System for measuring multiple mechanical parameters of soft material by using acupuncture process

Abstract

The invention discloses a system for measuring multiple mechanical parameters of a soft substance by using a needling process, and the system comprises a base which is fixed by using a sucker and is provided with a supporting seat at the top end; the stepping motor is fixed at the top end of the supporting seat and drives the sliding table to vertically move through a screw rod; the bridge type force sensor and the needle fixing device are connected to the sliding table through a supporting rod and used for fixing a needle and detecting the penetrating force in real time; the macro camera is arranged in the middle of the supporting seat through a clamping plate and used for shooting the surface deflection change of the soft material; a single chip microcomputer, a laser displacement sensor, a pulse generator, an RS485 digital-to-analog converter and a mobile power supply are arranged in the shell; the computer is used for receiving a force signal of the force sensor and a displacement signal of the laser displacement sensor, generating a force-displacement curve, and calculating the elastic modulus and the fracture toughness of the soft material through a preset algorithm in combination with deflection data of the macro camera; the method is high in spatial resolution and controllable in invasiveness.

Description

Technical Field

[0001] The present invention relates to the technical field of material testing and processing, and in particular to a system for measuring multiple mechanical parameters of soft materials by utilizing a needle puncture process. Background Art

[0002] Soft materials (such as gels, biological tissues, and polymers) are widely present in nature and in engineering applications. Their mechanical parameters (such as elastic modulus, fracture toughness, and shear modulus) directly determine their deformation, flow, and stability under external forces. By measuring these parameters, we can gain a deeper understanding of the physical properties of soft materials and their response mechanisms. Currently, there are many instruments at home and abroad that can measure the mechanical parameters of soft materials using different methods. For example, traditional mechanical testing instruments (such as tensile machines and compressors) are used to measure the elastic modulus and elongation at break of soft materials. However, soft materials are prone to large deformations, slippage, and even failure during testing. Rheometers, for example, determine the rheological properties and elastic modulus of a material by measuring the stress-strain relationship under shear or rotation, but they are not suitable for most soft materials.

[0003] Existing technology devices often use in vitro measurement devices, which are prone to large deformation or slippage, which can change the mechanical properties of biological tissues and fail to accurately reflect mechanical performance. However, in vivo measurement devices, such as instruments such as elastic imaging technology, have limited spatial resolution and are easily affected by human factors. Another example is implantable measurement based on microsensors, where miniature force sensors are implanted in the body to directly measure the elastic modulus of tissues or organs. However, this is an invasive procedure and requires solving problems such as biocompatibility and energy supply, which is technically difficult. These in vivo measurement devices are also very expensive, which is not conducive to their widespread use. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a system for measuring multiple mechanical parameters of soft matter using the acupuncture process, which is used to measure the elastic modulus, fracture toughness, viscoelasticity, relaxation, creep and other mechanical properties of soft matter. It solves the problem that current technical devices cause large deformation or even destruction of soft matter, while meeting the advantages of low cost, higher spatial resolution, and controllable invasiveness.

[0005] Technical solution: The system described in the present invention for measuring multiple mechanical parameters of soft matter using the acupuncture process includes: a base, a support base is provided at the top of which; a stepper motor is fixed to the top of the support base, driving the slide to move vertically through a screw; a bridge-type force sensor and a needle fixing device are connected to the slide, used to fix the needle and detect the penetration force in real time; a macro camera is arranged in the middle of the support base, used to capture the deflection changes on the surface of the soft matter; a shell is equipped with a single-chip microcomputer, a laser displacement sensor, a pulse generator, an RS485 digital-to-analog converter and a mobile power supply; a computer receives the force signal of the force sensor and the displacement signal of the laser displacement sensor, generates a force-displacement curve, and combines the deflection data of the macro camera to calculate the elastic modulus and fracture toughness of the soft matter through a preset algorithm.

[0006] Furthermore, the needle is a detachable structure, which is adaptable to needles of different diameters to meet measurement requirements.

[0007] Furthermore, the macro camera captures the dynamic deformation of the soft material surface during the acupuncture process in real time and uploads the data synchronously to the cloud server.

[0008] Furthermore, the preset algorithm includes: segmented analysis of the force-displacement curve during acupuncture to divide the insertion phase into the needling phase and the needling withdrawal phase; and solving the relationship between the insertion depth and stress distribution using differential equations:

[0009]

[0010] Solve the elastic modulus E by combining boundary conditions m,A and fracture toughness parameters.

[0011] The method of measuring multiple mechanical parameters of soft matter by using acupuncture process according to the present invention comprises the following steps:

[0012] (1) Controlling the stepper motor to drive the needle to penetrate the soft material at a preset speed, and synchronously collecting the force signal of the force sensor and the displacement signal of the laser displacement sensor;

[0013] (2) Recording the surface deflection of the soft material using a macro camera and correlating the data with the force-displacement curve;

[0014] (3) Calculate the stress value based on the force F at the deepest penetration and the needle diameter d

[0015] (4) Based on the differential equation and boundary conditions, solve the elastic modulus E of the soft material m,A and fracture toughness.

[0016] Furthermore, the penetration stage is divided into the non-penetration stage, the deepest penetration stage, the withdrawal stage to the deformation stability stage and the complete withdrawal stage. The force-displacement curve corresponding to each stage is used to calibrate the nonlinear mechanical response of the material.

[0017] Furthermore, the deflection data is used to correct the boundary conditions in the theoretical model, specifically: at 0 ≤ z < L2:

[0018]

[0019] At L2 ≤ Z < L2 + L1:

[0020]

[0021] Furthermore, the method is applicable to the in-situ measurement of mechanical parameters of soft materials such as gels, biological tissues or polymers, and the measurement spatial resolution reaches the sub-millimeter level.

[0022] Furthermore, the method is applicable A portable fetal heart rate monitoring device can realize the real-time extraction of fetal electrocardiogram signals by suppressing the maternal electrocardiogram components and pulse noise.

[0023] An electronic device according to the present invention includes a memory and a processor. The memory stores a computer program, and when the processor executes the program, any of the above methods is implemented.

[0024] A computer-readable storage medium according to the present invention stores a computer program, and when the program is executed by a processor, any of the above methods is implemented.

[0025] Advantageous effects: Compared with the prior art, the present invention has the following remarkable advantages: during the measurement process of the present invention, the measured soft material will not have problems of large deformation or even damage. At the same time, the present invention has a high spatial resolution and controllable invasiveness. It also has the advantages of low cost and being conducive to promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the device of the present invention;

[0027] Figure 2 It is a schematic diagram of the power system and data acquisition system of the present invention;

[0028] Figure 3 It is a schematic diagram of the experimental force-displacement of the present invention;

[0029] Figure 4 It is a graph of the change in the deflection of the skin-like gel of the present invention;

[0030] Figure 5 It is a diagram of the theoretical calculation model of the present invention

[0031] Figure 6 It is a comparison diagram of the theoretical calculated force-displacement of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

[0033] As Figure 1 shown, an embodiment of the present invention provides a system for measuring multiple mechanical parameters of soft matter during acupuncture, including a base. A support seat is provided at the top of the base, and a stepping motor is fixed at the top of the support seat. A sliding table is connected to a bridge-type force sensor and a needle fixing device by using a bracket. A macro camera is provided in the middle of the support seat for real-time observation of the patient's state. As Figure 2 shown, there is another housing, which is a schematic diagram of the power system and data acquisition system of the present invention. It includes a single-chip microcomputer, a laser displacement sensor, a pulse generator, an RS485 digital-to-analog converter, and a mobile power supply. When the device works, the speed and displacement of the stepping motor are controlled by the single-chip microcomputer. The stepping motor drives a screw rod, and then drives the sliding table. The sliding table is connected to the sensor to detect the penetration force during the acupuncture process, and at the same time is connected to the needle fixing device for vertical movement to achieve precise advancement and retraction of the needle. The needle is detachable and replaceable to meet different needs.

[0034] For data processing, the force sensor and the laser displacement sensor respectively transmit the force signal and the displacement signal to the computer to obtain a force-displacement curve, as Figure 3 shown. The tissue deformation state is photographed by the macro camera to obtain the surface deflection change of the skin-like gel, as Figure 4 shown. The acupuncture process is divided into four stages. Figure a is the stage before penetration, Figure b is the stage of penetrating to the deepest part, Figure c is the stage of pulling out until the gel deformation is stable, and Figure d is the stage of pulling out to the highest point, corresponding to the Figure 3 shown force-displacement curve. At the same time, the camera can monitor the patient's state in real time and upload the treatment data to the cloud in a timely manner. Combining the force-displacement curve and the deflection information, the tissue stiffness at the penetration position is calculated using a specific formula. The following is the formula calculation process:

[0035] First, the acupuncture model is simplified into the model as Figure 5 shown:

[0036] Among them, a is the radius of the needle, b is the radius of the soft matter, L1 is the distance that the needle penetrates into the soft matter, L2 is the distance from the bottom of the soft matter to the bottom of the needle, and a r-z coordinate system is established with the center of the bottom of the soft matter as the coordinate axis center.

[0037] Solve the differential equation:

[0038] At 0≤Z<L2:

[0039]

[0040] At L2≤Z<L2+L1:

[0041]

[0042] where, σ p is the magnitude of the stress applied to the tip of the fiber, is the average normal stress in the z - direction of the fiber, E f,A is the elastic modulus of the fiber, E m,A is the elastic modulus of the matrix, among which

[0043]

[0044] G f is the shear modulus of the fiber, G m is the shear modulus of the matrix.

[0045] By substituting the boundary conditions, the distribution of the average normal stress inside the needle can be obtained. The boundary conditions are as follows:

[0046]

[0047] The solution is obtained as follows:

[0048] When r = a, for 0 ≤ z < L2, the relationship of the normal stress of the matrix varying with z:

[0049]

[0050] where,

[0051] When r = a, for L2 ≤ Z < L_{1}+L2, the relationship of the normal stress of the matrix varying with z:

[0052]

[0053] Through the simplified relationship between deflection and normal stress:

[0054] <000015>

[0055] The relationship between the deflection and stress of the matrix when r = a is obtained:

[0056] For 0 ≤ z < L2:<00>

[0057]

[0058] For L2 ≤ z < L_{2}+L1, the deflection at the maximum height L_{1}+L2 is obtained:

[0059]

[0060] where is the distance where the force of the return needle segment is 0 in the curve, σp is the magnitude of the stress applied to the fiber tip:

[0061]

[0062] Where d is the diameter of the needle and F is the penetration force.

[0063] like Figure 6 As shown in Figure 2, the force-displacement curve of the acupuncture process was calculated using a theoretical formula and compared with the experimental results. The final stiffness of the soft material was obtained to be 0.1 MPa, which is basically consistent with the elastic modulus of the compression experiment.

Claims

1. A system for measuring multiple mechanical parameters of soft matter using acupuncture process, characterized in that: Comprising: A base (1), fixed by a suction cup (2), with a support base (3) provided at its top; a stepper motor (4), fixed to the top of the support base (3), driving a slide table (5) to move vertically through a screw; a bridge-type force sensor (6) and a needle fixing device (7), connected to the slide table (5) through a support rod (8), for fixing a needle (9) and detecting the piercing force in real time; a macro camera (10), arranged in the middle of the support base (3) through a clamping plate (11), for photographing the deflection change on the surface of the soft material; a housing (12), internally provided with a single-chip microcomputer (13), a laser displacement sensor (14), a pulse generator (15), a RS485 digital-to-analog converter (16) and a mobile power supply (17); a computer (18), receiving the force signal of the force sensor (6) and the displacement signal of the laser displacement sensor (13), generating a force-displacement curve, and combining the deflection data of the macro camera (9), calculating the elastic modulus and fracture toughness of the soft material through a preset algorithm.

2. The system for measuring multiple mechanical parameters of soft matter using acupuncture process according to claim 1, characterized in that: The needle is of a detachable structure, adapting needles of different diameters to meet the measurement requirements.

3. The system for measuring multiple mechanical parameters of soft matter using acupuncture process according to claim 1, characterized in that: The macro camera photographs the dynamic deformation on the surface of the soft material during the needle piercing process in real time, and synchronously uploads the data to a cloud server.

4. The system for measuring multiple mechanical parameters of soft matter using acupuncture process according to claim 1, characterized in that: Solve the elastic modulus E by combining boundary conditions m,A and fracture toughness parameters.

5. A method for measuring multiple mechanical parameters of soft matter using acupuncture process, characterized in that: The preset algorithm includes: a segmented analysis of the force-displacement curve during the needle piercing process, dividing the piercing stage and the needle retracting stage; combining differential equations to solve the relationship between the piercing depth and the stress distribution: Including the following steps: (1) Controlling the stepper motor to drive the needle to pierce the soft material at a preset speed, synchronously collecting the force signal of the force sensor and the displacement signal of the laser displacement sensor; (3) Calculate the stress value based on the force F at the deepest penetration and the needle diameter d (4) Based on the differential equation and boundary conditions, solve the elastic modulus E of the soft material m,A and fracture toughness.

6. The method for measuring multiple mechanical parameters of soft matter using acupuncture process according to claim 5, characterized in that: (2) Recording the deflection change on the surface of the soft material through the macro camera, and associating the data with the force-displacement curve; 7. The method for measuring multiple mechanical parameters of soft matter using acupuncture process according to claim 5, characterized in that: The piercing stage is divided into a non-piercing stage, a piercing-to-the-deepest stage, a pulling-out-to-the-deformation-stable stage and a completely pulling-out stage, and the force-displacement curves corresponding to each stage are used to calibrate the non-linear mechanical response of the material. The deflection data is used to correct the boundary conditions in the theoretical model. Specifically: the deflection distribution obtained through the macro camera is fitted using a theoretical formula to optimize the calculation result of the elastic modulus; the formula is as follows: At 0≤z<L2:

8. A method for measuring multiple mechanical parameters of soft matter using acupuncture process according to any one of claims 5 to 7, characterized in that: At L2≤Z<L2+L1:

9. An electronic device, characterized in that: The method is applicable to the in-situ mechanical parameter measurement of soft materials such as gels, biological tissues or polymers.

10. A computer-readable storage medium, characterized in that Including a memory and a processor, the memory stores a computer program, and when the processor executes the program, it implements the method according to any one of claims 5-8. Stores a computer program, and when the program is executed by the processor, it implements the method according to any one of claims 5-8.

Images