Nano-gold grating transmission microfluidic sensor based on surface plasmon resonance

Abstract

The invention provides a nano-gold grating transmission type microfluidic sensor based on plasma resonance, and the transmission type sensor includes: a silicon dioxide insulating substrate; a two-dimensional metal grating array formed on the silicon dioxide insulating substrate; a microfluidic cavity of the object to be measured; and a silicon dioxide insulating top cover, and a silicon dioxide grating structure is added, which is formed under the silicon dioxide insulating top cover. The area with strong electric field intensity of the structure is concentrated at the position of the cavity of the object to be measured, and the grating structure enhances the plasma resonance peak. As the period gradually increases, the transmission peak wavelength position of the same resonance mode appears red shifted. The model has the advantages of simple structure, easy large-area preparation, low cost, high sensitivity, easy detection for transmittance sensing, and is expected to become a new type of surface plasmon sensor device.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano optoelectronic technology, and in particular to a nano-gold grating transmission microfluidic sensor based on surface plasma resonance, which can enhance the transmission peak displacement of infrared light to an object to be measured, thereby achieving a transmission microfluidic sensor for highly sensitive detection of the refractive index of a medium. Background Art

[0002] In recent years, with the development of nano-micro-nano optoelectronic technology, emerging nanostructured surface plasmon resonance sensor devices have developed rapidly and cross-penetrated into other fields, with a wide range of application backgrounds, such as biochemistry, drug development, food monitoring, air monitoring, and so on.

[0003] Surface plasmon resonance (SPR) detection technology is a new type of biological detection technology. It has the advantages of high accuracy, real-time monitoring, and rapid detection. SPR is a surface plasmon wave excited by the strong coupling of two electromagnetic wave modes at the interface. Since the resonance peak position of the incident light is very sensitive to the background refractive index, the background refractive index changes caused by various factors can be effectively detected by analyzing the resonance peak position.

[0004] With the continuous development of science and technology, sensors have been widely used in biology, chemistry, medicine, food and other fields. However, traditional nanostructured surface plasmon resonance sensors are large in size, and the nanowires, nanoholes, nanocones and other structures used are generally prepared by electron beam etching or focused ion etching, which are slow to prepare and costly, making them unsuitable for large-scale industrial production. At the same time, the test spectrum of plasma resonance generally uses reflection spectrum, but when using a spectrophotometer to test the reflection spectrum, it is easily disturbed by the incident light, which brings certain difficulties to accurate testing. In addition, the spectral shift of existing nanostructured surface plasmon resonance sensors is usually very small and the sensitivity is not high. For example, the sensitivity of the nanowire structure sensor is 337nm / RIU (reference patent: CN201711336503-Refractive index measurement method and sensor system based on nanowire surface plasmon), and the sensitivity of the nanohole structure sensor is 671nm / RIU ("Hybrid Magnetoplasmonic Crystals Boost the Performance of Nanohole Arrays as Plasmonic Sensors", ACS Photonics, 2016, 3, 203-208).

[0005] However, with the continuous development of modern detection technology, plasma resonance sensing test systems tend to be miniaturized and integrated, and higher requirements are placed on the sensitivity and anti-interference ability of sensors. Summary of the invention

[0006] In order to solve the above technical problems existing in the existing plasma resonance sensors, the present invention proposes a nano-gold grating transmission type microfluidic sensor based on surface plasma resonance. The sensor of the present invention is relatively simple in structure, easy to prepare on a large scale, low in cost, high in sensitivity, and easy to detect for transmittance sensing. At the same time, by using microfluidics to precisely control trace fluids, the sensitivity of the sensor is further improved, avoiding waste and pollution of the test object.

[0007] The technical solution of the present invention to solve the above-mentioned problem is: a nano-gold grating transmission type microfluidic sensor based on plasma resonance, characterized in that it comprises: a cavity composed of a silicon dioxide insulator as a microfluidic cavity for an object to be detected, the bottom of the microfluidic cavity for an object to be detected is a silicon dioxide insulating substrate, and a two-dimensional metal grating array is arranged on the silicon dioxide insulating substrate; the top of the microfluidic cavity for an object to be detected is a silicon dioxide insulating top cover, and a two-dimensional insulating grating structure is arranged on the side of the silicon dioxide insulating top cover facing the microfluidic cavity for an object to be detected, The width of the two-dimensional insulating grating structure is 700-800nm, the period is 1200-1400nm, the thickness is 300-500nm, and the grating material is silicon dioxide; a flow inlet to be measured is arranged on one side of the bottom of the microfluidic cavity to be measured, and a flow outlet to be measured is arranged on the other side of the bottom of the microfluidic cavity to be measured; the two-dimensional metal grating array arranged on the silicon dioxide insulating substrate has a width of 700-800nm, a period of 1200-1400nm, and a thickness of 300-500nm,

[0008] The grating material is gold; the thickness of the microfluidic cavity of the object to be tested is 1200-1600nm;

[0009] The area with strong electric field intensity of the nano-gold grating transmission type microfluidic sensor based on plasma resonance is concentrated at the position of the microfluidic cavity of the object to be tested. The grating structure can enhance the plasma resonance peak according to the refractive index change of the object to be tested. △ n, the transmission peak wavelength shift value of the corresponding resonance mode △ λ, the sensitivity S is obtained by converting the functional relationship between the two.

[0010] As a preferred solution of the nano-gold grating transmission-type microfluidic sensor based on surface plasmon resonance described in the present invention, the thickness of the silicon dioxide insulating top cover is 500nm, and the thickness of the silicon dioxide insulating substrate is 400-600nm.

[0011] As a preferred solution of the nano-gold grating transmission microfluidic sensor based on surface plasmon resonance described in the present invention, a two-dimensional insulating grating structure is arranged on the side of the silica insulating top cover facing the cavity to be measured; the two-dimensional insulating grating structure has a width of 800nm, a period of 1200nm, a thickness of 300nm, and the grating material is silica.

[0012] As a preferred solution of the nano-gold grating transmission-type microfluidic sensor based on surface plasmon resonance described in the present invention, the two-dimensional metal grating array arranged on the silicon dioxide insulating substrate has a width of 800nm, a period of 1200nm, a thickness of 300nm, and the grating material is gold; the thickness of the object cavity to be measured is 1200nm, and the top cover of the microfluidic cavity is an inverted two-dimensional insulating grating structure, the shape and size of which are completely consistent with the two-dimensional metal grating structure arranged on the silicon dioxide insulating substrate, and the material is silicon dioxide.

[0013] As a preferred solution of the nano-gold grating transmission type microfluidic sensor based on surface plasmon resonance described in the present invention, the refractive index of the object to be measured is 1.32-1.74.

[0014] As a preferred solution of the nano-gold grating transmission-type microfluidic sensor based on surface plasmon resonance described in the present invention, the incident angle of the incident light beam is 0°.

[0015] As a preferred solution of the nano-gold grating transmission-type microfluidic sensor based on surface plasmon resonance described in the present invention, the two-dimensional metal grating array is prepared by the following preparation method, including the following steps: (1) providing a silicon dioxide substrate; (2) arranging a metal layer on the surface of the substrate; (3) arranging a patterned mask layer on the surface of the metal layer, wherein the mask layer has grating grooves, and the shape of the grating grooves is rectangular; (4) etching the metal layer; and (5) using a solvent to dissolve and remove the patterned mask layer.

[0016] The method for performing transmission spectrum detection on a nano-gold grating transmission type microfluidic sensor based on surface plasmon resonance described in the present invention comprises the following steps: (1) an incident light is emitted by a light source and vertically incident on the sensor surface; (2) a transmission spectrum of the incident light passing through a microfluidic cavity of the object to be tested is tested; (3) when the refractive index of the object to be tested changes, the change in the transmission spectrum is recorded; and (4) the change in the refractive index and concentration of the solution of the object to be tested in the microfluidic cavity is measured by moving the peak position of the transmission spectrum line.

[0017] The study found that by changing the period, thickness, metal material, microfluidic cavity size, light incident angle and other parameters of the metal grating structure, the position of the transmission peak and the magnitude of the transmittance can be effectively adjusted. As the grating period gradually increases, the transmission peak wavelength position of the same resonance mode appears red shifted. Reasonable adjustment of the size makes the area with the strongest electric field intensity of the structure concentrated at the location of the microfluidic cavity. According to the change of the refractive index of the object to be measured △ n, the transmission peak wavelength shift value of the corresponding resonance mode △ λ, the sensitivity S is obtained by converting the functional relationship between the two.

[0018] Compared with the prior art, the present invention has the following characteristics:

[0019] The present invention adopts a metal grating structure and an inverted silicon dioxide grating structure to form a microfluidic cavity. By detecting the transmission spectrum for refractive index sensing research, the area with strong electric field intensity can be concentrated at the position of the microfluidic cavity, that is, coincident with the object to be measured, thereby enhancing plasma resonance and greatly improving the sensitivity of the sensor.

[0020] The detection spectrum of the present invention is a transmission spectrum. When the transmission spectrum is tested by a spectrophotometer, it is not easily disturbed by incident light, which greatly improves the detection accuracy and has strong anti-interference performance.

[0021] The basic structure of the present invention is a metal grating, which is simple and easy to prepare and integrate on a large scale.

[0022] When manufacturing the sensor of the present invention, the transmission spectrum position of the sensor can be made optional by changing parameters such as the metal grating height, grating width, microfluidic cavity thickness, grating period, etc., thereby manufacturing a sensor for a specific detection range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A three-dimensional structural diagram of a nano-gold grating transmission-type microfluidic sensor (with an inverted silicon dioxide grating top cover added) based on surface plasmon resonance according to an embodiment of the present invention;

[0024] Figure 2 for Figure 1 The schematic cross-sectional view of the nano-gold grating transmission type microfluidic sensor along the XZ plane is shown;

[0025] Figure 3 is a transmission spectrum diagram of the sensor of Example 1;

[0026] Figure 4 This is a graph showing the dependence of the peak position of the transmission peak of Example 1 on the refractive index of the object to be measured;

[0027] Figure 5 is a transmission spectrum diagram of the sensor of Example 2;

[0028] Figure 6 This is a graph showing the dependence of the peak position of the transmission peak of Example 2 on the refractive index of the object to be measured;

[0029] Figure 7 is the transmission spectrum of the sensor of Example 3;

[0030] Figure 8 This is a graph showing the dependence of the peak position of the transmission peak of Example 3 on the refractive index of the object to be measured;

[0031] Fig. 9 is the transmission spectrum of the sensor of Example 4;

[0032] Fig.10 This is a graph showing the dependence of the peak position of the transmission peak of Example 4 on the refractive index of the object to be measured;

[0033] Fig.11 is the transmission spectrum of the sensor of Example 5;

[0034] Fig.12 This is a graph showing the dependence of the peak position of the transmission peak of Example 5 on the refractive index of the object to be measured. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the following is a detailed description of the present invention in conjunction with the following specific embodiments. Figure 1 To Attachment Fig.12 , the present invention is further described in detail. It should be noted that in the drawings or descriptions, similar or identical parts are all marked with the same figure numbers. The implementation methods not shown or described in the drawings are known to those of ordinary skill in the art. In addition, although the present invention may provide examples of parameters including specific values, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint.

[0036] The present invention provides a nano-gold grating transmission type microfluidic sensor based on plasma resonance. The area with strong electric field intensity of the structure is concentrated at the position of the cavity of the object to be measured. The grating structure enhances the plasma resonance peak. As the period gradually increases, the transmission peak wavelength position of the same resonance mode appears red shift, thereby ultimately improving the sensitivity of the sensor.

[0037] In an exemplary embodiment of the present invention, a nano-gold grating transmission type microfluidic sensor based on plasmon resonance is provided. Figure 2 for Figure 1 The schematic cross-sectional view of the nano-gold grating transmission type microfluidic sensor along the XZ plane is shown. Figure 2: 1 is a silicon dioxide insulating substrate; 2 is a two-dimensional metal grating array; 3 is a microfluidic cavity; 4 is a silicon dioxide insulating top cover; 5 is an inverted silicon dioxide grating structure; 6 is the fluid channel inlet, and 7 is the fluid channel outlet. △ n, the transmission peak wavelength shift value of the corresponding resonance mode △ λ, the sensitivity S is obtained by converting the functional relationship between the two.

[0038] A method for preparing a two-dimensional metal grating array comprises the following steps: 1) providing a silicon dioxide substrate; 2) arranging a metal layer on the surface of the substrate; 3) arranging a patterned mask layer on the surface of the metal layer, wherein the mask layer has grating grooves, and the shape of the grating grooves is rectangular; 4) etching the metal layer; and 5) removing the patterned mask layer by dissolving with a solvent.

[0039] A method for preparing a microfluidic cavity comprises the following steps: 1) placing a gold grating array below; 2) inverting a silicon dioxide grating array of the same size on the gold grating array, and adjusting the height of the microfluidic cavity by adjusting the height of the supporting wall.

[0040] A method for allowing an object to be tested to enter a microfluidic cavity comprises the following steps: a fluid channel inlet and outlet are opened on a silicon dioxide substrate, the object to be tested enters the microfluidic cavity through the fluid channel inlet, and flows out of the microfluidic cavity through the fluid channel outlet.

[0041] Objects to be tested with different refractive indices have different transmission spectra, so the objects to be tested can be identified based on the transmission spectra. A transmission spectrum testing method includes the following steps: 1) the incident light emitted by the light source is vertically incident on the sensor surface; 2) the transmission spectrum of the incident light passing through the microfluidic cavity of the object to be tested is tested; 3) when the refractive index of the object to be tested changes, the change of the transmission spectrum is recorded; 4) the change of the refractive index, concentration, etc. of the solution of the object to be tested in the microfluidic cavity is measured by the movement of the peak position of the transmission spectrum.

[0042] Embodiment 1: The thickness of the silicon dioxide insulating substrate is 500nm, the width of the two-dimensional metal grating array is 800nm, the period is 1300nm, the thickness is 300nm, and the grating material is gold. The thickness of the cavity to be tested is 1500nm. The thickness of the silicon dioxide insulating top cover (with an inverted silicon dioxide grating top cover added) is 500nm. The width of the insulating grating structure is 800nm, the period is 1300nm, the thickness is 300nm, and the material is silicon dioxide. The objects to be tested are 3%, 5%, and 7% glucose solutions, and the refractive indices are 1.31, 1.36, and 1.41, respectively. The peak position of the transmission peak moves most significantly in the range of 1600nm-1850nm, and the sensitivity is relatively high. According to the formula calculation, the sensitivity of the transmission type sensor can reach 1100nm / RIU, and the transmittance is 86.17%.

[0043] Embodiment 2: The thickness of the silicon dioxide insulating substrate is 500nm, the width of the two-dimensional metal grating array is 700nm, the period is 1200nm, the thickness is 300nm, and the grating material is gold. The thickness of the object cavity to be measured is 1500nm. The thickness of the silicon dioxide insulating top cover (with an inverted silicon dioxide grating top cover added) is 500nm. The width of the insulating grating structure is 800nm, the period is 1200nm, the thickness is 300nm, and the material is silicon dioxide. The transmission peak has the most obvious peak position movement in the range of 1500nm-1700nm, and the sensitivity is relatively high. According to the formula calculation, the sensitivity of the transmission type sensor can reach 1020nm / RIU, and the transmittance is 97.36%.

[0044] Embodiment 3: The thickness of the silicon dioxide insulating substrate is 500nm, the width of the two-dimensional metal grating array is 800nm, the period is 1200nm, the thickness is 200nm, and the grating material is gold. The thickness of the cavity to be measured is 1500nm. The thickness of the silicon dioxide insulating top cover (with an inverted silicon dioxide grating top cover added) is 500nm. The width of the insulating grating structure is 800nm, the period is 1200nm, the thickness is 300nm, and the material is silicon dioxide. The transmission peak has the most obvious peak position movement in the range of 1500nm-1700nm, and the sensitivity is relatively high. According to the formula calculation, the sensitivity of the transmission type sensor can reach 1020nm / RIU, and the transmittance is 85.54%.

[0045] Embodiment 4: The thickness of the silicon dioxide insulating substrate is 500nm, the width of the two-dimensional metal grating array is 800nm, the period is 1200nm, the thickness is 300nm, and the grating material is gold. The thickness of the object cavity to be measured is 1200nm. The thickness of the silicon dioxide insulating top cover (with an inverted silicon dioxide grating top cover added) is 500nm. The width of the insulating grating structure is 800nm, the period is 1200nm, the thickness is 300nm, and the material is silicon dioxide. The transmission peak has the most obvious peak position movement in the range of 1500nm-1700nm, and the sensitivity is relatively high. According to the formula calculation, the sensitivity of the transmission type sensor can reach 1080nm / RIU, and the transmittance is 73.25%.

[0046] Example 5: The thickness of the silicon dioxide insulating substrate is 500nm, the width of the two-dimensional metal grating array is 800nm, the period is 1200nm, the thickness is 300nm, and the grating material is gold. The thickness of the object cavity to be measured is 1500nm. The thickness of the silicon dioxide insulating top cover (with an inverted silicon dioxide grating top cover added) is 500nm. The width of the insulating grating structure is 800nm, the period is 1200nm, the thickness is 300nm, and the material is silicon dioxide. The peak position of the transmission peak moves most obviously, and the sensitivity is higher. According to the formula calculation, the sensitivity of the transmission type sensor can reach 1060nm / RIU, and the transmittance is 95.81%.

[0047] In summary, the present invention uses a grating structure to conduct transmission-type sensing research. The area with strong electric field intensity is concentrated at the position of the microfluidic cavity of the object to be tested, which meets certain conditions to excite surface plasmon resonance and enhance the plasma resonance peak. At the same time, the transmission spectrum is easy to detect and easy to integrate devices, thereby obtaining a nano-gold grating transmission-type microfluidic sensor based on surface plasmon resonance with high sensitivity. This transmission-type microfluidic sensor has a wide range of application backgrounds, such as biochemistry, drug development, food monitoring, air monitoring, etc.

[0048] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A nano-gold grating transmission type microfluidic sensor based on plasma resonance, characterized in that: The invention comprises: a cavity composed of a silicon dioxide insulator as a microfluidic cavity for an object to be tested, the bottom of the microfluidic cavity for an object to be tested is a silicon dioxide insulating substrate, and a two-dimensional metal grating array is arranged on the silicon dioxide insulating substrate; the top of the microfluidic cavity for an object to be tested is a silicon dioxide insulating top cover, and a two-dimensional insulating grating structure is arranged on the side of the silicon dioxide insulating top cover facing the microfluidic cavity for an object to be tested, wherein the width of the two-dimensional insulating grating structure is 700-800nm, the period is 1200-1400nm, the thickness is 300-500nm, and the two-dimensional insulating grating structure is 1000nm-1000nm. The gate structure material is silicon dioxide; a flow inlet for a flow to be measured is arranged on one side of the bottom of the microfluidic cavity for the object to be measured, and a flow outlet for a flow to be measured is arranged on the other side of the bottom of the microfluidic cavity for the object to be measured; the two-dimensional metal grating array arranged on the silicon dioxide insulating substrate has a width of 700-800nm, a period of 1200-1400nm, and a thickness of 300-500nm, and the material of the two-dimensional metal grating array is gold; the thickness of the microfluidic cavity for the object to be measured is 1200-1600nm; the thickness of the silicon dioxide insulating substrate is 400-600nm; The shape and size of the two-dimensional insulating grating structure are completely consistent with the two-dimensional metal grating structure; The area with strong electric field intensity of the nano-gold grating transmission type microfluidic sensor based on plasma resonance is concentrated at the position of the microfluidic cavity of the object to be tested. The grating structure can enhance the plasma resonance peak according to the change of the refractive index of the object to be tested. △ n , the transmission peak wavelength shift value of the corresponding resonance mode △ λ , the sensitivity is obtained by converting the functional relationship between the two S ; When the nano-gold grating transmission type microfluidic sensor is used, the detection spectrum is the transmission spectrum, and the transmission spectrum is tested by a spectrophotometer; By changing the width, thickness and period of the two-dimensional metal grating array and the two-dimensional insulating grating, the transmission spectrum position of the sensor is made optional.

2. The surface plasmon resonance-based nano-gold grating transmission microfluidic sensor according to claim 1, characterized in that: A two-dimensional insulating grating structure is arranged on one side of the silicon dioxide insulating top cover facing the cavity of the object to be measured; the width of the two-dimensional insulating grating structure is 800nm, the period is 1200nm, and the thickness is 300nm.

3. The surface plasmon resonance-based nano-gold grating transmission microfluidic sensor according to claim 1, characterized in that: The two-dimensional metal grating array arranged on the silicon dioxide insulating substrate has a width of 800nm, a period of 1200nm, and a thickness of 300nm; the thickness of the object cavity to be measured is 1200nm.

4. The surface plasmon resonance-based nano-gold grating transmission microfluidic sensor according to claim 1, characterized in that: The refractive index of the object to be measured is 1.32-1.

74.

5. The nano-gold grating transmission type microfluidic sensor based on surface plasmon resonance according to claim 1, characterized in that: The incident light beam has an incident angle of 0°.

6. The nano-gold grating transmission type microfluidic sensor based on surface plasmon resonance according to claim 1, characterized in that: The two-dimensional metal grating array is prepared by the following preparation method, comprising the following steps: (1) providing a silicon dioxide substrate; (2) arranging a metal layer on the surface of the substrate; (3) arranging a patterned mask layer on the surface of the metal layer, wherein the mask layer has grating grooves, and the shape of the grating grooves is rectangular; (4) etching the metal layer; and (5) removing the patterned mask layer by dissolving with a solvent.

7. A method for transmission spectrum detection using the nano-gold grating transmission type microfluidic sensor based on surface plasmon resonance as claimed in any one of claims 1 to 6, comprising the following steps: (1) The incident light emitted by the light source is vertically incident on the sensor surface; (2) The transmission spectrum of the incident light passing through the microfluidic cavity of the object to be tested is measured; (3) When the refractive index of the object to be tested changes, the change of the transmission spectrum is recorded; (4) The change of the refractive index and concentration of the solution of the object to be tested in the microfluidic cavity is measured by the movement of the peak position of the transmission spectrum line.

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