KR102525473B1 - Brain implantable flexible probe - Google Patents

Abstract

The present invention relates to a brain implantable flexible probe. Specifically, the invention relates to a brain implantable flexible probe coated with a biodegradable material, which has excellent bending rigidity and low electrode impedance. According to the present invention, a brain implantable flexible probe includes: a three-dimensional porous electrode; a 32 channel electrode; a layer; a needle; and a biodegradable material.

Description

Brain implantable flexible probe {BRAIN IMPLANTABLE FLEXIBLE PROBE}

The present invention relates to a brain implantable flexible probe. Specifically, the present invention relates to a brain-implantable flexible probe coated with a biodegradable material, which has excellent bending stiffness and low electrode impedance.

Brain functions that are responsible for complex functions such as learning and judgment are implemented by interactions between brain nerve cells. At this time, electrical signals are generated in brain nerve cells. Various attempts have been made to detect, record, and analyze electrical signals of brain neurons by inserting microelectrodes into the brains of rats. The first implantable microelectrodes were used in the 1950s, using single microelectrodes with a simple structure made by coating insulating materials on tungsten wires and stainless steel wires and exposing only the ends of the wires. did

However, with a single microelectrode, signals from several types of cranial nerve cells can be detected. In order to classify the signals of these brain nerve cells, research using micro wires has been conducted.

Extracellular recordings focus on detecting large-scale neuronal activity such as 'electrical signal codes' in vivo. Tetrodes, composed of four twisted microwires, have proven to be useful tools for simultaneous recording of multiple neurons because many single neurons can be isolated simultaneously.

The properties of a tetrode depend on the material, diameter and surface area of the tetrode. Various microelectrode materials such as tungsten, titanium, and gold, known as biocompatible materials, have been reported. Many attempts have been reported to reduce the electrode size to minimize tissue damage and obtain high neural network spatial resolution. As the size of the neural electrode becomes smaller, the impedance and thermal noise increase and the quality of the neural recording deteriorates.

A nerve electrode is a component that detects electrical signals exchanged between nerve cells in the brain and transmits them to the outside, or conversely, transmits artificial signals from the outside to the brain. It is considered an essential technology when realizing brain-machine interface (BMI) that connects the brain and computers or machines, or when making prosthetic arms and legs for the rehabilitation of amputated patients. Nerve electrodes had been developed before, but since they mainly used hard silicon substrates, they were difficult to attach to the wrinkled brain and the body rejected them severely.

There has been an attempt to develop a bendable electrode, but there is a problem that the metal and substrate are quickly separated inside the body, so it was only used for temporary animal experiments, and there is a problem that long-term installation is impossible.

Korean Patent Registration No. 10-1304319 Korean Patent Publication No. 10-2020-0138036

There are problems with existing neural electrodes, such as the fact that the impedance increases as the electrode is miniaturized and that it is difficult to attach it to the wrinkled brain due to the use of a hard silicon substrate.

In order to solve the above problems, a biodegradable material is coated in a U-shape to reduce the cross-sectional area and at the same time to provide a brain implantable flexible probe having excellent bending stiffness.

When the brain-implantable flexible probe is inserted into the brain, the biodegradable material melts and the surface of the electrode is exposed, the impedance is lowered, and the brain-implantable flexible probe, which was hard, becomes soft and bends well, thereby solving the above problem.

According to various embodiments, a brain implantable flexible probe includes a 3-dimensional porous electrode for lowering the electrochemical impedance of a neural electrode, a 32-channel electrode composed of 32 channels for measuring signals in various parts of a brain region, electrodes and leads, and It may include a melting needle made of a material that melts and disappears in a living body and a layer for electrical insulation from living tissue.

According to various embodiments, the brain implantable flexible probe includes a 3-dimensional porous electrode for lowering the electrochemical impedance of a neural electrode and a 32-channel electrode for measuring signals in various parts of a brain region. , a layer for electrical insulation between electrodes, wires, and living tissue, a melting needle composed of a material that melts and disappears in vivo, and a biodegradable material coated on the brain implantable flexible probe.

According to various embodiments, the biodegradable material may include sugar.

According to various embodiments, the biodegradable material may be coated in a U-shape.

According to various embodiments, the 32-channel electrode may be made of polystyrene, platinum, and iridium oxide.

According to various embodiments of the present invention, a brain implantable flexible probe having excellent rigidity may be provided by coating a biodegradable material on the brain implantable flexible probe.

According to various embodiments of the present invention, the brain implantable flexible probe is coated with a biodegradable material in a U-shape and has excellent rigidity, but when inserted into the brain, the biodegradable material is decomposed and soft. There is an effect that can provide a probe.

1 illustrates a neural signal processing system using wireless power transmission and reception according to various embodiments.
2A illustrates the structure of a neural signal processing device according to various embodiments.
FIG. 2B shows a real picture of a neural signal processing device according to various embodiments and a picture of a state embedded around the brain of a laboratory animal.
3 illustrates an embodiment in which a neural signal processing apparatus according to various embodiments operates.
4 illustrates formats of a 4-channel neural signal and a 32-channel neural signal transmitted from a neural signal processing device to an external electronic device according to various embodiments.
5A shows results of performing static evaluation on noise cancellation performance of a neural signal processing apparatus according to various embodiments.
5B shows a result of dynamic evaluation of noise cancellation performance of a neural signal processing apparatus according to various embodiments.
5C illustrates neural signals collected before and after a specific motion of a laboratory animal by a neural signal processing apparatus according to various embodiments.
6 illustrates a structure of a wireless power transmission device according to various embodiments.
7 illustrates an equivalent circuit of a first antenna and a second antenna of a wireless power transmission device according to various embodiments.
8 is a graph illustrating a change in current generated from a second antenna according to a change in a coupling coefficient (k) between a first antenna and a second antenna according to various embodiments.
9 is a diagram for explaining a difference between a solid coil and a litz coil, and a difference between a Single-Tx structure and a Repeater-Tx structure according to various embodiments.
10 shows a concept diagram of a wireless power transmission device according to various embodiments.
11 shows a state of a biodegradable neural electrode needle inserted into the brain according to various embodiments.
12 illustrates a state of a brain implantable flexible probe coated with sugar according to various embodiments.
13 illustrates a circuit diagram for measuring a change in impedance of an electrode according to coating according to various embodiments.
14 illustrates a graph of impedance change of a neural electrode according to a biodegradation process according to various embodiments.
15 illustrates a graph of physical change and impedance change of a biodegradable neural electrode needle according to brain tissue insertion time according to various embodiments.
In connection with the description of the drawings, the same or similar reference numerals may be used for the same or similar elements.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Since the present invention can have various changes and various forms, specific embodiments are illustrated in the drawings and described in detail. However, it should be understood that this is not intended to limit the present invention to the specific disclosed form, and includes all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing each figure, like reference numbers are used for like elements. In the accompanying drawings, the dimensions of the structures are shown enlarged or reduced than actual for clarity of the present invention.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, it should not be interpreted in an ideal or excessively formal meaning. don't

1 illustrates a neural signal processing system 100 using wireless power transmission and reception according to various embodiments.

According to various embodiments, the neural signal processing system 100 may include a neural signal processing device 101 and a wireless power transmission device 201 . The neural signal processing system 100 collects neural signals generated from the brain of a laboratory animal using the neural signal processing device 101, and transfers the collected neural signals to an external electronic device (eg, a computing device). An operation of analyzing the behavior of a laboratory animal by transmitting to the neural signal processing apparatus 101 and an operation of transmitting a command for collecting new experimental data reflecting the analyzed result to the neural signal processing apparatus 101 may be sequentially performed. In particular, the neural signal processing device 101 may include a flexible probe that can be inserted into the brain of a laboratory animal, and may collect nerve signals generated in the brain using a plurality of electrodes implemented in the flexible probe. there is. At this time, the neural signal processing device 101 may be implemented as a battery-free structure, and power required for operation of the neural signal processing device 101 is supplied from the wireless power transmission device 201. The transmitted wireless power can be used. The wireless power transmitter 201 may include a first antenna 211 for power input and a second antenna 212 (eg, a repeater antenna) for amplifying the power input. A detailed description of the structure of the neural signal processing device 101 will be described later with reference to FIG. 2A , and a detailed description of the structure of the wireless power transmission device 201 will be described later with reference to FIG. 6 .

2A illustrates a structure of a neural signal processing device 101 according to various embodiments.

FIG. 2B shows a real picture of the neural signal processing device 101 according to various embodiments and a picture of a state embedded around the brain of a laboratory animal.

According to various embodiments, the neural signal processing apparatus 101, which is embedded in the periphery of the brain of a laboratory animal and processes nerve signals, includes 32 electrodes inserted into the brain to collect 32 channels of nerve signals. A communication module including an implantable flexible probe, a low power Bluetooth (BLE) module, a sensor module including an acceleration sensor, and a litz wire coil for wirelessly receiving power from a wireless power transmission device A wireless power receiving module and a processor operatively connected to the modules.

Referring to FIG. 2A according to an embodiment, the neural signal processing device 101 may be implemented as a layered structure of the following components when implementing a product, and each component will be described in detail below. Meanwhile, referring to FIG. 2B , the neural signal processing device 101 may adopt a structure suitable for being embedded in the brain of a laboratory animal.

1st Parylene-PDMS (111): An encapsulation layer of biocompatible material that prevents absorption of body fluids and biochemical reactions in a bioburden environment and has soft physical properties

Full-wave rectifier (112): A circuit that receives wireless power and converts AC voltage to DC voltage

Indicator LED(113) : Red, Green LED indicating device status

Super capacitor (114): A super capacitor with large capacitance that maintains the voltage so that the device can still operate when the height of the device increases or the angle is twisted.

Circuit traces(115): Copper conductors on the PCB constituting the circuit

Polyimide substrate (116): A layer for electrical insulation between the wire of the circuit and other layer parts

Litz wire coil (117): A wireless power receiving coil composed of Litz wire that increases wireless power efficiency and makes mechanical properties softer

Flexible ferrite (118): Soft magnetic material layer to increase the efficiency of wireless power reception by inducing the path of the magnetic field to increase the amount of magnetic flux passing through the inside of the coil

Copper magnetic shield (119): A thin magnetic field protection layer made of copper to prevent EMI noise in circuits caused by strong magnetic fields.

Electrical ground plane (120): A wide electrical ground layer made of copper to effectively remove noise originating from input terminals and circuits.

Polyimide substrate (121): A layer for electrical insulation between the wire of the circuit and other layer parts

Circuit traces (122): A layer for efficient radiation of electrical leads and Bluetooth RF signals that make up the circuit

BLE microcontroller unit (123): Bluetooth low power microcontroller

3-axis accelerometer(124) : 3-axis accelerometer IC

Neural signal amplifier(125): IC for amplifying cranial nerve signals

RFI filter components (126): Filter elements composed of R and C to remove RF noise coming from the input terminal

2nd Parylene-PDMS (127): An encapsulation layer of biocompatible material that prevents absorption of body fluids and biochemical reactions in a bioburden environment and has soft physical properties

Brain implantable flexible probe 130: Device for collecting 32-channel neural signals by being inserted into the brain of laboratory animals

According to one embodiment, referring to FIG. 2A , the flexible probe 130 may include the following components.

3D porous electrode (131): 3D porous electrode for lowering the electrochemical impedance of the neural electrode

32Ch electrode (132): Electrodes composed of 32 channels for measuring signals in various parts of the brain area

Encapsulant (133): Layer for electrical insulation between electrodes, wires, and living tissue

Biodegradable needle (134): A melting needle composed of a material that melts and disappears in vivo and keeps it hard temporarily to place a flexible and long nerve electrode probe in the target area deep in the brain.

According to an embodiment, the processor included in the neural signal processing device 101, for example, executes software (e.g., a program) so that at least one other component of the neural signal processing device 101 (connected to the processor) e.g. hardware or software components), and can perform various data processing or calculations. According to one embodiment, as at least part of data processing or operation, the processor stores commands or data received from other components (eg, a sensor module or communication module) in a volatile memory, and stores the commands or data stored in the volatile memory. processing, and the resulting data can be stored in non-volatile memory. According to an embodiment, the processor may include a main processor (eg, a central processing unit or an application processor) or a secondary processor (eg, a sensor hub processor or a communication processor) that may operate independently of or together with the main processor. For example, when the neural signal processing device includes a main processor and an auxiliary processor, the auxiliary processor may use less power than the main processor or may be set to be specialized for a designated function. A secondary processor may be implemented separately from, or as part of, the main processor. According to one embodiment, the BLE microcontroller unit 123 may be implemented as an example of a processor of the neural signal processing device 101 .

According to an embodiment, the sensor module included in the neural signal processing device 101 detects an operating state of the neural signal processing device 101 or an external environmental state, and an electrical signal or data value corresponding to the detected state. can create According to one embodiment, the sensor module may include, for example, an acceleration sensor, a gyro sensor, a biosensor, or a temperature sensor.

According to an embodiment, the communication module included in the neural signal processing device 101 establishes a communication channel between the neural signal processing device 101 and an external electronic device (eg, a computing device or an external server), and establishes the communication channel. It can support communication through. According to an embodiment, the Bluetooth low power module may be implemented as an example of a communication module of the neural signal processing device 101 .

According to an embodiment, the wireless power reception module included in the neural signal processing device 101 may include a Litz wire coil 117, a rectifier circuit, and a converter. The power generated from the power source of the wireless power transmission device is transferred to the Litz wire coil 117 through the resonance coil of the wireless power transmission device, and resonates with the resonance coil by the magnetic resonance phenomenon, that is, the wireless power having the same resonance frequency value. delivered to the power receiving module. The power transmitted to the wireless power reception module is transferred to various hardware of the neural signal processing device 101 through a rectifier circuit and a converter. The rectifier circuit may rectify AC power into DC power, and the converter may convert DC power into a required voltage and provide it to various types of hardware. Power transmission by magnetic resonance is a phenomenon in which power is transferred between two LC circuits whose impedances are matched, and can transmit power over a longer distance with higher efficiency than power transmission by electromagnetic induction. According to one embodiment, the litz wire coil 117 may consist of individual insulated wires twisted or braided in a uniform pattern with the primary benefit of reducing AC losses in the high frequency windings. . The reason for using the Litz wire coil 117 is to make the surface area wider because the time-varying current due to the skin effect has a property of flowing only toward the surface of the wire, so that the current hardly flows in the middle of the wire. Since the skin effect of the wire can be prevented and the surface area can be widened, it is possible to prevent an increase in the resistance component of the coil.

FIG. 3 illustrates an embodiment in which a neural signal processing device (eg, the neural signal processing device 101 of FIG. 1 ) operates according to various embodiments.

According to various embodiments, the neural signal processing device 101 collects 32 channels of neural signals through 32 electrodes of a flexible probe (eg, the flexible probe 130 of FIG. 2 ) inserted into the brain of a laboratory animal. can The neural signal processing device 101 may amplify a small voltage signal in uV unit through the neural signal amplifier 125, remove RF noise through the RFI filter components 126, and ADC (Analog-to- The digital signal can be converted through a digital converter). The neural signal processing device 101 may transmit data converted into digital signals to a processor (eg, a BLE MCU).

According to one embodiment, referring to FIG. 3 , the processor of the neural signal processing device 101 may transmit 32-channel neural signals to an external electronic device (eg, a personal computer or smartphone) through a low power Bluetooth module. .

According to one embodiment, referring to FIG. 3 , the processor of the neural signal processing apparatus 101 may select 4-channel neural signals from 32-channel neural signals according to a predetermined criterion. According to an embodiment, the processor may check a request for selecting four specific channels from a user command generated by an external electronic device, and select neural signals of the four channels based on the request. According to one embodiment, the processor may check the number of spikes for a specific time period for 32 channels of neural signals, and the number of spikes during the specific time period is large (ie, the order of the active region is large) for 4 channels. Nerve signals can be selected. At this time, the 4-channel neural signal may be in the form of a raw signal. An external electronic device receiving the 4-channel neural signal may perform signal analysis using a technique such as spike sorting that determines the activity level of the nerve signal.

During the process of performing the above-described operation, the neural signal processing device 101 may wirelessly receive power from a wireless power transmission device (eg, the wireless power transmission device 201 of FIG. 1 ) and store the received power. It can be supplied to various hardware in the neural signal processing device 101. Specifically, in the wireless power reception process, the wireless power transmitted from the repeater antenna system may be received through the Litz wire coil 117 of the wireless power reception module, and the rectifier in the neural signal processing device 101 and A stable DC voltage of 3.3V may be supplied to the neural signal processing device 101 via a regulator.

FIG. 4 illustrates formats of a 4-channel neural signal and a 32-channel neural signal transmitted by a neural signal processing device (eg, the neural signal processing device 101 of FIG. 1 ) to an external electronic device according to various embodiments.

According to various embodiments, the processor of the neural signal processing device 101 may transmit a 4-channel neural signal or a 32-channel neural signal to an external electronic device through a Bluetooth low power module. According to an embodiment, the processor may allocate a size of 2 bytes per cycle to the neural signal of each channel. For example, referring to FIG. 4 , the processor may allocate a high byte (1 byte) and a low byte (1 byte) to the first to fourth channels, respectively. According to an embodiment, referring to FIG. 4 , the processor may include acceleration sensor data (ACC X, Y, Z-axis) acquired through an acceleration sensor and a voltage value (power) of power received through a wireless power receiving module. level) can be assigned a size of 4 bytes.

According to an embodiment, when transmitting 4-channel neural signals to an external electronic device, the processor transmits one packet having a size of 244 bytes including 30 cycles of neural signals, acceleration sensor data, and voltage values. can do. For example, referring to FIG. 4 , the processor generates 30 cycles of data, 4 bytes of acceleration sensor data, and voltage value data for 4 channels of neural signals each of which has a size of 8 bytes per cycle. It can be generated as one packet having a size of 244 bytes and transmitted to an external electronic device.

According to an embodiment, when transmitting 32-channel neural signals to an external electronic device, the processor transmits one packet having a size of 196 bytes including 3-cycle neural signals, acceleration sensor data, and voltage values. can do. For example, referring to FIG. 4 , the processor generates 3 cycles of data, 4 bytes of acceleration sensor data, and voltage data for 32 channels of neural signals each of which has a size of 64 bytes per cycle. It can be generated as one packet having a size of 196 bytes and transmitted to an external electronic device.

According to one embodiment, the 4-channel neural signal may be a raw signal composed of only action potential (AP) or a raw signal composed of AP and local field potential (LFP), and the 32-channel neural signal may be a raw signal composed only of LFP. .

FIG. 5A shows a result of performing static evaluation on noise cancellation performance of a neural signal processing device (eg, the neural signal processing device 101 of FIG. 1 ) according to various embodiments.

FIG. 5B shows a result of dynamic evaluation of the noise cancellation performance of the neural signal processing apparatus 101 according to various embodiments.

5C illustrates neural signals collected before and after a specific motion of a laboratory animal by the neural signal processing apparatus 101 according to various embodiments.

5a and 5b show that a signal simulating a brain nerve signal is input to the neural signal processing device 101 with equipment called FB128 before animal experiments, and stable operation and signal of the signal processing device 101 during wireless power transmission in various situations Shows the results of an experiment conducted to determine the level of noise of .

Referring to FIG. 5A, under wireless power transmission of a wireless power transmitter (eg, the wireless power transmitter 201 of FIG. 1), the neural signal processing device 101 according to the height with respect to the repeater antenna 212 as a reference You can know the configuration of the experiment and the signal result to check whether the signal measurement and Bluetooth communication work well. In the state where the neural signal processing device 101 is fixed at each height within the range of -20cm to +40cm, it can be confirmed that the neural signal processing device 101 sufficiently receives wireless power and measures the signal well without being affected by noise. .

Referring to FIG. 5B, it is the same experiment as in FIG. 5A, but signals are measured while moving the neural signal processing device 101 at slow and fast speeds within the range of -20 cm to +40 cm assuming a situation in which an actual laboratory animal is moving. shows a result. It can be confirmed that the neural signal processing device 101 stably operates without generating noise according to movement and speed even in a moving state.

Referring to FIG. 5C , it can be seen that under wireless power transmission, the neural signal processing apparatus 101 according to the present invention properly supplies power and stably transmits neural signal data to an external electronic device. Specifically, signal analysis can be performed using a technique such as spike sorting, which stably collects neural signals before and after the animal eats food and receives the corresponding data from an external electronic device to determine the level of activity of the nerve signals. .

6 illustrates a structure of a wireless power transmission device (eg, the wireless power transmission device 201 of FIG. 1 ) according to various embodiments.

According to various embodiments, the wireless power transmitter 201 includes a first antenna 211 for power input and a second antenna 211 for amplifying the power input by being spaced upward by a predetermined first distance from the first antenna. An antenna 212 may be included. For example, referring to FIG. 6, the second antenna 212 moves upward by a predetermined first distance d1 from the first antenna 211 in order to generate a high current value in relation to the first antenna 211. It may be spaced apart and installed in the wireless power transmission device 201. The first antenna 211 and the second antenna 212 have a shape surrounding a cage 213 accommodating a laboratory animal, and the second antenna 212 is in contact with the laboratory animal for the laboratory animal. Located at a point spaced upward by a predetermined second distance from the foot of the cage 213 for supporting the animal, the second antenna 212 is a wireless power reception module located around the brain of the laboratory animal. Power is transmitted wirelessly, but the wireless power reception module may include a litz wire coil. According to one embodiment, the second antenna 212 may be located within a predetermined third distance from the central point of the cage 213 . For example, referring to FIG. 6 , the second antenna 212 transmits high wireless power to the neural signal processing device 101 embedded in the head of a laboratory animal in relation to the neural signal processing device 101, It may be located at a point spaced apart from the center point of the cage 213 by a specific distance d2 within a range within a predetermined third distance from the center point of the cage 213 .

7 illustrates a first antenna (eg, the first antenna 211 of FIG. 1 ) and a second antenna (eg, the wireless power transmitter 201 of FIG. 1 ) and a second antenna (eg, the wireless power transmitter 201 of FIG. 1 ) according to various embodiments. : Shows an equivalent circuit of the first antenna 212 in FIG.

8 is a graph illustrating a change in current generated from the second antenna 212 according to a change in a coupling coefficient k between the first antenna 211 and the second antenna 212 according to various embodiments.

Parameters that can be derived from the equivalent circuit of FIG. 7 may be as follows. At this time, the Tx antenna represents the first antenna 211, and the repeater antenna represents the second antenna 212.

= Tx 안테나에 흐르는 전류

= current flowing through the Tx antenna

= Repeater 안테나에 흐르는 전류

= current flowing through the repeater antenna

= Tx 안테나 시스템의 전체 저항(Rs+Rtp)

= total resistance of the Tx antenna system (Rs+Rtp)

= Repeater 안테나 시스템의 전체 저항

= total resistance of the repeater antenna system

= 파워 소스의 출력 저항

= output resistance of the power source

= Tx 안테나 코일의 저항

= resistance of the Tx antenna coil

= Tx 안테나에 공급하는 전압

= Voltage supplied to the Tx antenna

= Tx 안테나의 인덕턴스

= Inductance of the Tx antenna

= Repeater 안테나의 인덕턴스

= Inductance of repeater antenna

= Tx 안테나의 공진주파수를 맞추기 위한 캐패시터의 캐패시턴스

= Capacitance of the capacitor to match the resonant frequency of the Tx antenna

= Repeater 안테나의 공진주파수를 맞추기 위한 캐패시터의 캐패시턴스

= Capacitance of the capacitor to match the resonant frequency of the repeater antenna

= Tx 안테나와 Repeater 안테나 사이의 결합 계수

= Coupling coefficient between Tx antenna and Repeater antenna

= 공진 주파수

= resonant frequency

According to an embodiment, the current Itx flowing through the first antenna 211 and the current Irep flowing through the second antenna 212 may be calculated according to Equation 1 below.

Regarding the parameters of [Equation 1], the newly added parameters may be as follows.

= Tx 안테나의 quality factor

= quality factor of Tx antenna

= Repeater 안테나의 quality factor

= quality factor of repeater antenna

Here, the quality factor of each antenna can be calculated by WL/R, where L represents Ltx and Lrep, R represents Rtx and Rrep, and W represents a resonant angular frequency. According to one embodiment, W may be 13.56 MHz.

According to an embodiment, k may be calculated according to [Equation 2] below.

M represents the mutual inductance of Ltx and Lrep.

Referring to <801> of FIG. 8, the wireless power transmitter 201 according to the present invention adopts both the first antenna 211 and the second antenna 212 (Repeater-Tx structure), so that the first antenna ( 211), it can be seen that the wireless power transmission efficiency is higher in the critically-coupled region of the k value compared to the Single-Tx structure adopting only 211).

According to an embodiment, the distance d between the first antenna 211 and the second antenna 212 is greater than the current Itx flowing through the first antenna 211 (current flowing through the second antenna 212). It may be a distance that has a value of k that causes a higher Irep). According to an embodiment, the distance d between the first antenna 211 and the second antenna 212 may be such that it has a k value that generates a maximum value of Irep. Referring to <802> and <803> of FIG. 8, the k value can be adjusted by adjusting the distance d between the first antenna 211 and the second antenna 212, and when an appropriate distance is obtained ( That is, when the value of k is in an appropriate range), the Repeater-Tx structure adopting both the first antenna 211 and the second antenna 212 has a larger current than the Single-Tx structure adopting only the first antenna 211. , and it can be seen that a stronger magnetic field is generated accordingly. At this time, normalized B means normalized magnetic flux density. Specifically, referring to <802>, a stronger magnetic field is generated in the Repeater-Tx structure than in the Single-Tx structure at the k value when the distance between the first antenna 211 and the second antenna 212 is 80 cm. Able to know.

According to an embodiment, the wireless power transmitter 201 may adopt Rtx of 50 ohms and Rrep of less than 10 ohms in order to increase power transmission efficiency.

9 is a diagram for explaining a difference between a solid coil and a litz coil, and a difference between a Single-Tx structure and a Repeater-Tx structure according to various embodiments.

9(a) is a graph showing the degree of wireless power reception according to the shape of the coil of the receiver in the case of a repeater antenna. Litz coil is a coil in which 100 thin wires are bundled and wound. Solid coil is wound with a wire having the same diameter as Litz coil, but consists of one thick wire. Planar coil is a coil made of thin patterns on the PCB. indicates In terms of reception efficiency, it can be seen that the planar coil is the worst, and the solid coil and the Litz coil show similar wireless power reception performance. However, referring to (b) of FIG. 9, in the case of a solid coil, since it is a coil made of one thick strand of wire, it has high mechanical rigidity and does not bend, whereas the Litz coil is composed of 100 thin strands, so Since the stiffness is relatively weak and can be bent, it can be seen that the soft and bendable Litz coil has an advantage when used as a wireless power receiving coil for an implantable device in the living body.

9 (c) and (d) show the output voltage of the receiving coil according to the height from the antenna in the case of the Single-Tx structure and the Repeater-Tx structure, respectively, to the size of the load (0.1k, 1k, 10k ohm). It is a graph that follows Overall, it can be seen that the case of the repeater antenna can transmit more power to a relatively high point. The height area shaded in green indicates an operational range of the Amplifier IC for measuring the neural signal in the circuit of the neural signal processing device 101, and indicates an area where the received voltage is 3.2V or more in the circuit. The area of the height indicated by the blue shade represents the range in which the BLE MCU can operate in the circuit of the neural signal processing device 101, and represents the area in which the received voltage is 1.7V or more in the circuit. For example, in order to select a monkey as an experimental animal, it means that the neural signal processing device 101 must operate up to a height of about 30 cm. know that it is possible.

10 shows a concept diagram of a wireless power transmission device 201 according to various embodiments.

The wireless power transmitter 201 according to an embodiment may be designed and implemented in various ways as shown in FIG. 10 . Referring to FIG. 10 according to an embodiment, the second antenna 212 may be located at a point spaced upward by a predetermined second distance d3 from the footrest 214 of the cage 213 for supporting laboratory animals. can

11 illustrates a state of a brain implantable flexible probe inserted into the brain according to various embodiments.

The brain implantable flexible probe 130 according to an embodiment may have different stiffness before and after being coated with a biodegradable material and inserted into the brain.

The biodegradable material may include sugar. However, it is not limited to this, but it is sufficient if it is a biodegradable material that can maintain a constant shape until inserted into the brain.

According to one embodiment, referring to FIG. 11 , the brain implantable flexible probe maintains a sugar-coated appearance when inserted into the brain. After that, sugar, a biodegradable substance, dissolves in the brain over time. When the sugar melts, the 3-dimensional porous electrodes and 32-channel electrodes in the brain implantable flexible probe can receive signals from the cranial nerves.

12 illustrates a state of a brain implantable flexible probe coated with sugar according to various embodiments.

A biodegradable material may be coated in a U-shape on the outside of the brain implantable flexible probe according to an embodiment. Referring to FIG. 12, the brain implantable flexible probe has excellent rigidity as sugar, a biodegradable material, changes from a rigid form to a soft form, thereby preventing damage to the brain. .

By coating the outside of the brain-implantable flexible probe with sugar, which is a U-shaped biodegradable material, the cross-sectional area can be minimized while increasing the bending rigidity of the brain-implantable flexible probe. As a result, there is an effect that the brain implantable flexible probe can be inserted into a desired part when inserted into the brain. Once inserted into the brain, the flexible probe has the effect of reducing brain damage as the biodegradable material softens according to the recording.

13 illustrates a circuit diagram for measuring a change in impedance of an electrode according to coating according to various embodiments.

As the biodegradable material coated in the brain implantable flexible probe according to various embodiments is decomposed in the brain, the change in impedance of the electrode was measured.

13 illustrates a circuit diagram for measuring a change in impedance of an electrode according to coating according to various embodiments.

<condition>

agarose gel

1 mM PBS

pH: 7.4

Electrochemical impedance spectroscopy

Open circuit delay: 120 second

Sine wave AC: 10 mV

Direct current component (offset DC): 0 V

Electrode size: 300㎛ ²

The change in electrode impedance was measured through Equation 3 below.

Z _a-e' : Amplifier input impedance value

Z _e' : Effective electrode impedance value

V _e' : Voltage value across resistance Z _a-e'-

V _e : Voltage value across the entire resistance

According to Equation 3, the signal loss before and after the biodegradable material melted was measured.

Z _e' value is 1M When Ω (at 1kHz), signal loss was about 7%. In contrast,

Z _e' value is 3M When Ω (at 1kHz), about 19% of signal loss occurred. Through this, it was confirmed that the larger the resistance value, the more signal loss occurs.

According to various embodiments, the 32-channel electrode may be made of polystyrene, platinum, and iridium oxide. The electrode may have a macro-porous structure. Through this, there is an effect of reducing the resistance of the electrode.

14 illustrates a graph of impedance change of a neural electrode according to a biodegradation process according to various embodiments.

The electrode impedance in the brain-implantable flexible probe according to an embodiment had an effect of lowering the impedance over time as the coated biodegradable material was directly exposed to the brain according to the recording.

Referring to FIG. 14, the impedance of the electrode 7 minutes after being inserted into the brain at 1 kHz is 1.505 M Ω, but it was confirmed that the impedance of the electrode 28 minutes after being inserted into the brain decreased by about 25% to the extent of showing 1.121 MΩ.

15 illustrates graphs of physical changes and impedance changes of neural electrodes according to brain tissue implantation time according to various embodiments.

Referring to FIG. 15, it can be seen that the rigidity of the brain implantable flexible probe before being inserted into the brain tissue is rigid, and the stiffness is soft according to the recording of the biodegradable material inserted into the brain tissue. You can check.

In addition, the electrochemical impedance of the electrode before being inserted into the brain tissue was 10 ⁴ kΩ, but after being inserted into the brain tissue, the electrochemical impedance of the electrode decreased to 10 ² kΩ.

Through this, it is possible to check the change in the stiffness of the brain implantable flexible probe and the electrochemical impedance of the electrode according to the brain tissue insertion time.

According to various embodiments, an apparatus for processing neural signals embedded in the periphery of the brain of a laboratory animal is a brain implantable flexible probe including 32 electrodes for collecting 32 channels of neural signals inserted into the brain. probe); A communication module including a Bluetooth Low Energy (BLE) module; A sensor module including an acceleration sensor; A wireless power reception module including a litz wire coil for wirelessly receiving power from a wireless power transmission device; and a processor, and while receiving power wirelessly through the Litz wire coil, the processor acquires the 32-channel neural signals collected through the flexible probe, and selects a predetermined value among the 32-channel neural signals. Four-channel neural signals may be selected according to criteria, and the four-channel neural signals may be set to be transmitted to an external electronic device through the Bluetooth Low Energy module.

According to various embodiments, the processor may be further configured to transmit the 32-channel neural signal to the external electronic device through the Bluetooth low energy module.

According to various embodiments, the processor checks the number of spikes for a specific time period for the 32-channel neurons, and as the predetermined criterion, the 4 channels in order of increasing number of spikes during the specific time period. It can be set to select the neural signal of

According to various embodiments, the neural signal processing apparatus further includes a neural signal amplifier, and the processor selects the 4-channel neural signal having a raw signal form according to the predetermined criterion. It can be set to control the neural signal amplifier to do so.

According to various embodiments, the 4-channel neural signal may be a raw signal composed of only action potential (AP) or a raw signal composed of AP and local field potential (LFP), and the 32-channel neural signal may be a raw signal composed only of LFP. can

According to various embodiments, the flexible probe may include a three-dimensional porous electrode for lowering the electrochemical impedance of the 32 electrodes.

According to various embodiments, the processor allocates a size of 2 bytes per cycle to the neural signal of each channel, and the acceleration sensor data acquired through the acceleration sensor and the power received through the wireless power reception module. A size of 4 bytes is allocated to the voltage value of , and when the 32-channel neural signal is transmitted to the external electronic device, the size of 196 bytes is obtained by including the 3-cycle neural signal, the acceleration sensor data, and the voltage value. When the 4-channel neural signal is transmitted to the external electronic device, one packet having a size of 244 bytes including the 30-cycle neural signal, the acceleration sensor data, and the voltage value is transmitted. can be set to transmit.

According to various embodiments, in the operating method of a neural signal processing apparatus embedded in the periphery of the brain of a laboratory animal and processing neural signals, the neural signal processing apparatus is inserted into the brain to collect 32-channel neural signals. A brain-implantable flexible probe including 32 electrodes for a brain implant, a communication module including a low-power Bluetooth (BLE) module, a sensor module including an acceleration sensor, and a LIT for receiving power wirelessly from a wireless power transmission device. A wireless power reception module including a wire (litz wire) coil, and a processor; and the method of operating the neural signal processing apparatus, while receiving power wirelessly through the litz wire coil, using the processor: An operation of acquiring the 32-channel neural signals collected through the flexible probe, an operation of selecting 4-channel neural signals from among the 32-channel neural signals according to a predetermined criterion, and an operation of selecting the 4-channel neural signals through the Bluetooth Low Energy module. It may include an operation of transmitting the nerve signal of the external electronic device.

According to various embodiments, the method may further include transmitting the 32-channel neural signal to the external electronic device through the Bluetooth low energy module.

According to various embodiments, the operation of selecting the 4-channel neural signals may include an operation of checking the number of spikes for a specific time period for the 32-channel neural signals, as the predetermined criterion, the spikes during the specific time period. It may include an operation of selecting the neural signals of the 4 channels in order of a large number of .

According to various embodiments, the operation of selecting the 4-channel neural signals may include controlling the neural signal amplifier to select the 4-channel neural signals having a raw signal form according to the predetermined criterion. can

According to various embodiments, the method includes an operation of allocating a size of 2 bytes per cycle to a neural signal of each channel, and acceleration sensor data acquired through the acceleration sensor and received through the wireless power reception module. The operation of allocating a size of 4 bytes to the voltage value of the applied power, and the operation of transmitting the 32-channel neural signals to the external electronic device may transmit the 32-channel neural signals to the external electronic device. and transmitting one packet having a size of 196 bytes including the 3-cycle neural signal, the acceleration sensor data, and the voltage value, and transmitting the 4-channel neural signal to the external electronic device. The operation of transmitting the 4-channel neural signal to the external electronic device includes transmitting one packet having a size of 244 bytes including the 30-cycle neural signal, the acceleration sensor data, and the voltage value. can include

According to various embodiments of the present disclosure, in a storage medium storing instructions readable by a computer, when the instructions are executed by a processor of a neural signal processing apparatus embedded in the periphery of the brain of a laboratory animal and processing neural signals, the Causes a neural signal processing device to perform at least one operation, and the neural signal processing device is a brain implantable flexible probe including 32 electrodes inserted into the brain to collect 32 channels of neural signals. ), a communication module including a low-power Bluetooth (BLE) module, a sensor module including an acceleration sensor, and a wireless power reception module including a litz wire coil for wirelessly receiving power from a wireless power transmission device. And, the at least one operation: while receiving power wirelessly through the Litz wire coil, by using the processor: obtaining the 32-channel neural signals collected through the flexible probe, the 32 An operation of selecting 4-channel neural signals from among channel neural signals according to a predetermined criterion and an operation of transmitting the 4-channel neural signals to an external electronic device through the Bluetooth Low Energy module.

According to various embodiments, a wireless power transmission apparatus may include a first antenna for power input; and a second antenna spaced upward from the first antenna by a predetermined first distance to amplify the power input, wherein the first antenna and the second antenna surround a cage accommodating a laboratory animal. shape, the second antenna is located at a point upwardly spaced apart by a predetermined second distance from the foot of the cage for supporting the laboratory animal, and the second antenna is located around the brain of the laboratory animal Power is wirelessly transmitted to a wireless power reception module for wireless power reception, and the wireless power reception module may include a litz wire coil.

According to various embodiments, the predetermined first distance is a distance having a k value that generates a higher second current Irep flowing through the second antenna than the first current Itx flowing through the first antenna, and , The first current and the second current may be calculated by Equation 1 below, respectively.

[Equation 1]

= Tx 안테나(상기 제1 안테나)의 전체 저항

= total resistance of the Tx antenna (the first antenna)

= Repeater 안테나(상기 제2 안테나)의 전체 저항

= total resistance of the repeater antenna (the second antenna)

= Tx 안테나에 공급하는 전압

= Voltage supplied to the Tx antenna

= Tx 안테나의 인덕턴스

= Inductance of the Tx antenna

= Repeater 안테나의 인덕턴스

= Inductance of repeater antenna

= Tx 안테나와 Repeater 안테나 사이의 결합 계수

= Coupling coefficient between Tx antenna and Repeater antenna

= 공진 주파수

= resonant frequency

= Tx 안테나의 quality factor

= quality factor of Tx antenna

= Repeater 안테나의 quality factor

= quality factor of repeater antenna

According to various embodiments, the predetermined first distance may be a distance having a k value that generates a maximum value of the second current.

According to various embodiments, the Rtx may be 50 ohms and the Rrep may be less than 10 ohms.

According to various embodiments, the second antenna may be located within a predetermined third distance from the central point of the cage.

Various embodiments of this document and terms used therein are not intended to limit the technical features described in this document to specific embodiments, but should be understood to include various modifications, equivalents, or substitutes of the embodiments. In connection with the description of the drawings, like reference numbers may be used for like or related elements. The singular form of a noun corresponding to an item may include one item or a plurality of items, unless the relevant context clearly dictates otherwise. In this document, "A or B", "at least one of A and B", "at least one of A or B", "A, B or C", "at least one of A, B and C", and "A Each of the phrases such as "at least one of , B, or C" may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof. Terms such as "first", "second", or "first" or "secondary" may simply be used to distinguish a given component from other corresponding components, and may be used to refer to a given component in another aspect (eg, importance or order) is not limited. A (e.g., first) component is said to be “coupled” or “connected” to another (e.g., second) component, with or without the terms “functionally” or “communicatively.” When mentioned, it means that the certain component may be connected to the other component directly (eg by wire), wirelessly, or through a third component.

100: Neural signal processing system using wireless power transmission and reception
101: neural signal processing device, 201: wireless power transmission device
211: first antenna, 212: second antenna

Claims (5)

a three-dimensional porous electrode for lowering the electrochemical impedance of the neural electrode;
32-channel electrodes composed of 32 channels for measuring nerve signals in brain regions;
A layer for electrical insulation between electrodes, wires, and living tissue;
Melting needles composed of substances that melt and disappear in vivo; and
It includes a biodegradable material coated on the brain implantable flexible probe,
The 32-channel electrode is made of polystyrene, platinum and iridium oxide,
The biodegradable material is coated in a U-shape,
The 32-channel electrode is designed so that the electrochemical impedance is 10 ⁴ kΩ before insertion into brain tissue and 10 ² KΩ after insertion into brain tissue,
Brain implantable flexible probe. delete According to claim 1,
The biodegradable material is sugar,
Brain implantable flexible probe.


delete delete

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