.

[Brief description of the drawings]

FIG. 1 (a) modeling of electrodes, skin (keratin, sweat glands), (b) function of stabilizing impedance of conductive gel, (c) higher than deduced in transcutaneous electrical stimulation (D) shows mounting with a microcurrent source array (composite electrode).

FIG. 2 is a view showing one embodiment of a composite electrode according to the present invention.

FIG. 3 is a diagram showing one circuit configuration of the composite electrode according to the present invention.

FIG. 4 is a system configuration diagram of electrical stimulation.

 ──────────────────────────────────────────────────続 き Continuing from the front page (71) Applicant 500409297 Hiroyuki Kajimoto 828-362 Shimokurata-cho, Totsuka-ku, Yokohama-shi, Kanagawa-ken Inventor Taro Maeda 1-2-19-1 Yanaka, Taito-ku, Tokyo (72) Inventor Naoki Kawakami, Ninety-nine, Carpenter-cho, Tottori-shi, Tottori, Japan (Reference) 4C053 BB02 JJ13 JJ24 JJ32

Claims (3)

[Claims] 1. An electrode for performing electrical stimulation from the skin surface, wherein the electrode is a composite electrode formed from a plurality of microelectrodes, and each of the microelectrodes is configured to control current. Composite electrode used for electrical stimulation. 2. The composite electrode according to claim 1, wherein said microelectrode is a constant current source. 3. The electrode according to claim 1, wherein the size of the microelectrode is determined by the density of sweat glands.