CN111721709B - A method and device for improving the signal-to-noise ratio of a silicon nanowire sensor using light modulation - Google Patents

Abstract

The invention provides a method and device for improving the signal-to-noise ratio of a silicon nanowire sensor by utilizing light modulation. The method includes: determining an optical excitation signal of a silicon nanowire sensor based on a carrier signal; acquiring a modulation signal of the silicon nanowire sensor to the measured object based on the optical excitation signal; using a lock-in amplifier to detect the carrier signal and the modulated signal is processed to obtain the target response signal of the silicon nanowire sensor to the measured object. The method of the invention utilizes the lock-in amplifier to transfer the signal spectrum of the target response signal of the silicon nanowire sensor to the frequency of the carrier signal, and then amplifies it to avoid the interference of the noise of the silicon nanowire sensor. The signal-to-noise ratio of the silicon nanowire sensor can be greatly improved, and the anti-interference ability of the sensor can be enhanced.

Description

A method and device for improving the signal-to-noise ratio of a silicon nanowire sensor using light modulation

Technical field:

The invention relates to the technical field of sensors, in particular to a method and a device for improving the signal-to-noise ratio of a silicon nanowire sensor by utilizing light modulation.

Background technique:

The sensitive unit of the silicon nanowire sensor is a silicon nanowire with a size of tens to hundreds of nanometers. Its sensing mechanism is that the measured object is attached to the surface of the silicon nanowire, which changes the charge distribution on the surface of the silicon nanowire, thereby resulting in a change in its surface potential. Due to the large specific surface area of nanowires, small changes in surface potential can also lead to large changes in bulk conductivity. Due to this extremely sensitive property to the outside, silicon nanowire sensors have obtained various successful application cases in biochemical sensing, so they have also attracted the attention of many researchers.

The successful application of silicon nanowire sensors in the detection of biochemical samples is mainly due to the following aspects: First, the properties that silicon nanowire bulk materials do not have, such as ultra-high specific surface area, so silicon nanowire sensors have traditional bulk materials. The incomparable sensitivity of the sensor; second, the silicon nanowire sensor is an electrical sensor, and the output signal can be directly read out by the processing circuit, which is convenient for signal processing; third, because the silicon nanowire sensor does not use some special materials, the material acquisition is simple It is convenient; fourth, by modifying different probes on the surface of the silicon nanowire sensor, different analytes can be detected, and the versatility is much stronger than that of sensors of special materials developed for specific analytes.

Sensors based on silicon nanowires have shown considerable application prospects in electronic information, life science, material chemistry, aerospace, defense technology and other fields. Especially in life science and material chemistry, it provides researchers with a new idea and becomes an important branch in the field of biochemical detection in the future. However, the silicon nanowire sensor also faces some difficulties in the application process. One of the most important points is that the silicon nanowire sensor has ultra-high sensitivity to the measured object, and it must also be extremely sensitive to interference signals, which makes the output of the silicon nanowire sensor. The signal-to-noise ratio of the signal is low, and it is difficult to extract a valid signal from the noise signal in many cases.

Invention content:

In view of the above-mentioned shortcomings of the prior art, the present invention discloses a method for improving the signal-to-noise ratio of a silicon nanowire sensor by utilizing light modulation.

The method includes:

determining the optical excitation signal of the silicon nanowire sensor based on the carrier signal;

based on the optical excitation signal, obtain the modulation signal of the silicon nanowire sensor to the measured object;

The carrier signal and the modulation signal are processed by a lock-in amplifier to obtain a target response signal of the silicon nanowire sensor to the measured object.

In an implementable solution, the acquiring the modulation signal of the silicon nanowire sensor to the measured object based on the optical excitation signal includes:

Under the optical excitation signal, adding a analyte with preset properties to be measured to the silicon nanowire sensor;

applying a preset current to both ends of the silicon nanowire sensor;

recording the response voltage of the silicon nanowire sensor to the measured object;

The response voltage is used as the modulation signal of the silicon nanowire sensor to the measured object.

In another implementable solution, the acquiring the modulation signal of the silicon nanowire sensor to the measured object based on the optical excitation signal includes:

Under the optical excitation signal, adding a analyte with preset properties to be measured to the silicon nanowire sensor;

Applying a preset voltage at both ends of the silicon nanowire sensor;

recording the response current of the silicon nanowire sensor to the measured object;

The response current is used as the modulation signal of the silicon nanowire sensor to the measured object.

Further, the predetermined property to be measured is a predetermined concentration or a predetermined pH, and the application of the measured object with the predetermined property to be measured to the silicon nanowire sensor under the optical excitation signal includes:

Under the optical excitation signal, applying a predetermined concentration or a predetermined pH of the analyte to the silicon nanowire sensor;

Control the concentration or pH gradient of the analyte.

Further, before the optical excitation signal of the measured object is determined based on the carrier signal, the method further includes:

Obtain the noise spectrum through the spectrum analyzer;

According to the noise spectrum, determine the target electrical signal;

The target electrical signal is used as the carrier signal.

In some possible implementations, the target electrical signal is a sinusoidal signal or a square wave signal.

Further, the present invention also provides a device for improving the signal-to-noise ratio of a silicon nanowire sensor by utilizing light modulation, the device includes a silicon nanowire sensor, a light source, a signal generator and a lock-in amplifier; wherein:

A signal generator for providing a carrier signal;

a light source for providing the silicon nanowire sensor with an optical excitation signal based on the carrier signal;

a silicon nanowire sensor, used for testing the measured object under the optical excitation signal, and obtaining the modulation signal of the silicon nanowire sensor on the measured object,

The lock-in amplifier is used for processing the carrier signal and the modulation signal to obtain the target response signal of the silicon nanowire sensor to the measured object.

Further, the optical excitation signal is an output signal of the light source. Further, the silicon nanowire sensor is specifically used for, under the optical excitation signal, to test the measured object with preset properties to be measured, and obtain the modulation signal of the silicon nanowire sensor to the measured object. .

Further, the device further includes: a voltage or current testing device for obtaining the response voltage of the silicon nanowire sensor to the measured object or the silicon nanowire sensor to the measured object under a preset current or a preset voltage. The response current of the test object.

The invention utilizes the lock-in amplifier to migrate the signal spectrum of the target response signal of the silicon nanowire sensor to the carrier signal frequency, and then amplifies it to avoid the interference of the noise of the silicon nanowire sensor. The signal-to-noise ratio of the silicon nanowire sensor can be greatly improved, and the anti-interference ability of the sensor can be enhanced.

Description of drawings:

1 is a structural diagram of the device for improving the signal-to-noise ratio of a silicon nanowire sensor by light modulation according to the present invention;

2 is a flow chart of the method for improving the signal-to-noise ratio of a silicon nanowire sensor by utilizing light modulation according to the present invention;

FIG. 3 is a flow chart of acquiring the modulation signal of the silicon nanowire sensor to the measured object in an embodiment;

FIG. 4 is a flow chart of acquiring the modulation signal of the silicon nanowire sensor to the measured object in another embodiment;

Fig. 5 is a schematic diagram of obtaining a modulated signal;

6 is a schematic diagram of modulating the amplitude of the carrier signal;

FIG. 7 is a schematic diagram of modulating the frequency of the carrier signal;

FIG. 8 is a schematic diagram of modulating the phase of the carrier signal;

FIG. 9 is a schematic diagram of the present invention using light modulation to improve the signal-to-noise ratio of the silicon nanowire sensor;

In the picture:

a is the change curve of the concentration of the analyte with time;

b is the signal curve of the carrier signal;

c is the signal curve of the modulated signal;

d is the signal curve of the AM signal;

e is the signal curve of the target response signal obtained based on the amplitude adjustment;

f is the signal curve of the FM signal;

g is the signal curve of the target response signal obtained based on frequency adjustment;

h is the signal curve of the phase-modulated signal;

k is the signal curve of the target response signal obtained based on the phase adjustment.

Detailed ways:

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention. In order to solve the problems existing in the prior art, the present invention provides a method for improving the signal-to-noise ratio of a silicon nanowire sensor by using light modulation. The method is applied to a device for improving the signal-to-noise ratio of a silicon nanowire sensor by using light modulation, such as As shown in Figure 1, the device includes:

Silicon nanowire sensors, light sources, signal generators, and lock-in amplifiers; of which:

A signal generator for providing a carrier signal;

a light source for providing the silicon nanowire sensor with an optical excitation signal based on a carrier signal;

It can be understood that the optical excitation signal is the output signal of the light source, which can be understood as the light intensity output by the light source.

Preferably, the light source may be 450 nm blue light.

The silicon nanowire sensor is used to test the measured object under the light excitation signal, and obtain the modulation signal of the silicon nanowire sensor to the measured object.

The lock-in amplifier is used to process the carrier signal and the modulation signal to obtain the target response signal of the silicon nanowire sensor to the measured object.

It can be understood that the lock-in amplifier can migrate the signal spectrum in the modulated signal to the frequency where the carrier signal is located, avoiding the interference of the preset noise target of the silicon nanowire sensor, so that the carrier signal and the modulation signal are processed by the lock-in amplifier. After processing, what is obtained is the target response signal with high signal-to-noise ratio.

Further, the silicon nanowire sensor is specifically used to test the measured object with preset properties to be measured under the optical excitation signal, and obtain the modulation signal of the silicon nanowire sensor to the measured object.

Further, the device further includes a voltage or current testing device for obtaining the response voltage of the silicon nanowire sensor to the measured object or the response current of the silicon nanowire sensor to the measured object under a preset current or preset voltage.

Further, as shown in Figure 2, the method includes:

S101, determining the optical excitation signal of the silicon nanowire sensor based on the carrier signal;

Specifically, to determine the optical excitation signal of the silicon nanowire sensor based on the carrier signal, the carrier signal is directly used as the excitation signal of the light source, and the optical excitation signal applied to the silicon nanowire sensor is provided for the light source.

Specifically, before step S101 is performed, the following steps are performed first:

Obtain the noise spectrum through the spectrum analyzer;

Specifically, the signal noise can be directly measured by a spectrum analyzer.

According to the noise spectrum, determine the target electrical signal;

It can be understood that after acquiring the noise spectrum, the target electrical signal can be selected according to the noise spectrum, for example, the target electrical signal can be a sine signal, a square wave signal or other signals, and based on the noise spectrum, the frequency range of the target electrical signal is determined, For example, in an implementable solution, when the noise obtained according to the noise spectrum is 1/f noise (also called flicker noise, the power spectral density of the current noise in the low frequency part is inversely proportional to the frequency f, and this noise is Called 1/f noise), the target electrical signal with a frequency between 1k and 5k can be selected.

The target electrical signal is used as the carrier signal.

Specifically, after the target electrical signal is selected, the target electrical signal is used as the carrier signal.

S103 , based on the optical excitation signal, obtain a modulation signal of the silicon nanowire sensor to the measured object.

Specifically, in an implementable solution, as shown in FIG. 3 , based on the optical excitation signal, acquiring the modulation signal of the silicon nanowire sensor to the measured object includes:

S304 , under the optical excitation signal, add a measured object with a preset property to be measured to the silicon nanowire sensor;

It can be understood that the selection of the analyte can be selected according to actual test requirements, for example, the analyte can be protein, nucleic acid, etc., which is not limited here. The predetermined property to be measured can be a predetermined concentration or a predetermined pH.

Further, under the optical excitation signal, applying the measured object with the preset to-be-measured property to the silicon nanowire sensor includes:

Under the light excitation signal, apply the analyte of preset concentration or preset pH to the silicon nanowire sensor;

Control the concentration or pH gradient of the analyte.

It can be understood that when adding the analyte to the silicon nanowire sensor, the concentration of the analyte or the pH gradient change can be controlled, for example, the concentration gradient of the analyte can be controlled to increase or decrease;

Alternatively, control the pH gradient of the analyte to increase or decrease.

In one embodiment, the nucleic acid can be used as the analyte, and it is determined that the concentration of the nucleic acid is increased with a time gradient with time as the change reference, and the initial concentration of the nucleic acid is specifically determined to be 0 fmol/L, and the termination concentration is 6 fmol/L, The gradient change amount was 1 fmol/L. Under this experimental setting, different concentrations of nucleic acid were added to the silicon nanowire sensor based on the above-mentioned optical excitation signal.

It can be understood that the above-mentioned increase in the concentration of the analyte according to the preset gradient (1 fmol/L) is only a preferred way. In other feasible solutions, the concentration of the analyte can also be decreased according to the preset gradient, or , in other feasible solutions, the concentration of the test substance can also be changed in a curve with time, which is not limited here.

S306, applying a preset current to both ends of the silicon nanowire sensor;

S308, record the response voltage of the silicon nanowire sensor to the measured object;

It can be understood that the silicon nanowire sensor is equivalent to a resistor, and a corresponding voltage value can be obtained after a current is applied to both ends of the resistor. The preset current can be set as required, which is not limited here.

The voltage value is the response voltage of the silicon nanowire sensor to the measured object. It can be understood that the response voltage may be the response voltage of the silicon nanowire sensor to the change of the concentration of the measured object obtained based on the test properties of the measured object or the response voltage of the silicon nanowire sensor to the change of the pH of the measured object.

S310, taking the response voltage as the modulation signal of the silicon nanowire sensor to the measured object.

It can be understood that, in this specification, the response signal of the silicon nanowire sensor to the object to be measured is: when the output signal of the silicon nanowire is stable, changing the properties of the object to be measured tested by the silicon nanowire sensor, such as changing the object to be measured. The concentration of the analyte changes its output signal, and the change in the output signal caused by the change in the properties of the analyte is called the response of the silicon nanowire sensor to the analyte.

Specifically, based on FIG. 5 , the above steps of acquiring modulated signals are specifically described as follows:

After determining the target electrical signal according to the acquired noise spectrum, the signal generator provides a carrier signal corresponding to the target electrical signal. In this specification, the target electrical signal corresponds to the carrier signal, which is a sinusoidal signal.

Further, taking the carrier signal as the excitation signal of the light source, it can be understood that the change of the optical excitation signal actually changes based on the change of the carrier signal, and the change curve of the optical excitation signal can be the same as the signal curve of the carrier signal, such as Curve a in Figure 5.

Further, under the above-mentioned changing optical excitation signal, the measured object is added to the silicon nanowire sensor. In FIG. 5 , the concentration of the measured object changes with time, and its change curve is shown as curve b in FIG. 5 .

Further, a preset current is applied to the silicon nanowire sensor, thereby obtaining a signal curve of the modulation signal of the silicon nanowire sensor to the measured object as shown in curve c in FIG. 5 .

Further, in another implementable solution, as shown in FIG. 4 , based on the optical excitation signal, acquiring the modulation signal of the silicon nanowire sensor to the measured object includes:

S316, under the light excitation signal, apply the measured object with the preset to-be-measured property to the silicon nanowire sensor;

S318, applying a preset voltage to both ends of the silicon nanowire sensor;

S320, record the response current of the silicon nanowire sensor to the measured object;

S322 takes the response current as the modulation signal of the silicon nanowire sensor to the measured object.

Specifically, the principle is the same as that described in steps S304-S310, and details are not repeated here.

S105 , using a lock-in amplifier to process the carrier signal and the modulation signal to obtain a target response signal of the silicon nanowire sensor to the measured object.

It can be understood that when the lock-in amplifier processes the carrier signal and the modulation signal, the amplitude of the carrier signal can be modulated, the frequency of the carrier signal can be modulated, or the phase of the carrier signal can be modulated.

In an implementable solution, the modulated signal obtained in FIG. 5 and the carrier signal can be input into the lock-in amplifier together for modulation, and the amplitude of the carrier signal can be modulated, and the lock-in amplifier is used for modulation and demodulation, and the demodulation is carried out by using the lock-in amplifier. The modulation result is shown in Fig. 6, where the curve d is the signal curve obtained by adjusting the amplitude, that is, the signal curve of the amplitude modulation signal, and the curve e is the signal curve of the target response signal obtained based on the amplitude adjustment.

Further, in other implementable solutions, the frequency of the carrier signal can also be modulated, and the modulation result is shown in FIG. 7 , wherein the curve f is the signal curve of the FM signal, and the curve g is obtained based on the frequency adjustment. The signal curve of the target response signal.

or,

The phase of the carrier signal can also be modulated, and the modulation result is shown in FIG. 8 , where the curve h is the signal curve of the phase-modulated signal, and the curve k is the signal curve of the target response signal obtained based on the phase adjustment.

In the modulation process of the lock-in amplifier, the modulator in the lock-in amplifier can be used to migrate the signal spectrum of the target response signal of the silicon nanowire sensor to the carrier signal frequency, and then amplify to avoid the noise of the silicon nanowire sensor. interference. The demodulator in the lock-in amplifier is used to demodulate the modulated signal, and at the same time, the frequency, phase or amplitude is detected, and the noise of non-same frequency and same phase is eliminated. The method has the advantage of greatly improving the signal-to-noise ratio of the silicon nanowire sensor and enhances the anti-interference ability of the sensor.

Further, as shown in FIG. 9 , the carrier signal and the modulation signal are processed by the lock-in amplifier to obtain the target response signal of the silicon nanowire sensor to the measured object, and then the target modulation signal is output to the computer for storage and display.

Above, the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the above-mentioned embodiments, those of ordinary skill in the art should understand that: it can still be used for the above-mentioned implementations The technical solutions described in the examples are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions in the embodiments of the present application.

Claims (9)

1. A method for improving the signal-to-noise ratio of a silicon nanowire sensor by light modulation, wherein the method comprises: Obtain the noise spectrum through the spectrum analyzer; According to the noise spectrum, determine the target electrical signal; Using the target electrical signal as a carrier signal; based on the carrier signal, determining an optical excitation signal of the silicon nanowire sensor; Based on the optical excitation signal, obtain the modulation signal of the silicon nanowire sensor to the measured object; The carrier signal and the modulation signal are processed by a lock-in amplifier to obtain a target response signal of the silicon nanowire sensor to the measured object. 2 . The method for improving the signal-to-noise ratio of a silicon nanowire sensor using optical modulation according to claim 1 , wherein the modulation signal of the silicon nanowire sensor to the measured object is obtained based on the optical excitation signal. 3 . include: Under the optical excitation signal, adding a analyte with preset properties to be measured to the silicon nanowire sensor; applying a preset current to both ends of the silicon nanowire sensor; recording the response voltage of the silicon nanowire sensor to the measured object; The response voltage is used as the modulation signal of the silicon nanowire sensor to the measured object. 3 . The method for improving the signal-to-noise ratio of a silicon nanowire sensor using optical modulation according to claim 1 , wherein the modulation signal of the silicon nanowire sensor to the measured object is obtained based on the optical excitation signal. 4 . include: Under the optical excitation signal, adding a analyte with preset properties to be measured to the silicon nanowire sensor; Applying a preset voltage at both ends of the silicon nanowire sensor; recording the response current of the silicon nanowire sensor to the measured object; The response current is used as the modulation signal of the silicon nanowire sensor to the measured object. 4. The method for improving the signal-to-noise ratio of a silicon nanowire sensor using light modulation according to claim 2 or 3, wherein the preset property to be measured is a preset concentration or a preset pH, and the Under the light excitation signal, applying the measured object with preset properties to be measured to the silicon nanowire sensor includes: Under the optical excitation signal, applying a predetermined concentration or a predetermined pH of the analyte to the silicon nanowire sensor; Control the concentration or pH gradient of the analyte. 5 . The method for improving the signal-to-noise ratio of a silicon nanowire sensor by light modulation according to claim 1 , wherein the target electrical signal is a sine signal or a square wave signal. 6 . 6. A device for improving the signal-to-noise ratio of a silicon nanowire sensor by light modulation, wherein the device comprises: a spectrum analyzer, a silicon nanowire sensor, a light source, a signal generator and a lock-in amplifier; wherein: Spectrum analyzer for acquiring noise spectrum; a signal generator for determining a target electrical signal according to the noise spectrum, and using the target electrical signal as a carrier signal; a light source for providing the silicon nanowire sensor with an optical excitation signal based on the carrier signal; a silicon nanowire sensor, used for testing the measured object under the optical excitation signal, and obtaining the modulation signal of the silicon nanowire sensor on the measured object, The lock-in amplifier is used for processing the carrier signal and the modulation signal to obtain the target response signal of the silicon nanowire sensor to the measured object. 7 . The device for improving the signal-to-noise ratio of a silicon nanowire sensor by light modulation according to claim 6 , wherein the light excitation signal is an output signal of the light source. 8 . 8 . The device for improving the signal-to-noise ratio of a silicon nanowire sensor using light modulation according to claim 7 , wherein the silicon nanowire sensor is specifically used for, under the light excitation signal, to perform a preset test to be measured. 9 . The properties of the measured object are tested, and the modulation signal of the silicon nanowire sensor to the measured object is obtained. 9 . The device for improving the signal-to-noise ratio of a silicon nanowire sensor by light modulation according to claim 6 , wherein the device further comprises: a voltage or current testing device, which is used for a preset current or a preset voltage under the preset current or preset voltage. 10 . , and obtain the response voltage of the silicon nanowire sensor to the measured object or the response current of the silicon nanowire sensor to the measured object.

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