CN111436932A - Liquid metal electroencephalogram electrode - Google Patents

Abstract

The invention discloses a liquid metal EEG electrode. After the EEG electrode is in contact with the scalp of a subject, the liquid metal with low melting point is melted by the body heat of the subject, and the melted metal droplets are heated by the gel network. Capillary and gravity, transfer to the surface of the gel, and the liquid metal droplets transferred to the surface of the gel are affected by its surface tension and directly contact the scalp at the contact point, and then the EEG signals are derived from the scalp stratum corneum, and the conductive coagulation is introduced. In the salt solution of the glue layer, the ions in the salt solution participate in electrical conduction, and finally transmit the EEG signal. The invention uses liquid metal instead of conductive glue as a contact medium, can avoid the influence of hair on electrode fixation and EEG measurement, and obtain purer EEG data; the overall structure is simple and universal, and is easy to manufacture and use.

Description

A liquid metal EEG electrode

technical field

The invention relates to the technical field of brain electrical signal acquisition, in particular to a liquid metal brain electrical electrode.

Background technique

Liquid metal refers to a class of alloys with a lower melting point, such as GaIn alloys, that can remain liquid at room temperature. Due to its good biocompatibility, stable chemical properties, and wide controllable melting point range, GaIn alloys have been widely used in flexible conductive materials and heat transfer materials.

EEG is an electrophysiological monitoring method for recording electrical activity of the brain, which is widely used in cognitive science, psychology and neuroelectrophysiological research, and provides effective clinical applications for sleep monitoring, anesthesia or coma depth assessment, epilepsy diagnosis and other clinical applications. reference basis. However, the nerve cells in the brain fire at weak amplitudes, and the collected EEG signals are often unstable and contain a lot of noise from the environment and electrical activity in other parts of the body. Not only that, the EEG acquisition electrode itself is also susceptible to environmental electromagnetic field interference, and the contact impedance and contact capacitance with the scalp further reduce the proportion of effective signals. Therefore, compared with EMG and ECG, accurate measurement and acquisition of EEG is more difficult.

At present, most of the common EEG acquisitions are realized by non-invasive electrodes, including dry electrodes and wet electrodes. Dry electrodes are usually made of metal sheets, which are light, compact, and simple in structure, but are not often used in scientific research and clinical fields due to poor contact with the skin and large signal noise. The wet electrode is filled with conductive gel between the scalp and the metal conductor, and the ions in the gel participate in the charge transfer between the scalp and the metal conductor, which greatly improves the contact effect. However, wet electrodes usually take a long time to prepare in the process of use, and the cost is relatively high. The paste-like gel used is very easy to adhere to the hair, which not only causes great material loss, but also brings inconvenience to the subjects. Therefore, there is an urgent need for a new type of EEG electrode that can combine the flexibility of dry electrodes and the contact efficiency of wet electrodes.

SUMMARY OF THE INVENTION

For solving the above problems, the technical scheme used in the present invention is:

A liquid metal electroencephalogram electrode, comprising a conductive gel layer, a contact point, a conductive shield layer, a fixed point and a shield wire; the back side of the conductive gel layer is adhered to the conductive shield layer, the front side is provided with a contact point, and the conductive A fixed point is welded on the shielding layer, and the shielded wire is connected to the conductive shielding layer through the fixed point.

The conductive gel layer is a circular polymer gel sheet with a network formed by a conductive polymer structure inside, and a salt solution is adsorbed inside the polymer network; a contact point is provided on one side of the conductive gel layer, and the interior of the contact point is filled. There is liquid metal, which is a GaIn alloy.

The conductive shielding layer is a metal disc, and the surface is anodized, which can shield the interference electric field in the environment, and at the same time transmit the electrical signal collected from the subcutaneous layer of the conductive gel layer to the fixed point; the back of the conductive shielding layer and the fixed point are The dots were sealed with electronic epoxy.

The fixed point is the welding point of the shielded wire and the conductive shielding layer, and both ends are welded by brazing; the shielded wire is a single-core metal mesh shielded wire.

The conductive shielding layer is sheathed with a shielding shell, a sealing sleeve, a connecting post, a sealing valve and a plug; the lower edge of the shielding shell is provided with a sealing sleeve, and the sealing sleeve is sealed with the conductive gel layer and the conductive shielding layer, so The lower end of the connecting column is connected to a fixed point and further extends to the bottom opening of the shielding shell, and a sealing valve is fixed at a position 2/3 away from the lower end of the connecting column; the shielding wire is connected to the connecting column through a plug.

The shielding shell is a bowl-shaped metal shell, the upper end is open, and a chamfer is arranged in the mouth. The shielding shell is placed flat and in a normal gravity environment, and the lower edge of the shielding shell is flush with the contact surface of the conductive gel layer.

The sealing sleeve is composed of small knots, the middle of the small knots is high and the surrounding area is low, and the small knots are tightly connected with no gaps.

The sealing valve is an elastic annular sheet with a small hole in the middle, which is glued to the connecting column, and the annular surface is in contact with the inner chamfer of the shielding shell mouth.

The plug is in the shape of a truncated cone, with a hole in the inner side, a metal elastic sheet in the hole is in contact with the connection post and conducts electricity, and the outer angle is slightly smaller than that of the shielding shell.

The beneficial effects of the present invention are:

1. Use liquid metal instead of conductive glue as the contact medium, and use the characteristics of high density of liquid metal to eliminate the interference of dirt, sweat and grease on the head epidermis, reduce the contact resistance, and increase the signal amplitude;

2. As a contact medium, liquid metal can penetrate into the skin to obtain more pure EEG data; the electrode pads used can avoid the influence of hair on EEG measurement to a certain extent, improve the sampling signal-to-noise ratio, and not too thick for hair. The subjects of the test no longer need to shave their heads before the test, which reduces the test requirements while improving the subject experience;

3. Two different forms of electrode structures are proposed, which can selectively perform single-point or multi-point signal acquisition. The overall structure is compact, simple to use, flexible and convenient, and easy for manufacturers to manufacture and customers to use.

Description of drawings

1 is a front view of the structure of a liquid metal EEG electrode in Embodiment 1 of the present invention;

2 is a bottom view of the structure of a liquid metal EEG electrode in Embodiment 1 of the present invention;

3 is a top view of the structure of a liquid metal EEG electrode in Embodiment 1 of the present invention;

4 is a front view of the structure of a liquid metal EEG electrode in Embodiment 2 of the present invention;

5 is a bottom view of the structure of a liquid metal EEG electrode in Embodiment 2 of the present invention;

FIG. 6 is a schematic structural diagram of a part of the sleeve of a liquid metal EEG electrode in Embodiment 2 of the present invention.

In the figure: 1. Conductive gel layer; 11. Contact point; 2. Conductive shielding layer; 3. Fixed point; 4. Shielded wire; 5. Shielding shell; 6. Sealing sleeve; 9. Plug.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Example 1: See Figures 1-3.

A liquid metal EEG electrode, comprising a conductive gel layer 1, a contact point 11, a conductive shielding layer 2, a fixed point 3 and a shielded wire 4; the back of the conductive gel layer 1 is adhered to the conductive shielding layer 2, and the front is mounted There is a contact point 11 , a fixed point 3 is welded on the conductive shielding layer 2 , and the shielded wire 4 is connected to the conductive shielding layer 2 through the fixed point 3 .

The conductive gel layer 1 is a circular polymer gel sheet with a network formed by a conductive polymer structure inside, and a salt solution is adsorbed inside the polymer network; The interior of the point 11 is filled with liquid metal, and the liquid metal is a GaIn alloy.

The conductive shielding layer 2 is a metal disc, the surface of which is anodized, which can shield the interference electric field in the environment, and at the same time transmit the electrical signals collected by the conductive gel layer 1 from the subcutaneous to the fixed point 3; the conductive shielding layer 2 The back and around the fixing point 3 are sealed with electronic epoxy.

The fixed point 3 is a welding point between the shielded wire 4 and the conductive shielding layer 2, and both ends are welded by brazing; the shielded wire 4 is a single-core metal mesh shielded wire.

The following is a specific method of using a liquid metal EEG electrode described in this embodiment:

1. Fix the electrode on the brain wave hood, and arrange the electrode placement according to the points to be collected;

2. After the electrodes are placed, there is no need to apply conductive glue on the subject's scalp, and the hood is directly placed on the subject's head;

3. After the head cover is fixed, gently move the electrodes so that the contact points 11 of the conductive gel layer 1 are expelled from the hair to the space between the contact points 11, so that the contact points 11 are in full contact with the subject's scalp;

4. After the electrode is in contact with the subject's scalp, the contact point 11 of the conductive gel layer 1 is heated by the subject's body heat conduction, and the low-melting liquid metal in the contact point melts;

5. The melted metal droplets are transferred to the surface of the gel through the capillary and gravity between the gel networks. Due to the contact angle between the gel and the scalp, the liquid metal droplets transferred to the surface of the gel are affected by its surface tension. , in direct contact with the subject's scalp at the point of contact;

6. Due to the high density of the liquid metal in direct contact with the subject's scalp, the dirt, sweat, etc. existing at the contact point and its surroundings will float on the surface of the liquid metal droplet to avoid contact with the scalp and cause the contact point 11 The resistance changes, affecting the accuracy of the measurement results.

7. The high density of liquid metal enables it to penetrate the stratum corneum of the epidermis and obtain purer EEG signals under the stratum corneum. Due to the influence of the force between metal atoms, from the contact point 11 to the liquid metal infiltrated under the skin, the conduction state can be maintained all the time.

8. The EEG signal is derived from under the stratum corneum and introduced into the salt solution of the conductive gel layer 1 . The ions in the salt solution participate in ion conduction, and finally transmit the signal through the shielded wire 4 .

Example 2: See Figures 4-6.

A liquid metal EEG electrode, comprising a conductive gel layer 1, a contact point 11, a conductive shielding layer 2, a fixed point 3 and a shielded wire 4; the back of the conductive gel layer 1 is adhered to the conductive shielding layer 2, and the front is mounted There is a contact point 11 , a fixed point 3 is welded on the conductive shielding layer 2 , and the shielded wire 4 is connected to the conductive shielding layer 2 through the fixed point 3 .

The conductive shielding layer 2 is sheathed with a shielding shell 5, a sealing sleeve 6, a connecting post 7, a sealing valve 8 and a plug 9; the lower edge of the shielding shell 5 is equipped with a sealing sleeve 6, which is connected to the conductive gel. The layer 1 and the conductive shielding layer 2 are hermetically connected, the lower end of the connecting column 7 is connected to the fixed point 3, and further extends to the bottom opening of the shielding shell 5, and the connecting column 7 is fixed with a sealing valve 8 at a position 2/3 away from the lower end; the The shielded wire is connected to the connection post 7 through the plug 9 .

The shielding shell 5 is a bowl-shaped metal shell with an open upper end and a chamfered corner. When the shielding shell 5 is placed flat and under normal gravity, the lower edge of the shielding shell 5 is flush with the contact surface of the conductive gel layer 1 .

The sealing sleeve 6 is composed of small knots, the middle of the small knots is high and the surrounding area is low, and the small knots are closely connected with each other, and there is no gap.

The sealing valve 8 is an elastic annular sheet with a small hole in the middle, which is glued to the connecting post 7 , and the annular surface is in contact with the inner chamfer of the shielding shell 5 .

The plug 9 is in the shape of a truncated cone, with a hole on the inner side, and a metal elastic sheet in the hole is in contact with the connecting post 7 to conduct electricity, and the outer angle is slightly smaller than that of the shielding shell.

The following is a specific method of using a liquid metal EEG electrode described in this embodiment:

1. Gently press the electrode on the subject's head to be measured;

2. Use a vacuum pump or aspirator to inhale from the bottom opening of the shielding case, and at the same time gently rotate the electrode, so that the sealing sleeve is discharged from the groove between the suites; in order to enhance the sealing, you can apply sealant or oil on the surface of the sealing sleeve in advance. .

3. After a stable negative pressure is formed inside the shielding shell, stop the suction, remove the suction device, and connect the plug. At this time, the sealing valve is closed due to the internal negative pressure, and is concave inward; under the action of negative pressure, the thrust of the valve membrane layer acts on the electrode sheet through the connecting column, and the electrode sheet is pressed to the surface of the subject's scalp.

4. After the electrode is in contact with the subject's scalp, the contact point 11 of the conductive gel layer 1 is heated by the subject's body heat conduction, and the low-melting liquid metal in the contact point melts;

5. The melted metal droplets are transferred to the surface of the gel through the capillary and gravity between the gel networks. Due to the contact angle between the gel and the scalp, the liquid metal droplets transferred to the surface of the gel are affected by its surface tension. , in direct contact with the subject's scalp at the point of contact;

6. Due to the high density of the liquid metal that is in direct contact with the subject's scalp, dirt, sweat, etc. existing at the contact point and its surroundings will float on the surface of the liquid metal droplet to avoid contact with the scalp and cause the contact point 11 The resistance changes, affecting the accuracy of the measurement results.

7. The high density of liquid metal enables it to penetrate the stratum corneum of the epidermis and obtain purer EEG signals under the stratum corneum. Due to the influence of the force between metal atoms, from the contact point 11 to the liquid metal infiltrated under the skin, the conduction state can be maintained all the time.

8. The EEG signal is derived from under the stratum corneum and introduced into the salt solution of the conductive gel layer 1 . The ions in the salt solution participate in ion conduction, and finally transmit the signal through the shielded wire 4 .

9. After the measurement is completed, lift the plug upwards, and the valve protrudes outwards, allowing the atmosphere to enter the interior of the shielding shell, and the negative pressure is released, and the electrode can be naturally removed and restored.

The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the specific embodiments of the present invention can still be modified. Or equivalent replacements, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention, should all be included in the scope of the claims of the present invention.

Claims (9)

1. The liquid metal electroencephalogram electrode is characterized by comprising a conductive gel layer (1), a contact point (11), a conductive shielding layer (2), a fixing point (3) and a shielding lead (4); the back surface of the conductive gel layer (1) is adhered to the conductive shielding layer (2), the front surface of the conductive gel layer is provided with a contact point (11), the conductive shielding layer (2) is welded with a fixing point (3), and the shielding wire (4) is connected with the conductive shielding layer (2) through the fixing point (3).

2. The liquid metal electroencephalogram electrode according to claim 1, wherein the conductive gel layer (1) is a circular polymer gel sheet, a network formed by a conductive polymer structure is arranged in the conductive gel sheet, and a salt solution is adsorbed in the polymer network; one side of the conductive gel layer (1) is provided with a contact point (11), and liquid metal is filled in the contact point (11), wherein the liquid metal is GaIn alloy.

3. The liquid metal electroencephalogram electrode according to claim 1, wherein the conductive shielding layer (2) is a metal wafer, the surface of the conductive shielding layer is subjected to anodic oxidation treatment, an interference electric field in the environment can be shielded, and meanwhile, an electric signal acquired from the subcutaneous part of the conductive gel layer (1) is transmitted to the fixed point (3); the back surface of the conductive shielding layer (2) and the periphery of the fixing point (3) are sealed by electronic epoxy resin.

4. The liquid metal electroencephalogram electrode according to claim 1, wherein the fixed point (3) is a welding point of the shielding lead (4) and the conductive shielding layer (2), and two ends of the fixed point are welded by brazing; the shielding lead (4) is a single-core metal mesh shielding wire.

5. The liquid metal electroencephalogram electrode according to any one of claims 1 to 4, wherein a shielding shell (5), a sealing sleeve (6), a connecting column (7), a sealing valve (8) and a plug (9) are sleeved outside the conductive shielding layer (2); a sealing sleeve (6) is arranged on the edge of the lower end of the shielding shell (5), the sealing sleeve (6) is hermetically connected with the conductive gel layer (1) and the conductive shielding layer (2), the lower end of the connecting column (7) is connected with the fixing point (3) and further extends to the opening at the bottom of the shielding shell (5), and a sealing valve (8) is fixed at a position 2/3 away from the lower end of the connecting column (7); the shielding lead is connected with the connecting column (7) through a plug (9).

6. The liquid metal electroencephalogram electrode according to claim 5, wherein the shielding shell (5) is a bowl-shaped metal shell, the upper end of the shielding shell is provided with an opening, a chamfer is arranged in the opening, and the edge of the lower end of the shielding shell (5) is flush with the contact surface of the conductive gel layer (1) in a flat and normal gravity environment.

7. The liquid metal electroencephalogram electrode as claimed in claim 5, wherein the sealing sleeve (6) is composed of nodules, the middle of each nodule is high, the periphery of each nodule is low, and the nodules are tightly connected without gaps.

8. The liquid metal brain electrode according to claim 5, wherein the sealing valve (8) is an elastic circular ring sheet with a small hole in the middle, which is glued to the connecting column (7), and the circular ring is in contact with the inner chamfer of the shielding shell (5).

9. The liquid metal electroencephalogram electrode as claimed in claim 5, wherein the plug (9) is in a circular truncated cone shape, the inner side of the plug is provided with a hole, a metal elastic sheet is arranged in the hole and is in contact with the connecting column (7) for conducting electricity, and the outer side angle of the plug is slightly smaller than that of the shielding shell.

Images