Piezoelectric micro-beam detection method and system for simulating cell contraction based on thermal stimulation
By applying a thermal excitation signal to a piezoelectric microbeam sensor to simulate myocardial cell contraction, a calibration model was established, which solved the problems of repeatability and accuracy in the detection of myocardial cell contractility in the prior art and achieved reliable quantitative detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QILU UNIVERSITY OF TECHNOLOGY (SHANDONG ACADEMY OF SCIENCES)
- Filing Date
- 2026-02-25
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies for detecting cardiomyocyte contractility suffer from poor repeatability and low success rates, making it difficult to establish stable and reliable quantitative detection standards, mainly due to their dependence on cell activity, adhesion status, and culture environment.
A piezoelectric microbeam detection method based on thermal excitation was adopted. By setting a temperature-sensitive material layer on the sensor and applying periodic thermal excitation signals to simulate cell contraction, a calibration model was established and replaced with real myocardial cells for detection.
It enables reliable, standardized, and quantitative detection of cardiomyocyte contractility, improves the repeatability and accuracy of the detection, and reduces the interference of biological variables.
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Figure CN122108401A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of piezoelectric microbeam detection technology, specifically a piezoelectric microbeam detection method and system based on thermal excitation to simulate cell contraction. Background Technology
[0002] The statements in this section only refer to the background technology related to this invention and do not necessarily constitute prior art.
[0003] Cardiac cardiomyocytes are the basic functional units of the heart muscle. Their contractile force is the direct driving force for the heart to pump blood and can reflect the functional state of the heart. Detecting the contractile force of cardiomyocytes not only helps to reveal the pathogenesis of cardiovascular and cerebrovascular diseases (CVDs), but also has important application value in drug screening and safety assessment.
[0004] The current mainstream method for detecting cardiomyocyte contractility involves directly seeding living cardiomyocytes onto the surface of microelectromechanical systems (MEMS) sensors (such as piezoelectric microbeams) for measurement. The contractile force of the cardiomyocytes causes nanoscale deformation of the microstructures (microbeams, micropillars), which is then detected via optical or electrical signals. However, this method is highly dependent on cell viability, adhesion, and culture environment, resulting in poor experimental repeatability, low success rate, and large data fluctuations, making it difficult to establish stable and reliable quantitative detection standards. Summary of the Invention
[0005] This invention provides a piezoelectric microbeam detection method and system based on thermal excitation to simulate cell contraction. A controllable contractile force is generated on a micro-curved beam sensor by using a temperature-controlled simulated material, thereby calibrating and establishing a mathematical model of the force-electric output relationship. After obtaining the calibration model, it is replaced with real cardiomyocytes, and their unknown contractile force can be deduced by measuring electrical signals.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention discloses a method for detecting piezoelectric microbeams based on thermal excitation simulating cell contraction, comprising the following steps: A piezoelectric microbeam sensor with a temperature-sensitive material layer on its surface is constructed; by applying a periodically varying thermal excitation signal to the temperature-sensitive material layer, it is caused to undergo periodic deformation and apply a periodic force to the piezoelectric microbeam sensor, thereby obtaining the first output electrical signal generated by the force. Based on the correspondence between the thermal excitation signal and the first output electrical signal, a calibration model for the piezoelectric microbeam sensor is established. Remove or replace the temperature-sensitive material layer, and culture or place target cardiomyocytes on the surface of the piezoelectric microbeam sensor; The second output electrical signal generated by spontaneous or stimulated contraction of cardiomyocytes is detected; the second output electrical signal is used as the input of the calibration model to calculate the quantitative value of cardiomyocyte contractility.
[0007] Furthermore, the piezoelectric microbeam sensor has a composite layered structure, comprising at least a flexible substrate made of PDMS (polydimethylsiloxane) and a piezoelectric functional layer made of PVDF (polyvinylidene fluoride).
[0008] Furthermore, the piezoelectric microbeam sensor is a microcantilever curved beam structure with a preset radius of curvature.
[0009] Furthermore, the temperature variation range of the periodically changing thermal excitation signal spans the phase transition temperature of the thermosensitive material layer to simulate the contraction and relaxation cycles of myocardial cells.
[0010] Furthermore, a calibration model is established, specifically: based on the extended dielectric theory, the force-electric coupling control equation of the piezoelectric microbeam sensor under periodic force is constructed and solved to obtain the quantitative mapping relationship between the thermal excitation signal, the deflection distribution of the piezoelectric microbeam sensor, and the first output electrical signal.
[0011] Furthermore, the temperature-sensitive material layer is a hydrogel material with a low critical dissolution temperature; the thermal excitation signal is used to drive the hydrogel material to undergo a hydrophilic-hydrophobic phase transition, thereby generating periodic volume changes and forces that match the contraction of myocardial cells.
[0012] Furthermore, the hydrogel material is poly(N-isopropylacrylamide) or its copolymer; the hydrogel material layer is uniformly coated on the surface of the piezoelectric microbeam sensor by spin coating or microfluidic method, and then cured by ultraviolet light to obtain a set thickness to simulate the mechanical dimensions of a single cell or cell cluster.
[0013] Furthermore, the process of establishing the calibration model includes: numerically discretizing and solving the force-electric coupling control equation and boundary conditions based on the differential quadrature method to obtain the numerical solution of the deflection distribution of the piezoelectric microbeam sensor and the first output electrical signal under the known periodic thermal excitation signal input; and then establishing an inversion mathematical model from the first output electrical signal to the equivalent force through parameter fitting.
[0014] Furthermore, after detecting the second output electrical signal generated during spontaneous or stimulated contraction of myocardial cells, the process also includes a signal processing step: filtering, amplifying, and converting the second output electrical signal to analog-to-digital conversion; extracting the characteristic voltage waveform synchronized with the myocardial cell beating cycle; and then inputting the processed signal data into a calibration model to calculate the quantitative dynamic parameters of the contractile force amplitude, contraction velocity, and relaxation velocity of a single myocardial cell beating.
[0015] A second aspect of the present invention discloses a piezoelectric microbeam detection system based on thermal excitation simulating cell contraction, comprising: Piezoelectric microbeam sensor module, with a temperature-sensitive material layer or cultured cardiomyocytes on its surface; The thermal excitation control module is used to apply periodically varying thermal excitation signals to the temperature-sensitive material layer; The signal detection module is configured to acquire a first output electrical signal and a second output electrical signal; The data processing module is configured to receive the second output electrical signal and calculate the quantitative value of the myocardial cell contractility through a calibration model.
[0016] Compared with existing technologies, one or more of the above technical solutions have the following beneficial effects: 1. By introducing a temperature-sensitive material layer and periodic thermal excitation, controllable and precisely reproducible physical stimulation replaces uncontrollable biological stimulation. In the core stage of sensor calibration, interference from biological variables such as cell activity, adhesion state, and culture environment is eliminated, resulting in extremely high consistency and repeatability in the model establishment phase. This lays the technical foundation for establishing the piezoelectric microbeam sensor as a reliable and standardized quantitative detection platform for cardiomyocyte contractility.
[0017] 2. A composite layered structure combining a flexible PDMS substrate and a PVDF piezoelectric functional layer is employed. On one hand, the excellent biocompatibility and flexibility of PDMS ensure the normal physiological activity of cardiomyocytes cultured on its surface and efficiently transmit cell contractile forces to the sensor body. On the other hand, the significant piezoelectric effect of PVDF material can sensitively convert minute mechanical deformations into measurable electrical signals. This composite structure achieves effective sensing of nano-Newtonian contractile forces of cardiomyocytes while maintaining biocompatibility.
[0018] 3. The piezoelectric microbeam sensor is designed as a microcantilever curved beam structure with a preset radius of curvature. Compared with a straight beam structure, this structure can generate greater strain and more significant deflection under the same load, thereby amplifying the piezoelectric output signal and effectively improving the sensor's detection sensitivity and signal-to-noise ratio, making it more suitable for detecting the weak contractile force generated by myocardial cells.
[0019] 4. By controlling the temperature variation range of the periodic thermal excitation signal to span the phase transition temperature of the temperature-sensitive material layer, a reversible and dramatic hydrophilic-hydrophobic transition and volume change can be driven in the material. This transition simulates the core mechanical behavior of myocardial cell contraction and relaxation cycles, making the excitation force generated during the calibration phase closer to real physiological contraction in amplitude, frequency, and waveform, thereby improving the physiological relevance of the calibration model and the accuracy of subsequent inversion calculation results.
[0020] 5. A calibration model is established by constructing force-electric coupling control equations based on extended dielectric theory. This theory, by introducing higher-order coupling terms such as strain gradient and electric field gradient, can more accurately describe the complex electromechanical coupling behavior of piezoelectric materials and structures at the micrometer scale. Compared with the traditional piezoelectric constitutive model, this method significantly improves the modeling accuracy and physical consistency of the mapping relationship from mechanical response (deflection) to electrical response (output potential) during microbeam bending deformation, providing a solid theoretical model for subsequent high-precision inverse calculation of cell contraction force.
[0021] 6. Hydrogels with low critical dissolution temperatures are selected as thermosensitive materials. Their phase transition behavior is clear and their response is reversible. Furthermore, their key mechanical parameters, such as elastic modulus and contractile strain, can be precisely controlled through chemical synthesis. This allows for flexible simulation of the mechanical properties of myocardial cells in different states (such as normal, hypertrophic, and diseased cells), making the calibration process more targeted and scalable. Attached Figure Description
[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0023] Figure 1 A schematic diagram of the laminated structure of a curved beam sensor provided in one or more embodiments of the present invention; Figure 2 A schematic diagram illustrating the physiological activity of cardiomyocytes on the PDMS surface, provided for one or more embodiments of the present invention; Figure 3 A schematic diagram illustrating the process of depositing a layer of synthetic polymer with material properties similar to cardiomyocytes on the surface of PDMS and simulating the contraction and relaxation of myocardial tissue by adjusting the temperature difference T, provided for one or more embodiments of the present invention. Figure 4 A schematic diagram of the piezoelectric microcantilever curved beam and its cylindrical coordinate system provided for one or more embodiments of the present invention; Figure 5 A schematic diagram illustrating the detection of myocardial cell contraction using a piezoelectric microcantilever curved beam model provided in one or more embodiments of the present invention; Figure 6 Δ provided for one or more embodiments of the present invention T At 40℃, the central angle θ 0 deflection w The impact; the total thickness of the beam L A diagram illustrating the impact; Figure 7 Δ provided for one or more embodiments of the present invention T At 40℃, the total thickness of the beam L For deflection wA diagram illustrating the impact; Figure 8 Δ provided for one or more embodiments of the present invention T At 40℃, the thickness of the piezoelectric layer n =2 μm Schematic diagram illustrating the impact on potential difference; Figure 9 Δ provided for one or more embodiments of the present invention T At 40℃, the thickness of the piezoelectric layer n =5 μm Schematic diagram illustrating the impact on potential difference; Figure 10 Δ provided for one or more embodiments of the present invention T At 40℃, the thickness of the piezoelectric layer n =10 μm Schematic diagram illustrating the impact on potential difference; Figure 11 Δ provided for one or more embodiments of the present invention T At 40℃, the thickness of the piezoelectric layer n =20 μm A schematic diagram illustrating the effect on the potential difference. Detailed Implementation
[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0026] As described in the background section, the current mainstream method for detecting cardiomyocyte contractility involves directly seeding living cardiomyocytes onto the surface of a microelectromechanical system (MEMS) sensor (such as a piezoelectric microbeam) for measurement. The contractility of the cardiomyocytes causes nanoscale deformation of the microstructures (microbeams, micropillars), which is then detected via optical or electrical signals. This method is highly dependent on cell viability, adhesion state, and culture environment, resulting in poor experimental repeatability, low success rate, and large data fluctuations, making it difficult to establish stable and reliable quantitative detection standards.
[0027] It is evident that while traditional MEMS sensors are highly sensitive, calibrating and interpreting their electrical signal output using real cells is extremely difficult (due to the unknown cellular forces). This solution provides a piezoelectric microbeam detection method based on thermal excitation simulating cell contraction. By using temperature-controlled simulated materials to generate controllable contractile forces on the micro-curved beam sensor, a mathematical model of the force-electrical output relationship can be calibrated and established. After obtaining the calibration model, replacing it with real cardiomyocytes allows the unknown contractile forces to be deduced by measuring the electrical signals.
[0028] The piezoelectric microbeam detection method based on thermal excitation to simulate cell contraction includes the following steps: Construct a piezoelectric microbeam sensor with a temperature-sensitive material layer on its surface; apply a periodically varying thermal excitation signal (Δ) to the temperature-sensitive material layer. T This causes periodic deformation and applies a periodic force to the piezoelectric microbeam sensor, acquiring the first output electrical signal generated by the force. φ1 ); Based on thermal excitation signal (Δ T ) and the first output electrical signal ( φ1 Based on the correspondence between the two, a calibration model for the piezoelectric microbeam sensor is established; Remove or replace the temperature-sensitive material layer, and culture or place target cardiomyocytes on the surface of the piezoelectric microbeam sensor; Detecting the second output electrical signal generated during spontaneous or stimulated contraction of cardiomyocytes ( φ2 ); with the second output electrical signal ( φ2 Using this as input to the calibration model, the quantitative value of myocardial cell contractility is calculated.
[0029] As a further implementation, the piezoelectric microbeam sensor is a composite layered structure, comprising at least a flexible substrate made of PDMS (polydimethylsiloxane) and a piezoelectric functional layer made of PVDF (polyvinylidene fluoride).
[0030] As a further implementation, the piezoelectric microbeam sensor is a microcantilever curved beam structure with a preset radius of curvature.
[0031] As a further implementation, the temperature-sensitive material layer is made of a polymer with a low critical dissolution temperature, which responds to thermal excitation signals (Δ... T Under the stimulation of ), a hydrophilic-hydrophobic transition occurs, resulting in macroscopic volume changes.
[0032] In this embodiment, the polymer with a low critical dissolution temperature can be poly-N-isopropylacrylamide or its copolymers or derivatives.
[0033] As a further implementation, the temperature variation range of the periodically changing thermal excitation signal (ΔT) spans the phase transition temperature of the temperature-sensitive material layer to simulate the contraction and relaxation cycles of myocardial cells.
[0034] As a further implementation method, the calibration model is established as follows: based on the extended dielectric theory, the force-electric coupling control equation of the piezoelectric microbeam sensor under periodic force is constructed and solved to obtain the thermal excitation signal (Δ). T ), deflection distribution of piezoelectric microbeam sensors ( w ), and the first output electrical signal ( φ 1) The quantitative mapping relationship between them.
[0035] The specific process of this solution is described in detail below. Figures 1-3 This demonstrates a microcantilever flexure sensor for detecting myocardial contractility, in which... Figure 1 The laminated structure of the curved beam sensor is shown. Figure 2 The physiological activities of cardiomyocytes on the PDMS surface were demonstrated. Figure 3 This demonstrates how a synthetic polymer with material properties similar to cardiomyocytes can be deposited on the surface of PDMS, and the contraction and relaxation of myocardial tissue can be simulated by adjusting the temperature difference T.
[0036] Step 1: Build a hardware testing platform.
[0037] like Figure 1 and Figure 2 As shown, a piezoelectric microcantilever beam platform was constructed, consisting of a PDMS (polydimethylsiloxane) elastic layer and a PVDF (polyvinylidene fluoride) piezoelectric layer. Temperature-sensitive materials containing target cardiomyocytes or simulated cardiomyocytes (target cardiomyocytes were used for detection, and temperature-sensitive materials containing simulated cardiomyocytes were used for modeling) were seeded onto the PDMS surface. Their excellent biocompatibility and flexibility ensured significant deflection of the microcantilever beam under myocardial contractile force, facilitating observation and analysis.
[0038] Step 2: Propose a physical simulation method for the contractile behavior of cardiomyocytes.
[0039] like Figure 3 As shown, in the modeling process, cardiomyocytes are idealized as a layer of temperature-sensitive elastic material. Using the principle of thermal analogy, the temperature difference Δ... T As an input stimulus, it simulates the contraction / relaxation cycle of myocardial cells.
[0040] The key constitutive parameters of this idealized material were determined based on myocardial physiological data: 1. Stimulus-Response: Defining the equivalent phase transition temperature T 0, making ΔT exist TWhen fluctuating around 0, the material produces active strain (10-15%) that matches the myocardium.
[0041] 2. Mechanical properties: The elastic modulus of the material is set as follows: ΔT The function is used to simulate the stiffness change of the myocardium from diastole (~10-50 kPa) to systole (modulus increases several times).
[0042] 3. Geometric Scale: The material thickness is determined based on the model scale, with the tissue scale referencing the chamber wall thickness (~10 mm) and the cell scale referencing the cell diameter (~20 μm).
[0043] Thermosensitive hydrogels (such as PNIPAM) can be used as the physical realization material. By adjusting its crosslinking degree, concentration, and microstructure, its strain (>10%), modulus (10-500 kPa), and response time (sub-second to second-level) can be made to approximate the physiological range of myocardium, making it suitable for the construction of biomimetic actuators. The synthesis process of this material is mature, and the raw materials are commercially available, but further optimization is needed to achieve precise matching with the dynamic mechanical properties of myocardium.
[0044] When the microbeam bends, the electromechanical coupling effect of the PVDF causes polarization, resulting in surface charge separation and the generation of an electric potential. φ That is, the first output electrical signal ( φ1 ).
[0045] The next step aims to establish the thermal excitation input Δ in the piezoelectric microcantilever curved beam platform. T With mechanical response (deflection) w and electrical response (electric potential) The mapping relationship between ).
[0046] Step 3: Establish a high-precision multiphysics coupling theoretical model.
[0047] Regarding the geometric characteristics of micro-cantilever curved beams, such as Figure 2 As shown, a model is established in cylindrical coordinates, and displacement components along each coordinate direction are defined. u i ( i = r , θ , y ).
[0048] in, , , ; In the above formula, R It is the radius of curvature of the beam. z It is the total thickness of the beam. w and u 0 represents the beam's deflection and initial displacement, respectively. ur , uθ and uy These represent the displacements of the microcantilever beam along the radial, length, and width directions, respectively.
[0049] The strain tensor is further derived from the displacement field. ε ij and strain gradient tensor η ijk This provides a theoretical basis for describing the mechanical behavior of materials at the microscale. Displacement is one such component. u i and strain ε ij and strain ε ij and strain gradient η ijk The relationship is as follows: , ; in, u i For displacement, ε ij In response to the situation.
[0050] During the modeling process, the Extended Electroelastic Theory was introduced: ; in, c ijkl and g ijklmn These are the material's elastic modulus and higher-order elastic coefficients, respectively. a ij and b ijkl These represent the dielectric constant of the material and higher-order electric field effects, respectively. P i and Q ij For the polarization tensor and polarization gradient, d ijk and f ijkl represents the piezoelectric coefficient and flexural coefficient of the material.
[0051] This theory significantly improves the modeling accuracy and physical consistency of electromechanical coupling behavior in microstructure systems by introducing the coupling relationship between stress, electric field, and their higher-order gradients. Within this theoretical framework, the system's energy density function per unit volume... U It is expressed as a function of strain, strain gradient, electric potential, electric field, and their associated coupling terms.
[0052] The expressions for stress, higher-order stress, electric field, and higher-order electric field are: ; ; ; ; Applying extended dielectric theory to this model, the internal energy density... U The expression is: ; Step 4, as follows Figure 5 As shown, a complete "input-output" mapping relationship is established.
[0053] right U Integrating the energy of the beam yields its total energy. U total : ; in, B It is the width of the beam. R It is the radius of curvature of the beam. θ 0 is the central angle of the curved beam.
[0054] By combining Hamilton's variational principle, the force and electrical control equations and boundary conditions of the micro-curved beam model are derived.
[0055] The forces in the micro-curved beam model are: ; ; The corresponding boundary conditions are: ; ; ; ; ; in, , , , ; in, c h Let be the elastic modulus of the beam. m , h , n These are the thicknesses of the cardiomyocyte-simulated layer, the elastic layer, and the piezoelectric layer, respectively. Figure 4 As shown, α is the coefficient of thermal expansion of the material.
[0056] ( ), ( ), ( ), ( ), ( ), ( )and See the appendix for details.
[0057] The electric control equation is: ; ; The corresponding boundary conditions are: ; in , Let be the vacuum permittivity of the material. Combining the above electrical control equations and boundary conditions, the polarization gradient of the beam model is obtained. P z and electric potential The expression: ; ; λ The expression is: ; ( See the appendix for details.
[0058] The governing equations fully consider microstructure scale effects, material heterogeneity, and multi-field interactions.
[0059] To solve this high-order coupled control equation system, the Differential Quadrature Method (DQM) is used for numerical discretization, combined with an iterative solution strategy to improve the stability and accuracy of the solution. The core idea is: function f ( x )about x of n The first-order partial derivative can be approximated by a weighted linear sum of the function values at all discrete points, i.e.: ; in A ij (n) for n Order weight coefficient matrix, N The number of discrete points.
[0060] Discretize the governing equations and boundary conditions; ; ; Discretization of the fixed-end boundary conditions of the microbeam: ; Discretization of boundary conditions at the free end of the microbeam: ; ; ; ; .
[0061] Based on the boundary conditions of the cantilever beam at the fixed and free ends, the beam's deflection can be obtained by solving the governing equations of the beam using an iterative method. w Along the central angle θ The distribution pattern of the piezoelectric layer in the curved beam is revealed. This result exposes the deformation behavior of the beam under load, which is particularly important for considering the bending characteristics of the structure. This is combined with the expression for the potential distribution of the piezoelectric layer in the curved beam. Derivation of electric potential The distribution trend along the thickness direction of the piezoelectric layer reveals the coupling mechanism between the local response characteristics and geometric deformation inside the piezoelectric layer.
[0062] Finally, multiphysics numerical simulations were completed using the MATLAB platform, and the input thermal excitation Δ was established. T With output mechanical response (deflection) w and electrical response (electric potential) The correspondence between ).
[0063] Based on the constitutive relation constructed using extended dielectric theory, under periodic thermal excitation conditions, the stress components... σij With temperature change Δ T There are explicit coupling terms between them, from which stress is derived. σij With temperature field Δ T The relationship was established, thereby establishing the equivalent contractile stress of the myocardium. σij Deflection with system output parameter w and electric potential φ The mapping relationship between them.
[0064] This completes the modeling stage for detecting cardiomyocyte contractility and allows us to move on to the stage of detecting the contractility of real cardiomyocytes. The specific steps are as follows: To achieve a physical simulation of the contraction / relaxation behavior of cardiomyocytes, a rapidly responsive thermosensitive hydrogel was used as the functional layer. The specific formulation and preparation process are as follows.
[0065] Formulation: Prepare a 10% (w / v) poly(N-isopropylacrylamide) (PNIPAM) prepolymer solution. The specific composition is: 1.0 g of N-isopropylacrylamide monomer (NIPAM), 0.01 g of crosslinking agent N,N'-methylenebisacrylamide (BIS) (1% of the total monomer mass), and 0.05 g of photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP), dissolved in 9 ml of deionized water to form a homogeneous solution.
[0066] Preparation method: Substrate treatment: The PDMS substrate is treated with oxygen plasma for 1 minute to enhance its surface hydrophilicity.
[0067] Film formation: The prepolymer solution was uniformly coated onto the treated PDMS surface using a spin coating method. The spin coating parameters were as follows: Step 1, 500 rpm for 10 seconds to spread the solution; Step 2, 2000 rpm for 30 seconds to form a uniform film.
[0068] Curing: The spin-coated sample is irradiated under ultraviolet light (wavelength 365 nm, intensity 15 mW / cm²) for 10 minutes to initiate free radical polymerization and form a stable temperature-sensitive hydrogel layer.
[0069] Post-treatment: The prepared sample was immersed in deionized water at 25°C (below its lower critical solution temperature LCST, approximately 32°C) for 24 hours to reach swelling equilibrium.
[0070] Key performance parameters: The PNIPAM hydrogel membrane prepared by the above method has a thickness of approximately 20 μm. Its equilibrium swelling ratio is 3.2 at 25°C and shrinks to 1.5 at 37°C, corresponding to approximately 15% in-plane shrinkage strain. Its elastic modulus is ~5 kPa at 25°C and increases to ~25 kPa at 37°C, effectively mimicking the stiffening characteristics of cardiomyocytes from relaxation to contraction.
[0071] A microbeam sensor is placed in the detection chamber, and a high-input-impedance preamplifier and data acquisition system are used to detect and record in real time the second output electrical signal generated by the PVDF piezoelectric layer when cells beat spontaneously or under electrical stimulation. φ 2). This signal presents a periodic voltage waveform synchronized with cell beating; The acquired raw signal φ 2. After filtering and noise reduction, the input is fed into the established calibration model, based on the established "potential". φ - Equivalent stress σ "The mapping relationship allows the φ2 value at each moment to be inversely calculated as the instantaneous equivalent shrinkage stress acting on the microbeam." σBased on the geometric dimensions of the microbeams, the absolute value of the contractile force (in nanonewtons, nN) generated by a single beat of the myocardial cell and the complete contractile dynamics curve are finally calculated.
[0072] from Figure 6 and Figure 7 It can be seen that the deflection w Along the central angle θ The direction gradually increases, reaching its maximum value at the free end. Figure 6 and Figure 7 The total thickness of the beam was further analyzed. L and central angle θ The effect of 0 on deflection. When other parameters remain constant, the initial value of the curved beam center angle... θ As 0 increases, the radius of curvature... R The reduction leads to an increase in the initial bending degree of the beam.
[0073] On the other hand, when the total thickness of the beam L When increased, deflection w The deflection shows a decreasing trend. According to the Euler-Bernoulli beam theory, the deflection of a cantilever beam... w With the moment of inertia of the cross section I Inversely proportional. For a rectangular cross-section, the moment of inertia... I With thickness L by L The increased rate of change of 3 leads to a significant increase in the beam's bending stiffness. Therefore, under the same external load, the beam will exhibit less deformation deflection.
[0074] like Figures 8-11 As shown, the distribution of electric potential along the thickness direction reflects the combined effect of these two coupling mechanisms, which must be considered in a unified manner in modeling and analysis in order to accurately describe the electromechanical coupling behavior in the microstructure. Figures 8-11 The thickness of the piezoelectric layer was also shown. n With respect to potential difference φ The effect of piezoelectric layer thickness. Results show that as the piezoelectric layer thickness increases... n The increase of piezoelectric coefficient d With flexural electrical coupling coefficient f The combined effect gradually weakens, leading to an overall potential difference. φ It shows a downward trend.
[0075] This method, by quantitatively detecting the contractile behavior of cardiomyocytes, not only provides a new technical approach for highly sensitive characterization of cardiomyocyte mechanical responses, but also reveals the coupled electromechanical behavior exhibited by cardiomyocytes in a physiological-like microenvironment. The constructed modeling framework can provide a theoretical basis and parameter reference for subsequent research on hybrid myocardial tissue engineering, experiments on the mechanical regulation of cardiac organoids, and multiphysics coupling simulations.
[0076] appendix: R It is the radius of curvature of the beam. m , h , n These are the trabecular cardiomyocyte simulation layers. c h Let be the elastic modulus of the beam. g The elastic coefficient; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; .
[0077] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A piezoelectric microbeam detection method based on thermal excitation simulating cell contraction, characterized in that, Includes the following steps: A piezoelectric microbeam sensor with a temperature-sensitive material layer on its surface is constructed; by applying a periodically varying thermal excitation signal to the temperature-sensitive material layer, it is caused to undergo periodic deformation and apply a periodic force to the piezoelectric microbeam sensor, thereby obtaining the first output electrical signal generated by the force. Based on the correspondence between the thermal excitation signal and the first output electrical signal, a calibration model for the piezoelectric microbeam sensor is established. Remove or replace the temperature-sensitive material layer, and culture or place target cardiomyocytes on the surface of the piezoelectric microbeam sensor; Detect the second output electrical signal generated during spontaneous or stimulated contraction of cardiomyocytes; Using the second output electrical signal as the input to the calibration model, the quantitative value of myocardial cell contractility is calculated.
2. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 1, characterized in that, The piezoelectric microbeam sensor has a composite layered structure, comprising at least a flexible substrate made of polydimethylsiloxane and a piezoelectric functional layer made of polyvinylidene fluoride.
3. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 1, characterized in that, The piezoelectric microbeam sensor is a microcantilever curved beam structure with a preset radius of curvature.
4. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 1, characterized in that, The temperature variation range of the periodically changing thermal excitation signal spans the phase transition temperature of the thermosensitive material layer to simulate the contraction and relaxation cycle of myocardial cells.
5. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 1, characterized in that, A calibration model is established, specifically: based on the extended dielectric theory, the force-electric coupling control equation of the piezoelectric microbeam sensor under periodic force is constructed and solved to obtain the quantitative mapping relationship between the thermal excitation signal, the deflection distribution of the piezoelectric microbeam sensor, and the first output signal.
6. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 1, characterized in that, The temperature-sensitive material layer is a hydrogel material with a low critical dissolution temperature; the thermal excitation signal is used to drive the hydrogel material to undergo a hydrophilic-hydrophobic phase transition, thereby generating periodic volume changes and forces that match the contraction of myocardial cells.
7. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 6, characterized in that, The hydrogel material is poly(N-isopropylacrylamide) or its copolymer; the hydrogel material layer is uniformly coated on the surface of the piezoelectric microbeam sensor by spin coating or microfluidic method, and then cured by ultraviolet light to obtain a set thickness to simulate the mechanical dimensions of a single cell or cell cluster.
8. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 1, characterized in that, The process of establishing the calibration model includes: numerically discretizing and solving the force-electric coupling control equation and boundary conditions based on the differential quadrature method to obtain the numerical solution of the deflection distribution of the piezoelectric microbeam sensor and the first output electrical signal under the known periodic thermal excitation signal input; and then establishing an inversion mathematical model from the first output electrical signal to the equivalent force through parameter fitting.
9. The piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in claim 1, characterized in that, After detecting the second output electrical signal generated when myocardial cells contract spontaneously or under stimulation, the process also includes a signal processing step: filtering, amplifying and converting the second output electrical signal to analog-to-digital conversion, extracting the characteristic voltage waveform synchronized with the myocardial cell beating cycle, and then inputting the processed signal data into a calibration model to calculate the quantitative dynamic parameters of the contractile force amplitude, contraction velocity and relaxation velocity of a single myocardial cell beating.
10. A piezoelectric microbeam detection system based on thermal excitation simulating cell contraction, used to implement the piezoelectric microbeam detection method based on thermal excitation simulating cell contraction as described in any one of claims 1-9, characterized in that, include: Piezoelectric microbeam sensor module, with a temperature-sensitive material layer or cultured cardiomyocytes on its surface; The thermal excitation control module is used to apply periodically varying thermal excitation signals to the temperature-sensitive material layer; The signal detection module is configured to acquire a first output electrical signal and a second output electrical signal; The data processing module is configured to receive the second output electrical signal and calculate the quantitative value of the myocardial cell contractility through a calibration model.