Experimental device and method for measuring shear flexoelectric coefficient of non-Newtonian fluid dielectric

Abstract

The invention discloses an experimental device and method for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric, and the experimental device comprises a halfpace-shaped container which is made of an insulator material, a cylindrical rotor which is located at the central axis of the interior of the container, a torque motor which is connected with the cylindrical rotor, and metal electrodes which are fixed on the upper and lower inner surfaces of the container. The charge amplifier is connected with the electrodes, the signal processing module is connected with the charge amplifier, the torque motor is used for rotating the cylindrical rotor to generate gradient velocity and strain on the non-Newtonian fluid in the container, and the non-Newtonian fluid dielectric generates shear strain gradient in the axial direction and the radial direction to generate flexoelectric effect electric polarization; polarized charges on the electrodes are sent to the charge amplifier through the electrodes and are converted into voltage signals, the voltage signals are transmitted to the signal processing module to obtain the number of charges, and the shear flexoelectric coefficient of the non-Newtonian fluid dielectric can be obtained by combining container structure parameters.

Description

Technical Field

[0001] The invention relates to the technical field of electromechanical coupling in material science, and in particular to an experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric and a loading method thereof. Background Art

[0002] The flexoelectric effect refers to the phenomenon that electric polarization is generated due to strain gradient, or material deformation is generated due to electric field gradient. As a mechanoelectric coupling property widely present in all dielectric materials, the flexoelectric effect is regarded as a promising alternative to the piezoelectric effect. It has been studied and applied in solid dielectric materials and liquid crystal materials. Although the flexoelectric effect in non-Newtonian fluid dielectric materials may have an important impact on the research of bioelectronics, programmed droplets, energy harvesting and ionic electronic devices, it cannot be studied due to the lack of theoretical and experimental methods. Summary of the invention

[0003] In order to fill the gaps in relevant theories and application fields, the purpose of the present invention is to provide an experimental device for measuring the shear flexoelectric coefficient of non-Newtonian fluid dielectrics and its loading method. The shear strain gradient in the non-Newtonian fluid is generated by designing the measuring device, and the flexoelectric effect in the non-Newtonian fluid dielectric is generated, so as to solve and calculate the shear flexoelectric coefficient of the non-Newtonian fluid dielectric.

[0004] In order to achieve the above objectives, the present invention adopts the following technical solutions.

[0005] An experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric comprises a terraced container 1 made of an insulating material, a cylindrical rotor 2 located on the central axis of the terraced container 1, a torque motor 3 connected to the upper end of the cylindrical rotor, a first electrode 4-1 fixed to the upper inner surface of the terraced container 1, a second electrode 4-2 fixed to the lower inner surface of the terraced container 1, a charge amplifier 5 connected to the first electrode 4-1 and the second electrode 4-2, and a signal processing module 6 connected to the output end of the charge amplifier 5; the torque motor 3 applies torque to the non-Newtonian fluid inside the terraced container 1 through the cylindrical rotor 2, the non-Newtonian fluid dielectric generates shear flow strain gradients along the axial and radial directions to generate electric polarization, and polarized charges with opposite signs and the same magnitude are induced on the first electrode 4-1 and the second electrode 4-2.

[0006] The terraced container 1 and the cylindrical rotor 2 are made of high-impedance insulator materials to ensure that there is no direct charge transfer between the first electrode 4 - 1 and the second electrode 4 - 2 .

[0007] The first electrode 4 - 1 and the second electrode 4 - 2 are made of highly conductive metal.

[0008] The measurement accuracy of the charge amplifier 5 can meet the micro-charge measurement requirements of non-Newtonian fluid dielectrics.

[0009] The measuring method of the experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric is described, wherein a torque motor 3 is used to apply torque to the non-Newtonian fluid inside a stepped container 1 through a cylindrical rotor 2, and the non-Newtonian fluid dielectric generates shear flow strain gradients in the axial and radial directions to generate electric polarization, and polarized charges with opposite signs and the same magnitude are induced on the first electrode 4-1 and the second electrode 4-2; the shear flexoelectric coefficient of the non-Newtonian fluid dielectric can be solved by solving the flexoelectric effect equation in combination with the measured charge amount and the structural parameters of the stepped container.

[0010] The method for solving the shear flexoelectric coefficient of the non-Newtonian fluid dielectric is as follows:

[0011] The cylindrical rotor 2 causes the corresponding shear flow of the non-Newtonian fluid in the axial torsion, and the cylindrical coordinate system is established with the bottom center of the terraced container 1 as the origin. Where ρ is the radial coordinate, is the circumferential coordinate, z is the axial coordinate; the shear stress of non-Newtonian fluid is expressed as:

[0012]

[0013] Where τ is the shear stress, η is the viscosity of the non-Newtonian fluid, V is the flow velocity, γ is the shear strain, t is the time; the radius is R 1 The cylindrical rotor 2 rotates in a cyclic sinusoidal form at a rotation frequency f, and the above equation (1) can be expressed as:

[0014]

[0015] Integrating over time t gives:

[0016]

[0017] Where V 0 is the surface velocity amplitude of the cylindrical rotor, R 2 (z) is the radius R of the terraced container 2 Relative to the size of coordinate z; in order to simplify the calculation, under the assumption of low rotation frequency and rotation speed, the strain amplitude is used, and the shear strain gradient along the z direction is:

[0018]

[0019] The average strain gradient along the z direction is generalized to:

[0020]

[0021] where h is the axial distance between the first electrode and the second electrode, both electrodes are immersed in the fluid; then the shear strain at z = 0 and z = h is:

[0022]

[0023] Among them, R 2max and R 2min are respectively the radius R of the terraced container 2 The maximum and minimum values ​​of

[0024] V 0 =ω 0 R 1 =2πfθ 0 R 1 (7)

[0025] Among them, ω 0 and θ 0 are the maximum angular velocity and average rotation angle amplitude of the rotation respectively; considering that the areas of the electrodes are different, the average area A is used av :

[0026]

[0027] Among them, A h and A 0 are the cross-sectional areas of the stepped container when z = h and z = 0 respectively; the flexoelectric effect of the material is expressed by the flexoelectric coefficient and the strain gradient as follows:

[0028]

[0029] Among them, P i , μ eff , γ and x are the polarization degree, effective flexoelectric coefficient, shear strain and shear strain gradient direction respectively; the polarization degree is described as the ratio of charge to charge distribution area; combining equations (5) and (9) to obtain the shear flexoelectric coefficient formula of non-Newtonian fluid dielectric:

[0030]

[0031] Among them, Q 0 is the measured charge;

[0032] The electric polarization of the non-Newtonian fluid dielectric is obtained by applying torque displacement to the cylindrical rotor 2, and the charge quantity Q measured by the signal processing module 6 and the charge amplifier 5 is converted into 0 , substituting into formula (10) we can solve the shear flexoelectric coefficient of the non-Newtonian fluid dielectric.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1) The present invention fills the blank in the field of measuring the shear flexoelectric coefficient of non-Newtonian fluid dielectrics.

[0035] 2) The present invention adopts a simple experimental measurement device, has lower processing requirements and smaller experimental difficulty, and can realize real-time measurement of shear flexoelectric effects of different types of non-Newtonian fluid dielectric materials.

[0036] In conclusion, the flexoelectric coefficient of liquid materials is obtained by the experimental device and the measurement method of the present invention, which fills the gaps and shortcomings of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the measurement system of the present invention DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, an experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric comprises a terraced container 1 made of an insulating material, a cylindrical rotor 2 located at the central axis of the terraced container 1, a torque motor 3 connected to the upper end of the cylindrical rotor, a first electrode 4-1 fixed to the upper inner surface of the terraced container 1, a second electrode 4-2 fixed to the lower inner surface of the terraced container 1, a charge amplifier 5 connected to the first electrode 4-1 and the second electrode 4-2, and a signal processing module 6 connected to the output end of the charge amplifier 5; the torque motor 3 applies torque to the non-Newtonian fluid inside the terraced container 1 through the cylindrical rotor 2, and the non-Newtonian fluid dielectric generates shear flow strain gradients in the axial and radial directions to generate electric polarization, and polarized charges with opposite signs and the same magnitude are induced on the first electrode 4-1 and the second electrode 4-2. By combining the measured charge amount with the structural parameters of the terraced container, solving the flexoelectric effect equation can solve the shear flexoelectric coefficient of the non-Newtonian fluid dielectric.

[0040] The method for solving the shear flexoelectric coefficient of the non-Newtonian fluid dielectric is as follows:

[0041] The cylindrical rotor 2 causes the corresponding shear flow of the non-Newtonian fluid in the axial torsion, and the cylindrical coordinate system is established with the bottom center of the terraced container 1 as the origin. Where ρ is the radial coordinate, is the circumferential coordinate, z is the axial coordinate; the shear stress of non-Newtonian fluid is expressed as:

[0042]

[0043] Where τ is the shear stress, η is the viscosity of the non-Newtonian fluid, V is the flow velocity, γ is the shear strain, t is the time; the radius is R 1 The cylindrical rotor 2 rotates in a cyclic sinusoidal form at a rotation frequency f, and the above equation (1) can be expressed as:

[0044]

[0045] Integrating over time t gives:

[0046]

[0047] Where V 0 is the surface velocity amplitude of the cylindrical rotor, R 2 (z) is the radius R of the terraced container 2 Relative to the size of coordinate z; in order to simplify the calculation, under the assumption of low rotation frequency and rotation speed, the strain amplitude is used, and the shear strain gradient along the z direction is:

[0048]

[0049] The average strain gradient along the z direction is generalized to:

[0050]

[0051] where h is the axial distance between the first electrode and the second electrode, both electrodes are immersed in the fluid; then the shear strain at z = 0 and z = h is:

[0052]

[0053] Among them, R 2max and R 2min are respectively the radius R of the terraced container 2 The maximum and minimum values ​​of

[0054] V 0 =ω 0 R 1 =2πfθ 0 R 1 (7)

[0055] Among them, ω 0 and θ 0 are the maximum angular velocity and average rotation angle amplitude of the rotation respectively; considering that the areas of the electrodes are different, the average area A is used av :

[0056]

[0057] Among them, A h and A 0are the cross-sectional areas of the stepped container when z = h and z = 0 respectively; the flexoelectric effect of the material is expressed by the flexoelectric coefficient and the strain gradient as follows:

[0058]

[0059] Among them, P i , μ eff , γ and x are the polarization degree, effective flexoelectric coefficient, shear strain and shear strain gradient direction respectively; the polarization degree is described as the ratio of charge to charge distribution area; combining equations (5) and (9) to obtain the shear flexoelectric coefficient formula of non-Newtonian fluid dielectric:

[0060]

[0061] Among them, Q 0 is the measured charge;

[0062] The electric polarization of the non-Newtonian fluid dielectric is obtained by applying torque displacement to the cylindrical rotor 2, and the charge quantity Q measured by the signal processing module 6 and the charge amplifier 5 is converted into 0 , substituting into formula (10) we can solve the shear flexoelectric coefficient of the non-Newtonian fluid dielectric.

[0063] As a preferred embodiment of the present invention, the terraced container 1 and the cylindrical rotor 2 are made of high-impedance insulator materials to ensure that there is no direct charge transmission between the first electrode 4-1 and the second electrode 4-2.

[0064] As a preferred embodiment of the present invention, the first electrode 4-1 and the second electrode 4-2 are made of highly conductive metal having a surface oxide dielectric with limited and uniform thickness and stable chemical properties. While preventing the system from undergoing chemical reactions to produce unexpected external electrical signals, it can also have good conduction characteristics for charge information of a smaller order of magnitude to achieve accurate measurement.

[0065] As a preferred embodiment of the present invention, the measurement accuracy of the charge amplifier 5 can meet the micro-charge measurement requirements of non-Newtonian fluid dielectrics.

Claims

1. An experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric, characterized in that: The invention comprises a terraced container (1) made of an insulating material, a cylindrical rotor (2) located on the central axis of the terraced container (1), a torque motor (3) connected to the upper end of the cylindrical rotor, a first electrode (4-1) fixed to the upper inner surface of the terraced container (1), a second electrode (4-2) fixed to the lower inner surface of the terraced container (1), a charge amplifier (5) connected to the first electrode (4-1) and the second electrode (4-2), and a signal processing module (6) connected to the output end of the charge amplifier (5); the torque motor (3) applies torque to the non-Newtonian fluid inside the terraced container (1) through the cylindrical rotor (2), and the non-Newtonian fluid dielectric generates shear flow strain gradients in the axial and radial directions to generate electric polarization, and polarized charges with opposite signs and the same magnitude are induced on the first electrode (4-1) and the second electrode (4-2).

2. The experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric according to claim 1, characterized in that: The terraced container (1) and the cylindrical rotor (2) are made of high-impedance insulating materials to ensure that there is no direct charge transmission between the first electrode (4-1) and the second electrode (4-2).

3. The experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric according to claim 1, characterized in that: The first electrode (4-1) and the second electrode (4-2) are made of highly conductive metal.

4. The experimental device for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric according to claim 1, characterized in that: The measurement accuracy of the charge amplifier (5) can meet the micro-charge measurement requirements of non-Newtonian fluid dielectrics.

5. The method for measuring the shear flexoelectric coefficient of a non-Newtonian fluid dielectric according to any one of claims 1 to 4, characterized in that: A torque motor (3) is used to apply torque to a non-Newtonian fluid inside a terraced container (1) via a cylindrical rotor (2), and the non-Newtonian fluid dielectric generates shear flow strain gradients in the axial and radial directions to generate electric polarization, and polarized charges with opposite signs and the same magnitude are induced on a first electrode (4-1) and a second electrode (4-2); the shear flexoelectric coefficient of the non-Newtonian fluid dielectric can be solved by solving the flexoelectric effect equation in combination with the measured charge amount and the structural parameters of the terraced container.

6. The measuring method according to claim 5, characterized in that: The method for solving the shear flexoelectric coefficient of the non-Newtonian fluid dielectric is as follows: The cylindrical rotor (2) causes a corresponding shear flow of the non-Newtonian fluid in the axial torsion, and a cylindrical coordinate system is established with the center of the bottom of the terraced container (1) as the origin. Where ρ is the radial coordinate, is the circumferential coordinate, z is the axial coordinate; the shear stress of non-Newtonian fluid is expressed as: Wherein, τ is shear stress, η is non-Newtonian fluid viscosity, V is flow field velocity, γ is shear strain, and t is time; a cylindrical rotor (2) with a radius of R1 rotates at a rotation frequency f in a cyclic sinusoidal form, and the above equation (1) is expressed as: Integrating over time t gives: Where V0 is the surface velocity amplitude of the cylindrical rotor, R2(z) is the radius R2 of the terraced container relative to the coordinate z; in order to simplify the calculation, under the assumption of low rotation frequency and speed, the strain amplitude is used, and the shear strain gradient along the z direction is: The average strain gradient along the z direction is generalized to: where h is the axial distance between the first electrode and the second electrode, both electrodes are immersed in the fluid; then the shear strain at z = 0 and z = h is: Among them, R 2max and R 2min are the maximum and minimum values ​​of the radius R2 of the terraced container, respectively, and V0=ω0R1=2πfθ0R1(7) Among them, ω0 and θ0 are the maximum angular velocity and the average rotation angle amplitude of the rotation respectively; considering that the areas of the electrodes are different, the average area A is used av : Among them, A h and A0 are the cross-sectional areas of the terraced container when z = h and z = 0 respectively; the flexoelectric effect of the material is expressed by the flexoelectric coefficient and the strain gradient as follows: Among them, P i , μ eff , γ and x are the polarization degree, effective flexoelectric coefficient, shear strain and shear strain gradient direction respectively; the polarization degree is described as the ratio of charge to charge distribution area; combining equations (5) and (9) to obtain the shear flexoelectric coefficient formula of non-Newtonian fluid dielectric: Where Q0 is the measured charge; The electric polarization of the non-Newtonian fluid dielectric is obtained by applying torque displacement to the cylindrical rotor (2), and the charge quantity Q0 measured by the signal processing module (6) and the charge amplifier (5) is substituted into the formula (10) to solve the shear flexoelectric coefficient of the non-Newtonian fluid dielectric.

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