A pu / pedot:pss stretchable conductive fiber with a skin-core structure and a preparation method thereof

Abstract

The application provides a PU / PEDOT:PSS stretchable conductive fiber with a skin-core structure and a preparation method thereof, the stretchable conductive fiber has a core-shell structure, polyurethane is used as a shell layer, and acid-doped poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) hydrogel is used as an inner core (inner nucleus), the PEDOT:PSS hydrogel inner core has good conductivity but very low strength, and the high-elasticity PU outer shell endows the PU / PEDOT:PSS stretchable conductive fiber with high mechanical properties, so that the conductive fiber has good conductivity, sensitivity, mechanical strength and stretch resilience, and therefore, the conductive fiber can be used as a strain sensing fiber in a strain sensor, and the strain sensor prepared from the conductive fiber has high sensitivity coefficient and a wide sensing strain range, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the fields of electrochemistry and wearable smart materials, specifically to a PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure and its preparation method. Background Technology

[0002] The rise and development of wearable electronic devices and intelligent robots will bring tremendous changes to human life in the future. To meet the application needs of wearable devices on the human body, ideal wearable materials or devices need to have sufficient flexibility to adapt to and simulate the large-scale deformation and movement of the human body. As an important branch of wearable electronic devices, wearable smart fabrics have attracted considerable attention and interest from researchers.

[0003] One-dimensional linear materials possess characteristics such as small size, light weight, good flexibility, and weavability, making them highly promising for applications in wearable smart fabrics. Currently, various materials (such as metals, carbon materials, and conductive polymers) are being used in the development and manufacturing of these one-dimensional linear materials.

[0004] Conductive polymers possess excellent conductivity comparable to metals. Furthermore, compared to metals, conductive polymers are composed of lightweight elements with longer molecular chains, resulting in greater weight, flexibility, and biocompatibility. Therefore, conductive polymers are gradually replacing metals and are increasingly widely used in flexible wearable electronic devices and smart fabrics.

[0005] PEDOT:PSS is an excellent conductive polymer composite system. It is prepared by chemically doping PEDOT with hydrophilic PSS during the synthesis process, exhibiting excellent electrochemical and hydrophilic properties and good skin compatibility. Previous research has led to the development of numerous smart materials and devices based on PEDOT:PSS, including conductive materials, smart sensors, flexible supercapacitors, and smart actuators.

[0006] Among them, a series of smart strain sensing fibers based on PEDOT:PSS have been developed for real-time monitoring of human vital signs and limb activities. However, the preparation process is often quite complex, and the resulting sensing fibers are difficult to balance high sensitivity and a large strain sensing range. Summary of the Invention

[0007] Based on the aforementioned technical background, the inventors made pioneering efforts and discovered that by using polyurethane (PU) as the shell and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) hydrogel as the inner core, a PU / PEDOT:PSS stretchable conductive fiber with a shell-core structure is obtained. PU as the shell endows the stretchable conductive fiber with good tensile resilience, while PEDOT:PSS as the inner core endows the fiber with good conductivity. This gives the stretchable conductive fiber excellent mechanical properties, sensitivity, and conductivity. The strain sensor made from this fiber has the advantages of high sensitivity coefficient and large strain sensing range, showing promising application prospects. Furthermore, this stretchable conductive fiber is prepared using a microfluidic device, which is simple to prepare and allows for flexible assembly of the microfluidic device, thus completing this invention.

[0008] The first aspect of the present invention is to provide a PU / PEDOT:PSS stretchable conductive fiber with a core-shell structure, wherein the stretchable conductive fiber has PU as the shell and PEDOT:PSS hydrogel as the inner core.

[0009] The second aspect of the present invention is to provide a method for preparing PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure as described in the first aspect of the present invention, wherein the preparation method uses polyurethane and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid as raw materials and is carried out by a microfluidic device.

[0010] A third aspect of the present invention is to provide the use of a PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure as described in the first aspect of the present invention, or a PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure prepared by the preparation method described in the second aspect of the present invention, which can be used as a strain sensing fiber in a strain sensor. Attached Figure Description

[0011] Figure 1 The resistivity test results of Examples 1 to 5 are shown in bar charts;

[0012] Figure 2 The resistivity test results of Examples 1 and 6-9 are shown in bar charts;

[0013] Figure 3 The ΔR / R0-strain diagrams of the stretchable conductive fibers prepared in Examples 1-3 are shown.

[0014] Figure 4 The ΔR / R0-strain diagrams of the stretchable conductive fibers prepared in Examples 1 and 4-5 are shown.

[0015] Figure 5 The ΔR / R0-strain diagrams of the stretchable conductive fibers prepared in Examples 1 and 6-9 are shown.

[0016] Figure 6 The stress-strain curves of the stretchable conductive fibers prepared in Examples 1 and 6-9 are shown.

[0017] Figure 7 A scanning electron microscope image of the stretchable conductive fiber prepared in Example 1 is shown.

[0018] Figure 8 A scanning electron microscope image of the cross-section of the stretchable conductive fiber prepared in Example 1 is shown. Detailed Implementation

[0019] The present invention will now be described in detail, and its features and advantages will become clearer and more apparent from these descriptions.

[0020] The first aspect of the present invention is to provide a PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure, the stretchable conductive fiber being made of polyurethane (PU) and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) via a capillary microfluidic device.

[0021] The stretchable conductive fiber has an outer shell and an inner core, with the inner core encased within the outer shell. It has a polyurethane (PU) shell and a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid hydrogel (PEDOT:PSS) inner core.

[0022] The PEDOT:PSS hydrogel core has low strength, while the highly elastic PU shell gives the PU / PEDOT:PSS stretchable conductive fiber good mechanical strength and tensile resilience. The PEDOT:PSS hydrogel core imparts good conductivity to the fiber, giving it both excellent conductivity and mechanical properties, along with high sensitivity. This stretchable conductive fiber can be used as a strain-sensing fiber for monitoring the external environment.

[0023] The mass ratio of the PU shell to the PEDOT:PSS hydrogel core is 0.4:1 to 2:1, preferably 0.6:1 to 1.5:1, and more preferably 1.2:1.

[0024] The PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure described in this invention has a uniform diameter, ranging from 0.5 mm to 2.0 mm, and exhibits a core-sheath composite structure with coaxial inner and outer layers.

[0025] This stretchable conductive fiber has good tensile resilience, with a tensile strain of 440-520% and a resistivity of 600-2250 Ω / cm. The strain sensor made from it has a sensitivity coefficient of up to 3500 and an inductive strain of up to 235%.

[0026] The second aspect of the present invention is to provide a method for preparing PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure as described in the first aspect of the present invention, wherein the preparation method uses polyurethane and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid as raw materials and is carried out by a microfluidic device.

[0027] The microfluidic device is a coaxial multilayer capillary microfluidic device, including three microfluidic channels: an inner layer, a middle layer, and an outer layer. An acid-doped PEDOT:PSS suspension flows out from the inner layer microfluidic channel as the inner layer fluid, a PU solution flows out from the middle layer microfluidic channel as the middle layer fluid, and a mixed solution flows out from the outer layer microfluidic channel as the outer layer coagulation bath fluid. The fluids are injected into the microfluidic needle through the corresponding fluid inlet at different pumping rates by an injection pump, forming a stable laminar flow in the outlet capillary.

[0028] The acid-doped PEDOT:PSS suspension is prepared by using an aqueous solution of PEDOT:PSS and a dopant, while the PU solution is prepared by dissolving PU in a solvent.

[0029] In this invention, the solid content of the acid-doped PEDOT:PSS suspension is 1-50 mg / mL, preferably 3-40 mg / mL, and more preferably 5-35 mg / mL.

[0030] Experiments have shown that as the solid content of the PEDOT:PSS suspension increases, the initial conductivity of the stretchable conductive fiber increases, and its electrical sensitivity gradually increases.

[0031] The dopant of the acid-doped PEDOT:PSS suspension is selected from one or more of sulfuric acid, hydrochloric acid, oxalic acid, phytic acid, and toluenesulfonic acid, with sulfuric acid being preferred.

[0032] The concentration of acid in the acid-doped PEDOT:PSS suspension is 0.01–1 mol / L, preferably 0.03–0.5 mol / L, and more preferably 0.05–0.15 mol / L.

[0033] The conductivity of stretchable conductive fibers is affected by the sulfuric acid concentration in the PEDOT:PSS suspension. As the sulfuric acid concentration increases, the conductivity of the conductive fibers decreases. Simultaneously, the sulfuric acid concentration also affects the molding of the stretchable conductive fibers. If the sulfuric acid concentration is too low, the PEDOT:PSS suspension is in a dispersed state, which is not conducive to the molding of conductive fibers. If the sulfuric acid concentration is too high, the viscosity of the PEDOT:PSS suspension increases, the fluidity decreases, and it is easy to cause clogging of the microfluidic device needle. When the sulfuric acid concentration is within the above-mentioned range, conductive fibers with stable morphology and structure can be continuously prepared, and the resulting stretchable conductive fibers have high conductivity.

[0034] The concentration of the PU solution is 100–400 mg / mL, preferably 120–270 mg / mL, and more preferably 160–240 mg / mL.

[0035] The concentration of the PU solution significantly affects the strength and modulus of the PU shell, thereby influencing the mechanical strength of the stretchable conductive fiber. The inventors have discovered that as the concentration of the PU solution increases, the conductivity, sensitivity, and elongation at break of the resulting stretchable conductive fiber increase. When the concentration of the PU solution is within the aforementioned range, the stretchable conductive fiber exhibits good conductivity, mechanical strength, and tensile resilience.

[0036] The solvent of the PU solution is selected from one or more of DMSO (dimethyl sulfoxide), DMF (dimethylformamide), xylene, CYC (cyclohexanone), acetone, methyl isobutyl ketone, ethyl acetate, butyl acetate and THF (tetrahydrofuran), preferably selected from one or two of DMSO and DMF, and more preferably DMSO.

[0037] The solvent in the middle layer PU solution fluid diffuses into the water coagulation bath, causing the PU to solidify and form a PU shell.

[0038] The mixed solution is selected from one or more of water, DMSO (dimethyl sulfoxide), DMF (N,N-dimethylformamide), and CYC (cyclohexanone), preferably from one or more of water, DMSO and DMF, and more preferably from water and DMSO.

[0039] The volume ratio of water to DMSO is 4:6 to 9:1, with a preferred volume ratio of 6:4 to 8:2.

[0040] At this ratio, the difference in solvent diffusion rate between the middle and inner fluids can be adjusted, thereby optimizing the surface smoothness of the PU shell and reducing the bubble content in the PU shell.

[0041] By changing the pumping ratio of the outer, middle, and inner fluids, the flow rate of the outer, middle, and inner fluids can be controlled, thereby adjusting the diameter and morphology of the PEDOT:PSS hydrogel conductive core in the resulting fiber.

[0042] The flow rate of the PEDOT:PSS suspension is 1–8 mm / s, preferably 1.6–4 mm / s, and more preferably 3–3.5 mm / s.

[0043] The flow rate of the PU solution is 0.5–2 mm / s, preferably 0.7–1.8 mm / s, and more preferably 1–1.5 mm / s.

[0044] The flow rate of the mixed solvent is 1.5 to 4 mm / s, preferably 2 to 3.5 mm / s, and more preferably 2.5 to 3 mm / s.

[0045] When the flow rate is within the above range, the PEDOT:PSS suspension, PU solution, and mixed solvent form a laminar flow, which is beneficial for microfluidic molding and forms a stretchable conductive composite fiber with a linear PEDOT:PSS hydrogel core. The stretchable conductive fiber obtained at the above flow rate has a coaxial core-sheath composite structure with a diameter of 1 mm, and has both good conductivity and tensile resilience.

[0046] A third aspect of the present invention is to provide the use of a PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure as described in the first aspect of the present invention, or a PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure prepared by the preparation method described in the second aspect of the present invention, which can be used as a strain sensing fiber in a strain sensor.

[0047] The beneficial effects of this invention are as follows:

[0048] (1) The stretchable conductive fiber described in this invention is a PU / PEDOT:PSS conductive fiber with a core-sheath structure. The highly elastic PU shell gives it good tensile resilience, and the tensile strain can reach up to 520%.

[0049] (2) The change in the size and shape of the core of the stretchable conductive fiber will cause the fiber resistance to change, making it suitable as a strain sensing fiber for monitoring the strain of external objects. It is made by a microfluidic device and has the advantages of simple preparation method and flexible assembly of microfluidic device.

[0050] (3) The conductive PEDOT:PSS core of the stretchable conductive fiber described in this invention has a large diameter and a relatively straight morphology, which are both beneficial to achieving better sensing.

[0051] (4) The stretchable conductive fiber described in this invention can be used as a strain sensing fiber in a strain sensor. The stretchable strain sensor made from it has both high sensitivity and wide strain sensing range. The sensitivity coefficient of the strain sensor can reach up to 3500, and the inductive strain can reach 235%.

[0052] Example

[0053] The present invention is further illustrated by specific examples below. These embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0054] Example 1

[0055] A PEDOT:PSS suspension (Clevios Ph1000) doped with 0.1M H2SO4 was used as the inner layer fluid, with a PEDOT:PSS solid content of 30 mg / mL. A PU / DMSO solution (240 mg / mL) was used as the middle layer fluid, and a water / DMSO mixed solvent (7:3 volume ratio of water to DMSO) was used as the outermost coagulation bath fluid. These solutions were injected into the microfluidic needle at different rates through the corresponding fluid inlets using an injection pump, forming a stable laminar flow in the capillary channel. The flow rates of the outer, middle, and inner laminar layers in the microfluidic molding needle were controlled at V. out =2.5~3mm / s; V mid =1~1.5mm / s; V in =3~3.5mm / s, the solvent in the middle layer PU / DMSO solution diffuses into the outer layer coagulation bath fluid, causing PU to solidify and form a PU shell, thereby generating a PU / PEDOT:PSS stretchable conductive fiber with a shell and core structure, where PU is the outer shell layer and PEDOT:PSS hydrogel is the conductive inner core.

[0056] Example 2

[0057] The stretchable conductive fibers were prepared in a manner similar to that in Example 1, except that the solid content of PEDOT:PSS was 20 mg / mL.

[0058] Example 3

[0059] The stretchable conductive fiber was prepared in a manner similar to that in Example 1, except that the solid content of PEDOT:PSS was 10 mg / mL.

[0060] Example 4

[0061] The stretchable conductive fiber was prepared in a similar manner to that in Example 1, except that a PEDOT:PSS suspension was formed using a 0.2M H2SO4-doped PEDOT:PSS solution as the inner fluid, and the solid content of PEDOT:PSS was 30 mg / mL.

[0062] Example 5

[0063] The stretchable conductive fiber was prepared in a manner similar to that in Example 1, except that a PEDOT:PSS suspension was formed using a 0.3M H2SO4-doped PEDOT:PSS solution as the inner fluid, and the solid content of PEDOT:PSS was 30 mg / mL.

[0064] Example 6

[0065] The stretchable conductive fibers were prepared in a manner similar to that in Example 3, except that the concentration of the PU / DMSO solution was 220 mg / mL.

[0066] Example 7

[0067] The stretchable conductive fibers were prepared in a manner similar to that in Example 3, except that the concentration of the PU / DMSO solution was 200 mg / mL.

[0068] Example 8

[0069] The stretchable conductive fibers were prepared in a manner similar to that in Example 3, except that the concentration of the PU / DMSO solution was 180 mg / mL.

[0070] Example 9

[0071] The stretchable conductive fibers were prepared in a manner similar to that in Example 3, except that the concentration of the PU / DMSO solution was 160 mg / mL.

[0072] Experimental Example

[0073] Experiment Example 1: Resistance Test

[0074] The resistance of the stretchable conductive fibers prepared in Examples 1 to 9 was tested. The specific test process is as follows: 3-4 cm fiber samples were cut, and two copper wires were inserted into the inner cores at both ends of the fiber and fixed with light-cured epoxy resin. The fiber samples were connected to an electrochemical workstation and set to IT mode. After setting the initial voltage, the resistance value was calculated from the current value and the initial voltage value.

[0075] The test results of Examples 1-5 are as follows: Figure 1 As shown, the test results of Examples 1 and 6-9 are as follows: Figure 2 As shown.

[0076] from Figure 1 As can be seen, with the increase of solid content in PEDOT:PSS solution, the resistivity of stretchable conductive fiber gradually decreases and the conductivity significantly increases. With the increase of sulfuric acid concentration, the conductivity of stretchable conductive fiber gradually decreases and the resistivity is 600-2250 Ω / cm.

[0077] from Figure 2 As can be seen, with the increase of PU solution concentration, the resistivity of stretchable conductive fibers gradually decreases and the conductivity gradually increases, with a resistivity of 600–1600 Ω / cm.

[0078] Experimental Example 2: ΔR / R0 - Stress Test (Sensitivity Test)

[0079] Sensitivity tests were performed on the stretchable conductive fibers obtained in Examples 1-9. The specific test process is as follows: 3-4 cm fiber samples were cut, and two copper wires were inserted into the inner cores at both ends of the fiber and fixed with light-cured epoxy resin. The fiber samples were connected to an electrochemical workstation and set to IT mode. After setting the initial voltage, the tensile testing machine was started and the speed was set to 60 mm / min. The relative resistance change value was calculated from the current change value and the initial voltage value, and the strain was calculated from the initial fiber length and time.

[0080] The test results of Examples 1-3 are as follows: Figure 3 As shown, the test results of Examples 1 and 4-5 are as follows: Figure 4 As shown, the test results of Examples 1 and 6-9 are as follows: Figure 5 As shown.

[0081] Figure 3 In this study, the sensitivity of stretchable conductive fibers gradually increases with the increase of the solid content of the PEDOT:PSS suspension. This is because the increase in the solid content of the PEDOT:PSS suspension leads to an increase in the initial conductivity of the fibers, resulting in a larger change in relative resistance during stretching and thus a higher sensitivity, reaching up to 3500 Ω and inductively modulating up to 235%.

[0082] Figure 4 In the study, as the concentration of H2SO4 increases, the sensitivity of stretchable conductive fibers gradually decreases. This is because the increase in H2SO4 concentration causes the stretchable conductive fibers to maintain a high conductivity after stretching, with a relatively small change in resistance and low sensitivity. The sensitivity can reach up to 3500, and the inductive strain can reach 235%.

[0083] Figure 5 In this process, as the concentration of PU solution increases, the sensitivity of stretchable conductive fibers gradually increases, reaching a maximum of 3500 and inductively modulating up to 235%.

[0084] Experimental Example 3: Stress-Strain Test

[0085] Stress-strain tests were performed on the stretchable conductive fibers prepared in Examples 1 and 6-9. The specific test procedure is as follows: 3-4 cm fiber samples were cut, and both ends were fixed with UV-cured epoxy resin. The fiber ends were then fixed with upper and lower clamps of a tensile testing machine, and the test was conducted at a speed of 60 mm / min. The test results are as follows: Figure 6 As shown.

[0086] from Figure 6 As can be seen, with the increase of PU concentration, the modulus of the resulting fiber increases and the mechanical strength also increases, but the elongation at break decreases slightly, and the tensile strain can reach 440% to 520%.

[0087] Experiment Example 4: Scanning Electron Microscopy Test

[0088] The stretchable conductive fiber prepared in Example 1 was subjected to scanning electron microscopy (SEM) testing, and the test results are as follows: Figure 7 As shown, the cross-sectional test results are as follows: Figure 8 As shown.

[0089] from Figure 7 As can be seen, the stretchable conductive fiber is linear, with a relatively smooth surface and a uniform diameter of 0.5–2.0 mm. Figure 8 As can be seen, the cross-section of the conductive fiber has a core-shell structure.

[0090] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing a PU / PEDOT:PSS stretchable conductive fiber with a core-sheath structure, characterized in that, This stretchable conductive fiber uses polyurethane (PU) as the outer shell and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) hydrogel as the inner core. The mass ratio of the PU shell to the PEDOT:PSS hydrogel core is 0.6:1 to 1.5:

1. The stretchable conductive fiber has a diameter of 0.5–2.0 mm, a tensile strain of 440–520%, and a resistivity of 600–2250 Ω / cm. Strain sensors made from this fiber can achieve a sensitivity coefficient of up to 3500 and an inductive strain of up to 235%. The preparation method includes using polyurethane and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid as raw materials and preparing them using a microfluidic device. Acid-doped PEDOT:PSS suspension is used as the inner layer fluid, PU solution is used as the middle layer fluid, and mixed solvent is used as the outer layer coagulation bath fluid. The mixed solvent is selected from water and DMSO, wherein the volume ratio of water to DMSO is 4:6 to 9:1; The solid content of the acid-doped PEDOT:PSS suspension is 10–30 mg / mL; The dopant in the acid-doped PEDOT:PSS suspension is sulfuric acid. The acid concentration in the acid-doped PEDOT:PSS suspension is 0.03–0.5 mol / L. The concentration of the PU solution is 120–270 mg / mL.

2. The preparation method according to claim 1, characterized in that, The acid concentration in the acid-doped PEDOT:PSS suspension is 0.05–0.15 mol / L.

3. The preparation method according to claim 1, characterized in that, The concentration of the PU solution is 160–240 mg / mL; The solvent of the PU solution is selected from one or more of DMSO, DMF, xylene, cyclohexanone, acetone, methyl isobutyl ketone, ethyl acetate, butyl acetate, and tetrahydrofuran.

4. The preparation method according to claim 1, characterized in that, The flow rate of PEDOT:PSS suspension is 1–8 mm / s; The flow rate of the PU solution is 0.5–2 mm / s; The flow rate of the mixed solvent is 1.5–4 mm / s.

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