A method for preparing a flexible ionic piezoelectric material

Abstract

This invention discloses a method for preparing a flexible ion piezoelectric material, comprising the following steps: (1) preparation of a click chemical reaction prepolymer: polyethylene glycol diacrylate as an olefin monomer is mixed uniformly with a multi-thiol monomer to form a prepolymer; (2) polyethylene glycol, an ion medium, and an alkaline catalyst are added to the prepolymer, mixed uniformly in an ice-water bath, injected into an inverted structure mold, and heated to solidify to obtain a flexible ion piezoelectric material. The ion piezoelectric material prepared by the method of this invention has high sensitivity and high stability, and can generate a significant electrical signal under weak pulse pressure (<0.1 kPa), while maintaining zero volatilization and zero leakage for more than 30 days, thereby ensuring long-term signal stability.

Description

Technical Field

[0001] This invention relates to a method for preparing flexible ion piezoelectric materials. Background Technology

[0002] As people pay increasing attention to health issues, continuous and accurate blood pressure monitoring has become a core requirement for cardiovascular health management. Traditional cuff blood pressure monitors can only provide instantaneous readings, while catheter-based blood pressure monitors, although considered the "gold standard," are invasive procedures and difficult to widely use in outpatient or home settings. Therefore, non-invasive, continuously recording flexible sensors have become a research hotspot.

[0003] Existing flexible sensors include hydrogel-based capacitive sensors, ionogel sensors, and flexible ion-conductive materials. However, while hydrogel-based capacitive sensors offer high sensitivity, the easy evaporation of water causes signal drift (limiting their lifespan to <24 hours), resulting in insufficient stability. Ionogel sensors, while highly sensitive, are prone to ion leakage and mechanical creep, leading to insufficient stability and short lifespan. Existing flexible ion-conductive materials often employ free radical polymerization, resulting in severe chain transfer and termination during the reaction process. This leads to a highly heterogeneous cross-linked network (containing numerous suspended chains and locally dense regions). This irregular network structure generates severe stress concentration and energy dissipation under pressure, causing slow material rebound and signal lag. Furthermore, the randomness of ion transport channels results in a low piezoelectric coefficient, typically <10 mV / kPa. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for preparing flexible ion piezoelectric materials. The ion piezoelectric materials prepared by this method have high sensitivity and high stability. They can generate significant electrical signals under weak pulse pressure (<0.1kPa) and can maintain zero volatilization and zero leakage for more than 30 days, thereby ensuring long-term signal stability.

[0005] Technical solution: The preparation method of the flexible ion piezoelectric material of the present invention includes the following steps:

[0006] (1) Preparation of the prepolymer solution by clicking chemical reaction: Polyethylene glycol diacrylate (PEGDA) is mixed with polythiol monomers as olefin monomers to form a prepolymer solution;

[0007] (2) Polyethylene glycol (PEG) (in this invention, PEG is used as an additive to enhance the interaction with cations, promote the dissociation of anions, and improve the conductivity of the material), ionic medium and alkaline catalyst are added to the prepolymer liquid, mixed evenly in an ice-water bath, injected into an inverted structure mold, and heated to solidify to obtain a flexible ionic piezoelectric material.

[0008] The polymer matrix is ​​constructed through click chemistry to form a geometric network with a uniform topology (a regular cross-linked network structure). The polymer network and the ionic medium form selective ion transport channels through π-cation interactions, ion-dipole interactions, or cooperative hydrogen bonds. Under pressure, directional ion migration occurs. This structural feature enables the ion piezoelectric material to selectively transport ions of a certain charge, thereby obtaining high piezoelectric sensitivity.

[0009] In step (1), the multi-thiol monomer is a tetrafunctional thiol compound and a difunctional thiol compound; the tetrafunctional thiol compound is pentaerythritol tetrakis(3-mercaptopropionic acid) ester (CAS No.: 7575-23-7); the difunctional thiol compound is 2,2′-(1,2-ethylenedioxy)diethylthiol (CAS No.: 14970-87-7); the molar ratio of polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) ester and 2,2′-(1,2-ethylenedioxy)diethylthiol is 3~7:1~3:1~2.

[0010] In step (2), the ionic medium is one of 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), lithium bis(trifluoromethanesulfonyl)imide, ionic liquid 1-ethyl-3-methylimidazolium dicyandiamide salt, or ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]); the amount of the ionic medium added is 50% of the total mass of the gel (here, the gel refers to the final ionic piezoelectric material). The alkaline catalyst is one of triethylamine, diethylamine, or ethylamine, and the amount of the alkaline catalyst added is 4.5 × 10⁻⁶ of the total mass of the gel. -7 %; the amount of polyethylene glycol added is 15% of the total mass of the gel.

[0011] In step (2), the cavity surface of the anti-structure mold has a microstructure; the microstructure is a pyramid array structure, a hemispherical array structure, or a cylindrical array structure, used to amplify local deformation and induce asymmetric extrusion of ion channels, further increasing sensitivity. The heating and curing temperature is 60~80℃, and the curing time is 2~2.5 hours. In flexible ion piezoelectric materials, the strong interaction between the functional groups on the polymer chain segments and ions of a certain type of charge promotes the rapid transport of oppositely charged ions, thereby rapidly forming a significant piezoelectric voltage signal.

[0012] This invention utilizes click chemistry to construct a robust cross-linked network, coupling the reversible piezoelectric effect with an ionic conductive network. This generates a significant electrical signal even under weak pulse pressure (<0.1 kPa), improving sensitivity by an order of magnitude compared to traditional ionic hydrogels. The ionic liquid is anchored to the click chemistry cross-linked network through hydrogen bonds and other interactions, achieving zero volatilization and zero leakage for over 30 days, ensuring long-term signal stability. Furthermore, its bulk modulus is close to that of human skin, allowing for comfortable attachment to the radial artery region and continuous pulse wave capture without the need for a pressure cuff. This provides a foundation for the development of next-generation wearable blood pressure monitoring devices, such as integrating flexible ionic piezoelectric materials into metal sheets or flexible fabric electrodes, attaching them to the radial artery at the wrist for pulse wave monitoring: pressure acting on the surface microstructure creates stress concentration, driving ions to selectively migrate along a non-covalent network, generating a significant piezoelectric voltage signal; and for synchronous ECG monitoring: the material's high ionic conductivity allows for the capture of human bioelectrical signals at the same sensing interface.

[0013] This invention constructs a near-ideal polymer network through click chemistry. The uniform mesh size ensures that the material exhibits extremely low hysteresis and extremely high resilience under long-term cyclic pressure. By introducing other polymers into the polymer network, differentiated non-covalent binding energies are formed with the anions / cations in the ionic liquid, thereby generating a directional ion flow under pressure. This enhanced non-covalent interaction is more uniformly distributed in the well-ordered network, amplifying the difference in migration rates between anions and cations, thus enhancing the piezoelectric output. Simultaneously, the presence of microstructures further amplifies the local deformation gradient, thereby further enhancing the piezoelectric output. The high conductivity of the ionic piezoelectric material is used as an electrophysiological signal transmission channel (ECG), while its high piezoelectric coefficient is used to capture mechanical deformation (pulse wave). The homogeneous superposition and subsequent decoupling of the two signals are achieved through a circuit equivalent model.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The ion piezoelectric material prepared by the present invention has ultra-high sensitivity. Benefiting from the synergy of microstructure and selective transport, the ion piezoelectric coefficient is significantly improved (exceeding 1000mV / kPa); (2) The ion piezoelectric material prepared by the present invention has long-term stability. Non-covalent interaction effectively anchors the ionic liquid in the polymer network, which enhances the dissociation of anions and solves the problem of leakage of ion media; (3) The ion piezoelectric material prepared by the present invention also has good biocompatibility, which enables it to be applied to the skin for a long time; (4) The ion piezoelectric material prepared by the present invention can be used as a sensor for continuous monitoring of cardiovascular parameters. When used as a sensor, it can realize the synchronous acquisition of pulse wave and ECG signal, providing a more accurate data source for calculating continuous blood pressure through pulse wave transit time (PTT). Attached Figure Description

[0015] Figure 1 The voltage response of the flexible ion piezoelectric material prepared in Example 2 at 0.08 kPa is shown.

[0016] Figure 2 This is a schematic diagram illustrating the interaction between active functional groups on the polymer chain of the ion piezoelectric material of the present invention and cations.

[0017] Figure 3 The equivalent circuit diagram is shown when testing blood pressure using the flexible ion piezoelectric material prepared in Example 2.

[0018] Figure 4 A comparison chart showing the results of continuous 24-hour blood pressure testing between a blood pressure testing device constructed using the flexible ion piezoelectric material prepared in Example 2 and a finger clip blood pressure monitor.

[0019] Figure 5 This is a schematic diagram of the structure of a titanium sheet electrode integrated based on flexible ion piezoelectric material.

[0020] Figure 6 The voltage response of the flexible ion piezoelectric material prepared in Example 11 at 0.08 kPa is shown.

[0021] Figure 7 This is a schematic diagram illustrating the principle of piezoelectric signal generation using the ion piezoelectric material of the present invention.

[0022] Figure 8 This is a schematic diagram of a dual-mode sensor constructed based on the ion piezoelectric material of the present invention being attached to the radial artery to collect electrocardiogram-pulse wave composite signals;

[0023] Figure 9 This is a schematic diagram of the ECG-pulse wave composite waveform and a schematic diagram with feature point annotations. Detailed Implementation

[0024] Example 1

[0025] A method for preparing a flexible ion piezoelectric material includes the following steps:

[0026] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate (Shanghai Mairui Chemical Technology Co., Ltd.), pentaerythritol tetrakis(3-mercaptopropionic acid) (Shanghai Mairui Chemical Technology Co., Ltd.) and 2,2′-(1,2-ethylenedioxy)diethylthiol (Sigma-Aldrich Reagent Co., Ltd.) were mixed evenly in a molar ratio of 5:2:1 to obtain the prepolymer solution;

[0027] (2) Preparation of ion piezoelectric materials: 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide (Shanghai Titan Technology Co., Ltd.) accounting for 50% of the total gel mass and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7Triethylamine (wt%) from Sinopharm Chemical Reagent Co., Ltd. was stirred and cooled in an ice-water bath (stirring and cooling means that the temperature of the mixed liquid drops to about 0°C) and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0028] Example 2

[0029] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0030] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 5:2:1 to obtain the prepolymer solution;

[0031] (2) Preparation of ion-piezoelectric materials: Polyethylene glycol (Sigma-Aldrich Reagent Co., Ltd.) accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (Shanghai Titan Technology Co., Ltd.) accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0032] Example 3

[0033] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0034] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 5:2:1 to obtain the prepolymer solution;

[0035] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazolium dicyandiamide salt (Shanghai Titan Technology Co., Ltd.) accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0036] Example 4

[0037] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0038] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 5:2:1 to obtain the prepolymer solution;

[0039] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0040] Example 5

[0041] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0042] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) ester and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 7:3:1 to obtain the prepolymer solution;

[0043] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0044] Example 6

[0045] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0046] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) ester and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 3:1:1 to obtain the prepolymer solution;

[0047] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0048] Example 7

[0049] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0050] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) ester and 2,2′-(1,2-ethylenedioxydioxo)diethylthiol are mixed evenly in a molar ratio of 4:1:2 to obtain the prepolymer solution;

[0051] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0052] Example 8

[0053] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0054] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 5:2:1 to obtain the prepolymer solution;

[0055] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% diethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0056] Example 9

[0057] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0058] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 5:2:1 to obtain the prepolymer solution;

[0059] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% ethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0060] Example 10

[0061] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0062] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 5:2:1 to obtain the prepolymer solution;

[0063] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to an 80°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0064] Example 11

[0065] The method for preparing the flexible ion piezoelectric material of the present invention includes the following steps:

[0066] (1) Preparation of prepolymer solution: First, polyethylene glycol diacrylate, divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2′-(1,2-ethylenedioxydioxo)diethyl mercaptan are mixed evenly in a molar ratio of 4:1:2:1 to obtain the prepolymer solution;

[0067] (2) Preparation of ion piezoelectric materials: Polyethylene glycol accounting for 15% of the total gel mass, 1-ethyl-3-methylimidazolium dicyandiamide salt (Shanghai Titan Technology Co., Ltd.) accounting for 50% of the total gel mass, and 4.5 × 10⁻⁶ ppm of the total gel mass were added to the prepolymer solution. -7 wt% triethylamine was stirred and cooled in an ice-water bath, and then injected into an inverse structure mold (the cavity surface of the inverse structure mold has a microstructure; the microstructure is a pyramid array structure). The mold was then transferred to a 60°C oven for heating and curing for 2 hours to obtain a flexible ion piezoelectric material.

[0068] pass Figure 2 It is understood that the active functional groups on the polymer chain of the ion piezoelectric material of the present invention can effectively restrict the movement of cations through strong interaction with cations, thereby further increasing the diffusion rate difference of oppositely charged ions, and thus achieving a high ion piezoelectric coefficient.

[0069] The flexible ion piezoelectric material prepared in Example 2 was integrated into a titanium sheet electrode (such as...). Figure 5 After (as shown), an insulating material was pressed onto it, and the voltage response was detected using a CHI 760E electrochemical workstation and a nanovoltmeter. The material produced an average voltage response of approximately 90 mV under a pressure of only 0.08 kPa (as shown). Figure 1 As shown in the figure, the calculated sensitivity exceeds 1000mV / kPa.

[0070] After integrating the flexible ion-piezoelectric materials prepared in Examples 1, 3-7 with titanium sheet electrodes (other electrode materials such as conductive carbon electrodes can also be used), they were pressed with an insulating material, and the voltage response was detected using a CHI 760E electrochemical workstation and a nanovoltmeter. The average voltage generated by the materials under a pressure of 0.08 kPa was less than 60 mV, and the calculated sensitivity was less than 750 mV / kPa. This is because the ion medium used in Examples 3-4 itself has a small diffusion difference between anions and cations, and the interaction force between the corresponding anions and cations and the active functional groups on the polymer chain is also small. Therefore, the migration speed of anions and cations does not differ significantly, resulting in a low piezoelectric coefficient.

[0071] After integrating the flexible ion-piezoelectric materials prepared in Examples 8-10 into titanium sheet electrodes, they were pressed with an insulating material, and the voltage response was detected using a CHI 760E electrochemical workstation and a nanovoltmeter. The materials could produce an average voltage response of about 90 mV under a pressure of only 0.08 kPa, and the calculated sensitivity exceeded 1000 mV / kPa.

[0072] After integrating the flexible ionic piezoelectric material prepared in Example 11 into a titanium sheet electrode, it was pressed with an insulating material. Due to the strong π-cation interaction between the benzene ring and the imidazole cation, the free movement of the cation was further restricted, resulting in an approximately 45% increase in the measured ionic piezoelectric coefficient. The material produced an average voltage response of approximately 124 mV even under a pressure of only 0.08 kPa (e.g., ...). Figure 6 As shown in the figure, the calculated sensitivity exceeds 1550mV / kPa.

[0073] like Figure 8 As shown, the dual-mode sensor includes a flexible ion piezoelectric material (using the flexible ion piezoelectric material prepared in Example 11); the ion piezoelectric material is attached to the radial artery at the wrist of one arm of the human body, and a metal electrode is fixed to the side of the ion piezoelectric material away from the skin. A commercial gel electrode is attached to the other arm. The metal electrode and the commercial gel electrode are respectively connected to the electrode / interface of the single-channel differential signal acquisition module through wires. In this structure, the human body forms a conductive circuit through the metal electrode, the commercial gel electrode, and the wires, such as... Figure 3 As shown.

[0074] The single-channel differential signal acquisition module synchronously receives the composite signal of human electrocardiogram (ECG) and pulse wave from the dual-mode sensor. The arterial pulse wave signal is a piezoelectric voltage generated by the periodic pressure applied to an ion-piezoelectric material at the radial artery in the wrist. The ECG signal originates from the human body itself. Due to the high ionic conductivity of the ion-piezoelectric material, the bioelectrical signal can be captured by acquiring the potential difference between the metal electrode and the commercial gel electrode. The two signals are coupled without delay through the same channel. The single-channel differential signal acquisition module processes the output signal from the dual-mode sensor, outputting a time-series composite electrical signal that simultaneously contains both ECG and arterial pulse wave signals at the same time reference. The acquisition module then transmits this composite electrical signal to the processor, which processes it to calculate a blood pressure estimate.

[0075] The results were compared using commercially available finger-clip blood pressure monitors (measured values) with estimated values ​​obtained from tests based on ion-piezoelectric materials (e.g., Figure 4 As shown), Figure 4 As shown, the values ​​of the two are highly consistent, proving the reliability of the material. The ion piezoelectric material prepared by this invention can generate a high voltage response under slight pressure, and its value is highly consistent with that of a professional finger clip blood pressure monitor, and can maintain continuous and stable monitoring for more than 24 hours.

[0076] The processor's method for processing composite electrical signals includes the following steps:

[0077] S1. Acquire the time-series composite electrical signal output by a single differential acquisition channel. The composite electrical signal contains both electrocardiogram signal and arterial pulse wave signal at the same time reference. Simultaneously acquire the reference blood pressure parameters for the same time period as the composite electrical signal. The reference blood pressure parameters include systolic blood pressure, diastolic blood pressure and / or mean arterial pressure.

[0078] S2. Preprocess the composite electrical signal, including power frequency suppression, baseline drift correction and bandwidth limitation, to obtain the composite waveform of electrocardiogram and pulse wave;

[0079] S3. Perform beat-by-beat location of ECG and pulse wave feature points on the composite waveform. Based on the ECG and pulse wave feature points, calculate the beat-by-beat arrival time and pulse wave morphology features within the same beat cycle. The morphology features include rise time, pulse wave width, amplitude ratio, area features, and first / second derivative features.

[0080] S4. Using the pulse arrival time and pulse wave morphology characteristics within the same beat cycle and the baseline blood pressure parameters as a sample, construct a blood pressure estimation dataset. Based on the blood pressure estimation dataset, construct a blood pressure estimation model. The blood pressure estimation model is a mapping function constructed based on the blood pressure parameters and pulse arrival time within the same beat cycle, or a data-driven model with the pulse arrival time and pulse wave morphology characteristics within the same beat cycle as input features and the baseline blood pressure parameters as target features.

[0081] S5. Real-time acquisition of the time series composite electrical signal of the subject under test, extraction of pulse arrival time and pulse wave morphology features, input into the blood pressure estimation model, and obtain blood pressure parameter estimates.

[0082] Power frequency suppression is used to suppress narrowband power frequency interference and its harmonic components; baseline drift correction is used to remove low-frequency trend terms or baseline drift terms; bandwidth limitation is used to suppress high-frequency noise and interference outside the target frequency band, where the target frequency band is the frequency band related to subsequent feature point detection.

[0083] A method for locating ECG and pulse wave feature points using composite waveforms, and calculating the pulse arrival time and pulse wave morphology characteristics within the same beat cycle based on the ECG and pulse wave feature points.

[0084] like Figure 9As shown, the ECG signal contains R-wave feature points. When the confidence level of R-wave detection is lower than the threshold or the R-wave is difficult to reliably locate, an equivalent ECG feature point located within the same QRS complex and stably located can be used as a substitute starting point. The equivalent ECG feature point can be the point of maximum amplitude or maximum rising slope within the QRS segment. The location of the ECG R-wave or equivalent ECG feature point can be achieved by peak detection, template matching, or adaptive thresholding: Peak detection can perform local maxima search on the enhanced ECG-related components within the R-wave candidate window, and eliminate spurious peaks by combining refractory period and peak width constraints; Template matching can perform normalized correlation matching between the QRS segment within the candidate window and a preset or adaptively updated template, taking the point with the maximum correlation coefficient as the location result and using the correlation coefficient as the matching score; Adaptive thresholding can estimate the noise level and peak statistics within a sliding window, dynamically update the detection threshold, and determine the candidate peak amplitude or energy envelope as an R-wave or equivalent ECG feature point when it exceeds the threshold and meets the rhythm constraint. One or more pulse wave feature points can be identified in the pulse wave. These feature points include trough 1, inflection point, main wave, tidal wave, dicrotic wave, and trough 2. Trough 1 corresponds to the foot of the pulse wave in the current beat cycle signal, the inflection point corresponds to the point of maximum upward slope, and trough 2 corresponds to the valley point of the pulse wave's decline phase after the main wave. Pulse wave feature point localization uses ECG feature points as a reference, and a preset arrival window is constructed thereafter to search for one or more feature points among trough 1, inflection point, main wave, tidal wave, dicrotic wave, and trough 2. For example, trough 1 can be determined by combining threshold crossing and the starting position of the derivative turning from negative to positive; the inflection point can be determined by the position corresponding to the maximum value of the first derivative of the pulse wave in the rising segment; the main wave can be determined by the local maximum value after trough 1; and the dicrotic wave can be determined by the local minimum value and / or the position corresponding to the second derivative feature in the falling segment after the main wave. A composite waveform contains multiple consecutive beat cycles. A beat cycle is defined as the signal segment between two adjacent sequentially detected ECG R waves or equivalent ECG feature points. For each beat cycle, the pulse wave feature points corresponding to that cycle are detected in the composite waveform, and the beat arrival time of that cycle is further calculated. For a composite waveform containing N effective beat cycles, N sets of one-to-one combinations of ECG feature points and pulse wave feature points can be obtained, and N beat arrival times and N sets of pulse wave morphological features can be calculated accordingly. The beat arrival time is calculated after obtaining the feature points. For example, the time interval from the ECG R wave or equivalent ECG feature point to the inflection point and the time interval to the main wave can be calculated separately to obtain the beat arrival time under different definitions. When the trough 1 or diabetic wave is difficult to locate stably, the pulse wave segment can be correlated with the template within the arrival window, and the equivalent beat arrival time can be obtained by the time shift corresponding to the highest correlation, thereby improving the continuity of the beat arrival time.

[0085] The pulse wave morphology and pulse arrival time correspond to the same beat cycle and are calculated from the pulse wave feature points within that beat cycle. The pulse wave morphology may include rise time, pulse wave width, amplitude ratio, area characteristics, and first / second derivative characteristics. For example, rise time can be defined as the time interval from trough 1 to the main wave; pulse wave width can be defined as the time interval from trough 1 to trough 2; amplitude ratio can be defined as at least one of the ratio of the main wave amplitude to the tidal wave amplitude, or the ratio of the main wave amplitude to the dicrotic wave amplitude; area characteristics can be defined as the area enclosed by the pulse wave envelope between trough 1 and trough 2; first derivative characteristics may include the maximum slope of the rising segment, the minimum slope of the falling segment, and their corresponding times; second derivative characteristics may include at least one of the second derivative values ​​at the inflection point, the extreme values ​​of the second derivative in the falling segment after the main wave, and their corresponding times.

[0086] The blood pressure estimation model establishes a mapping relationship between stroke arrival time and pulse wave morphology characteristics and systolic blood pressure, diastolic blood pressure, and / or mean arterial pressure.

[0087] The pulse arrival time and pulse wave morphology characteristics corresponding to the same beat cycle are combined to form input features. The baseline blood pressure parameters collected within that beat cycle are used as target features to form a blood pressure estimation dataset. A blood pressure estimation model is then constructed based on this dataset to output estimated blood pressure parameters. These estimated blood pressure parameters may include systolic blood pressure, diastolic blood pressure, and / or mean arterial pressure.

[0088] In all embodiments of this invention, the pulse arrival time and pulse wave morphology are used as inputs to the blood pressure estimation model because changes in blood pressure cause variations in arterial wall tension, compliance, and pulse wave propagation velocity, further affecting the time interval between ECG feature points and the pulse wave arrival at relevant feature points, as well as the pulse wave waveform morphology. Specifically, when blood pressure rises, arterial compliance decreases and pulse wave propagation velocity increases, thus altering the pulse arrival time. Simultaneously, the pulse wave rise time, width, peak value, area characteristics, and derivative characteristics also change with hemodynamic status. Therefore, the pulse arrival time and pulse wave morphology corresponding to the same beat cycle signal can characterize the hemodynamic status related to the blood pressure parameters of that cycle and can be used to establish an estimation model for blood pressure parameters.

[0089] Blood pressure estimation models can be mechanistic models or data-driven models. Mechanistic models are function mapping models based on beat-time, specifically constructing a mapping function using blood pressure parameters and beat-time.

[0090] BP=a / (PAT 2 )+b

[0091] Wherein, BP represents any one of the systolic blood pressure, diastolic blood pressure, or mean arterial pressure to be estimated; PAT represents the pulse arrival time corresponding to the same beat-cycle signal; and a and b represent model parameters. Model parameters a and b can be set separately for different blood pressure parameters. Model parameters a and b can be obtained by fitting a reference blood pressure parameter with the corresponding pulse arrival time. After the mechanistic model is constructed, the pulse arrival time obtained by the above processing of the newly acquired composite signal is input into the mechanistic model, which can output the blood pressure estimate corresponding to the beat-cycle signal.

[0092] The data-driven model is a machine learning model or deep learning model based on multi-feature input; in this embodiment, the data-driven model is preferably a fully connected neural network model. Taking the fully connected neural network model as an example, the fully connected neural network model uses the pulse arrival time and pulse wave morphology features corresponding to the same beat-cycle signal as input, and uses the corresponding reference blood pressure parameters as supervision labels for training, thereby establishing a nonlinear mapping relationship between input features and blood pressure parameters. The fully connected neural network model includes an input layer, one or more hidden layers, and an output layer, wherein the input layer is used to receive the pulse arrival time and pulse wave morphology features, and the output layer is used to output the estimated values ​​of systolic blood pressure, diastolic blood pressure, and / or mean arterial pressure. During training, the input features can be normalized, and the backpropagation algorithm is used to iteratively update the network parameters to reduce the error between the model output value and the reference blood pressure parameters. After training, the pulse arrival time and pulse wave morphology features obtained by the above processing of the newly acquired composite signal are input into the trained fully connected neural network model, which outputs the estimated values ​​of systolic blood pressure, diastolic blood pressure, and / or mean arterial pressure corresponding to the beat-cycle signal, thereby realizing continuous blood pressure estimation.

[0093] This invention constructs an elastic polymer network with highly uniform pore size and a regular crosslinking point distribution through click chemistry, effectively reducing energy dissipation and significantly improving mechanical resilience and long-term stability under cyclic loading. By introducing an ionic medium into the regular network and utilizing non-covalent interactions such as π-cation interactions, ion-dipole interactions, and multiple hydrogen bonds to construct ion-selective transport channels, combined with the stress concentration effect generated by the surface microstructure, an ultra-high ionic piezoelectric coefficient is achieved. This material can not only achieve non-invasive pulse wave monitoring through highly sensitive piezoelectric response, but also simultaneously acquire electrocardiogram (ECG) signals using its ionic conductivity, realizing multi-dimensional real-time monitoring of cardiovascular health status.

Claims

1. A method for preparing a flexible ion piezoelectric material, characterized in that, Includes the following steps: (1) Preparation of the prepolymer solution by clicking chemical reaction: Polyethylene glycol diacrylate is mixed with polythiol monomers as olefin monomers to form a prepolymer solution; (2) Polyethylene glycol, ionic medium and alkaline catalyst are added to the prepolymer liquid, mixed evenly in an ice water bath, injected into the inverse structure mold, and heated and cured to obtain a flexible ionic piezoelectric material.

2. The method for preparing the flexible ion piezoelectric material according to claim 1, characterized in that: In step (1), the multi-thiol monomer includes a tetrafunctional thiol compound and a difunctional thiol compound; the tetrafunctional thiol compound is pentaerythritol tetrakis(3-mercaptopropionic acid) ester. The bifunctional thiol compound is 2,2′-(1,2-ethylenedioxy)bis(ethyl)thiol.

3. The method for preparing the flexible ion piezoelectric material according to claim 2, characterized in that: The molar ratio of polyethylene glycol diacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) ester and 2,2′-(1,2-ethylenedioxy)diethylthiol is 3~7:1~3:1~2.

4. The method for preparing the flexible ion piezoelectric material according to claim 1, characterized in that: In step (2), the ionic medium is one of 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonylimide), 1-ethyl-3-methylimidazolium dicyandiamide salt or 1-butyl-3-methylimidazolium hexafluorophosphate.

5. The method for preparing the flexible ion piezoelectric material according to claim 4, characterized in that: The amount of ionic medium added is 50% of the total mass of the gel.

6. The method for preparing the flexible ion piezoelectric material according to claim 1, characterized in that: In step (2), the alkaline catalyst is one of triethylamine, diethylamine or ethylamine.

7. The method for preparing the flexible ion piezoelectric material according to claim 1, characterized in that: In step (2), the amount of the alkaline catalyst added is 4.5 × 10⁻⁶ of the total mass of the gel. -7 %; the amount of polyethylene glycol added is 15% of the total mass of the gel.

8. The method for preparing the flexible ion piezoelectric material according to claim 1, characterized in that: In step (2), the cavity surface of the reverse structure mold has a microstructure.

9. The method for preparing the flexible ion piezoelectric material according to claim 1, characterized in that: The microstructure is a pyramid array structure, a hemispherical array structure, or a cylindrical array structure.

10. The method for preparing the flexible ion piezoelectric material according to claim 1, characterized in that: In step (2), the heating and curing temperature is 60~80℃ and the curing time is 2~2.5 hours.

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