阅读说明：本技术 一种葡萄糖溶液介电特性的测量方法 (Method for measuring dielectric property of glucose solution ) 是由 肖夏 胡敏 于 2019-09-01 设计创作，主要内容包括：本发明涉及一种葡萄糖水溶液的介电特性测量方法,包括下列步骤：葡萄糖溶液的配制；介电特性的测定；确定测试频率范围后对不同浓度的葡萄糖溶液进行测试,测量得到葡萄糖溶液相对介电常数ε′、介电损耗ε″和频率之间的关系；将在相对介电常数ε′、介电损耗ε″随频率变化的数据中选取合适的频点范围,在该频点范围内拟合成Debye公式,用Debye公式描述葡萄糖溶液的介电性质,绘制频率-相对介电常数和频率-电导率的关系图。(The invention relates to a method for measuring dielectric properties of a glucose aqueous solution, which comprises the following steps: preparing a glucose solution; measuring the dielectric property; determining a test frequency range, testing glucose solutions with different concentrations, and measuring to obtain a relation between a relative dielectric constant epsilon ', a dielectric loss epsilon' and frequency of the glucose solution; selecting a proper frequency point range from the data of the change of the relative dielectric constant epsilon 'and the dielectric loss epsilon' along with the frequency, fitting the frequency point range into a Debye formula, describing the dielectric property of the glucose solution by using the Debye formula, and drawing a relation graph of frequency-relative dielectric constant and frequency-conductivity.)

1. A method for measuring dielectric characteristics of an aqueous glucose solution, comprising the steps of:

(1) preparing a glucose solution: preparing 11 groups of solutions with the interval of 100mg/dl from 0mg/dl to 1000mg/dl by glucose and industrial distilled water according to a specific ratio.

(2) Measurement of dielectric characteristics: correctly connecting a computer, a vector network analyzer and a coaxial probe, and after calibration is finished, placing a beaker filled with a glucose solution below the probe to ensure that liquid in the measuring beaker is tightly contacted with the surface of the coaxial probe so as to prevent air gaps;

(3) after the test frequency range is determined, carrying out 2-4 times of tests on glucose solutions with different concentrations, calculating the average value of the results to be used as the final measurement result, and measuring to obtain the relation between the relative dielectric constant epsilon ', the dielectric loss epsilon' and the frequency of the glucose solution;

(4) selecting a proper Frequency point range from the data of the change of the relative dielectric constant epsilon 'and the dielectric loss epsilon' along with the Frequency, fitting the Frequency point range into a Debye formula, describing the dielectric properties of the glucose solution by using the Debye formula, wherein the dielectric properties comprise the relative dielectric constant and the Conductivity, calculating the Conductivity according to the measured dielectric loss epsilon ', and finally drawing a relation graph of Frequency-dielectric constant epsilon' and Frequency-Conductivity sigma.

Technical Field

The invention belongs to the technical field of solution dielectric property detection, data fitting, noninvasive blood glucose measurement and the like.

Background

Currently, the incidence of diabetes as a global disease is increasing. However, many non-invasive and minimally invasive methods do not avoid physical pain and mental stress on the patient, and meanwhile, the risk of infection exists, and the method is not suitable for long-term continuous monitoring. People urgently hope that an accurate method for non-invasive detection of blood sugar is born. Currently, many scholars attempt to achieve non-invasive blood glucose detection by studying the response characteristics of blood glucose concentration to electromagnetic signals. Blood samples of humans are often resource-scarce and costly to conduct relevant research. Human whole blood contains glucose, other essential substances and water in an amount of about 50% of its volume. In addition, soft tissue contains up to 80% water. Therefore, in order to design and verify the effectiveness of related devices such as sensors or to design in vitro experiments that verify the feasibility of related simulation studies, blood is often approximated by a glucose/water solution as a preliminary/initial step. Therefore, complex permittivity models for glucose/water solutions of different concentrations play an important role and should be accurate. One study was performed by Karacolak et al. Continuous blood glucose monitoring for glucose-dependent plasma dielectric properties of the Cole-Cole model. The values reported above pertain to plasma, with 92% of the volume consisting of water. Thus, similar behavior is expected for glucose/water solutions as well. That is, as the concentration of the glucose solution increases, both the dielectric properties and the conductivity decrease. However, the measurement data of complex dielectric constants of glucose/water solutions of different concentrations in the high frequency band and the data of fitting the Debye model for simulation modeling are poor.

The electrical characteristic measurement technology based on the open end coaxial probe method can carry out fast, real-time, accurate and quantitative broadband measurement on the electrical characteristics of the glucose aqueous solution. Therefore, the invention realizes the nondestructive rapid detection of the glucose aqueous solution based on the coaxial probe and the network analyzer, and fits the Debye equation according to the electrical characteristics of the glucose aqueous solutions with different concentrations under different frequencies, so that the invention can be applied to the dispersion modeling in the noninvasive blood glucose detection, and is beneficial to the experimental verification of related research.

Disclosure of Invention

The invention provides a method for measuring dielectric properties of different glucose concentrations of 200MHz-10 GHz. The method is a testing method based on a coaxial probe and a network analyzer, and is used for testing the electrical characteristics of a plurality of groups of aqueous solutions with different glucose concentrations, and the corresponding electrical characteristic parameters are functions changing along with frequency. A unipolar Debye model is developed as a function of the change of the electrical characteristics of glucose solutions with different concentrations along with the frequency by selecting the corresponding relation between the dielectric properties and the frequency under partial frequency points from the measured data, and a new method and a new thought are provided for noninvasive blood glucose detection. The technical scheme is as follows:

a method for measuring dielectric characteristics of an aqueous glucose solution, comprising the steps of:

(1) preparing a glucose solution: preparing 11 groups of solutions with the interval of 100mg/dl from 0mg/dl to 1000mg/dl by glucose and industrial distilled water according to a specific ratio.

(2) Measurement of dielectric characteristics: the computer, the vector network analyzer and the coaxial probe are correctly connected, and after the calibration is finished, the beaker filled with the glucose solution is placed below the probe to ensure that the liquid in the measuring beaker is tightly contacted with the surface of the coaxial probe so as to prevent the generation of air gaps.

(3) And after the test frequency range is determined, carrying out 2-4 times of tests on the glucose solution with different concentrations, calculating the average value of the results to be used as the final measurement result, and measuring to obtain the relation between the relative dielectric constant epsilon ', the dielectric loss epsilon' and the frequency of the glucose solution.

(4) Selecting a proper Frequency point range from the data of the change of the relative dielectric constant epsilon 'and the dielectric loss epsilon' along with the Frequency, fitting the Frequency point range into a Debye formula, describing the dielectric properties of the glucose solution by using the Debye formula, wherein the dielectric properties comprise the relative dielectric constant and the Conductivity, calculating the Conductivity according to the measured dielectric loss epsilon ', and finally drawing a relation graph of Frequency-dielectric constant epsilon' and Frequency-Conductivity sigma.

Drawings

FIG. 1 shows Frequency-Dielectric constant (Frequency vs. Dielectric constant) at partial concentration

FIG. 2 shows Frequency-Conductivity plots at partial concentrations measured.

FIG. 3200mg/dl glucose solution relative permittivity measurements and formulaic fit values versus frequency

FIG. 4200mg/dl glucose solution relative permittivity measurements and formulaic fit values versus frequency

FIG. 5 shows dielectric constant fit plots of three different glucose solutions at different frequency points

FIG. 6 conductivity fit chart for three different glucose solutions at different frequency points

Detailed Description

The invention provides a method for measuring dielectric properties of different glucose concentrations of 200MHz-10 GHz. The method is a testing method based on a coaxial probe and a network analyzer, and is used for testing the electrical characteristics of a plurality of groups of aqueous solutions with different glucose concentrations, and the corresponding electrical characteristic parameters are functions changing along with frequency. A unipolar Debye model is developed as a function of the change of the electrical characteristics of glucose solutions with different concentrations along with the frequency by selecting the corresponding relation between the dielectric properties and the frequency under partial frequency points from the measured data, and a new method and a new thought are provided for noninvasive blood glucose detection. The experimental method is as follows:

(1) preparing a glucose solution: preparing 11 groups of solutions with the interval of 100mg/dl from 0mg/dl to 1000mg/dl by glucose and industrial distilled water according to a specific ratio.

(2) Determination of dielectric properties of glucose solutions: correctly connecting a computer, a vector network analyzer and a coaxial probe, adjusting the position of a coaxial transmission cable, carrying out necessary calibration work on the vector network analyzer before carrying out a measurement experiment, preheating the network analyzer for 30min, setting relevant parameter ranges, and calibrating a tail end open-circuit coaxial high-temperature probe of the network analyzer by respectively adopting air, a short-circuit device and deionized water. The measurement value sensitivity of the open-end coaxial probe is ensured to be less than 0.5. After calibration was completed, the beaker with the glucose solution was placed under the probe to ensure that the liquid in the measurement beaker was in intimate contact with the surface of the coaxial probe to prevent air gaps.

(3) And after the test frequency range is determined, carrying out 2-4 times of tests on the glucose aqueous solutions with different concentrations, calculating the average value of the results to be used as the final measurement result, and measuring to obtain the relation among the relative dielectric constant epsilon ', the dielectric loss epsilon' and the frequency of the glucose solution.

(4) And selecting a proper frequency point range from the data of the change of the relative dielectric constant epsilon 'and the dielectric loss epsilon' along with the frequency, and fitting the frequency point range into a Debye formula (1). The dielectric properties (relative permittivity and conductivity) of the glucose solution can be described later using the Debye equation. The conductivity can be calculated from the measured dielectric loss ε' by the equation (2). Finally, the Frequency-Dielectric constant (Frequency-relative Dielectric constant ∈') and the Frequency-Conductivity (Frequency-Conductivity σ) can be plotted.

σ(ω)＝ωε₀ε″(ω) (2)

Wherein σ represents the electrical conductivity; ω 2 × pi f is the measurement angular frequency. ε' is the real part of the complex permittivity, commonly referred to as the relative permittivity; ε "is the imaginary part of the complex dielectric constant, commonly referred to as the dielectric loss; epsilon₀Is a dielectric constant in vacuum,. epsilon_∞Is the relative dielectric constant at infinite frequency, tau is the relaxation time, epsilon_sIs the relative static dielectric constant.

(5) The unknown parameter ε in the above formula (1)_∞、ε_sτ was fitted to a function related to glucose concentration by fitting test data, and the parameters of the Debye equation were fitted as follows:

ε_∞(x)＝1.073*x²+2.29*x+9.824 (3)

ε_s(x)＝0.1594*x²-0.6874*x+79.11 (4)

τ(ps)＝0.205*x²+0.2879*x+9.21 (5)

wherein x represents units of g/dl.

The technical scheme of the invention is specifically explained by the identification of several unknown glucose solutions to be detected as follows:

(1) preparing 11 groups of solutions with the interval of 100mg/dl of 0mg/dl-1000mg/dl and the glucose and industrial distilled water according to a specific ratio, and storing properly according to related requirements. Before testing, each group of glucose solution to be tested is controlled to be placed in a room temperature environment of about 24 ℃, and real-time temperature measurement is carried out by using an electronic thermometer with high precision and quick measurement response so as to eliminate temperature errors;

(2) determination of dielectric properties of glucose solutions: correctly connecting a computer, a vector network analyzer and a coaxial probe, adjusting the position of a coaxial transmission cable, carrying out necessary calibration work on the vector network analyzer before carrying out a measurement experiment, preheating the network analyzer for 30min, setting relevant parameter ranges, and calibrating a tail end open-circuit coaxial high-temperature probe of the network analyzer by respectively adopting air, a short-circuit device and deionized water. The measurement value sensitivity of the open-end coaxial probe is ensured to be less than 0.5. After calibration was complete, the different glucose solutions were placed in order into a 25mg/dl beaker for the test. The beaker filled with the glucose solution is placed below the probe and is placed on a lifting platform with the length of 80mm and the width of 60mm, so that the liquid in the measuring beaker is ensured to be in close contact with the surface of the coaxial probe to prevent air gaps. Meanwhile, the measuring frequency range is preset to be 200-1000 MHz through software on a computer, and 981 linear sampling points are preset.

(3) Measuring 11 groups of glucose solutions to be measured for 4 times, taking the average value of the 4 measurement results as the final test result of the unknown glucose solution to be measured, and wiping the probe completely after each measurement to avoid introducing other related errors; the glucose solution was measured for the relationship between the relative dielectric constant ε ', the dielectric loss ε' and the frequency.

(4) And selecting a proper frequency point range from the data of the change of the relative dielectric constant epsilon 'and the dielectric loss epsilon' along with the frequency, and fitting the frequency point range into a Debye formula (1). The dielectric properties (relative permittivity and conductivity) of the glucose solution can be described later using the Debye equation. The conductivity can be calculated from the measured dielectric loss ε' by the equation (2). Finally, the Frequency-Dielectric constant (Frequency-relative Dielectric constant ∈') and the Frequency-Conductivity (Frequency-Conductivity σ) can be plotted. FIG. 1 and FIG. 2 show the relative dielectric constant and conductivity of glucose solutions measured experimentally in 100mg/dl,400mg/dl and 900mg/dl as examples. It can be seen that its regularity is: both the dielectric constant and conductivity decrease with increasing glucose concentration.

σ(ω)＝ωε₀ε″(ω) (2)

Wherein σ represents the electrical conductivity; ω 2 × pi f is the measurement angular frequency. ε' is the real part of the complex permittivity, commonly referred to as the relative permittivity; ε "is the imaginary part of the complex dielectric constant, commonly referred to as the dielectric loss; epsilon₀Is a dielectric constant in vacuum,. epsilon_∞Is the relative dielectric constant at infinite frequency, tau is the relaxation time, epsilon_sIs the relative static dielectric constant.

(5) The unknown parameter ε_∞、ε_sτ was fitted to a function related to glucose concentration by fitting test data, and the parameters of the Debye equation were fitted as follows:

ε_∞(x)＝1.073*x²+2.29*x+9.824 (3)

ε_s(x)＝0.1594*x²-0.6874*x+79.11 (4)

τ(ps)＝0.205*x²+0.2879*x+9.21 (5)

wherein x represents units of g/dl.

The calculation parameter epsilon required by the formula (1) can be calculated through the formulas (3), (4) and (5)_∞、ε_sτ, the electrical properties versus frequency for different glucose concentrations can be reconstructed by substituting these several parameters into equation (1). FIGS. 3 and 4 demonstrate the dielectric constant and conductivity measurements and the formulaic fit values, respectively, versus frequency for a 0.2g/dl (200mg/dl) glucose solution. FIGS. 5 and 6 depict the dielectric properties of Debye reconstituted glucose solutions at 100mg/dl,400mg/dl and 900mg/dl, which are in accordance with the experimentally measured rules of FIG. 1 and FIG. 2: both the dielectric constant and conductivity decrease with increasing glucose concentration. The parameters of the Debye fitting can well reproduce experimental data, which shows that the dielectric property of the method for simulating the glucose concentration is accurate along with the frequency change relationship, and the method can be used for dispersion treatment in noninvasive blood glucose measurement research and the design of other electromagnetic devices.