CN112945932A - Sweat sensor for detecting sweat marker and detection method - Google Patents

Abstract

The application discloses a sweat sensor for detecting sweat markers and a detection method. The sweat sensor comprises a microfluidic chip and a SERS substrate which are arranged in a stacked mode, so that sweat absorbed into a microfluidic channel of the microfluidic chip can reach the SERS substrate. Therefore, the sweat marker can be analyzed with high sensitivity, and the structure and the processing steps of the wearable equipment can be simplified.

Description

Sweat sensor for detecting sweat marker and detection method

Technical Field

The invention relates to the technical field of biosensors, in particular to a sweat sensor for detecting a sweat marker and a detection method.

Background

The human body sweat mainly comprises 98-99% of water (pH value is 4.2-7.5), sodium chloride (about 300mg/100mL), and 1-2% of physiological markers (including a small amount of urea, lactic acid, fatty acid, glucose and the like).

When a human body is doing exercise or working in a high temperature environment, a large amount of sweat can flow out. When a patient is rescued, the fluid infusion amount is required to be input according to the sweating amount of the patient so as to prevent the patient from suffering from life failure. When Na + is less than 58.4mg, K + is less than 10mg and Cl-is less than 45.4mg in each liter of sweat, a series of problems will occur to a human body, so that the human body is obviously allergic to the stimulation of sight and hearing, the regulating capacity of the antibody of the body is reduced, and symptoms such as muscle spasm, dehydration, even coma and the like can occur.

Current wearable sweat detection is largely divided into colorimetric and electrochemical methods. The colorimetric method has insufficient sensitivity and can only carry out qualitative or semi-quantitative analysis, which is determined by the colorimetric reaction per se; the electrochemical method needs to design a complex and precise two-electrode or three-electrode system, and an energy (electric energy) supply system is usually equipped, so that the preparation and processing difficulty of the whole wearable device is increased.

Disclosure of Invention

In order to solve the above problems, the present application provides a sweat sensor and a detection method for detecting a sweat marker, which can conveniently detect a physiological marker.

According to one technical scheme of this application, sweat sensor that this application sweat marker detected, including the micro-fluidic chip and the SERS base that stack up set up to make absorb to sweat in the miniflow channel of micro-fluidic chip can reach the SERS base.

Micro-fluidic chip

The microfluidic chip is a microfluidic channel with the size of tens to hundreds of microns constructed on the chip by adopting a semiconductor-like micro-electro-mechanical processing technology. The microfluidic chip can be prepared by molding, hot pressing, LIGA technique, laser ablation technique, soft lithography, etc. or other methods known in the art.

The following soft lithography is an example to illustrate a method for preparing the microfluidic chip in the present application, including the following steps: i) first, the silicon wafer was washed twice with isopropanol and acetone, dried with N2, and then baked at 200 ℃. & 250 ℃ for 60-90min to remove moisture. The SU8-2002 photoresist was then spun onto a cleaned silicon wafer for 1 minute at a spin speed of 3000-3500rpm to form an adhesive layer. Thereafter, the SU8-2075 photoresist was spin coated on top of the SU8-2002 photoresist layer at 1000-. ii) the photoresist coated silicon wafer was assembled with each layer using a high resolution transparent mask and exposed to a mercury lamp for 2.5 minutes (2.5-3min) to allow photo-induced crosslinking reaction to form a pattern. Then, the silicon wafer is baked at 95-100 deg.C for 1010-12 min. iii) the silicon wafer was immersed in a developer solution to remove the unexposed areas and then at 140-150 deg.C for 100-120 min. iv) 1H, 1H, 2H, 2H-perfluorooctyldichlorosilane with release agent was connected to the mold through microfluidic channels in an oven at 60 ℃ for 40-45 min. v) preparing Polydimethylsiloxane (PDMS) and a curing agent in a volume ratio of 10:1 to 15:1 to form a PDMS prepolymer. Before curing, the PDMS prepolymer was placed in a vacuum chamber to remove air bubbles. A certain amount of the PDMS prepolymer solution without bubbles was uniformly poured on the processed mold, and then baked at 75-80 ℃ for 25-30min to form a PDMS slab. The PDMS slab was peeled off the mold.

The specific shape of the microchannel in the microfluidic chip of the present application can be designed and replaced into a specific shape, for example, the cross-sectional area of the microchannel is appropriately reduced, and the length of the microchannel is reduced to accelerate the time for sweat to reach the SERS substrate.

SERS substrate

SERS, a surface enhanced Raman scattering method, refers to the adsorption of a molecule to be detected on the surface of a rough SERS material, so that the Raman signal of an object to be detected can be further enhanced (10 < -6 > -10 < -15 >). The preparation of the SERS active substrate is a precondition for obtaining a higher Raman enhancement signal, the enhancement effects of different enhancement substrates on a sample are very different, and the enhancement effects of SERS can be influenced by factors such as the material of the SERS active substrate, the shape and the size of nanoparticles, the adsorption amount and the distance of a detector on the active substrate, and the like.

The SERS substrate may be prepared in a form known in the art, such as electrochemical roughening, molecular self-assembly, screen printing, photolithography, and the like.

One example of a method for preparing the SERS substrate of the present application is described. First, a uniform and close-packed PS monolayer colloidal crystal of PS spheres with a diameter of 150nm was prepared on a clean n-type Si (100) wafer by a gas/liquid interface self-assembly and bulk transfer technique. Then, the silicon is mixedThe PS colloid monolayer on the substrate is placed in an oven at the temperature of 110-120 ℃ for 60-70s, so that the PS balls are in planar contact with the silicon substrate. Then, at a power of 210W, SF₆SF was performed in a conventional reactive ion etcher at a flow rate of 36sccm and a pressure of 2.3Pa₆And (4) plasma etching. Here, a PS colloid monolayer was used as a mask. After etching for 30-45s, well-arranged Si nano-cone arrays are formed on the silicon wafer. The residual etched PS spheres at the top of the silicon nanocones were removed by calcination in air at 400 ℃. And finally, sputtering and depositing a nano silver layer on the Si nanocone array by a magnetron sputtering technology to obtain the SERS substrate.

The greater the roughness of the SERS substrate, preferably, the stronger the SERS signal.

According to the type of the marker to be detected, some well-known functional modifications of the SERS substrate are required in some cases.

The sweat sensor can further comprise an encapsulation layer which is stacked and arranged on one surface of the microfluidic core far away from the SERS substrate. The material of the encapsulation layer can be quartz.

The sweat sensor can further comprise a skin adhesive layer which is stacked and arranged on one surface of the SERS substrate far away from the microfluidic chip.

In another technical scheme of the application, the detection method of the sweat marker is implemented by adopting the sweat sensor.

The detection method specifically comprises the following steps:

causing the sweat sensor worn on the skin to adsorb sweat;

acquiring a Raman spectrum signal formed after scattering by the SERS substrate of the sweat sensor;

and obtaining the concentration of the sweat marker according to the Raman spectrum signal.

Here, "obtaining the concentration of the sweat marker from the raman spectrum signal" may be performed in accordance with a principle or a method known in the art of quantitative analysis of the concentration by raman spectrum, which is outlined herein.

The sweat sensor comprises a microfluidic chip and a SERS substrate which are arranged in a stacked mode, so that sweat absorbed into a microfluidic channel of the microfluidic chip can reach the SERS substrate. Therefore, the sweat marker can be analyzed with high sensitivity, and the structure and the processing steps of the wearable equipment can be simplified.

Drawings

Fig. 1 is a graph showing the intensity ratio of vitamin concentration to raman spectrum wavenumber in application example 1 of the present application.

FIG. 2 is a graph showing the intensity ratio of cortisol concentration to Raman spectrum wavenumber according to example 2 of the present application.

Fig. 3 is a graph showing the intensity ratio of the picouric acid concentration to the raman spectrum wavenumber in application example 3 of the present application.

Detailed Description

The following are specific examples of the present application and further describe the technical solutions of the present application, but the present application is not limited to these examples.

Material

Unless otherwise specified, the following materials are all commercially available.

Example 1

(preparation of sweat sensor)

The microfluidic chip was fabricated by standard soft lithography. i) First, a silicon wafer was washed twice with isopropyl alcohol and acetone, dried with nitrogen gas, and then baked at 200 ℃ for 90min to remove moisture. Then, SU8-2002 photoresist was spin coated on the cleaned silicon wafer at a spin speed of 3000rpm for 5 minutes to form an adhesive layer. Thereafter, SU8-2075 photoresist was spin coated on top of the SU8-2002 photoresist layer at 1000rpm for 5 minutes, and this step was repeated twice. ii) the photoresist coated silicon wafer was assembled with each layer using a high resolution transparent mask and exposed to a mercury lamp for 2.5min for photo-induced crosslinking reaction to form a pattern. Thereafter, the silicon wafer was baked at 95 ℃ for 12 min. iii) the silicon wafer was immersed in a developer solution to remove the unexposed areas and then baked at 140 ℃ for 120 min. iv) 1H, 1H, 2H, 2H-perfluorooctyldichlorosilane with release agent was connected to the mold through microfluidic channels in an oven at 60 ℃ for 45 min. v) preparing Polydimethylsiloxane (PDMS) and a curing agent in a 10:1 volume ratio to form a PDMS prepolymer. Before curing, the PDMS prepolymer was placed in a vacuum chamber to remove air bubbles. An amount of the PDMS prepolymer solution without bubbles was poured uniformly onto the processed mold and then baked at 75 ℃ for 30min to form a PDMS slab. The PDMS slab was peeled off the mold.

A preparation method of the SERS substrate. First, a uniform and close-packed PS monolayer colloidal crystal of PS spheres with a diameter of 150nm was prepared on a clean n-type Si (100) wafer by a gas/liquid interface self-assembly and bulk transfer technique. The PS colloidal monolayer on the silicon substrate was then placed in an oven at 110 ℃ for 70s, and the PS spheres were brought into planar contact with the silicon substrate. Then, at a power of 210W, SF₆SF was performed in a conventional reactive ion etcher at a flow rate of 36sccm and a pressure of 2.3Pa₆And (4) plasma etching. Here, a PS colloid monolayer was used as a mask. After etching for 45s, well-aligned arrays of Si nanopyramids were formed on the silicon wafer. The residual etched PS spheres at the top of the silicon nanocones were removed by calcination in air at 400 ℃. And finally, sputtering and depositing a nano silver layer on the Si nanocone array by a magnetron sputtering technology to obtain the SERS substrate. The SERS substrate was cut and fixed at a circular hole in the microchannel layer in embodiment one and fixed with 502 glue.

Example 2

(preparation of sweat sensor)

The microfluidic chip was fabricated by standard soft lithography. i) First, a silicon wafer was washed twice with isopropyl alcohol and acetone, dried with nitrogen gas, and then baked at 250 ℃ for 60min to remove moisture. SU8-2002 photoresist was then spin coated on the cleaned silicon wafer at a spin speed of 3500rpm for 1 minute to form an adhesive layer. Thereafter, SU8-2075 photoresist was spin coated on top of the SU8-2002 photoresist layer at 1200rpm for 1 minute, and this step was repeated twice. ii) the photoresist coated silicon wafer was assembled with each layer using a high resolution transparent mask and exposed to a mercury lamp for 3min to perform a photo-induced crosslinking reaction to form a pattern. Thereafter, the silicon wafer was baked at 100 ℃ for 10 min. iii) the silicon wafer was immersed in a developer solution to remove the unexposed areas and then baked at 150 ℃ for 100 min. iv) 1H, 1H, 2H, 2H-perfluorooctyldichlorosilane with release agent was connected to the mold through microfluidic channels in an oven at 70 ℃ for 45 min. v) preparing Polydimethylsiloxane (PDMS) and a curing agent in a 15:1 volume ratio to form a PDMS prepolymer. Before curing, the PDMS prepolymer was placed in a vacuum chamber to remove air bubbles. An amount of the PDMS prepolymer solution without bubbles was poured uniformly onto the processed mold and then baked at 80 ℃ for 25min to form a PDMS slab. The PDMS slab was peeled off the mold.

A preparation method of the SERS substrate. First, a uniform and close-packed PS monolayer colloidal crystal of PS spheres with a diameter of 150nm was prepared on a clean n-type Si (100) wafer by a gas/liquid interface self-assembly and bulk transfer technique. The PS colloidal monolayer on the silicon substrate was then placed in an oven at 120 ℃ for 60s to bring the PS spheres into planar contact with the silicon substrate. Then, at a power of 250W, SF₆SF was performed in a conventional reactive ion etcher at a flow rate of 40sccm and a pressure of 2.8Pa₆And (4) plasma etching. Here, a PS colloid monolayer was used as a mask. After etching for 30s, well-arranged Si nanocone arrays were formed on the silicon wafer. The residual etched PS spheres at the top of the silicon nanocones were removed by calcination in air at 450 ℃. And finally, sputtering and depositing a nano silver layer on the Si nanocone array by a magnetron sputtering technology to obtain the SERS substrate. The SERS substrate was cut and fixed at a circular hole in the microchannel layer in embodiment one and fixed with 502 glue.

Example 3

(preparation of sweat sensor)

The microfluidic chip was fabricated by standard soft lithography. i) First, the silicon wafer was washed twice with isopropanol and acetone, dried with nitrogen gas, and then baked at 220 ℃ for 72min to remove moisture. Then, SU8-2002 photoresist was spin coated on the cleaned silicon wafer at a spin speed of 3200rpm for 3 minutes to form an adhesive layer. Thereafter, the SU8-2075 photoresist was spin coated on top of the SU8-2002 photoresist layer at 1000-. ii) the photoresist coated silicon wafer was assembled with each layer using a high resolution transparent mask and exposed to a mercury lamp for 2.8min for photo-induced crosslinking reaction to form a pattern. Thereafter, the silicon wafer was baked at 98 ℃ for 11 min. iii) the silicon wafer was immersed in a developer solution to remove the unexposed areas and then baked at 145 deg.C for 110 min. iv) 1H, 1H, 2H, 2H-perfluorooctyldichlorosilane with release agent was connected to the mold through microfluidic channels in an oven at 60 ℃ for 43 min. v) preparing Polydimethylsiloxane (PDMS) and a curing agent in a 13:1 volume ratio to form a PDMS prepolymer. Before curing, the PDMS prepolymer was placed in a vacuum chamber to remove air bubbles. An amount of the PDMS prepolymer solution without air bubbles was poured uniformly onto the processed mold and then baked at 78 ℃ for 28min to form a PDMS slab. The PDMS slab was peeled off the mold.

A preparation method of the SERS substrate. First, a uniform and close-packed PS monolayer colloidal crystal of PS spheres with a diameter of 150nm was prepared on a clean n-type Si (100) wafer by a gas/liquid interface self-assembly and bulk transfer technique. The PS colloidal monolayer on the silicon substrate was then placed in an oven at 115 ℃ for 65s, with the PS spheres in planar contact with the silicon substrate. Then, at a power of 230W, SF₆SF was performed in a conventional reactive ion etcher at a flow rate of 38sccm and a pressure of 2.5Pa₆And (4) plasma etching. Here, a PS colloid monolayer was used as a mask. After etching for 38s, well-aligned arrays of Si nanopyramids were formed on the silicon wafer. The residual etched PS spheres at the top of the silicon nanocones were removed by calcination in air at 420 ℃. And finally, sputtering and depositing a nano silver layer on the Si nanocone array by a magnetron sputtering technology to obtain the SERS substrate. The SERS substrate was cut and fixed at a circular hole in the microchannel layer in embodiment one and fixed with 502 glue.

Application example 1

(sweat sensor for vitamin detection in sweat)

Dripping about 5 mu L of PBS solution of vitamin C with the concentration of 0,0.02,0.05,0.1,0.2,0.25,0.5,1,5 and 10mM into the micro-cavity of 6 micro-fluidic chips fixed with the nano-silver SERS substrate respectively, and detecting the 6 micro-fluidic chips respectively by a handheld micro-confocal laser Raman spectrometer at the wavelength of 785nm to obtain the vitamin C with the wave number of 1000cm^-1、1240cm^-1、1386cm^-1、1630cm^-1Four characteristic peaks. The concentration of vitamin C is used as the abscissa, and the Raman signal is used at 1386cm^-1、1630cm^-1The intensity ratio of the two wavenumbers is plotted as the ordinate to create a calibration curve, as shown in FIG. 1.

Application example 2

(sweat sensor for detecting Cortisol contained in sweat)

In contrast to application example 1, the cortisol concentration was 125,250,500,750,1000 nM; the characteristic peak of cortisol is distributed at 1146cm^-1、1269cm^-1、1344cm^-1、1378cm^-1、1432cm^-1、1450cm^-1、1504cm^-1(ii) a Raman signal at 1504cm^-1The signal intensity of (A) was plotted against the lactate concentration as a standard curve, as shown in FIG. 2.

Application example 3

(sweat sensor for detecting uric acid contained in sweat)

Different from the application example 1, the concentration of the uric acid is 0,2,4,6,8 and 10 mM; the characteristic peak distribution of uric acid is 500cm^-1、690cm^-1、1390cm^-1、1600cm^-1(ii) a With Raman signal at 1600cm^-1The signal intensity of (a) was plotted against the uric acid concentration as a standard curve, as shown in FIG. 3.

The specific embodiments described herein are merely illustrative of the spirit of the application. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the present application as defined by the appended claims.

Claims (6)

1. A sweat sensor for detecting sweat markers is characterized by comprising a microfluidic chip and an SERS substrate which are arranged in a stacked mode, so that sweat absorbed into a microfluidic channel of the microfluidic chip can reach the SERS substrate.

2. The sweat sensor of claim 1 further including an encapsulation layer disposed on a surface of the microfluidic core remote from the SERS substrate.

3. A sweat sensor according to claim 2, wherein the encapsulation layer is a quartz encapsulation layer.

4. The sweat sensor of claim 1 further including a skin adhesive layer laminated to a surface of the SERS substrate remote from the microfluidic chip.

5. A method of detecting sweat markers, the method being performed using the sweat sensor of claim 1.

6. The detection method according to claim 5, characterized by comprising the steps of:

causing the sweat sensor worn on the skin to adsorb sweat;

acquiring a Raman spectrum signal formed after scattering by the SERS substrate of the sweat sensor;

and obtaining the concentration of the sweat marker according to the Raman spectrum signal.

Images