A functional conductive hydrogel and a preparation method and application thereof
By preparing functional conductive hydrogels with adjustable conductivity, modulus, and tensile properties, the problem of balancing electrochemical performance, mechanical compliance, and biocompatibility in conductive gels for sensing interfaces has been solved, achieving the effects of simplified processing and improved reliability, and making them suitable for multi-mode bioelectronic applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2024-11-29
- Publication Date
- 2026-07-24
AI Technical Summary
Existing conductive gels are difficult to balance with electrochemical performance, mechanical compliance and biocompatibility in sensing interfaces, and the processing methods are limited, making it impossible to controllably process sensing interfaces with specific shapes and structures according to different application scenarios.
A functional conductive hydrogel with adjustable conductivity, modulus and tensile properties was prepared by mixing carbon-based nanomaterials and PEDOT:PSS solution, freeze-drying, adding F127DA solution and photocuring. The hydrogel was then processed using photopatterning and 3D printing technology.
It achieves an effective balance between conductivity, mechanical properties and biocompatibility, simplifies the processing, improves the repeatability and reliability of the preparation, and is suitable for multi-mode bioelectronic applications.
Smart Images
Figure CN119751917B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of hydrogel technology, and in particular to a functional conductive hydrogel, its preparation method, and its application. Background Technology
[0002] Flexible and stretchable conductive gels have attracted great interest in biomedical applications, such as skin sensors, implantable medical electronic devices, and biosensor chips, due to their excellent mechanical properties, biocompatibility, and combined ionic and electronic conductivity. In all these applications, the effectiveness of the sensing interface depends on the stability and reliability of the electromechanical coupling between the living organism structure and the sensing interface under various load conditions and deformations. However, conductive gels currently face two main challenges in their use as sensing interfaces: firstly, the improvement of the electrochemical performance of conductive gels often contradicts good mechanical compliance and biocompatibility, making it difficult to achieve an effective balance between seamless structural integration and stable functional signal transduction in gel-based sensing interface interfaces; secondly, limitations imposed by traditional processing methods (drop casting, molding) prevent the controllable fabrication of gel-type sensing interfaces with specific shapes, structures, and properties for different application scenarios. Therefore, developing multifunctional conductive hydrogels with high conductivity, low modulus stretchability, excellent biocompatibility, and processability is of great significance for the robust construction of seamless bioelectronic interfaces in multi-modal application scenarios.
[0003] Functional conductive gels typically employ two main preparation strategies. One involves physical blending, coupling metal-based nanoparticles and nanowires, carbon-based conductive nanomaterials, and conductive polymers primarily based on PEDOT:PSS as a sensing network with a gel network that provides mechanical flexibility. However, due to the strong interactions between nanofillers, the solubility of the conductive fillers is low, and the uniformity of the conductive network is poor. This results in a significant decrease in conductivity while increasing the stretchability of the hydrogel, and insufficient scalability of the processing method. To address this challenge, researchers have attempted to improve the dispersibility of nanofillers by adding surfactants, but this process easily introduces non-biocompatible small molecule residues into the gel network. Alternatively, they have used post-treatment methods such as dehydration, acid soaking, and thermal annealing to reduce the proportion of insulating chains and improve the density of the conductive network. However, these lengthy and rigorous post-treatment processes hinder the immediate use of gel-based electronic devices and limit the feasibility of integrating biological tissues with electronic devices to construct in-situ sensing platforms on demand. Another preparation strategy is typically applicable to water-soluble conductive polymers such as PEDOT:PSS. By forming an interpenetrating polymer network through in-situ polymerization or phase separation of monomers in a stretchable gel network, the mechanical and electrical properties of the conductive gel are greatly improved. However, most formulations are cumbersome and the synthesis conditions are harsh, resulting in low reproducibility between batches and poor reliability in applications. To date, while promoting the development of high-performance conductive gels with more flexible and simple formulations, it is still necessary to continuously optimize the processing and post-processing methods of conductive hydrogels, allowing for the gradual integration of multifunctional conductive hydrogels with bioelectronic devices from two-dimensional to three-dimensional fabrication processes through precise and scalable manufacturing strategies. Summary of the Invention
[0004] This application provides a functional conductive hydrogel with adjustable modulus and tensile properties, photo-patternable and 3D printable properties, as well as its preparation method and multi-scenario and multi-modal applications. It aims to solve the problems of existing conductive hydrogel formulations with complex and demanding synthesis conditions, low reproducibility between sample batches leading to poor reliability of gel-type electronic devices in applications, and the limitations of post-processing methods on the processing accuracy and scalable process integration of conductive hydrogels.
[0005] In a first aspect, this application provides a method for preparing a functional conductive hydrogel, the method comprising: adding carbon-based nanomaterials to a PEDOT:PSS solution and sonicating in an ice bath to obtain a mixed solution of carbon-based nanomaterials and PEDOT:PSS; freeze-drying the mixed solution of carbon-based nanomaterials and PEDOT:PSS to obtain dual-conductive filler fibers; adding F127DA powder to a photoinitiator solution and stirring in an ice bath to obtain an F127DA solution; dispersing the dual-conductive filler fibers in the F127DA solution by stirring in an ice bath to obtain a uniformly dispersed conductive gel precursor ink; and reacting the conductive gel precursor ink under photocuring conditions to obtain the functional conductive hydrogel.
[0006] Furthermore, the concentration of the PEDOT:PSS solution is 1.3% w / v; the mass ratio of the carbon-based nanomaterial to the PEDOT:PSS solution is (2.5-10):25; the carbon-based nanomaterial includes carbon nanotubes and graphene; wherein the carbon nanotubes include one or more of single-walled, multi-walled, hydroxyl- or carboxyl-modified carbon nanotubes.
[0007] Furthermore, the freeze-drying process specifically includes: rapidly cooling the mixed solution of the carbon-based nanomaterial and PEDOT:PSS in liquid nitrogen, and then freeze-drying it for 72 hours.
[0008] Furthermore, the photoinitiator in the photoinitiator solution is lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP). LAP is a photoinitiator with good water solubility and biocompatibility, widely used in the photocuring of hydrogels and bioinks. Compared with the traditional initiator Irgacure 2959, it has higher water solubility and photoinitiation efficiency, and its photoexcitation wavelength covers 365–405 nm, making it more suitable for biological applications. The concentration of the lithium phenyl-2,4,6-trimethylbenzoyl phosphite is 0.25% w / v. The concentration of the photoinitiator can be adjusted according to the desired curing effect, but excessively high photoinitiator concentration may affect the overall cell compatibility of the functional conductive hydrogel.
[0009] Furthermore, the concentration of the F127DA solution is (5% to 30%) w / v.
[0010] Furthermore, the concentration of the dual conductive filler fiber is 27.5 mg / mL to 35 mg / mL, and the stirring time in an ice bath is 48 h.
[0011] Furthermore, the photocuring conditions specifically involve irradiation with ultraviolet light at a wavelength of 365 nm for a time of 1 min to 10 min.
[0012] Secondly, this application provides a functional conductive hydrogel prepared by the above-described method, wherein the functional conductive hydrogel has adjustable conductivity, modulus and tensile properties, and can be photo-patterned and 3D printed.
[0013] Thirdly, this application provides the application of the aforementioned functional conductive hydrogel in multimodal wearable applications and in the field of acquiring body electrophysiological signals.
[0014] Furthermore, the application method includes: applying the functional conductive hydrogel in the form of a patch to multimodal sensing applications of skin, strain, and humidity; or, fabricating the functional conductive hydrogel into a flexible thin-film electronic device by 3D printing.
[0015] Compared with the prior art, this application has at least the following advantages:
[0016] 1. The functional conductive hydrogel precursor solution in this application can achieve a processing accuracy of 20μm-500μm through optical patterning, and can also be used to freely fabricate customized sensor devices through 3D printing. It can achieve a balance of excellent electromechanical properties without complicated post-processing steps, providing a material and process basis for the on-demand integrated fabrication of future in-situ biosensing platforms.
[0017] 2. The functional conductive hydrogel precursor solution in this application, by adjusting the ratio between PEDOT:PSS, carbon nanotubes and F127DA, produces a functional conductive hydrogel with adjustable conductivity, modulus and tensile properties, which can achieve an effective balance between conductivity, mechanical properties, biocompatibility and processability.
[0018] 3. The functional conductive hydrogel in this application is prepared by physical dispersion and photocrosslinking without adding any volatile or biotoxic reagents or requiring a chemical reaction process. The simple and controllable preparation process enables the functional conductive hydrogel to have batch-to-batch reproducibility, improving its stability and reliability in application. Attached Figure Description
[0019] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.
[0020] Figure 1 A schematic flowchart of the method for preparing the functional conductive hydrogel provided for the implementation of this application;
[0021] Figure 2 A schematic diagram illustrating the adjustable conductivity, modulus, and tensile properties of the functional conductive hydrogel provided in this application example;
[0022] Figure 3 A sample image of a functional conductive hydrogel provided as an example in this application;
[0023] Figure 4 The functional conductive hydrogel provided in this application example is used for electrocardiogram signal recording.
[0024] Figure 5 Example diagram of the application of functional conductive hydrogel as a strain sensing patch provided in this application;
[0025] Figure 6 Example diagram of the application of functional conductive hydrogel for humidity sensing provided in this application;
[0026] Figure 7 A diagram of a functional conductive hydrogel film electrode provided for an example of this application.
[0027] In the figure, 101-carbon nanotubes, 102-PEDOT:PSS solution, 103-mixed solution of carbon nanotubes and PEDOT:PSS, 104-freeze dryer, 105-double conductive filler fiber, 106-photoinitiator solution, 107-F127DA powder, 108-F127DA solution, 109-conductive hydrogel precursor ink, 110-functional conductive hydrogel;
[0028] 701 - Substrate layer, 702 - Sensing circuit, 703 - Insulating encapsulation layer, 704 - Sensing site, 705 - Encapsulation site. Detailed Implementation
[0029] The present application will now be described in detail with reference to specific embodiments.
[0030] Example 1
[0031] Figure 1 This is a schematic flowchart of the method for preparing the functional conductive hydrogel provided in Embodiment 1 of this application.
[0032] See Figure 1 This application provides a method for preparing a functional conductive hydrogel, the method comprising:
[0033] S1. 5 mg, 10 mg, 15 mg, and 20 mg of carbon nanotubes 101 were added to 4 mL of commercially available 1.3% (w / v) PEDOT:PSS solution 102 and sonicated in an ice bath for 80 min at an ultrasonic power of 250 W to obtain a mixed solution 103 of carbon nanotubes and PEDOT:PSS. The solution changed from dark blue to black.
[0034] Among them, carbon nanotubes include, but are not limited to, different types of carbon nanotubes such as single-walled, multi-walled, and hydroxyl or carboxyl modified carbon nanotubes. In addition to carbon nanotubes, graphene, which has similar properties to carbon nanotubes, can also be dispersed using the above method.
[0035] S2. The mixed solution 103 of carbon nanotubes and PEDOT:PSS is placed in a liquid nitrogen tank for rapid cooling, and then transferred to a freeze dryer 104 for freeze drying for 72 hours to form a double conductive filler fiber 105.
[0036] In S2, one photoinitiator, including but not limited to lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP) and Irgacure 2959, can be dissolved in PBS to prepare a 0.25% (w / v) photoinitiator solution 106. It should be noted that excessively high photoinitiator concentrations can lead to over-crosslinking after light exposure, making precise patterning impossible; conversely, excessively low concentrations can result in failure to crosslink after light exposure. Therefore, an appropriate photoinitiator concentration needs to be selected based on the desired performance of the functional conductive hydrogel.
[0037] S3. Dissolve F127DA powder 107 in photoinitiator solution 106 to prepare a 10% F127DA solution 108. The recommended concentration of F127DA solution 108 can be varied between 5% and 30%. Similarly, a suitable concentration of F127DA can be selected according to the required functional conductive hydrogel properties.
[0038] S4. The freeze-dried dual conductive filler fiber 105 obtained in S2 is dispersed in 2 mL of F127DA solution 108 obtained in S3, and stirred in an ice bath for 48 h to finally form conductive hydrogel precursor ink 109 with carbon nanotube concentrations of 2.5 mg / mL, 5 mg / mL, 7.5 mg / mL and 10 mg / mL, and PEDOT:PSS concentration remains constant at 25 mg / mL.
[0039] S5. Conductive hydrogel precursor ink 109, after being molded with a mold of a specific size and cross-linked with 365nm ultraviolet light, can yield a functional conductive hydrogel 110 with specific shape, modulus and tensile properties.
[0040] It should be noted that the preparation process of the conductive hydrogel precursor ink 109 provided in this application embodiment involves the preparation process of dual conductive filler hydrogel ink, and this preparation process is also applicable to the preparation of single conductive filler hydrogel ink.
[0041] When preparing pure carbon nanotube hydrogel ink, carbon nanotube powder can be directly ultrasonically dispersed in F127DA solution and ultrasonicated for 80 minutes at 250W power to obtain a uniform, photocurable carbon nanotube hydrogel precursor ink.
[0042] When preparing pure PEDOT:PSS hydrogel ink, commercially available PEDOT:PSS solution can be freeze-dried to form PEDOT:PSS fibers, and then stirred and dissolved in F127DA solution to obtain a uniform PEDOT:PSS hydrogel precursor ink that can be photocured.
[0043] See Figure 2 The functional conductive hydrogels in this application embodiment achieve adjustable elastic modulus, tensile properties, and electrical conductivity by changing the concentration of carbon nanotubes and PEDOT:PSS.
[0044] Specifically, at low carbon nanotube concentrations, the maximum elongation of the carbon nanotube hydrogel can reach 530%. As the carbon nanotube content increases, the elastic modulus of the carbon nanotube hydrogel gradually increases while the elongation at break gradually decreases. When the carbon nanotube content exceeds 7.5 mg / mL, the decreasing trend of elongation at break tends to level off.
[0045] The addition of PEDOT:PSS introduces flexible polymer segments, thereby reducing the overall modulus of the gel. At the same carbon nanotube concentration, the modulus of the dual conductive filler hydrogel is reduced by 2 to 3 times compared to the carbon nanotube monomer hydrogel, making it closer to the modulus of human tissue.
[0046] The conductivity of carbon nanotube monomer hydrogels initially increased and then gradually stabilized with increasing carbon nanotube content. The conductivity of the dual-conductive filler hydrogel was significantly improved compared to the monomer hydrogel, indicating that PEDOT:PSS not only effectively promotes the dispersion of carbon nanotubes but also acts as a conductive bridge connecting the nodes between carbon nanotubes. However, when the carbon nanotube content exceeds 7.5 mg / mL, the conductivity of FPC no longer increases significantly but instead shows a decreasing trend. This trend is due to the breakage and reduction of branches in the continuous conductive network within the nanocomposite material caused by the aggregation of carbon nanotubes at high concentrations.
[0047] See Figure 3 This functional conductive hydrogel can be optically patterned under the action of a photomask, with a processing accuracy of up to 20μm.
[0048] By optimizing the proportion of conductive filler components, this functional conductive hydrogel possesses flexibly adjustable modulus (Young's modulus as low as 90 kPa), elongation (strain up to 520%), conductivity (440 S / m), and 3D printing characteristics. The functional conductive hydrogel can achieve on-demand rapid curing and molding through UV light induction, exhibiting good biocompatibility. It can not only serve as an "electronic tattoo" for multimodal applications such as strain and humidity sensing, but also effectively stimulate the sciatic nerve in vivo under low voltage.
[0049] Electrode arrays that can be freely printed using 3D printing technology can achieve stable attachment to brain tissue and real-time monitoring of electrophysiological signals, providing a more suitable bioelectronic sensing interface for multi-modal application scenarios from in vivo to in vitro.
[0050] Example 2
[0051] The functional conductive hydrogel prepared by the above method is applied in multimodal scenarios such as skin sensing, strain sensing, and humidity sensing.
[0052] The implementation method of functional conductive hydrogel sensing patches as skin sensing is as follows:
[0053] The functional conductive hydrogel prepared by the method in Example 1 was fabricated into a 10mm diameter. × 10mm × A 100μm functional conductive hydrogel film is used as a functional conductive hydrogel sensing patch for skin sensing. For example... Figure 4 The results showed that commercial gel patches and functional conductive hydrogel sensing patches for skin sensing were respectively attached to the chest muscles near the human heart and connected to an electrocardiogram (ECG) monitoring device. By comparing the intensity of the recorded signals, it was found that the functional conductive hydrogel sensing patch for skin sensing, thanks to its excellent conformal adhesion and low interfacial impedance, had a peak-to-peak amplitude of ECG signals that was 3 times higher than that of commercial patch-type gel electrodes. This demonstrated a higher signal-to-noise ratio and signal fidelity than commercial electrodes, indicating that the highly conductive FPCH gel has the ability to transmit small electrical signals.
[0054] The implementation method of functional conductive hydrogel sensing patches as strain sensors is as follows:
[0055] The functional conductive hydrogel prepared by the method in Example 1 was fabricated into 20mm diameters. × 5mm × A 100μm rectangular functional conductive hydrogel strip is used to connect the two ends of a silver sheet and the functional conductive hydrogel strip with silver paste. The silver wires soldered on the silver sheet are connected to a digital multimeter to measure the resistance, resulting in a functional conductive hydrogel sensing patch for strain sensing.
[0056] like Figure 5 As shown, a functional conductive hydrogel sensing patch for strain sensing is fixed to the area to be tested using a PU film. The resistance of the functional conductive hydrogel sensing patch for strain sensing changes with the deformation of the test area. The gel patch can serve as an "electronic tattoo on the skin," covering the monitoring of everything from minute movements with small deformations to large strain movements with deformations exceeding 50%.
[0057] The implementation method of functional conductive hydrogel sensing patches as humidity sensors is as follows:
[0058] The functional conductive hydrogel prepared by the method in Example 1 was fabricated into 20mm diameters. × 5mm × A 100μm rectangular functional conductive hydrogel strip is used. The two ends of the silver sheet and the functional conductive hydrogel strip are connected by silver paste, and the entire strip is fixed on a glass slide. This facilitates the handling of samples during testing, resulting in a functional conductive hydrogel sensing patch for humidity sensing.
[0059] See Figure 6 A humidity environment was set up to test the functional conductive hydrogel sensing patch. A humidifier was placed in a sealed plastic box to change the humidity inside the box, and a hygrometer was used to monitor the humidity changes inside and outside the box in real time.
[0060] The response performance of this functional conductive hydrogel under different humidity levels was tested by controlling humidity gradients and handling samples.
[0061] Example 3
[0062] The implementation method of functional conductive hydrogels as in vivo electroencephalogram (EEG) signal recording thin-film electrodes is as follows:
[0063] See Figure 7 This application provides a gel-type thin film electrode, which includes a substrate layer 701 and an insulating encapsulation layer 703. An encapsulation site 705, a sensing line 702, and a sensing site 704 are sequentially connected between the substrate layer 701 and the insulating encapsulation layer 703.
[0064] The substrate 701 includes materials such as tough gel, PDMS, photoresist, and PI.
[0065] The sensing circuit 702 is a functional conductive hydrogel prepared by the method in Example 1.
[0066] The insulating encapsulation layer 703 includes materials with dielectric properties such as PDMS, photoresist, PI, and silk fibroin.
[0067] Conductive gel precursor ink 109 was prepared according to the method in Example 1, see [link to Example 1]. Figure 7A gel sensing circuit 702 is printed on a 50μm substrate layer 701 according to a custom path plan. The conductive gel circuit is then cured for 10 minutes with a 365nm wavelength, 20W UV curing lamp to ensure the stability of the sensing circuit's molding and electrochemical performance. Then, an insulating encapsulation layer 703, which exposes the sensing sites 704 after femtosecond laser processing, is coupled to the sensing circuit. The flexible FPC board is connected to the encapsulation sites 705 with silver paste. Finally, the boundaries of the electrode are sealed with silicone to form a 16-channel thin-film electrode that can be used for in vivo EEG signal monitoring.
[0068] A 16-channel gel electrode and a commercially available thin-film electrode were simultaneously implanted into the lateral cortex of rats. Electrophysiological recording instruments were then used to acquire cortical electroencephalogram (EEG) signals. Comparison of the field potential signal recording quality between the two types of electrodes revealed that the commercial electrode, being relatively rigid, was prone to displacement within the brain tissue during testing, resulting in continuous superposition of high-frequency noise into the low-frequency field potential signal. The functional conductive hydrogel electrode, on the other hand, exhibited better conformability to the rat cortex, showing no significant positional shift during recording. It also demonstrated higher signal fidelity over the same time period and was less susceptible to noise interference.
[0069] Therefore, considering the combined effects of the above embodiments, this application can be used to prepare functional conductive hydrogels with characteristics such as optical patterning, excellent conductivity, adjustable modulus and tensile properties, and 3D printing capability. Furthermore, the prepared gel-based sensor devices have broad application prospects in multimodal wearable applications and in the acquisition of in vivo electrophysiological signals.
[0070] Those skilled in the art will understand that the above-described embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this application. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.
Claims
1. A method for preparing a functional conductive hydrogel, characterized in that, The preparation method includes: Carbon-based nanomaterials were added to a PEDOT:PSS solution and sonicated in an ice bath to obtain a mixed solution of carbon-based nanomaterials and PEDOT:PSS. The mixed solution of the carbon-based nanomaterial and PEDOT:PSS was freeze-dried to obtain dual-conductive filler fibers. F127DA powder was added to a photoinitiator solution and stirred in an ice bath to obtain an F127DA solution; The dual conductive filler fiber was dispersed in the F127DA solution by ice bath stirring to obtain a uniformly dispersed conductive gel precursor ink; the conductive gel precursor ink was reacted under photocuring conditions to obtain the functional conductive hydrogel. The concentration of the PEDOT:PSS solution was 1.3% w / v; The mass ratio of the carbon-based nanomaterial to the PEDOT:PSS solution is (2.5~10):25; The carbon-based nanomaterial is a carbon nanotube or graphene; wherein the carbon nanotube includes one or more of single-walled, multi-walled carbon nanotubes, and carbon nanotubes modified with hydroxyl or carboxyl groups. The concentration of the F127DA solution is (5%~30%) w / v.
2. The method for preparing the functional conductive hydrogel according to claim 1, characterized in that, The freeze-drying process specifically includes: rapidly cooling the mixed solution of the carbon-based nanomaterial and PEDOT:PSS in liquid nitrogen, and then freeze-drying it for 72 hours.
3. The method for preparing the functional conductive hydrogel according to claim 1, characterized in that, The photoinitiator in the photoinitiator solution is lithium phenyl-2,4,6-trimethylbenzoyl phosphite; the concentration of lithium phenyl-2,4,6-trimethylbenzoyl phosphite is 0.25% w / v.
4. The method for preparing the functional conductive hydrogel according to claim 1, characterized in that, The concentration of the dual conductive filler fiber is 27.5 mg / mL to 35 mg / mL, and the stirring time in an ice bath is 48 h.
5. The method for preparing the functional conductive hydrogel according to claim 1, characterized in that, The photocuring conditions specifically involve irradiation with ultraviolet light at a wavelength of 365nm for 1 to 10 minutes.
6. The functional conductive hydrogel prepared by the method of any one of claims 1 to 5, characterized in that, The functional conductive hydrogel has adjustable conductivity, modulus and tensile properties, and can be photo-patterned and 3D printed.
7. The use of the functional conductive hydrogel as described in claim 6 in the preparation of sensing patches for skin sensing, strain sensing or humidity sensing.
8. The application of the functional conductive hydrogel as described in claim 6 in the preparation of in vivo electroencephalogram (EEG) signal recording thin film electrodes.