Disclosure of Invention
Aiming at the problems or part of the problems, the purpose of the scheme is to provide a novel flexible electrode structural design with the real-time adjustable detection position. By designing and preparing the conductive magnetic fluid detection layer capable of moving at will, the detection position of the electrode can be changed at will on the premise of not changing the integral position of the electrode, stable adhesion between the electrode substrate and the skin can be ensured to ensure high-quality signal detection, and meanwhile discomfort and damage caused by the adhesion of the electrode to the skin during the position changing are avoided.
According to the flexible electrode, the flexible electrode comprises a conductive magnetic fluid, a substrate and an encapsulation layer, the substrate and the encapsulation layer are combined to form a cavity, the conductive magnetic fluid is limited in the cavity, the conductive magnetic fluid is made of a semi-solid conductive material and can deform and move under the action of external force or a magnetic field, holes are formed in the substrate, the surface of the encapsulation layer corresponding to the conductive magnetic fluid is pressed, the conductive magnetic fluid is pressed to be in contact with the skin through a plurality of holes locally, electrophysiological signals of the skin are collected, the conductive magnetic fluid passing through the holes can return to the cavity space under the action of the magnetic field, the adhesion between the substrate and the skin is greater than the gravity of the electrode, the adhesion between the conductive magnetic fluid and the skin, and the flexible electrode can collect signals stably under different skin states.
In one embodiment of the above technical solution, the conductive magnetic fluid is connected to an external device using a wire.
In one embodiment of the above technical scheme, the conductive magnetic fluid comprises 35-65% of solvent, 2-18% of polymer, 15-40% of magnetic particles, 0-25% of conductive material and 0.1-10% of additive by mass, wherein the solvent is water or ethanol, the polymer is polyethylene glycol, dextran, polyvinylpyrrolidone or liquid silica gel, the magnetic particles are ferric oxide, ferroferric oxide, nickel or rubidium-iron-boron powder, the conductive material is metal particles, carbon material or conductive polymer, and the additive is polymer cross-linking agent, glycerol, polyethylene glycol, sodium chloride or potassium chloride.
In one embodiment of the above technical scheme, the flexible and stretchable polymer film is made of one or more of polyurethane, silicone rubber, fluororubber, styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), isoprene-substituted butadiene block styrene polymer (SIS) and parylene.
In one embodiment of the foregoing aspect, the flexible stretchable polymer film has a thickness of 100 nm to 10 mm.
In one embodiment of the foregoing aspect, the magnetic field is provided by a magnet.
In one embodiment of the foregoing technical disclosure, the holes are regular or irregular or a combination of regular and irregular shapes, and have an area ofThe distance between the hole and the edge of the adjacent hole is 0.1 mu m-10 mm.
In an embodiment of the foregoing technical solution, the conductive magnetic fluid is a plurality of conductive magnetic fluids.
In a second aspect, the disclosure provides a flexible electrode, where the flexible electrode includes a cavity, the bottom of the cavity is adhered to skin through physical action or an adhesive, and a conductive magnetic fluid is arranged in the cavity, and presses the surface of the cavity corresponding to the position of the conductive magnetic fluid, so that the conductive magnetic fluid can contact with the skin through a hole at the bottom of the cavity, and an electrophysiological signal of the skin is collected.
In one embodiment of the above technical solution, the bottom of the cavity is made of a flexible and stretchable polymer film, and the adhesion force between the flexible and stretchable polymer film and the skin is larger than the weight of the electrode itself and the adhesion force between the conductive magnetic fluid and the skin.
The electrode has the beneficial technical effects that the detection position can be adjusted at any time by only attaching the electrode once, so that the material waste and time consumption during electrode replacement and detection position adjustment are avoided, and the possible skin discomfort, damage and the like can be reduced.
Detailed Description
Based on the background technology, the prior art has the problems that the existing fixed structure type electrode cannot change the detection position after being attached, the targeted nerve or muscle is difficult to be rapidly and accurately monitored or positioned, the existing multi-channel electrode can simultaneously carry out electrophysiological signal test on a plurality of positions of a large area to realize accurate positioning, but the multi-channel electrode has higher cost and higher requirements on the complexity and performance of acquisition equipment, and the body surface electrode at the existing movable position has insufficient adhesiveness and stability on the body surface and is difficult to realize reliable use under different states and positions of skin.
The scheme provides a flexible electrode structural design capable of changing positions in real time, and can realize electrophysiological signal detection of any position in a large-area by adjusting the position of the conductive magnetic fluid to randomly change the electrode detection position on the premise that the position of the integral electrode is not changed after single attachment, so that the problems that the position of a traditional structure fixed electrode cannot be adjusted after attachment, and a series of problems such as time waste, material waste, skin discomfort or damage caused by electrode replacement or electrode reattachment due to the need of replacement of the detection position are solved.
How the embodiments of the present application may be carried out will now be described in detail and with reference to the accompanying drawings, wherein it will be apparent that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, based on the embodiments herein, which would be apparent to one of ordinary skill in the art without undue burden are within the scope of the present application.
Structural design of electrode (one)
The electrode comprises a substrate, conductive magnetic fluid and a packaging layer, wherein the substrate, the conductive magnetic fluid and the packaging layer form a sandwich structure, and the substrate and the packaging layer are combined to form a cavity, so that the conductive magnetic fluid is limited in the cavity. The substrate is located at the bottom of the electrode and is in direct contact with the skin. The packaging layer is positioned on the upper part of the electrode, and the edge of the packaging layer can be assembled with the flexible substrate in an adhesive mode or in other detachable modes. A cavity space is formed between the encapsulation layer and the substrate. In this space, a conductive magnetic fluid as a sensing portion of the electrode is defined therein.
The conductive magnetic fluid can freely move, cannot leak, and cannot contact with the external environment. The substrate has a hole therein. Before the electrode is used, the conductive magnetic fluid can stay on the flexible substrate due to the higher viscosity of the conductive magnetic fluid, and the conductive magnetic fluid cannot leak or contact the skin through holes in the substrate, namely, the conductive magnetic fluid is separated from the skin through the substrate. After the electrode is attached to the skin, the packaging layer area of the upper layer of the conductive magnetic fluid is pressed, and the conductive magnetic fluid is pressed to contact with the skin through the holes on the substrate, so that the physiological electric signal can be collected.
After the signal acquisition is finished, the conductive magnetic fluid can be sucked back into the cavity space between the substrate and the packaging layer from the holes on the substrate by using a magnet or a magnetic field generated in real time.
When the detection position is changed, the magnet or a magnetic field generated in real time can be utilized, after the position of the conductive magnetic fluid between the substrate and the packaging layer is changed, the conductive magnetic fluid is pressed to contact with the skin through the holes of the substrate for signal detection, so that the electrode is attached once, the position can be adjusted at any time for electrophysiological signal detection in a certain area, and the problems that the conventional electrode is fixed in acquisition point and cannot be moved, the multichannel electrode is high in cost and complex in acquisition equipment, and the existing movable electrode is poor in body surface stability are solved.
Referring to the electrode shown in fig. 1, the electrode is composed of a substrate ③, a conductive magnetic fluid ②, and an encapsulation layer ①. The substrate has circular holes arranged regularly, but the size, shape and arrangement of the holes can be further designed. The conductive magnetic fluid is connected with external equipment through a wire ④. Referring to fig. 2, the position of the conductive magnetic fluid may be changed using a magnet, and (a) in fig. 2 illustrates the position before the position of the conductive magnetic fluid is changed using a magnet, and (b) in fig. 2 illustrates the position after the right magnetic fluid of the two magnetic fluids is moved rightward by the magnet. Referring to fig. 3 and 4, the state of the conductive magnetic fluid before and after pressing, respectively. Before pressing, the conductive magnetic fluid is positioned between the substrate and the packaging layer, and after pressing, the conductive magnetic fluid is extruded into a plurality of holes to be in contact with the skin ⑥.
Therefore, when the electrode substrate is adhered to the skin, the electrode detection position can be changed on the premise of not changing the whole position of the electrode, so that the material and time cost for changing the electrode and the detection position are avoided, and the occurrence of discomfort, damage and the like of the skin can be reduced.
When the whole cavity space formed by the substrate and the packaging layer is conductive magnetic fluid, signal acquisition of the skin area covered by the whole electrode area can be realized. If a magnet or a magnetic field is arranged on the packaging layer, whether the conductive magnetic fluid is in contact with the skin or not can be controlled. Magnets ⑤ are used in fig. 2.
(II) Material selection
The substrate is preferably a flexible stretchable film material so that the substrate can form a certain adhesion with the skin by physical or chemical action and can be processed into a film structure with holes.
The encapsulation layer is preferably a flexible stretchable film material so that the prepared electrode is entirely flexible, deformable, stretchable.
The conductive magnetic fluid material needs higher magnetic attraction deformation capability, certain conductivity, viscosity and shape retention. Has low adhesion to skin, and does not adhere to the substrate and encapsulation layer. The conductive magnetic fluid can not automatically diffuse through the holes of the flexible substrate in a static state, can be contacted with the skin through the holes of the substrate after being pressed, has low interface impedance when being contacted with the skin, ensures high-quality signals, and avoids discomfort and damage caused by the adhesion of the conductive magnetic fluid to the skin when the position is changed.
The electrode thus assembled is a flexible electrode capable of being closely adhered to the skin without causing discomfort.
Method for preparing electrode (III)
(3.1) Substrate
The substrate is preferably a flexible stretchable polymer film capable of forming a strong adhesion to the skin by physical action of itself or by an adhesive.
A polymer film with a microporous structure is prepared, the thickness of the film is preferably between 100nm and 10mm (including boundaries and any values in the boundaries), and the size and the shape are not limited. The material used is preferably a flexible material with good biocompatibility, including but not limited to one or more of polyurethane, silicone rubber, fluororubber, styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), isoprene-substituted butadiene block styrene polymer (SIS), parylene and the like. The materials can ensure that the adhesion force between the prepared substrate and the skin is greater than the gravity of the electrode and the adhesion force between the conductive magnetic fluid and the skin, so that the flexible electrode can stably acquire signals in different states of the skin.
The preparation method of the film comprises printing, knife coating, pouring, spin coating, hot pressing and the like, wherein micropores on the film can be in regular shapes such as circles, squares, triangles and the like, or irregular shapes, or a combination of the regular shapes and the irregular shapes, the sizes of the holes can be consistent or inconsistent, and the area size is controlled to be the same as that of the filmThe distance between the hole and the edge of the adjacent hole is 0.1 mu m-10 mm.
The accuracy of the hole shape and spacing to the signal acquired by the flexible electrode can be determined through simulation.
The preparation of the micropores can be carried out by template method, mechanical cutting, laser cutting and other methods.
One side of the substrate may be optionally coated with a layer of adhesive, which may be a biocompatible pressure sensitive adhesive, silicone, or the like.
(3.2) Conductive magnetic fluid
The conductive magnetic fluid is a semi-solid conductive material, can deform and move under the action of external force or magnetic field, and can collect and conduct electrophysiological signals. Its adhesion to the skin is less than the adhesion of the overlying flexible stretchable film to the skin, thus facilitating its release from the skin.
The conductive magnetic fluid is prepared from the components including a solvent, a polymer, magnetic particles, a conductive material, an additive and the like, wherein the mass ratio of the components is 35% -65%, 2% -18%, 15% -40%, 0% -25% and 0.1% -10% respectively. The mass ratio of each component comprises a boundary value, and the conductive magnetic fluid obtained based on the mass ratio can realize certain adhesion with the skin and is convenient to separate from the skin. The solvent is water, ethanol, etc., the polymer is polyethylene glycol, dextran, polyvinylpyrrolidone, liquid silica gel, etc., the magnetic particles are ferric oxide, ferroferric oxide, nickel, rubidium-iron-boron powder, etc., the conductive material is metal particles, carbon material, conductive polymer, etc., and the additive is polymer cross-linking agent, glycerol, polyethylene glycol, sodium chloride, potassium chloride, etc.
The prepared conductive magnetic fluid has high magnetic attraction deformation capability, certain viscosity and shape retention, low skin adhesiveness and interface impedance, and is not adhered to a substrate and a packaging layer, so that the electrode can be quickly changed to a detection position, the skin is not damaged, and a high-quality electrophysiological signal can be obtained.
(3.3) Packaging layer
Preparing a polymer film with the same shape and size as the flexible substrate, wherein the thickness of the film is 100 nm-10 mm, the used material is flexible material with good biocompatibility, including but not limited to one or more compounds of polyurethane, silicon rubber, fluororubber, styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), isoprene-substituted butadiene block styrene polymer (SIS), parylene and the like, and the preparation method of the film includes but not limited to printing, doctor-blading, printing, pouring, spin coating, hot pressing and the like.
It should be noted that the encapsulation layer may be of a different material than the substrate layer.
(3.4) Electrode
And placing the conductive magnetic fluid between the flexible substrate and the packaging layer, fixing a wire at the edge of the substrate, respectively connecting the conductive magnetic fluid with the collection equipment, and then bonding the flexible substrate with the edge of the packaging layer to obtain the flexible electrode capable of changing the position in real time. The conductive magnetic fluid can stay on the flexible substrate due to its viscosity and conformality before the electrode is used, and cannot leak through the holes on the substrate or contact with skin.
When the detection position is required to be changed, the magnet is used for attracting the conductive magnetic fluid to change the position between the flexible substrate and the packaging layer, then the conductive magnetic fluid is pressed to contact with the skin through the hole of the flexible substrate to realize signal detection, and finally after the test is finished, the magnet is used for sucking the conductive magnetic fluid from the hole of the flexible substrate to the position between the flexible substrate and the sealing layer.
Verification of experiment
(4.1) Example 1
The preparation of the flexible substrate comprises the steps of preparing a layer of film with the thickness of 2mm and the size of 5 multiplied by 5 and cm by using the silicone rubber Ecoflex through a casting template and curing at room temperature, and then forming uniformly distributed round through micropores with the diameter of 1 and mm on the film through a mechanical punching mode, wherein the hole-to-hole distance is 3 mm.
The preparation method of the conductive magnetic fluid comprises the steps of (1) weighing a proper amount of PVA powder, and fully dissolving the PVA powder in deionized water to obtain a PVA solution with the concentration of 15 wt%. (2) The ferroferric oxide (particle size is 100 nm, purity is 99%) 4.58 and g, PVA solution 11.3 and g and additive (PVA cross-linking agent borax) 0.17 and g are respectively weighed and mixed to obtain solvent, polymer, magnetic particles and additive accounting for 59.9%, 10.5%, 28.5% and 1.1%, and then the mixture is stirred at the room temperature for 2 minutes at the speed of 2000 and rpm to ensure uniform mixing of the components and complete natural cross-linking of PVA, and finally the conductive magnetic fluid is obtained.
Preparation of encapsulation layer a1 mm thick 5 x 5 cm thin film was prepared by casting a template using silicone rubber Ecoflex and curing at room temperature.
And (3) assembling the electrode, namely placing a proper amount of conductive magnetic fluid between the flexible substrate and the packaging layer, fixing a lead at the edge of the substrate, respectively connecting the conductive magnetic fluid and the acquisition equipment, and then bonding the flexible substrate and the edge of the packaging layer to obtain the flexible electrode capable of changing the position in real time.
The electrode is used by attaching the electrode after cleaning the skin at the arm, lightly pressing the packaging layer area of the upper layer of the conductive magnetic fluid by hand, collecting signals when the arm makes a fist-making action after the conductive magnetic fluid is pressed and contacts with the skin through the hole on the flexible substrate, sucking the conductive magnetic fluid back into a cavity space between the conductive magnetic fluid and the packaging layer through the hole on the flexible substrate after a single test is finished, changing the positions of the conductive magnetic fluid on the flexible substrate and the packaging layer, then pressing the conductive magnetic fluid to contact with the skin through the hole of the flexible substrate, collecting signals when the arm makes a fist-making action again, and sucking the conductive magnetic fluid out of the flexible substrate and the packaging layer through the magnet after the final test is finished.
(4.2) Example 2
The preparation of the flexible substrate comprises the steps of preparing a layer of round film with the thickness of 5 mm and the diameter of 6 cm by using a method of pouring a template and solidifying at room temperature by using silicone rubber Ecoflex, and then generating evenly distributed round through micropores with the diameter of 500 nm on the round film by a mechanical punching mode, wherein the hole-to-hole distance is 1 mm.
The preparation method of the conductive magnetic fluid comprises (1) weighing a proper amount of PVA powder, and fully dissolving the PVA powder in deionized water to obtain a PVA solution with the concentration of 15 wt%. (2) Respectively weighing and mixing ferric oxide (particle size is 100 nm, purity is 99%) 5.5 g, PVA solution 11.5 g and additive (PVA cross-linking agent borax) 0.2 g to obtain solvent, polymer, magnetic particles and additive with the ratio of 56.83%, 10.03%, 31.98% and 1.16%, stirring at room temperature for 2 min at 2000 rpm speed to ensure uniform mixing of the components, and finishing natural cross-linking of PVA to finally obtain the conductive magnetic fluid.
Preparation of the encapsulation layer a round film with a thickness of 2 mm a and a diameter of 6 cm a was prepared by casting a template using silicone rubber Ecoflex and curing at room temperature.
And (3) assembling the electrode, namely placing a proper amount of conductive magnetic fluid between the flexible substrate and the packaging layer, fixing a lead at the edge of the substrate, respectively connecting the conductive magnetic fluid and the acquisition equipment, and then bonding the flexible substrate and the edge of the packaging layer to obtain the flexible electrode capable of changing the position in real time.
The electrode is used by attaching the electrode after cleaning the skin at the arm, lightly pressing the packaging layer area of the upper layer of the conductive magnetic fluid by hand, collecting signals when the arm makes a fist-making action after the conductive magnetic fluid is pressed and contacts with the skin through the hole on the flexible substrate, sucking the conductive magnetic fluid back into a cavity space between the conductive magnetic fluid and the packaging layer through the hole on the flexible substrate after a single test is finished, changing the positions of the conductive magnetic fluid on the flexible substrate and the packaging layer, then pressing the conductive magnetic fluid to contact with the skin through the hole of the flexible substrate, collecting signals when the arm makes a fist-making action again, and sucking the conductive magnetic fluid out of the flexible substrate and the packaging layer through the magnet after the final test is finished.
(4.3) Example 3
The preparation of the flexible substrate comprises the steps of preparing a layer of round film with the thickness of 5 mm and the diameter of 6cm by using a method of pouring a template and solidifying at room temperature by using silicone rubber Ecoflex, and then generating evenly distributed round through micropores with the diameter of 1 mm on the round film by a mechanical punching mode, wherein the hole-to-hole distance is 3 mm.
The preparation method of the conductive magnetic fluid comprises (1) weighing a proper amount of PVA powder, and fully dissolving the PVA powder in deionized water to obtain a PVA solution with the concentration of 20 wt%. (2) Ferroferric oxide (particle size 100nm, purity 99%) 4.46: 4.46 g, carbon nanotube 0.51: 0.51 g, PVA solution 12: 12 g, additive (PVA cross-linking agent borax) 0.86: 0.86 g are weighed and mixed to obtain solvent, polymer, magnetic particles, conductive material, additive accounting for 53.84%, 13.46%, 25.01%, 2.86%, 4.82%, and stirring at room temperature for 2 minutes at 2000: 2000 rpm speed to ensure uniform mixing of the components, finally obtaining conductive magnetic fluid.
Preparation of the encapsulation layer, namely preparing a layer of round film with the thickness of 5mm and the diameter of 6 cm by using SEBS-toluene solution with the mass fraction of 10 percent through a spin coating method.
The electrode is used, the electrode is attached after the skin at the back is cleaned, the packaging layer area of the upper layer of the conductive magnetic fluid is lightly pressed by hands, after the conductive magnetic fluid is pressed and contacts the skin through the holes on the flexible substrate, signal acquisition is carried out when the flexible substrate is bent, and after the single test is finished, the conductive magnetic fluid is sucked back into the cavity space between the conductive magnetic fluid and the packaging layer through the holes on the flexible substrate by using the magnet.
(4.4) Example 4
Fig. 5 and 6 illustrate the electromyographic signals of the conductive magnetic fluid before and after movement when using the prepared flexible electrode. In both figures, (a) in fig. 5 and 6 is the electromyographic signal of channel 1, and (b) in fig. 5 and 6 is the electromyographic signal of channel 2. As can be seen from the two figures, the myoelectric signal quality of the two channels before and after the moving position is higher, and different signal forms are shown at different positions. The flexible electrode employs two conductive magnetic fluids.
In other embodiments, however, the number of conductive magnetic fluids within the cavity of the flexible electrode may be 1, 3, or more. The conductive magnetic fluid can be split into a plurality of pieces under the condition of magnetic field or manual extrusion, and is positioned to the corresponding position under the control of magnetic field or external force to form an electrophysiological signal acquisition array, and the electrode is not complicated due to the fact that the number of channels is increased, so that the equipment cost can be reduced. Likewise, the conductive magnetic fluid may be composed of a plurality of conductive magnetic fluids.
(4.5) Example 5
Under the condition that the detection position does not need to be adjusted, the number of conductive magnetic fluid in the flexible electrode cavity can be 1, the area is full of the cavity, and the height can meet the requirement of being sucked back to the cavity space from the hole.
The flexible electrode can be used as a device or a sensor for collecting physiological electric signals and can also be used as a local electric stimulation device.
Although embodiments of the present disclosure have been described above with reference to the accompanying drawings, the present disclosure is not limited to the specific embodiments and fields of application described above, which are merely illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may make numerous forms, and departures from the present disclosure as come within the scope of the invention as defined in the appended claims.