CN116960212A - Low-noise integrated biological photoelectric electrode microprobe and preparation method thereof - Google Patents

Abstract

The invention discloses a low-noise integrated biological photoelectric electrode microprobe and a preparation method thereof, wherein the microprobe comprises the following components: the LED comprises a light emitting diode, a plurality of microelectrode pairs with a difference function, a noise isolation groove and an external circuit; wherein, the emitting diode structure includes in proper order: the semiconductor light-emitting diode comprises a substrate material, n-type gallium nitride, an active layer, p-type gallium nitride, a transparent conducting layer, an insulating passivation layer, a light-emitting diode anode and cathode structure, and is used for emitting light and activating biological nerve cells; each microelectrode pair comprises a first microelectrode used for detecting biological signals and a second microelectrode used for collecting noise so as to perform differential processing on the biological signals and improve the signal to noise ratio, and the microelectrode pairs are symmetrically arranged on the insulating passivation layer along the longitudinal axis direction; the noise isolation groove penetrates through the substrate material and is used for separating the anode and the microelectrode pair of the light-emitting diode so as to reduce noise; the external circuit is used for eliminating noise and amplifying biological signals. The invention can eliminate noise without increasing the process and greatly improve the signal-to-noise ratio of the signal.

Description

A low-noise integrated biophotoelectrode microprobe and preparation method

Technical field

The invention belongs to the technical field of biophotoelectrodes, and in particular relates to a low-noise integrated biophotoelectrode microprobe and a preparation method.

Background technique

Optogenetics refers to technology that combines optical and genetic means to precisely control the activity of specific neurons. Optogenetic tools, as photoelectrodes, play an important role in neuroscience research and need to have the functions of specific targeted light regulation and recording of neural signals. Photoelectrodes are mainly divided into two types: coupled light source type and integrated type. Coupled light source type photoelectrodes rely on optical fibers, laser sources, and external coupling equipment, which limits the development of wireless and intelligent photoelectrodes; integrated photoelectrodes no longer rely on External light sources have greater freedom and flexibility, so integrated photoelectrodes will become an inevitable development trend in optogenetic tools.

However, the light source driving module of the integrated photoelectrode will generate injected electrical signals during operation, which may cause electromagnetic radiation interference and power frequency noise to the recording of biological signals. Therefore, suppressing and eliminating electromagnetic radiation interference has become one of the difficult problems that photoelectrodes must solve, which has a crucial impact on improving the quality of collected biological signals.

The existing noise reduction methods of integrated biophotoelectrodes mainly include adding a metal shielding layer to the probe to isolate noise, changing the substrate doping, pulse shaping, and placing LEDs and microelectrodes on the front and back of the probe respectively. , but this method cannot completely eliminate noise, and the added shielding layer will also increase process steps and production costs.

Contents of the invention

The purpose of the present invention is to provide a low-noise integrated biophotoelectrode microprobe and a preparation method to solve the technical problem that the noise reduction method of the existing integrated biophotoelectrode is complicated and the noise cannot be completely eliminated.

The purpose of the present invention can be achieved through the following technical solutions:

A low-noise integrated biophotoelectrode microprobe, including:

A light-emitting diode structure, a plurality of microelectrode pairs with differential functions, a noise isolation tank and an external circuit structure; each of the microelectrode pairs includes a first microelectrode and a second microelectrode, and the first microelectrode is used to detect biological signals. , the second microelectrode is used to collect noise to differentially process the biological signal and improve the signal-to-noise ratio;

Wherein, the light-emitting diode structure includes from bottom to top: substrate material, n-type gallium nitride, active layer, p-type gallium nitride, transparent conductive layer, insulating passivation layer, light-emitting diode anode and light-emitting diode cathode, Used to emit light and activate biological nerve cells;

Each of the microelectrode pairs is symmetrically arranged on the insulating passivation layer along the longitudinal axis;

The noise isolation groove is etched symmetrically along the longitudinal axis and penetrates into the substrate material to spatially and physically separate the light-emitting diode anode and the plurality of microelectrode pairs to reduce noise;

The external circuit structure matches the two-channel noise during biological signal collection, eliminates the noise and amplifies the biological signal.

Optionally, each of the microelectrode pairs includes: the first microelectrode and the second microelectrode symmetrically distributed along the longitudinal axis direction, the first microelectrode wire and the second microelectrode wire arranged symmetrically, and a first microelectrode pad and a second microelectrode pad symmetrically distributed along the longitudinal axis.

Optionally, each microelectrode pair also includes:

Spaced microelectrode windows and noise windows, the microelectrode window is provided on the first microelectrode, the noise window is provided on the second microelectrode wire; or the microelectrode window is provided on the On the second microelectrode, the noise window is set on the first microelectrode wire.

Optionally, the light-emitting diode anode includes:

LED anode electrode, LED anode wire and LED anode pad.

Optionally, the noise isolation groove is formed by etching a groove in the substrate material to spatially connect the anode wire of the light-emitting diode to the two microelectrodes and two microelectrode wires of each of the microelectrode pairs. physical separation to reduce noise.

The invention also provides a method for preparing a low-noise integrated biophotoelectrode microprobe, which includes:

n-type gallium nitride, active layer, and p-type gallium nitride are grown sequentially on the substrate material, a transparent conductive layer is prepared through photolithography and magnetron sputtering processes, and the transparent conductive layer is patterned through a lift-off process to prepare The transparent anode and electromagnetic shielding layer of the light-emitting diode;

Etch the epitaxial wafer to n-type gallium nitride through photolithography and plasma etching processes, and then etch the noise isolation trench to the substrate material;

Activating the active layer at high temperature, preparing an insulating passivation layer through photolithography and plasma-enhanced chemical vapor deposition processes, and patterning the insulating passivation layer with a buffered oxide etching solution using a wet etching process to prepare Get the cathode window and anode window;

Through photolithography and electron beam evaporation processes, a metal film is prepared in a high vacuum environment, and a lift-off process is used to pattern the metal film to prepare a light-emitting diode anode and a light-emitting diode cathode;

Through photolithography and plasma-enhanced chemical vapor deposition processes, the silicon dioxide passivation layer is prepared in a gas environment of SiH4 and N2O, high vacuum and a high temperature environment of 350°C, and a dry etching process is used to pattern the silicon dioxide isolation layer. to prepare anode pad window and cathode pad window;

Through photolithography and electron beam evaporation processes, a metal film is prepared in a high vacuum environment, and a lift-off process is used to pattern the metal film to prepare multiple microelectrode pairs with differential functions;

Through photolithography and plasma-enhanced chemical vapor deposition processes, the silicon dioxide passivation layer is prepared in a gas environment of SiH4 and N2O, high vacuum and a high temperature environment of 350°C, and a dry etching process is used to pattern the silicon dioxide isolation layer. to prepare microelectrode windows, noise windows, microelectrode pad windows, anode pad windows, and cathode pad windows.

Optionally, preparing the light-emitting diode anode and the light-emitting diode cathode includes:

A light-emitting diode anode electrode, a light-emitting diode anode wire, a light-emitting diode anode pad, a light-emitting diode cathode electrode, a light-emitting diode cathode wire and a light-emitting diode cathode pad are prepared.

Optionally, preparing multiple microelectrode pairs with differential functions includes:

A plurality of microelectrode pairs are prepared. Each microelectrode pair includes a first microelectrode and a second microelectrode symmetrically distributed along the longitudinal axis, a first microelectrode wire and a second microelectrode wire arranged symmetrically, and a first microelectrode wire and a second microelectrode wire arranged symmetrically along the longitudinal axis. There are first microelectrode pads and second microelectrode pads symmetrically distributed in the axial direction, the first microelectrode is used for biological signal detection, and the second microelectrode is used for differentiation.

Optionally, the metal film is a 50nm titanium metal film or a 150nm gold metal film.

The invention provides a low-noise integrated biophotoelectrode microprobe and a preparation method. The microprobe includes: a light-emitting diode structure, a plurality of microelectrode pairs with differential functions, a noise isolation groove and an external circuit structure; The microelectrode pair includes a first microelectrode and a second microelectrode. The first microelectrode is used to detect biological signals. The second microelectrode is used to collect noise to differentially process the biological signals and improve signal-to-noise. Ratio; wherein, the light-emitting diode structure includes from bottom to top: substrate material, n-type gallium nitride, active layer, p-type gallium nitride, transparent conductive layer, insulating passivation layer, light-emitting diode anode and light-emitting diode The cathode is used to emit light and activate biological nerve cells; each of the microelectrode pairs is symmetrically arranged on the insulating passivation layer along the longitudinal axis; the noise isolation groove is symmetrically etched along the longitudinal axis and penetrates to the lining The base material is used to physically separate the light-emitting diode anode and the plurality of microelectrode pairs in space to reduce noise; the external circuit structure matches the two-channel noise during biological signal collection and eliminates the noise. and amplify the biological signal.

In view of this, the beneficial effects brought by the present invention are:

The light-emitting diode structure of the present invention includes, from bottom to top: substrate material, n-type gallium nitride, active layer, p-type gallium nitride, transparent conductive layer, insulating passivation layer, light-emitting diode anode and light-emitting diode cathode. Multiple microelectrode pairs with differential functions are symmetrically arranged on the insulating passivation layer along the longitudinal axis. The noise isolation groove is etched symmetrically along the longitudinal axis, starting from n-type gallium nitride and penetrating from top to the third layer of insulating passivation. The production process is simple and does not require additional process steps. Without losing the quality of biological signals, it can eliminate most of the noise interference collected by the integrated biophotoelectrode, greatly improving It improves the signal-to-noise ratio of biological signals and can obtain pure and undistorted biological signals more efficiently.

At the same time, microelectrode pairs with differential functions are also universal and can be applied to most existing photoelectrodes without making major changes to the device; differential microelectrode pairs can be used to detect the uniformity and stability of microprobes. Robustness, the circuit can also be adjusted according to different electrode properties to make the collected signals more uniform. Therefore, the invention also has the advantages of simple production process, low cost, universality, and the ability to detect the robustness and uniformity of the device. .

Description of the drawings

Figure 1 is a three-dimensional view of the low-noise integrated biophotoelectrode microprobe of the present invention after etching the mesa;

Figure 2 is a perspective view of the low-noise integrated biophotoelectrode microprobe of the present invention after preparing a transparent conductive layer;

Figure 3 is a perspective view of the low-noise integrated biophotoelectrode microprobe of the present invention after preparing the insulating passivation layer 1;

Figure 4 is a three-dimensional view of the low-noise integrated biophotoelectrode microprobe of the present invention after preparing a light-emitting diode metal electrode;

Figure 5 is a perspective view of the low-noise integrated biophotoelectrode microprobe of the present invention after preparing the insulating passivation layer 2;

Figure 6 is a perspective view of the low-noise integrated biophotoelectrode microprobe of the present invention after preparing the microelectrode metal;

Figure 7 is a perspective view of the low-noise integrated biophotoelectrode microprobe of the present invention after preparing the insulating passivation layer 3;

Figure 8 is a side view of the low-noise integrated biophotoelectrode microprobe of the present invention after each layer is peeled off;

Figure 9 is a perspective view of the low-noise integrated biophotoelectrode microprobe of the present invention after each layer is peeled off;

Figure 10 is a top view of the low-noise integrated biophotoelectrode microprobe of the present invention;

Figure 11 is a schematic diagram of the external circuit and working principle of the low-noise integrated biophotoelectrode microprobe of the present invention;

Figure 12 is a schematic flow chart of the preparation method of the low-noise integrated biophotoelectrode microprobe of the present invention.

Among them, substrate material-1, n-GaN-2, noise isolation trench-3, active layer-4, p-GaN-5, transparent conductive layer-6, anode window-7, cathode window-8, first Insulating passivation layer-9, anode electrode and wire-10, anode pad-11, cathode electrode and wire-12, cathode pad-13, second insulating passivation layer-14, microelectrode-15, microelectrode wire -16, microelectrode pad-17, third insulating passivation layer-18, microelectrode window-19, noise window-20, signal voltage dividing circuit-21, differential amplifier circuit-22, first microelectrode-23, Second microelectrode-24.

Detailed ways

Terminology explanation:

Differential circuit: When there is a difference in the voltage between the two input terminals of the circuit, the circuit reduces the same part of the two voltages and only outputs the different part of the voltage; for example: the input voltage at the + input terminal is A+B, the input voltage at the - input terminal is A, then the output voltage is (A+B)-(A)=B.

Integrated biophotoelectrode: A tool used to study optogenetics. It is in the shape of a slender probe with LEDs, microelectrodes, etc. integrated at the top, and the end is the pad of the circuit. When the probe is working, the LED emits light under the action of pulse voltage, stimulating biological neurons to generate nerve impulses. The microelectrodes are used to record the signals generated by the impulses of biological neurons.

Noise: When the probe is working, the microelectrode will not only collect biological neuron signals, but will also be affected by LED pulse electrical signals and light, producing noise. Excessive noise may mask biological signals.

Embodiments of the present invention provide a low-noise integrated biophotoelectrode microprobe and a preparation method to solve the technical problem that the noise reduction method of the existing integrated biophotoelectrode is complicated and the noise cannot be completely eliminated.

In order to facilitate understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. There is shown in the drawing a preferred embodiment of the invention. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the invention belongs. The terminology used herein in the description of the invention is for the purpose of describing specific embodiments only and is not intended to limit the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Optogenetic tools need to have two functions during their development: specific targeted light regulation and recording of neural signals. These tools are called photoelectrodes, and their role is to control light and record neural activity. At present, photoelectrodes can be mainly divided into two types: coupled light source type and integrated type.

Coupled light source photoelectrodes rely on optical fibers, laser sources and external coupling devices. These constraints limit the development of wireless and intelligent photoelectrodes. To overcome these limitations, integrated photoelectrodes are considered an inevitable development trend in optogenetic tools. Integrated photoelectrodes no longer rely on external light sources, giving them greater freedom and flexibility.

However, the light source driving module of the integrated photoelectrode will generate injected electrical signals during operation, which may cause electromagnetic radiation interference and power frequency noise to the recording of biological signals. Therefore, suppressing and eliminating electromagnetic radiation interference has become one of the difficult problems that photoelectrodes must solve, which has a crucial impact on improving the quality of collected biological signals. In addition, the recording capabilities of photoelectrodes can be further improved to achieve higher temporal and spatial resolutions to better capture and interpret dynamic changes in neural activity.

In summary, optogenetic tools as photoelectrodes play an important role in neuroscience research. By solving challenges such as electromagnetic radiation interference, photoelectrodes can be continuously improved and optimized to provide us with more accurate and high-quality neural signal recording and light regulation capabilities, promoting further development in the field of neuroscience.

Existing integrated photoelectrodes mainly have the following shortcomings:

(1) One or more metal shielding layers are used to isolate the interference of electrical signals on the microelectrodes: the preparation process is complex, the cost is high, the shielding effect is not good enough, leakage of electromagnetic interference still exists, and light-induced noise cannot be shielded.

(2) Reduce noise through an external filter circuit: Noise cannot be completely eliminated, and noise close to the frequency of biological signals cannot be eliminated. The circuits are complex and can easily distort biological signals.

The purpose of the present invention is to provide a low-noise integrated biophotoelectrode microprobe and a preparation method, which can eliminate the large noise collected by the integrated biophotoelectrode without adding process steps and without losing the quality of biological signals. Partial noise interference greatly improves the signal-to-noise ratio of biological signals and obtains pure and undistorted biological signals more efficiently. On this basis, the present invention also has the advantages of simple production process, low cost, universality, and the ability to detect device robustness and uniformity.

Please refer to Figure 1 to Figure 11, a low-noise integrated biophotoelectrode microprobe, including:

A light-emitting diode structure, a plurality of microelectrode pairs with differential functions, a noise isolation tank and an external circuit structure; each of the microelectrode pairs includes a first microelectrode and a second microelectrode, and the first microelectrode is used to detect biological signals. , the second microelectrode is used to collect noise to differentially process the biological signal and improve the signal-to-noise ratio;

Wherein, the light-emitting diode structure includes from bottom to top: substrate material, n-type gallium nitride, active layer, p-type gallium nitride, transparent conductive layer, insulating passivation layer, light-emitting diode anode and light-emitting diode cathode, Used to emit light and activate biological nerve cells;

Each of the microelectrode pairs is symmetrically arranged on the insulating passivation layer along the longitudinal axis;

The noise isolation groove is etched symmetrically along the longitudinal axis and penetrates into the substrate material to spatially and physically separate the light-emitting diode anode and the plurality of microelectrode pairs to reduce noise;

The external circuit structure matches the two-channel noise during biological signal collection, eliminates the noise and amplifies the biological signal.

The low-noise integrated biophotoelectrode microprobe provided by the embodiment of the present invention mainly includes four parts: a light-emitting diode structure, a plurality of microelectrode pairs with differential functions, a noise isolation groove, and an external circuit structure. The working principle is: when working, the microprobe device is inserted into the biological brain tissue, and the device is immersed in the biological solution. The top of the microprobe is closest to the nerve cells of the brain tissue; the light-emitting diode structure is illuminated and passed through the microprobe with differential function. The electrode pair collects the electrophysiological signals of biological nerve cells, and finally removes the noise through the external circuit structure.

The working principle of the light-emitting diode structure (photodiode) is: by connecting the forward voltage to the anode pad 11 and grounding the cathode pad 13, the current will flow into the photodiode p-type gallium nitride through the anode electrode (anode contact) and the wire. 5 region, the n-type gallium nitride 2 flows through the active layer 4, and the current flows out from the cathode pad 13. During this process, the light-emitting diode lights up and activates the biological nerve cells, but at the same time, changes in current, voltage and illumination will also generate electrical noise and optical noise on the microelectrode 15 and the microelectrode wire 16 . Since the entire microprobe device has a symmetrical design, the effects of current, voltage and light on the two microelectrodes 15 and microelectrode wires 16 symmetrically distributed along the longitudinal symmetry axis of the device are basically the same, and the final noise amplitude and phase are basically the same. same.

In some embodiments, the plurality of microelectrode pairs with differential functions include: microelectrodes 15 symmetrically distributed along the longitudinal axis, symmetrically routed microelectrode wires 16 and microelectrode pads 17 . The working principle of the microelectrode pair with differential function is as follows: the microelectrode 15 is located above the photodiode and is closest to the biological nerve cells. When the biological nerve cells are activated, the microelectrode 15 passes through the microelectrode on the third insulating passivation layer 18. The electrode window 19 collects biological signals.

Specifically, each microelectrode pair includes: a first microelectrode and a second microelectrode symmetrically distributed along the longitudinal axis, a first microelectrode wire and a second microelectrode wire symmetrically routed, and a first microelectrode wire symmetrically distributed along the longitudinal axis. the first microelectrode pad and the second microelectrode pad.

In some embodiments, each microelectrode pair with differential function further includes:

The microelectrode window and the noise window are spaced apart. The microelectrode window can be set on the first microelectrode, and the noise window can be set on the second microelectrode wire; or, the microelectrode window can be set on the second microelectrode, and the noise window can be set on the second microelectrode. The window can be provided on the first microelectrode lead.

It can be understood that for a biophotoelectrode microprobe, microelectrode windows are set on half of the number of microelectrodes, and noise windows are set on the microelectrode leads corresponding to the remaining number of microelectrodes. Specifically, microelectrode windows 19 distributed in a staggered manner are left above half of the number of microelectrodes 15, and noise windows 20 are left on the microelectrode wires 16 connected to the remaining half of the number of microelectrodes 15.

In one embodiment, the microelectrode pair structure with differential function includes microelectrode windows 19 with spaced windows and a noise window design. These designs are all designed to ensure that the noise between the two symmetrical signals is the same. Only biological signals have No difference.

It can be understood that for any microelectrode pair with differential function, if there is a microelectrode window 19 on the microelectrode 15, there will be no noise window 20 on the corresponding microelectrode wire 16; if there is no microelectrode window 19 on the microelectrode 15, If the electrode window 19 is formed, a noise window 20 is left on the corresponding microelectrode wire 16. That is to say, for a certain microelectrode pair, either the microelectrode window 19 is left on the first microelectrode, or the noise window 20 is left on the second microelectrode wire 16. The microelectrode window 19 is designed according to the shape of the microelectrode 15, and the noise window 20 is designed according to the shape of the microelectrode wire 16. Each microelectrode pair includes a microelectrode with a microelectrode window 19 for biological signal detection and a microelectrode with a noise window 20 for differentiation.

In one embodiment, the insulating passivation layer may include a first insulating passivation layer 9 and a second insulating passivation layer 14 .

Take the pair of microelectrodes closest to the top of the probe in Figure 11, namely the first microelectrode 23 and the second microelectrode 24, as an example: among the two symmetrical microelectrode pairs with differential functions, only one remains. Microelectrode window 19. The microelectrode with the microelectrode window (the first microelectrode 23) can collect biological signals. The microelectrode on the other side (the second microelectrode 24) has no microelectrode window, and the biological signals are insulated and passivated. Layer 18 is shielded, and biological signals cannot be collected. Since the entire microprobe device has a symmetrical design and the insulating passivation layer is made of transparent silicon dioxide, the effects of current, voltage and light on the two microelectrodes 15 and microelectrode wires 16 symmetrically distributed along the longitudinal symmetry axis of the device Basically the same, when the device is not inserted into biological tissue, the amplitude and phase of the collected noise are the same.

After the microprobe device is inserted into the biological tissue, since the first microelectrode 23 and the microelectrode window 19 are located at the top of the probe, they are in direct contact with the biological tissue and solution, and are closest to the nerve cells that are stimulated by light and generate biological nerve signals. Therefore, biological signals can be collected, but part of the electrical noise and optical noise will also be diverted through the biological solution. At the same time, the noise generated by living organisms will also be collected by microelectrodes through the solution. In order to offset the noise difference between the first microelectrode 23 and the second microelectrode 24 caused by the microelectrode window 19, a noise window 20 is opened on the wire of the second microelectrode 24. The noise window 20 can divert the electrical noise and optical noise on the second microelectrode while simultaneously collecting biological noise. Since the noise window 20 is at a certain distance from the microprobe head, biological signals will not be collected. Therefore, before and after being inserted into the biological tissue, the first microelectrode 23 and the second microelectrode 24 are affected by noise exactly the same, and the first microelectrode 23 can collect biological signals, but the second microelectrode 24 cannot collect biological signals.

In some embodiments, the noise isolation trench physically separates the anode wire of the light-emitting diode from the microelectrode 15 and the microelectrode wire 16 through grooves etched into the substrate material to effectively reduce electrical noise.

The working principle of the noise isolation groove is: electrical noise is mainly caused by the potential change of the photodiode anode. By etching the symmetrical noise isolation groove 3 on the sapphire substrate, the anode electrode and wire 10 of the photodiode can be connected to the microelectrode 15 and The conductors 16 are physically separated in space to effectively reduce electrical noise.

It can be understood that the noise isolation groove separates the source of most electrical noise: the anode wire of the photodiode from the microelectrodes and wires that collect biological signals by deeply etching grooves into the substrate, which can reduce the amplitude of electrical noise. value.

It should be noted that the anode electrode and wire 10 of the light-emitting diode and the cathode electrode and wire 12 of the light-emitting diode are all integrated structures. The anode electrode and wire 10 of the light-emitting diode lead the wires to the anode pad 11 through the anode window 7. The cathode electrode and wires of the light-emitting diode are 12 Lead the wire through the cathode window 8 to the cathode pad 13.

In some embodiments, the external circuit structure includes a signal voltage dividing circuit and a differential amplification circuit. The signal voltage dividing circuit is used to match the two noises during biological signal collection, and the differential amplification circuit is used to eliminate noise and amplify the biological signal.

The working principle of the external circuit structure is as follows: As shown in Figure 11, the microelectrode pads connected to the first microelectrode 23 and the second microelectrode 24 are respectively connected to the inputs v1 and v2 of the signal voltage dividing circuit, and the signal voltage is divided. Circuit 21 can adjust the magnitude of the two signals. If there is a difference in the noise between the two paths and the differential result is unsatisfactory, the resistance of the adjustable resistor r1 or r3 can be adjusted to match the two signals so that the amplitude of the noise is the same. The input-output relationship of the signal voltage dividing circuit is: V1=v1*r2/(r1+r2); V2=v2*r4/(r3+r4).

Connect V1 and V2 to the differential amplifier circuit, Vo=R4*V1*(R1+R2)/{r1*(R3+R4)}–V2*R2/R1;

Generally speaking, let R1=R3 and R2=R4, then Vo=(V1-V2)*R2/R1.

Therefore, in the line 1 drawn from the first microelectrode 23, v1 contains biological signals + noise, and in the line 2 drawn from the second microelectrode, v2 contains noise, and the noise magnitudes of v1 and v2 are equalized through the signal voltage dividing circuit; Then connect the two signals to the differential amplifier circuit, and the final collected signal is

Vo＝(V1-V2)*R2/R1

={v1*r2/(r1+r2)-v2*r4/(r3+r4)}*R2/R1

={(biological signal+noise)*r2/(r1+r2)-(noise)v2*r4/(r3+r4)}*R2/R1

=Biological signal*r2/(r1+r2)*R2/R1.

In some embodiments, through the structural design of a low-noise integrated biophotoelectrode device and its external circuit structure based on microelectrode pairs with differential functions, interference noise during biological signal collection can finally be eliminated and pure biological signals can be obtained. It can greatly improve the signal-to-noise ratio of biological signals.

The microelectrode pairs with differential functions in the embodiments of the present invention are also universal. Most photoelectrodes currently available can be used without making major changes to the device, just by modifying the design of the top insulating passivation layer. Reduces most noise.

In addition, the production of biophotoelectrodes is different, and the performance noise of each microprobe is slightly different. The use of microelectrode pair design with differential function can detect the uniformity and robustness of the microprobe device. It can also Adjust the circuit according to different electrode properties to make the collected signals more uniform.

In some embodiments, the symmetrical device structure design of the microprobe, including the light-emitting diode and its wire bonding pad, as well as the symmetrical shape design of the microelectrodes and wires, makes the noise between the symmetrically distributed microelectrodes the same, and makes the device and the uniformity of the collected signals is improved.

In the low-noise integrated biophotoelectrode microprobe provided by the embodiment of the present invention, the light-emitting diode structure includes from bottom to top: substrate material, n-type gallium nitride, active layer, p-type gallium nitride, transparent conductive layer, Insulating passivation layer, light-emitting diode anode and light-emitting diode cathode. Each microelectrode pair is symmetrically arranged on the insulating passivation layer along the longitudinal axis. The noise isolation groove is etched symmetrically along the longitudinal axis and penetrates into the substrate material. The production process is simple. , without adding process steps, without losing the quality of biological signals, it can eliminate most of the noise interference collected by the integrated biological photoelectrode, greatly improve the signal-to-noise ratio of biological signals, and obtain pure signals more efficiently. Undistorted biological signals.

At the same time, the structure of microelectrode pairs with differential functions is also universal and can be applied to most existing photoelectrodes without making major changes to the device; microelectrode pairs with differential functions can be used to detect the uniformity of microprobes and robustness, and can also adjust the circuit according to different electrode properties to make the collected signals more uniform. Therefore, embodiments of the present invention also have simple production processes, low cost, universality, and the ability to detect device robustness and Uniformity and other advantages.

Referring to Figure 12, the present invention also provides an embodiment of a method for preparing a low-noise integrated biophotoelectrode microprobe, including:

n-type gallium nitride, active layer, and p-type gallium nitride are grown sequentially on the substrate material, a transparent conductive layer is prepared through photolithography and magnetron sputtering processes, and the transparent conductive layer is patterned through a lift-off process to prepare The transparent anode and electromagnetic shielding layer of the light-emitting diode;

Etching the epitaxial wafer to n-type gallium nitride through photolithography and ICP (plasma etching) processes, and then etching the noise isolation trench to the substrate material;

Activating the active layer at high temperature, preparing an insulating passivation layer through photolithography and plasma-enhanced chemical vapor deposition processes, and patterning the insulating passivation layer with a buffered oxide etching solution using a wet etching process to prepare Get the cathode window and anode window;

Through photolithography and electron beam evaporation processes, a metal film is prepared in a high vacuum environment, and a lift-off process is used to pattern the metal film to prepare a light-emitting diode anode and a light-emitting diode cathode;

Through photolithography and plasma-enhanced chemical vapor deposition processes, the silicon dioxide passivation layer is prepared in a gas environment of SiH4 and N2O, high vacuum and a high temperature environment of 350°C, and a dry etching process is used to pattern the silicon dioxide isolation layer. to prepare anode pad window and cathode pad window;

Through photolithography and electron beam evaporation processes, a metal film is prepared in a high vacuum environment, and a lift-off process is used to pattern the metal film to prepare a microelectrode pair structure with differential functions;

Through photolithography and plasma-enhanced chemical vapor deposition processes, the silicon dioxide passivation layer is prepared in a gas environment of SiH4 and N2O, high vacuum and a high temperature environment of 350°C, and a dry etching process is used to pattern the silicon dioxide isolation layer. The microelectrode window, the noise window, and the microelectrode pad window are prepared.

As shown in Figure 1, after the low-noise integrated biophotoelectrode microprobe provided by the embodiment of the present invention is etched on the mesa, the light-emitting diode structure includes from bottom to top: substrate material (such as sapphire substrate) 1, n-type Gallium nitride (n-GaN) 2, active layer 4, p-type gallium nitride 5 (p-GaN), noise isolation grooves are etched symmetrically along the longitudinal axis and penetrate into the substrate material.

As shown in Figure 2, based on Figure 1, an indium tin oxide transparent conductive layer 6 is prepared on n-type gallium nitride 2 and p-type gallium nitride 5. The transparent conductive layer 6 prepared on the p-type gallium nitride 5 serves as the anode of the light-emitting diode structure. Although the transparent electrode can increase the current injection area and improve the light transmittance, it is not convenient to lead out long leads and pads, so some The area is set aside for preparing the anode window 7 of the metal structure; the indium tin oxide transparent conductive layer 6 prepared on the n-type gallium nitride 2 serves as the electromagnetic shielding structure of the entire biophotoelectrode, and a noise isolation groove 3 is also left of opening.

As shown in FIG. 3 , based on FIG. 2 , a first insulating passivation layer 9 of silicon dioxide is prepared on the transparent conductive layer 6 . Leave openings in the anode window 7 and the cathode window 8, and also leave an opening in the noise isolation groove 3.

As shown in Figure 4, on the basis of Figure 3, titanium/gold (50/150nm) was used to prepare the anode and cathode structures of the light-emitting diode structure. Specifically, the anode of the light-emitting diode includes: the anode electrode and the wire 10 of the light-emitting diode, and the anode pad 11 of the light-emitting diode; the cathode of the light-emitting diode includes: the cathode electrode and the wire 12 of the light-emitting diode, and the cathode pad 13 of the light-emitting diode.

As shown in Figure 5, on the basis of Figure 4, a second insulating passivation layer 14 is prepared, leaving windows for the anode pad 11 and cathode pad 13 for subsequent wiring, and leaving a window for the noise isolation trench 3.

As shown in Figure 6, on the basis of Figure 5, titanium/gold (50/150nm) was used to prepare a symmetrically laid out microelectrode pair structure with differential functions. The specific structure includes microelectrodes 15 symmetrically distributed along the longitudinal axis, symmetrically routed microelectrode wires 16 and microelectrode pads 17 .

As shown in Figure 7, on the basis of Figure 6, prepare the third insulating layer 18 of silicon dioxide, leave openings at the anode window 7 and cathode window 8, and also leave the opening of the noise isolation trench 3; add half of the amount Leave a cross-staggered distribution of microelectrode windows 19 above the microelectrodes, and leave a noise window 20 on the microelectrode wires connected to the remaining half of the microelectrodes at a certain distance from the microelectrodes; leave a microelectrode pad 17 windows.

In Figures 8 and 9, the microprobes from bottom to top are: sapphire substrate 1, n-type GaN2, active layer 4, p-type gallium nitride 5, transparent conductive layer 6, and first insulating passivation layer 9 , LED anode electrode and wire 10, anode pad 11, cathode electrode and wire 12, cathode pad 13 (cathode and anode metal contact, wire and pad 10-13), second insulating passivation layer 14, microelectrode 15 , microelectrode wires 16 and microelectrode pads 17 (microelectrodes, wires and pads 15-17), and a third insulating passivation layer 18.

Figure 10 is a top view of the low-noise integrated biophotoelectrode microprobe of the present invention; from left to right are the microelectrode window 19, the noise window 20, the noise isolation groove 3, the microelectrode pad 17, and the light-emitting diode cathode pad 13. and LED anode pad 11.

Figure 11 is a schematic diagram of the external circuit and circuit working principle of the low-noise integrated biophotoelectrode microprobe of the present invention; in the figure, the two lines connected to the microelectrode pair closest to the top of the probe are taken as an example. Line 1 starts from the first Starting from the microelectrode window 19 of the microelectrode 23, the signal v1 is connected to the external circuit through the microelectrode pad 17, and then connected to the signal voltage dividing circuit 21 to obtain the signal V1, and then V1 is input to the positive input end of the differential amplifier circuit; line 2 Starting from the second microelectrode 24 covered by the third insulating passivation layer 18, there is a noise window 20 on the microelectrode wire connected to the second microelectrode 24, the signal v2 is connected to the external circuit through the microelectrode pad 17, and then The signal V2 is input into the signal voltage dividing circuit 21 to obtain the signal V2, and then the signal V2 is input into the negative input terminal of the differential amplifier circuit; finally, the output biological signal Vo is obtained at the output terminal of the differential amplifier circuit.

The signal voltage dividing circuit in Figure 11 has a 2-input and 2-output structure, consisting of four resistors: r1, r2, r3, and r4. The specific structure is: one end of the adjustable resistor r1 is connected to the microelectrode signal v1, and the other end is connected to the circuit output V1 and the resistor r2; the resistor r2 is connected to the circuit output terminal V1 and ground respectively; one end of the adjustable resistor r3 is connected to the microelectrode output signal v2, and the other end is connected to the microelectrode output signal v2. Connect the circuit output V2 and the resistor r4. The resistor r4 is connected to the circuit output terminal V2 and ground respectively.

The differential amplifier circuit in Figure 11 has a 2-input and 1-output structure, consisting of a differential operator and 4 resistors. The specific structure is: one end of the resistor R3 is connected to the signal voltage dividing circuit output V1, and the other end is connected to the positive input of the differential operator. terminals and resistor R4, one end of resistor R4 is connected to resistor R3 and the positive input end of the operational amplifier (differential operator), and the other end is connected to ground; one end of resistor R3 is connected to the signal voltage dividing circuit output V2, and the other end is connected to the negative input of the differential operator. terminal and resistor R2; one end of resistor R2 is connected to resistor R1 and the negative input end of the differential operator, and the other end is connected to the output end of the differential operator; finally, the output biological signal is obtained at the output end of the differential operator.

Specifically, preparing the LED anode and the LED cathode includes: preparing the LED anode electrode, the LED anode wire, the LED anode pad, the LED cathode electrode, the LED cathode wire and the LED cathode pad.

Specifically, preparing a microelectrode pair structure with differential functions includes: preparing microelectrodes symmetrically distributed along the longitudinal axis, symmetrically routed microelectrode wires, and microelectrode pads.

In a preferred embodiment, the metal film uses a 50nm titanium metal film or a 150nm gold metal film.

Another embodiment of the preparation method of a low-noise integrated biophotoelectrode microprobe provided by the present invention includes the following steps:

N-type gallium nitride, active layer and p-type gallium nitride are grown sequentially on the sapphire substrate;

A transparent conductive layer of indium tin oxide is prepared in a high vacuum argon environment through photolithography and magnetron sputtering processes;

Pattern the indium tin oxide transparent conductive layer through a lift-off process to prepare the transparent anode and electromagnetic shielding layer of the light-emitting diode;

A good ohmic contact is formed between the indium tin oxide transparent conductive layer and p-type gallium nitride through a rapid thermal annealing process;

Etch the epitaxial wafer to n-type gallium nitride through photolithography and ICP (plasma etching) processes, and then etch the noise isolation trench to the sapphire substrate;

High temperature activates the active layer;

Through photolithography and plasma-enhanced chemical vapor deposition processes, a silicon dioxide isolation layer is prepared in a gas environment of SiH4 and N2O, high vacuum and a high temperature environment of 350°C, and a wet etching process is used with a buffered oxide etching solution. The silicon dioxide isolation layer is patterned to prepare a cathode window and an anode window;

Through photolithography and electron beam evaporation processes, a metal film is prepared in a high vacuum environment, and a lift-off process is used to pattern the metal film to prepare a light-emitting diode anode electrode, a light-emitting diode anode wire, a light-emitting diode anode pad, and a light-emitting diode cathode electrode. , LED cathode wire and LED cathode pad;

Through photolithography and plasma-enhanced chemical vapor deposition processes, the silicon dioxide passivation layer is prepared in a gas environment of SiH4 and N2O, high vacuum and a high temperature environment of 350°C, and a dry etching process is used to pattern the silicon dioxide isolation layer. to prepare an anode pad window and a cathode pad window;

Through photolithography and electron beam evaporation processes, a metal film is prepared in a high vacuum environment, and a lift-off process is used to pattern the metal film to prepare microelectrodes, microelectrode wires, and microelectrode pads;

Through photolithography and plasma-enhanced chemical vapor deposition processes, the silicon dioxide passivation layer is prepared in a gas environment of SiH4 and N2O, high vacuum and a high temperature environment of 350°C, and a dry etching process is used to pattern the silicon dioxide isolation layer. to prepare microelectrode windows, noise windows, microelectrode pad windows, anode pad windows, and cathode pad windows.

Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, devices and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be described again here.

In the embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or can be integrated into another system, or some features can be ignored, or not implemented. On the other hand, the coupling or direct coupling or communication connection between each other shown or discussed may be through some interfaces, and the indirect coupling or communication connection of the devices or units may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or they may be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated units can be implemented in the form of hardware or software functional units.

If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or contributes to the existing technology or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium , including several instructions to cause a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in various embodiments of the present invention. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program code.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the foregoing embodiments. The recorded technical solutions may be modified, or some of the technical features thereof may be equivalently replaced; however, these modifications or substitutions shall not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of each embodiment of the present invention.

Claims (10)

1. A low noise integrated bio-photoelectric electrode microprobe, comprising:

the LED structure, a plurality of microelectrode pairs with differential function, a noise isolation groove and an external circuit structure; each microelectrode pair comprises a first microelectrode and a second microelectrode, wherein the first microelectrode is used for detecting biological signals, and the second microelectrode is used for collecting noise so as to perform differential processing on the biological signals and improve signal-to-noise ratio;

wherein, the LED structure comprises from bottom to top in turn: the semiconductor device comprises a substrate material, n-type gallium nitride, an active layer, p-type gallium nitride, a transparent conducting layer, an insulating passivation layer, a light-emitting diode anode and a light-emitting diode cathode, which are used for emitting light and activating biological nerve cells;

Each microelectrode pair is symmetrically arranged on the insulating passivation layer along the longitudinal axis direction;

the noise isolation grooves are symmetrically etched along the longitudinal axis direction and penetrate through the substrate material, and are used for carrying out spatial physical separation on the anode of the light-emitting diode and the microelectrode pairs so as to reduce noise;

the external circuit structure is matched with two paths of noise during biological signal acquisition, so that the noise is eliminated and the biological signal is amplified.

2. The low noise integrated bio-photoelectric electrode microprobe according to claim 1, wherein each of the pairs of microelectrodes comprises: the first microelectrode and the second microelectrode are symmetrically distributed along the longitudinal axis direction, the first microelectrode lead and the second microelectrode lead of the symmetrical wiring, and the first microelectrode bonding pad and the second microelectrode bonding pad are symmetrically distributed along the longitudinal axis direction.

3. The low noise integrated bio-photoelectrode microprobe according to claim 2, wherein each of said pairs of microelectrodes further comprises:

a microelectrode window and a noise window which are spaced apart from each other, wherein the microelectrode window is arranged on the first microelectrode, and the noise window is arranged on the second microelectrode lead; or the microelectrode window is arranged on the second microelectrode, and the noise window is arranged on the first microelectrode wire.

4. The low noise integrated bio-photoelectric electrode microprobe according to claim 1, wherein the light emitting diode anode comprises:

the LED comprises an LED anode electrode, an LED anode wire and an LED anode pad.

5. The low noise integrated bio-photoelectrode microprobe according to claim 4 wherein said noise isolation trench physically separates said led anode wire from two microelectrodes, two microelectrode wires of each said microelectrode pair by etching into a recess of said substrate material to reduce noise.

6. The low noise integrated bio-photoelectric electrode microprobe according to claim 1, wherein the external circuit structure comprises a signal dividing circuit and a differential amplifying circuit, two paths of noise are matched when the bio-signal is collected by the signal dividing circuit, and the noise is eliminated and the bio-signal is amplified by the differential amplifying circuit.

7. The preparation method of the low-noise integrated biological photoelectric electrode microprobe is characterized by comprising the following steps of:

sequentially growing n-type gallium nitride, an active layer and p-type gallium nitride on a substrate material, preparing a transparent conductive layer through photoetching and magnetron sputtering processes, and patterning the transparent conductive layer through a stripping process to prepare a transparent anode and an electromagnetic shielding layer of the light-emitting diode;

Etching the epitaxial wafer to n-type gallium nitride through photoetching and plasma etching processes, and then etching a noise isolation groove to a substrate material;

activating the active layer at high temperature, preparing an insulating passivation layer through photoetching and a plasma enhanced chemical vapor deposition process, and patterning the insulating passivation layer by using a buffer oxide etching solution through a wet etching process to prepare a cathode window and an anode window;

preparing a metal film in a high vacuum environment through photoetching and electron beam evaporation processes, and patterning the metal film by utilizing a stripping process to prepare a light-emitting diode anode and a light-emitting diode cathode;

preparing a silicon dioxide passivation layer in a gas environment of SiH4 and N2O and a high vacuum environment at a high temperature of 350 ℃ by photoetching and a plasma enhanced chemical vapor deposition process, and patterning a silicon dioxide isolation layer by a dry etching process to prepare an anode pad window and a cathode pad window;

preparing a metal film in a high vacuum environment through photoetching and electron beam evaporation processes, and patterning the metal film by utilizing a stripping process to prepare a plurality of microelectrode pairs with a differential function;

the silicon dioxide passivation layer is prepared in a gas environment of SiH4 and N2O and a high vacuum environment at 350 ℃ through photoetching and a plasma enhanced chemical vapor deposition process, and the silicon dioxide isolation layer is patterned through a dry etching process to prepare a microelectrode window, a noise window, a microelectrode pad window, an anode pad window and a cathode pad window.

8. The method for preparing the low-noise integrated biophotovoltaic microprobe according to claim 7, wherein preparing the light emitting diode anode and the light emitting diode cathode comprises:

the anode electrode, the anode lead, the anode bonding pad, the cathode electrode, the cathode lead and the cathode bonding pad of the light-emitting diode are prepared.

9. The method for preparing a low noise integrated type biopolar microprobe according to claim 7, wherein preparing a plurality of microelectrode pairs having a differential function comprises:

the method comprises the steps of preparing a plurality of microelectrode pairs, wherein each microelectrode pair comprises a first microelectrode and a second microelectrode which are symmetrically distributed along the longitudinal axis direction, a first microelectrode wire and a second microelectrode wire which are symmetrically arranged, a first microelectrode bonding pad and a second microelectrode bonding pad which are symmetrically distributed along the longitudinal axis direction, the first microelectrode is used for detecting biological signals, and the second microelectrode is used for differentiating.

10. The method for preparing the low-noise integrated type biopolar microprobe according to claim 7, wherein the metal film is a titanium metal film of 50nm or a gold metal film of 150 nm.