CN107389502B - A method and system for measuring liquid viscosity - Google Patents

Abstract

The invention discloses a method and system for measuring liquid viscosity. The method includes: establishing the actual relationship model of the flow length and time when the liquid is in capillary flow in the micro/nano channel; determining the relationship model between the dynamic viscosity of the liquid and the actual fitting slope: Determine the value of the unknown parameter, determine the expression of the relationship model between the dynamic viscosity of the liquid and the actual fitting slope; determine the dynamic viscosity of the liquid according to the fitting slope of the actual capillary flow process of the liquid. Using the method or system of the present invention, the dynamic viscosity can be directly determined by fitting the slope, and the required liquid amount is very small, and the measurement is accurate.

Description

A method and system for measuring liquid viscosity

technical field

The present invention relates to the field of liquid measurement, in particular to a method and system for measuring liquid viscosity.

Background technique

Viscosity is one of the important physical quantities that characterize the properties of liquids, reflecting the ability of liquids to resist deformation. Accurate measurement of viscosity is of great significance to petrochemical, medical, national defense and other fields. The existing viscosity measurement method is mainly the capillary method. Because the capillary tube method is simple and practical, the current measuring devices designed based on the capillary tube method have a wide range of applications. The principle of the capillary tube method is the Hagen-Poiseuille formula. The liquid is driven by external pressure to flow through the capillary tube, the pressure difference at both ends of the capillary tube and the flow rate of the liquid are measured and corrected, and the viscosity of the liquid can be calculated. At present, the main problems of the device for measuring viscosity based on the capillary method are: it is difficult to accurately measure the pressure difference and flow rate, and more experimental liquids are required for the measurement (the inner diameter of the capillary tube in the measuring device is generally of the order of mm, and the required experimental liquid is in the tens of milliliters), but sometimes the experimental liquid that can be provided is very limited (for example, blood or some physiological fluid samples are generally tens of microliters). If the capillary method is still used for measurement at this time, the accuracy of the measurement results is very low , and may not even be able to measure the viscosity of liquids, all of which bring challenges to the development of capillary measurement technology.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and a system for measuring the viscosity of a liquid, which can measure the viscosity of the liquid with very little liquid and improve the accuracy of the measurement.

For achieving the above object, the present invention provides the following scheme:

A method of measuring the viscosity of a liquid, the method comprising:

Model the actual relationship between liquid flow length and time:

where a and b are unknown parameters related to the channel depth, A _exp is the actual fitting slope, l(t) is the flow distance of the liquid at time t, σ is the surface tension of the liquid, and θ _e is the equilibrium between the liquid and the channel wall contact angle, η is the fluid dynamic viscosity, h is the channel height;

Determine the relationship between the hydrodynamic viscosity and the actual fitted slope:

Determine the values of the unknown parameters a and b, determine the relationship model

From the actual fitted slope of the liquid flow, the dynamic viscosity of the liquid is determined.

Optionally, the determining the values of the unknown parameters a and b specifically includes:

Use N kinds of known liquids to carry out N groups of experiments, where N is an integer greater than 1;

According to the formula Obtain the fitting slope A _exp of each group of experiments in the N groups of experiments;

According to the formula Obtain the theoretical slope _ALW of each group of experiments in the N groups of experiments;

Obtain the ratio of the fitted slope and the corresponding theoretical slope of each group of experiments in the N groups of experiments, and get: where A _exp(k) represents the fitting slope obtained from the kth group of experiments, k=1, 2,...N, A _LW(k) represents the theoretical slope corresponding to the kth group of experiments, and σ _(k) represents the kth group of experiments The surface tension of the liquid in the experiment, θ _e(k) represents the equilibrium contact angle between the liquid and the channel wall in the k-th group of experiments, η _(k) represents the theoretical value of the dynamic viscosity of the liquid in the k-th group of experiments;

According to the relevant parameters of the known liquids in the N groups of experiments, the corresponding parameters of the known liquids in each group of experiments are obtained. parameters, wherein the relevant parameters include the liquid surface tension σ _(k) , the equilibrium contact angle θ _e(k) between the liquid and the channel wall, and the theoretical value of the liquid dynamic viscosity η _(k) ;

Determine the values of the a and the b.

Optionally, after determining the values of a and b, the method further includes:

Obtain the relationship model of flow length and time in the liquid flow process corresponding to M groups of channels with different depths The values of the unknown parameters a _(i) and b _(i) in , where M is an integer greater than 1, where a _(i) and b _(i) are unknown parameters related to the channel depth h _(i) , the channel depth h _(i) is the depth of channel i;

The relationship function h=f(a,b) between the channel depth h and the unknown parameters a, b and the relationship function a=g(b) between the unknown parameters a and b are determined.

A system for measuring the viscosity of a liquid, the system comprising:

The relationship model building module of flow length and time is used to establish the actual relationship model of liquid flow length and time: where a and b are unknown parameters related to the channel depth, A _exp is the actual fitting slope, l(t) is the flow distance of the liquid at time t, σ is the surface tension of the liquid, and θ _e is the equilibrium between the liquid and the channel wall contact angle, η is the fluid dynamic viscosity, h is the channel height;

The model determination module for the relationship between hydrodynamic viscosity and actual fitting slope is used to determine the relationship model between hydrodynamic viscosity and actual fitting slope:

an unknown parameter determination module for determining the values of the unknown parameters a and b to determine the relationship model

The dynamic viscosity determination module is used for determining the dynamic viscosity of the liquid according to the actual fitting slope of the liquid flow.

Optionally, the unknown parameter determination module specifically includes:

An experiment control unit, used to perform N groups of experiments using N kinds of known liquids, where N is an integer greater than 1;

Fitting slope acquisition module, which is used according to the formula Obtain the fitting slope A _exp of each group of experiments in the N groups of experiments;

Theoretical slope acquisition unit, which is used according to the formula Obtain the theoretical slope _ALW of each group of experiments in the N groups of experiments;

The ratio calculation unit is used to calculate the ratio of the fitted slope of each group of experiments in the N groups of experiments to the corresponding theoretical slope, and obtain: where A _exp(k) represents the fitting slope obtained from the kth group of experiments, k=1, 2,...N, A _LW(k) represents the theoretical slope corresponding to the kth group of experiments, and σ _(k) represents the kth group of experiments The surface tension of the liquid in the experiment, θ _e(k) represents the equilibrium contact angle between the liquid and the channel wall in the k-th group of experiments, η _(k) represents the theoretical value of the dynamic viscosity of the liquid in the k-th group of experiments;

The liquid parameter calculation unit is used to obtain the corresponding parameters of the known liquid in each group of experiments according to the relevant parameters of the known liquid in the N groups of experiments parameters, wherein the relevant parameters include the liquid surface tension σ _(k) , the equilibrium contact angle θ _e(k) between the liquid and the channel wall, and the theoretical value of the liquid dynamic viscosity η _(k) ;

An unknown parameter determination unit for determining the values of a and b.

Optionally, the system further includes:

The unknown parameter determination module corresponding to the channels of different depths is used to obtain the relationship model between the flow length and time in the liquid flow process corresponding to the M groups of channels of different depths after determining the values of a and b The values of the unknown parameters a _(i) and b _(i) in , where M is an integer greater than 1, a _(i) and b _(i) are unknown parameters related to the channel depth h _(i) , and the channel depth h _{( i)} is the depth of channel i;

The relationship function determination module is used to determine the relationship function h=f(a,b) between the channel depth h and the unknown parameters a and b and the relationship function a=g(b) between the unknown parameters a and b.

A device for measuring liquid viscosity, the device comprising: a power supply, a sample introduction device, a micro/nano channel, a temperature control device, a controller, and a data acquisition device;

the power supply is connected to the sampling device; the output end of the sampling device is connected to the inlet of the micro/nano channel, and the outlet of the micro/nano channel is directly connected to the atmosphere;

The first output end of the controller is connected to the input end of the sampling device; the second output end of the controller is connected to the input end of the temperature control device; the micro/nano channel is located in the temperature control device internal;

The data collection device is used to collect the flow distance and time of the liquid;

The input end of the controller is connected to the data acquisition device, and is used for using the relationship model between the flow length of the liquid and the time according to the distance and time of the liquid collected by the data acquisition device

Obtain the actual fitted slope A _exp , which is also used to combine the theoretical relationship between liquid flow length and time Determine the values of the unknown parameters a and b, and determine the relationship model between the hydrodynamic viscosity and the actual fitted slope According to the actual fitting slope of the liquid flow, determine the dynamic viscosity of the liquid, where l(t) represents the flow distance of the liquid at time t, σ represents the surface tension of the liquid, η represents the dynamic viscosity of the liquid, h represents the channel height, θ _e represents the equilibrium contact angle between the liquid and the channel wall, a and b are unknown parameters related to the channel depth.

Optionally, the data acquisition device specifically includes: a group E of photoelectric components, a timing circuit, and a first data processing device; wherein E is an integer greater than 2;

Each group of optoelectronic components includes an optical transmitter and an optical receiver, the E optical emitters of the E group of optoelectronic components are sequentially located below the micro/nano channel, and the E optical receivers of the E group of optoelectronic components are sequentially positioned above the micro/nano channels, and are arranged corresponding to the E light emitters;

E light receivers of the E group photoelectric components are connected to the timing circuit;

The first data processing device is connected to the output end of the timing circuit, and is used to obtain liquid according to the distance between the E groups of optoelectronic components and the time when the liquid in the micro/nano channel reaches each group of optoelectronic components E group flow distance and time.

Optionally, the data acquisition device specifically includes: F light sources, F photoelectric sensors, and a second data processing device; wherein F is an integer greater than 2;

The F light sources are in one-to-one correspondence with the F photoelectric sensors; the F photoelectric sensors are sequentially located above the micro/nano channel, the F light sources are sequentially located below the micro/nano channel, and The F photoelectric sensors are relatively arranged;

The second data processing device is connected to the output ends of the F photoelectric sensors, and is used to obtain the information according to the distance between the F photoelectric sensors and the time when the liquid in the micro/nano channel reaches each photoelectric sensor. Group F flow distance and time for liquids.

Optionally, the measuring device further includes: a display device, the input end of the display device is connected to the third output end of the controller, for displaying the dynamic viscosity data of the liquid output by the controller.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

Using the relationship between the liquid flow distance and time in the micro/nano channel, the relationship model between the dynamic viscosity and the actual fitting slope is determined, and then the dynamic viscosity can be directly determined by the fitting slope, and the amount of liquid required is very small. Fewer cases of viscosity measurement, increasing the accuracy of the measurement while avoiding wasting large amounts of liquid. The measuring device of the present invention uses channels with a depth of micrometers or even nanometers as capillaries to reduce the use of experimental liquids, and the liquids flow into the micro/nano channel group driven by capillary pressure, and no external pressure device or pressure measuring components are required; Simple operation, easy to carry, fast measurement and reliable results.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

Fig. 1 is the flow chart of the method for measuring liquid viscosity of the present invention;

Fig. 2 is the system structure diagram of the present invention measuring liquid viscosity;

Fig. 3 is the device structure diagram of the present invention measuring liquid viscosity;

4 is a structural diagram of Embodiment 1 of a data acquisition device;

FIG. 5 is a structural diagram of Embodiment 2 of the data acquisition device.

Detailed ways

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 are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Fig. 1 is the flow chart of the method for measuring liquid viscosity of the present invention. As shown in Figure 1, the method includes:

Step 101: Establish a model of the actual relationship between liquid flow length and time. The actual relationship model is established as: where a and b are unknown parameters related to the channel depth, that is, the values of a and b are different if the channel depth is different, l(t) represents the flow distance of the liquid at time t, σ represents the surface tension of the liquid, η represents the dynamic viscosity of the liquid, h is the height of the channel, θ _e is the equilibrium contact angle between the liquid and the channel wall, and θ _d is the dynamic contact angle between the liquid and the channel wall.

For a rectangular channel with a depth h and a width w, when the incompressible Newtonian liquid is capillary flow in the micro/nano channel, the Newtonian kinetic equation is:

where l(t) is the flow distance of the liquid at time t, l′(t) is the first derivative of l(t), l″(t) is the second derivative of l(t), ρ is the liquid density, and σ is the Liquid surface tension, θ _e is the equilibrium contact angle between the liquid and the channel wall, η is the liquid dynamic viscosity, h is the channel height, w is the channel width, and g is the gravitational acceleration. For micro/nano-scale channels, the inertial force term can be ignored and the influence of the gravity term, and in the micro/nano channel, the channel depth is much smaller than the channel width (ie h<<w), so the theoretical relationship between the liquid flow length and time can be deduced as: where A _LW is the theoretical slope, That is, when the liquid is determined, its related parameters are determined, and the theoretical relationship between the flow length and time can be obtained by using the theoretical relationship. This theoretical relationship is the current macroscopic theoretical model for predicting the capillary flow process, which is LW model. For a channel of a certain depth h, if the liquid surface tension σ, the equilibrium contact angle θ _e between the liquid and the channel wall, and the liquid dynamic viscosity η remain unchanged during the liquid flow, then the flow distance l(t) is the same as A linear relationship, that is, A _LW is a constant. Observing the model, if you know the channel depth h, and the related parameters (liquid surface tension σ, the equilibrium contact angle θ _e between the liquid and the channel wall, the liquid dynamic viscosity η), you can use this model to predict the liquid in micro/nano. velocity in the channel, thereby designing the micro/nanofluidic system according to the experimental needs. Based on this model, a large number of scholars have carried out experimental studies, and mainly obtained the following three conclusions: 1. The qualitative analysis results show that the current flow trend of the capillary flow process in the micro/nano channel can be predicted by the existing macro theoretical model, that is, the flow When the flow distance l(t) and 2. The quantitative analysis results show that the current macroscopic theoretical prediction model cannot explain the experimental phenomenon well, and the flow velocity of the liquid in the experiment is generally lower than the theoretical prediction value, that is, the fitting slope of the experimental results (A _exp ) < Theoretical slope (A _LW ); 3. It is not certain what causes the deviation between the experimental value and the theoretical value. That is to say, the current macroscopic theoretical model cannot accurately predict the capillary flow process in the micro/nano channel, and therefore cannot accurately predict the dynamic viscosity of the liquid. Therefore, in practical application, it is necessary to establish a new model based on the theoretical relationship, that is, the new model established by the present invention. Based on the model established by the present invention, the dynamic viscosity of the liquid can be accurately measured.

Step 102: Determine the relationship model between the hydrodynamic viscosity and the actual fitting slope. According to the actual relationship model in step 103, the relationship model between the fluid dynamic viscosity and the actual fitting slope is derived:

Step 103: Determine the values of the unknown parameters a and b, thereby determining the relationship model between the hydrodynamic viscosity and the actual fitting slope expression.

The specific process of determining the unknown parameters is as follows:

Use N kinds of known liquids to carry out N groups of experiments, where N is an integer greater than 1;

According to the formula Obtain the fitting slope A _exp of each group of experiments in the N groups of experiments;

According to the formula Obtain the theoretical slope _ALW of each group of experiments in the N groups of experiments;

Obtain the ratio of the fitted slope and the corresponding theoretical slope of each group of experiments in the N groups of experiments, and get: where A _exp(k) represents the fitting slope obtained from the kth group of experiments, k=1, 2,...N, A _LW(k) represents the theoretical slope corresponding to the kth group of experiments, and σ _(k) represents the kth group of experiments The surface tension of the liquid in the experiment, θ _e(k) represents the equilibrium contact angle between the liquid and the channel wall in the k-th group of experiments, η _(k) represents the theoretical value of the dynamic viscosity of the liquid in the k-th group of experiments;

According to the relevant parameters of the known liquids in the N groups of experiments, the corresponding parameters of the known liquids in each group of experiments are obtained. parameters, wherein the relevant parameters include the liquid surface tension σ _(k) , the equilibrium contact angle θ _e(k) between the liquid and the channel wall, and the theoretical value of the liquid dynamic viscosity η _(k) ;

Determine the values of the a and b.

This process is to use the known parameters of the known liquid (including the dynamic viscosity of the liquid is known, and the theoretical value of the dynamic viscosity of the liquid refers to the known viscosity of the known liquid) to conduct experiments, so as to determine the unknown parameters of the model and determine the model. The expression of , and then the dynamic viscosity of the liquid can be determined by using this model when the dynamic viscosity of the liquid is unknown.

Since a and b are parameters related to the channel, the values of parameters a and b are unchanged when the channel parameters are unchanged, that is, the relationship between the corresponding actual fitting slope and dynamic viscosity. It is fixed. This method of determining the values of parameters a and b is more suitable for obtaining the values of parameters a and b through liquid experiments when the number of channels is small or even only one, which is relatively fast.

When the channel parameters change (the channel height h changes), the parameters a and b change, and the relationship model Also varies due to changes in parameters a and b. Therefore, in the case of channel changes, the relationship between the channel height h and the parameters a and b can be obtained through several sets of experiments, then when the channel height is known, there is no need to conduct experiments with multiple groups of known liquids to determine the parameter a. and b, the values of parameters a and b can be determined directly according to the relationship between the channel height h and the parameters a and b, and the corresponding model is easy to determine. The specific process of determining the relationship between the channel height h and the parameters a and b is:

Obtain the relationship model of flow length and time in the liquid flow process corresponding to M groups of channels with different depths The values of the unknown parameters a _(i) and b _(i) in , where M is an integer greater than 1, a _(i) and b _(i) are unknown parameters related to the channel depth h _(i) , and the channel depth h _{( i)} is the depth of channel i;

The relationship function h=f(a,b) between the channel depth h and the unknown parameters a, b and the relationship function a=g(b) between the unknown parameters a and b are determined.

This method of determining the values of parameters a and b is more suitable for a large number of channels. At this time, it takes a lot of time and liquid to determine the values of parameters a and b by performing liquid experiments on each channel, and the efficiency is low. Therefore, through a limited number of channels After determining the values of parameters a and b in the liquid experiment, determine the relationship function between the channel depth and parameters a and b, you can directly determine the values of parameters a and b according to the channel depth, so as to directly determine the relationship model, which can greatly save time and avoid waste, At the same time, the efficiency of model determination is improved.

Step 104: Determine the dynamic viscosity of the liquid according to the actual fitting slope. In the case where the channel wall and the liquid are determined, the relevant parameters of the liquid are determined, then the model is used According to the actual fitting slope, the dynamic viscosity η of the liquid can be obtained.

Fig. 2 is a system structure diagram of the present invention for measuring liquid viscosity. As shown in Figure 2, the system includes:

The relationship model establishment module 201 between the flow length and time is used to establish the actual relationship model between the liquid flow length and time: where a and b are unknown parameters related to the channel depth, A _exp is the actual fitting slope, l(t) is the flow distance of the liquid at time t, σ is the liquid surface tension, η is the liquid dynamic viscosity, and h is the channel height , θ _e represents the equilibrium contact angle between the liquid and the channel wall, θ _d represents the dynamic contact angle between the liquid and the channel wall;

The relationship model determination module 202 between the hydrodynamic viscosity and the actual fitting slope is used to determine the relation model between the hydrodynamic viscosity and the actual fitting slope:

The unknown parameter determination module 203 is used to determine the values of the unknown parameters a and b, and determine the relationship model

The unknown parameter determination module 203 specifically includes:

An experiment control unit, used to perform N groups of experiments using N kinds of known liquids; N is an integer greater than 1;

Fitting slope acquisition module, which is used according to the formula Obtain the fitting slope A _exp of each group of experiments in the N groups of experiments;

Theoretical slope acquisition unit, which is used according to the formula Obtain the theoretical slope _ALW of each group of experiments in the N groups of experiments;

The ratio calculation unit is used to calculate the ratio of the fitted slope of each group of experiments in the N groups of experiments to the corresponding theoretical slope, and obtain: where A _exp(k) represents the fitting slope obtained from the kth group of experiments, k=1, 2,...N, A _LW(k) represents the theoretical slope corresponding to the kth group of experiments, and σ _(k) represents the kth group of experiments The surface tension of the liquid in the experiment, θ _e(k) represents the equilibrium contact angle between the liquid and the channel wall in the k-th group of experiments, η _(k) represents the theoretical value of the dynamic viscosity of the liquid in the k-th group of experiments;

The liquid parameter calculation unit is used to obtain the corresponding parameters of the known liquid in each group of experiments according to the relevant parameters of the known liquid in the N groups of experiments parameters, wherein the relevant parameters include the liquid surface tension σ _(k) , the equilibrium contact angle θ _e(k) between the liquid and the channel wall, and the theoretical value of the liquid dynamic viscosity η _(k) ;

An unknown parameter determination unit for determining the values of a and b.

The kinematic viscosity determination module 204 is configured to determine the kinematic viscosity of the liquid according to the actual fitting slope of the liquid flow.

The system further includes: a module for determining unknown parameters corresponding to channels of different depths, which is used to obtain a relationship model between flow length and time in the liquid flow process corresponding to M groups of channels with different depths after determining the values of a and b. The values of the unknown parameters a _(i) and b _(i) in , where M is an integer greater than 1, a _(i) and b _(i) are unknown parameters related to the channel depth h _(i) , and the channel depth h _{( i)} is the depth of channel i;

The relationship function determination module is used to determine the relationship function h=f(a,b) between the channel depth h and the unknown parameters a and b and the relationship function a=g(b) between the unknown parameters a and b.

Fig. 3 is the structure diagram of the device for measuring liquid viscosity according to the present invention. As shown in FIG. 3 , the measurement device includes: a power supply 301 , a sample introduction device 302 , a micro/nano channel 303 , a temperature control device 304 , a controller 305 , a data acquisition device 306 , and a display device 307 .

The power supply 301 is connected to the sampling device 302;

The output end of the sampling device 302 is connected to the inlet of the micro/nano channel 303, and the outlet of the micro/nano channel 303 is directly connected to the atmosphere; the first output end of the controller 305 is connected to the input end of the sampling device 302; the sampling device 302 is a In an open system, manual injection can be selected, or automatic injection can be realized by controlling the injection device through the controller 305.

The second output end of the controller 305 is connected to the input end of the temperature control device 304; the micro/nano channel 303 is located inside the temperature control device; the temperature control device 304 is used to control the temperature of the micro/nano channel 303 according to the instruction of the controller 305, thereby Controls the temperature of the liquid inside. Due to the small size of the micro/nano channel 303, the amount of liquid required is extremely small. When such a small amount of liquid enters the micro/nano channel 303, the liquid and the channel wall are fully contacted for heat exchange, and the liquid temperature will instantly approach the channel wall temperature, which can be approximated Considering that the liquid temperature is equal to the wall temperature, the purpose of controlling the liquid temperature can be achieved.

The data collection device 306 is used to collect the flow distance and time of the liquid; the data collection device 306 can adopt two structures:

(1) FIG. 4 is a structural diagram of the first embodiment of the data acquisition device. As shown in FIG. 4 , the data acquisition device includes: an E group of photoelectric components 401 , where E is an integer greater than 2 (the first photoelectric components 10 are arranged in sequence in the figure). , the second optoelectronic component 11, the third optoelectronic component 12, the fourth optoelectronic component 13, the fifth optoelectronic component 14, the sixth optoelectronic component 15), the timing circuit 402, and the first data processing device 403; each group of optoelectronic components 401 includes a An optical transmitter 4011 and an optical receiver 4012, the E optical transmitters of the E group optoelectronic components 401 are located under the micro/nano channel 404 in turn, and the E optical receivers 4012 of the E group optoelectronic components 401 are located in sequence. The top of the micro/nano channel is arranged corresponding to the E light emitters; the E light receivers 4012 of the E group photoelectric components 401 are connected to the timing circuit 402 ; the first data processing device 403 It is connected to the output end of the timing circuit 402, and is used to obtain the E group flow of the liquid according to the distance between the E group photoelectric components 401 and the time when the liquid in the micro/nano channel 404 reaches each group of photoelectric components distance and time. In a specific implementation, two adjacent groups of optoelectronic components may be set at a distance of 1 μm to 100 μm. During the measurement process, the liquid flows through the micro/nano channel 404 under the action of capillary force. When the first group of optoelectronic components 10 detects the passage of the liquid end face in the micro/nano channel 404, the timing circuit 402 records the time. The second optoelectronic component 11, the third optoelectronic component 12, the fourth optoelectronic component 13, the fifth optoelectronic component 14, and the sixth optoelectronic component 15 respectively record the time when the liquid end face passes by the timing circuit 402, and the data is finally transmitted to the first data processing device In 403, the first data processing device 403 obtains multiple sets of flow distances and times of the liquid according to the distance between the recording time and the photoelectric component 401.

(2) FIG. 5 is a structural diagram of Embodiment 2 of the data acquisition device. As shown in FIG. 5 , the data acquisition device includes: F light sources 501 , F photoelectric sensors 502 (photocells can be used), and a second data processing device 503 ; the F light sources 501 correspond to the F photoelectric sensors 502 one-to-one ; F is an integer greater than 2, the F photosensors 502 are sequentially located above the micro/nano channel 504, and the F light sources 501 are sequentially located below the micro/nano channel 504, opposite to the F photosensors 502 Setting; the second data processing device 503 is connected to the output ends of the F photosensors 502 for reaching each photosensor according to the distance between the F photosensors 502 and the liquid in the micro/nano channel 504 time to obtain the flow distance and time of group F of the liquid. During measurement, the LED light source 501 emits light. When the liquid flows, the light is blocked, and the photocell 502 cannot receive the light signal and changes. The system converts this light signal into an electrical signal and records it, that is, automatically records the flow of the liquid. time.

The input end of the controller 305 is connected to the data acquisition device 306, and is used for using the relationship model of the liquid flow length and time according to the liquid distance and time collected by the data acquisition device 306 Obtain the actual fitted slope A _exp , which is also used to combine the theoretical relationship between liquid flow length and time Determine the values of the unknown parameters a and b, and determine the relationship model between the hydrodynamic viscosity and the actual fitted slope According to the actual fitting slope of the liquid flow, determine the dynamic viscosity of the liquid, where l(t) represents the flow distance of the liquid at time t, σ represents the surface tension of the liquid, η represents the dynamic viscosity of the liquid, h represents the channel height, θ _e represents the equilibrium contact angle between the liquid and the channel wall, a and b are unknown parameters related to the channel depth.

The measuring device further includes a display device 307 , the input end of the display device 307 is connected to the third output end of the controller 305 for displaying the hydrodynamic viscosity data output by the controller 305 .

In order to improve the measurement efficiency, the micro/nano channel 303 includes a plurality of channels with different depths, and there are at least 5 channel depths; in order to avoid infection, the channels in the micro/nano channel 303 are all disposable; /Nanochannels are long straight. The channel with a depth of nanometers is used as a capillary to reduce the use of experimental liquid, and the liquid flow is driven by capillary pressure, eliminating the need for a differential pressure measurement system. The micro/nano channel with a depth of nanometers requires a very small amount of liquid, which can be less than 1 μl; the micro/nano channel is one-time use, avoids infection, does not need to clean the device, and the channel processing technology is mature; the device is simple, and the liquid is in the capillary. It flows into the micro/nano channel driven by pressure, no external pressure device is required, and no pressure measurement components are required; the operation is simple, easy to carry, and the measurement is fast and the result is reliable.

The measurement process of the whole measurement device is as follows:

For the micro/nano channel 303 with known depths h ₁ , h ₂ , h ₃ , h ₄ , h ₅ , first remove the micro syringe pump in the sampling device 302 and suck a simple Newtonian liquid (such as ionized water), then put the micro-syringe pump into the sampling device 302;

Turn on the power supply 301 and the controller 305, turn on the temperature control device 304, wait for it to work stably, the sampling device 302 sends the Newtonian liquid to the inlet of the micro/nano channel 303, and the liquid flows into the micro/nano channel 303 under the action of capillary force The data acquisition device 306 measures the distance of the liquid at different times. Taking the data acquisition device shown in FIG. 4 as an example, the process is as follows: when the liquid end face passes through the photoelectric component 10, the timing circuit 402 records the time _t1 . , in the same way, the photoelectric components 11, 12, 13, 14, 15 respectively record the time t ₂ , t ₃ , t ₄ , t ₅ , t ₆ when the liquid end face flows, and all the data are transmitted to the first data processing device 403 , the first data processing device 403 obtains 6 groups of data of flow distance l and time t according to the distance between the photoelectric components and the times t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , and t ₆ ;

The controller 305 receives the collected data (6 groups of data of flow distance l and time t) transmitted by the first data processing device 403 in the data collection device 306, and obtains and records the experimental slopes A _exp1 and A _exp2 of the experimental data by fitting and recording. , A _exp3 , A _exp4 , A _exp5 ;

In the same way, then use other Newtonian liquids (such as isopropanol, ethanol, 70% glycerol, 30% glycerol, etc.) to carry out similar experiments to obtain the slope A _exp of each experiment, and the controller 305 will record the depth channel according to each depth channel. (For example, if 5 channels are included, corresponding to 5 channel depths, the viscosity of 5 kinds of liquids to be tested can be measured at one time) A _exp /A _LW and (σ·cosθ _e /η) values of the liquid experiment in the liquid experiment, each The experimental data corresponding to the depth channel is used as a set of data, and the relationship between A _exp /A _LW and (σ·cosθ _e /η) is drawn in the rectangular coordinate system, so that according to the formula Get the a and b values of the depth channel. The five groups of a and b values obtained in turn are fitted to obtain the relationship between the a and b values and the channel depth, as well as the relationship between the a and b values. We can obtain h=f(a,b) and a=f (b), that is to say, for any channel with a known depth of h (the depth is on the order of nanometers), it can be directly calculated according to the known h=f(a,b) and a=f(b) The a and b values corresponding to the depth channel, so as to determine the model corresponding to the depth channel

Combined with the fitting slope, the dynamic viscosity of the liquid in the depth channel can be obtained by using the above formula;

The display device 307 displays the measured value of the kinematic viscosity in real time.

The present invention uses the device for measuring liquid viscosity, and the specific embodiment 1 of measuring according to the method for measuring liquid viscosity:

It is known that the channel depth h=68nm of a single channel in the micro/nano channel. In the specific operation, first remove the micro-syringe pump in the sampling device, absorb ethanol, and then put the micro-syringe pump into the sampling device;

Turn on the power supply and controller, turn on the temperature control device, and wait for it to work stably. The sampling device sends ethanol to the inlet of the channel group, and the liquid flows into the single channel under the action of capillary force. The data acquisition device measures the distance of the liquid at different times. , the process is as follows: when the liquid end surface passes through the photoelectric component 10, the timing circuit records the time t ₁ , and similarly, the time t 2 , t 3 , and the time t ₂ , t ₃ , and t ₄ , t ₅ , t ₆ , all data are transmitted to the first data processing device, the first data processing device will according to the distance between the photoelectric components and the time t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , t ₆ to obtain 6 groups of data of flow distance l and time t;

The controller obtains and records the experimental slope A _exp of this group of experimental data according to the data fitting of 6 groups of flow distances l and time t;

Then use isopropanol, 70% glycerol, and 30% glycerol to carry out similar experiments respectively, to obtain the experimental slope A _exp , the controller will record A _exp /A _LW and (σ·cosθ _e of each fluid experiment recorded) /η) value, draw the relationship between A _exp /A _LW and (σ·cosθ _e /η) in the Cartesian coordinate system, according to the formula Get a and b values. It can be obtained from the fitted line, a=0.86107, b=-0.00983, to determine the model corresponding to the depth channel

Finally, use a micro syringe pump to suck the liquid to be tested (deionized water), repeat the above steps, use the timing circuit to record the flow distance of the liquid to be tested at different times, and use the above model to obtain the viscosity of the liquid to be tested, which is about 1.008cP, which is basically consistent with the viscosity value of deionized water in the existing literature.

The present invention uses the device for measuring liquid viscosity, and the specific embodiment 2 of measuring according to the method for measuring liquid viscosity:

It is known that the channel depth h=116nm of a single channel in the micro/nano channel. During the specific operation, first remove the micro-syringe pump in the sampling device, absorb ethanol, and then put the micro-syringe pump into the sampling device;

Turn on the power supply and controller, turn on the temperature control device, and wait for it to work stably. The sampling device sends ethanol to the inlet of the channel group, and the liquid flows into the single channel under the action of capillary force. The data acquisition device measures the distance of the liquid at different times. , the process is as follows: when the liquid end surface passes through the photoelectric component 10, the timing circuit records the time t ₁ , and similarly, the time t 2 , t 3 , and the time t ₂ , t ₃ , and t ₄ , t ₅ , t ₆ , all data are transmitted to the first data processing device, the first data processing device will according to the distance between the photoelectric components and the time t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , t ₆ to obtain 6 groups of data of flow distance l and time t;

The controller obtains and records the experimental slope A _exp of this group of experimental data according to the data fitting of 6 groups of flow distances l and time t;

Then use isopropanol and 30% glycerol to carry out similar experiments respectively to obtain the experimental slope A _exp , and the controller will record the values of A _exp /A _LW and (σ·cosθ _e /η) of each fluid experiment , draw the relationship between A _exp /A _LW and (σ·cosθ _e /η) in the Cartesian coordinate system, according to the formula Get a and b values. It can be obtained from the fitted line, a=1.0593, b=-0.0097, to determine the model corresponding to the depth channel

Finally, use a micro syringe pump to suck the liquid to be tested (deionized water), repeat the above steps, use the timing circuit to record the flow distance of the liquid to be tested at different times, and use the above model to obtain the viscosity of the liquid to be tested, which is about 1.010cP, this value is basically consistent with the viscosity value of deionized water in the existing literature, and is basically consistent with the measurement data in the 68nm deep channel.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

In this paper, specific examples are used to illustrate the principles and implementations of the present invention. The descriptions of the above embodiments are only used to help understand the methods and core ideas of the present invention; meanwhile, for those skilled in the art, according to the present invention There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (8)

1. a kind of method for measuring liquid viscosity, which is characterized in that the described method includes:

Establish the actual relationship model of liquid length of flow and time:

Wherein a and b is related with channel depth Unknown parameter, A_expFor actual fit slope, l (t) indicates the flow distance of t moment liquid, and σ indicates surface tension of liquid, θ_e Indicate that the equilibrium contact angle between liquid and conduit wall, η indicate hydrodynamic viscosity, h indicates channel height；

Determine the relational model between hydrodynamic viscosity and practical fit slope:

The value for determining unknown parameter a and b determines the relational model The value of the determining unknown parameter a and b, specifically includes: being tested using the corresponding N group that carries out of liquid known to N kind, N is whole greater than 1 Number；According to formulaObtain every group in the experiment of N group The fit slope A of experiment_exp；According to formulaObtain every group in the experiment of N group The theoretical slope A of experiment_LW；The fit slope of every group of experiment in the experiment of N group and the ratio of theory of correspondences slope are obtained, is obtained:Wherein A_exp(k)The fit slope that expression kth group is tested, k=1,2 ... ... N, A_LW(k)Indicate that kth group tests corresponding theoretical slope, σ_(k)Indicate surface tension of liquid in the experiment of kth group, θ_e(k)Indicate kth Equilibrium contact angle in group experiment between liquid and conduit wall, η_(k)Indicate the theoretical value of hydrodynamic viscosity in the experiment of kth group；Root According to the relevant parameter of the known liquid of N group experiment, it is corresponding to obtain liquid known to every group of experimentGinseng Number, wherein the relevant parameter includes surface tension of liquid σ_(k), equilibrium contact angle θ between liquid and conduit wall_e(k), liquid it is dynamic The theoretical value η of power viscosity_(k)；Determine the value of a and the b；

According to the actual fit slope that liquid flows, the dynamic viscosity of the liquid is determined.

2. the method according to claim 1, wherein after the value of the determination a and b, further includes:

The relational model of length of flow and time during the corresponding liquid flowing in the channel of acquisition M group different depthIn unknown parameter a_(i)And b_(i)Value, wherein M is big In 1 integer, a_(i)And b_(i)For with channel depth h_(i)Related unknown parameter, channel depth h_(i)For the depth of channel i；

Determine the pass between the relation function h=f (a, b) and unknown parameter a and b between channel depth h and unknown parameter a, b It is function a=g (b).

3. a kind of system for measuring liquid viscosity, which is characterized in that the system comprises:

Length of flow and the relational model of time establish module, for establishing the actual relationship mould of liquid length of flow and time Type:Wherein a and b is related with channel depth Unknown parameter, A_expFor actual fit slope, l (t) indicates the flow distance of t moment liquid, and σ indicates surface tension of liquid, θ_e Indicate that the equilibrium contact angle between liquid and conduit wall, η indicate hydrodynamic viscosity, h indicates channel height；

Hydrodynamic viscosity and practical fit slope relational model determining module, for determining hydrodynamic viscosity and practical fitting Relational model between slope:

Unknown parameter determining module determines the relational model for determining the value of unknown parameter a and bThe unknown parameter determining module, specifically includes: experiment control list Member, for being tested using the corresponding N group that carries out of liquid known to N kind；Fit slope obtains module, for according to formulaThe fitting for obtaining every group of experiment in the experiment of N group is oblique Rate A_exp；Theoretical slope acquiring unit, for according to formulaObtain the experiment of N group In every group of experiment theoretical slope A_LW；Ratio calculation unit, for calculate N group experiment in every group of experiment fit slope and The ratio of theory of correspondences slope, obtains:Wherein A_exp(k)Indicate that kth group is tested The fit slope arrived, k=1,2 ... ... N, A_LW(k)Indicate that kth group tests corresponding theoretical slope, σ_(k)It indicates in the experiment of kth group Surface tension of liquid, θ_e(k)Indicate the equilibrium contact angle in the experiment of kth group between liquid and conduit wall, η_(k)It indicates in the experiment of kth group The theoretical value of hydrodynamic viscosity；Liquid parameter computing unit, the related ginseng of the known liquid for being tested according to the N group Number, it is corresponding to obtain liquid known to every group of experimentParameter, wherein the relevant parameter includes liquid surface Power σ_(k), equilibrium contact angle θ between liquid and conduit wall_e(k), hydrodynamic viscosity theoretical value η_(k)；Unknown parameter determines single Member, for determining the value of a and b；

Dynamic viscosity determining module, the actual fit slope for being flowed according to liquid, determines the dynamic viscosity of the liquid.

4. system according to claim 3, which is characterized in that the system also includes:

The corresponding unknown parameter determining module in different depth channel after the value for determining a and b, obtains the different depths of M group The relational model of length of flow and time during the corresponding liquid flowing in the channel of degree

In unknown parameter a_(i)And b_(i)Value, wherein a_(i)And b_(i)For with channel depth h_(i)Related unknown parameter, channel depth h_(i)For the depth of channel i；

Relation function determining module, for determine the relation function h=f (a, b) between channel depth h and unknown parameter a, b with And the relation function a=g (b) between unknown parameter a and b.

5. a kind of device for measuring liquid viscosity, which is characterized in that described device includes: power supply, sampling device, micrometer/nanometer Channel, temperature control device, controller, data acquisition device；

The power supply connects the sampling device；The output end of the sampling device and the entrance in the micrometer/nanometer channel connect It connects, the outlet in the micrometer/nanometer channel leads directly to atmosphere；

First output end of the controller connects the input terminal of the sampling device；The second output terminal of the controller connects The input terminal of the temperature control device；The micrometer/nanometer channel is located inside the temperature control device；

The data acquisition device is used to acquire flow distance and the time of liquid；

The input terminal of the controller connects the data acquisition device, the liquid for acquiring according to the data acquisition device Away from discrete time, the length of flow of liquid and the relational model of time are utilized

Obtain actual fit slope A_exp, also For combining the theoretical relationship of liquid length of flow and time The value for determining unknown parameter a and b determines the relational model between hydrodynamic viscosity and practical fit slopeAccording to the actual fit slope that liquid flows, the liquid is determined Dynamic viscosity, wherein l (t) indicates the flow distance of t moment liquid, and σ indicates that surface tension of liquid, η indicate that hydrodynamic is viscous Degree, h indicate channel height, θ_eIndicate that the equilibrium contact angle between liquid and conduit wall, a and b are related with channel depth unknown Parameter.

6. device according to claim 5, which is characterized in that the data acquisition device specifically includes: E group photoelectricity group Part, timing circuit, the first data processing equipment；Wherein E is the integer greater than 2；

Every group of photoelectric subassembly includes an optical transmitting set and an optical receiver, E optical transmitting set of the E group photoelectric subassembly according to The secondary lower section positioned at the micrometer/nanometer channel, E optical receiver of the E group photoelectric subassembly are sequentially located at the micron/receive The top in rice grain pattern road is correspondingly arranged with the E optical transmitting set；

E optical receiver of the E group photoelectric subassembly is connected with the timing circuit；

First data processing equipment is connect with the output end of the timing circuit, for according to the E group photoelectric subassembly it Between distance and the micrometer/nanometer channel in liquid reach time of each group of photoelectric subassembly, obtain the E group flowing of liquid away from Discrete time.

7. device according to claim 5, which is characterized in that the data acquisition device specifically includes: F light source, F Photoelectric sensor, the second data processing equipment；Wherein F is the integer greater than 2；

The F light source and the F photoelectric sensor correspond；The F photoelectric sensor be sequentially located at the micron/ The top of nanochannel, the F light source are sequentially located at the lower section in the micrometer/nanometer channel, with the F photoelectric sensor It is oppositely arranged；

Second data processing equipment is connect with the output end of the F photoelectric sensor, for according to the F photoelectric transfer Liquid reaches the time of each photoelectric sensor in the distance between sensor and the micrometer/nanometer channel, obtains the F of liquid Group flow distance and time.

8. device according to claim 5, which is characterized in that the measuring device further include: display device, the display The input terminal of device connects the third output end of the controller, for showing the hydrodynamic viscosity number of the controller output According to.