An on-line preparation method of a flexible strain sensing fiber

Abstract

The present invention discloses an on-line preparation method of flexible strain-sensing fibers. By using the microfluidic spinning technology and a three-channel coaxial spinning needle, the fiber forming and the in-situ polymerization of polyaniline are realized synchronously, and polyaniline / polyurethane conductive composite fibers are continuously prepared. During the preparation process, the growth morphology of polyaniline can be effectively regulated by changing the spinning and reaction conditions, including polyaniline particles, polyaniline nanowires, etc. The prepared polyaniline / polyurethane conductive composite fibers have a diameter of 180 - 240 μm and a conductivity of 0.3 - 20 S / m; the conductive composite fibers can be directly used as flexible strain sensors, with a maximum strain response of 100% - 300%, a sensitivity coefficient in the linear region of 10 - 54, and a linearity of 0.918 - 0.996; and the strain-sensing fibers are convenient to be integrated with clothing fabrics by sewing, which can greatly improve the wearing comfort of smart clothing.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel fiber materials, and relates to an on-line preparation method of a flexible strain sensing fiber. Background Art

[0002] The rapid development of flexible electronics science and the fast-paced lifestyle in today's society have greatly promoted people's demand for safe, efficient, comfortable and wearable flexible electronic devices. Flexible strain sensors have attracted extensive attention in the fields of sports training equipment, medical monitoring equipment, intelligent robots, etc. because they can convert various external strain stimuli into electrical signals to reflect human motion and physiological information. Therefore, developing high-performance flexible strain sensors with high sensitivity and high linearity has important practical value and significance.

[0003] Although thin-film-based flexible strain sensors have advantages such as multiple sensing and wide applicability, they have problems such as poor breathability, poor compatibility with human skin or textile clothing, and difficulty in mass production. In contrast, strain sensing fibers not only have the ability to sense strain, but also have clothing advantages such as flexibility, comfort, and breathability. They are easy to be integrated into clothing fabrics through textile processing technology, and better meet the development needs of wearable flexible electronics, with great potential.

[0004] Among the many conductive materials that can be used to prepare flexible strain sensing fibers, the conductive polymer polyaniline (PANI) has become a better candidate because of its easy availability of raw materials, simple synthesis method, and good chemical stability. At present, the methods for preparing polyaniline conductive composite fibers mainly include blending spinning with polymer materials and generating conductive polyaniline on the fiber surface through chemical oxidative polymerization or electrochemical deposition. The blending spinning method mainly has problems such as uneven dispersion of polyaniline powder, low conductive density, unsatisfactory conductivity of composite fibers, and poor sensing performance. In the surface treatment method, whether it is the in-situ polymerization method or the electrochemical deposition method, the fiber material needs to be pre-soaked in aniline solution, and then the polymerization of aniline monomers is initiated by adding an oxidant or applying an electric current, and finally polyaniline conductive composite fiber materials are prepared. These methods are time-consuming and laborious, and it is difficult to control the generation rate and growth morphology of polyaniline during the polymerization process, and it is difficult to realize the large-scale continuous production of polyaniline conductive composite fibers. At present, there is still a lack of advanced on-line in-situ polymerization process of polyaniline and a one-step mass preparation method of polyaniline conductive composite fibers.

[0005] Therefore, how to organically combine the advanced spinning technology with the chemical synthesis of polyaniline synchronously to improve the production efficiency and application effect of polyaniline conductive composite fibers has become the key technical problem in constructing high-performance conductive polymer-based flexible strain sensing fibers. Summary of the Invention

[0006] The object of the present invention is to provide an on-line preparation method for flexible strain sensing fibers to solve the above problems.

[0007] The technical solution of the present invention is as follows:

[0008] An on-line preparation method for flexible strain sensing fibers, characterized by comprising the following steps:

[0009] (1) Set up a coaxial microfluidic chip with three channels. The three channels are successively set as the first channel, the second channel and the third channel from the inside to the outside. The outlet end of the first channel extends into the outlet end of the second channel, and the outlet end of the second channel extends into the outlet end of the third channel;

[0010] (2) Dissolve the fiber-forming polymer polyurethane in the organic solvent N,N-dimethylformamide, and seal and stir magnetically until completely dissolved to obtain a polyurethane spinning solution;

[0011] (3) Prepare a protonic acid doping solution containing aniline monomers;

[0012] (4) Prepare an oxidant solution;

[0013] (5) Conduct microfluidic spinning: Put the polyurethane spinning solution, the protonic acid doping solution containing aniline monomers and the oxidant solution into the first syringe, the second syringe and the third syringe respectively. The first syringe, the second syringe and the third syringe are respectively connected to the first microfluidic pump, the second microfluidic pump and the third microfluidic pump. The first syringe is connected to the first channel of the microfluidic chip through the first spinning catheter, the second syringe is connected to the second channel of the microfluidic chip through the second spinning catheter, and the third syringe is connected to the third channel of the microfluidic chip through the third spinning catheter. The polyurethane spinning solution, the protonic acid doping solution containing aniline monomers and the oxidant solution are respectively extruded from the first spinning catheter, the second spinning catheter and the third spinning catheter, and respectively enter the first channel, the second channel and the third channel. The polyurethane spinning solution successively contacts the protonic acid doping solution containing aniline monomers and the oxidant solution in the spinning channel and gradually forms, and in-situ polymerization reaction occurs synchronously on the surface to obtain initial fibers, and then the fibers are extruded from the needle head into a glass dish;

[0014] (6) Let the initial fibers stand still to allow the polymerization reaction to proceed fully, and finally wash with deionized water and dry to obtain flexible strain sensing fibers, and wind and collect them.

[0015] Further, in step (1), the distance from the outlet end of the first channel to the outlet end of the second channel is 10-20 mm, and the distance from the outlet end of the second channel to the outlet end of the third channel is 10-20 mm.

[0016] Further, in step (2), the concentration of the polyurethane spinning solution is 8-12 wt.%.

[0017] Further, in step (3), the content of aniline monomer is 0.01-0.5 M, and the protonic acid is any one of hydrochloric acid, sulfuric acid, perchloric acid, camphorsulfonic acid, and dodecylbenzenesulfonic acid. When the protonic acid is hydrochloric acid, the concentration of the hydrochloric acid is 0.1-1 M.

[0018] Further, in step (4), the oxidant is any one of ammonium persulfate, potassium dichromate, ferric chloride, hydrogen peroxide, sodium hypochlorite, and vanadium pentoxide. When the oxidant is ammonium persulfate, the concentration of the ammonium persulfate is 0.1-1 M.

[0019] Further, in step (5), the flow rate of the polyurethane spinning solution in the first channel is 1-2 ml / h, the flow rate of the protonic acid-doped solution containing aniline monomer in the second channel is 2-8 ml / h, and the flow rate of the oxidant solution in the third channel is 2-8 ml / h.

[0020] Further, in step (5), the temperature of the microfluidic spinning is 5-25 °C.

[0021] Further, in step (6), the standing time is 2-6 h.

[0022] Further, in step (6), the diameter of the flexible strain sensing fiber is 180-240 μm, the conductivity is 0.3-20 S / m, the maximum strain response is 100%-300%, the sensitivity coefficient in the linear region is 10-54, and the linearity is 0.918-0.996.

[0023] The present invention provides an on-line preparation method for flexible strain sensing fibers, and its advantages are as follows:

[0024] 1. The preparation method of the present invention is simple, the process flow is concise. The microfluidic chip is used to replace the spinning coagulation bath and the polymerization reactor, opening up a new on-line preparation method different from traditional blend spinning and in-situ polymerization by impregnation, getting rid of the multi-process and non-uniformity of the conventional step-by-step preparation method, and realizing the one-step uniform and continuous preparation of polyaniline conductive composite fibers;

[0025] 2. The present invention can effectively control the growth morphology of polyaniline, including polyaniline particles, polyaniline nanowires, etc., by changing the spinning and reaction conditions to meet the actual application requirements of multi-scale polyaniline;

[0026] 3. The adhesion fastness of the polyaniline on the surface of the composite fiber prepared by the present invention is higher. Since the polymerization reaction starts from the front-end spinning solution, there are many binding sites and a long binding time. At the same time, during the solvent exchange process, aniline can penetrate into the interior of the main fiber and take root, thus forming a more firm interfacial bond;

[0027] 4. The flexible strain sensing fiber prepared by the present invention can be directly integrated with the clothing fabric by sewing, which is of great significance in the development and application of intelligent clothing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of a microfluidic spinning chip used in the on-line preparation method of a flexible strain sensing fiber according to the present invention. Among them, Ⅰ is the first channel, Ⅱ is the second channel, and Ⅲ is the third channel;

[0029] Figure 2 It is a schematic diagram of the preparation process of the on-line preparation method of a flexible strain sensing fiber according to the present invention. Among them, 1 is the first syringe, 2 is the second syringe, 3 is the third syringe, 4 is the first microfluidic pump, 5 is the second microfluidic pump, 6 is the third microfluidic pump, 7 is the first spinning conduit, 8 is the second spinning conduit, 9 is the third spinning conduit, 10 is the microfluidic chip, and 11 is the glass dish;

[0030] Figure 3 It is a morphological electron micrograph of a flexible strain sensing fiber prepared in Example 1 by the on-line preparation method of a flexible strain sensing fiber according to the present invention;

[0031] Figure 4 It is a morphological electron micrograph of a flexible strain sensing fiber prepared in Example 2 by the on-line preparation method of a flexible strain sensing fiber according to the present invention;

[0032] Figure 5 It is a strain sensing performance test diagram of the flexible strain sensing fiber prepared by the on-line preparation method of a flexible strain sensing fiber according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The object of the present invention is to provide an on-line preparation method of a flexible strain sensing fiber. Using an elastic high polymer thermoplastic polyurethane (TPU) as a raw material, adopting microfluidic spinning technology and in-situ polymerization process, improving a three-channel coaxial microfluidic chip, introducing aniline monomer and oxidant into the spinning channel, enabling the fiber to simultaneously undergo an in-situ polymerization reaction during the forming process, and uniformly growing conductive polyaniline with different morphologies on the fiber surface by controlling the spinning conditions, thereby preparing a flexible strain sensing fiber with excellent strain sensing performance and directly applicable to intelligent sportswear. Specifically as follows:

[0034] An on-line preparation method of a flexible strain sensing fiber is realized through the following steps:

[0035] (1) Design a three-channel coaxial-like microfluidic chip. Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the microfluidic spinning chip used in the preparation method of the flexible strain sensing fiber described in the present invention. As Figure 1 shown, the three channels of the coaxial-like microfluidic chip are sequentially defined as the first channel Ⅰ, the second channel Ⅱ, and the third channel Ⅲ from the inside to the outside. The distance d1 from the outlet end of the first channel Ⅰ to the outlet end of the second channel Ⅱ is 10 - 20 mm, and the distance d2 from the outlet end of the second channel Ⅱ to the outlet end of the third channel Ⅲ is 10 - 20 mm.

[0036] (2) Dissolve the fiber-forming polymer polyurethane in the organic solvent N,N-dimethylformamide, and seal and magnetically stir until it is completely dissolved to obtain a polyurethane spinning solution with a solution concentration of 8 - 12 wt.%.

[0037] (3) Prepare a protonic acid doping solution containing 0.01 - 0.5 M aniline monomer. Among them, the protonic acid can be hydrochloric acid, sulfuric acid, perchloric acid, camphorsulfonic acid, dodecylbenzenesulfonic acid, etc. Preferably, the doping acid is hydrochloric acid with a concentration of 0.1 - 1 M.

[0038] (4) Prepare an oxidant solution. Among them, the oxidant can be ammonium persulfate, potassium dichromate, ferric chloride, hydrogen peroxide, sodium hypochlorite, vanadium pentoxide, etc. Preferably, the oxidant is ammonium persulfate with a concentration of 0.1 - 1 M.

[0039] (5) Conduct microfluidic spinning. Please refer to Figure 2 , Figure 2 which is a schematic diagram of the preparation process of the on-line preparation method of the flexible strain sensing fiber described in the present invention. As Figure 2As shown, a polyurethane spinning solution, a protonic acid-doped solution containing aniline monomers (protonic acid-aniline doped solution), and an oxidant solution are respectively placed in a first syringe 1, a second syringe 2, and a third syringe 3. Under the action of uniform extrusion by a first microfluidic pump 4, a second microfluidic pump 5, and a third microfluidic pump 6, they are injected into a first channel Ⅰ, a second channel Ⅱ, and a third channel Ⅲ of a microfluidic chip 10 through a first spinning conduit 7, a second spinning conduit 8, and a third spinning conduit 9. The flow rate of the polyurethane solution in the first channel Ⅰ is 1 - 2 ml / h, the flow rate of the protonic acid-aniline doped solution in the second channel Ⅱ is 2 - 8 ml / h, and the flow rate of the oxidant solution in the third channel Ⅲ is 2 - 8 ml / h. The polyurethane spinning solution in the first channel Ⅰ in the microfluidic chip 10 gradually solidifies into fibers under the action of the solvents and solutes in the second channel Ⅱ and the third channel Ⅲ, and an in-situ polymerization reaction of aniline occurs on the surface. The microfluidic chip serves as a coagulation bath and a microreactor during this process. Finally, the formed fibers are received by a glass dish 11 after being extruded from the microfluidic chip 10, and thus initial fibers are obtained. The temperature of the above spinning and reaction environment is 5 - 25°C.

[0040] (6) Let the initial fibers stand for 2 - 6 h to allow the polymerization reaction to proceed fully. Finally, wash with deionized water, dry, and wind and collect.

[0041] During the above preparation process, by changing the spinning and reaction environment temperature, the growth morphology of polyaniline can be regulated, including polyaniline particles, polyaniline nanowires, etc.

[0042] The diameter of the polyaniline / polyurethane conductive composite fiber prepared by the above method is 180 - 240 μm, and the conductivity is 0.3 - 20 S / m. The prepared polyaniline / polyurethane conductive composite fiber can be directly used as a flexible strain sensor, with a maximum strain response of 100% - 300%, a sensitivity coefficient in the linear region of 10 - 54, and a linearity of 0.918 - 0.996. This strain-sensing fiber is convenient to be integrated with clothing fabrics in a sewing manner, greatly improving the wearing comfort of smart clothing.

[0043] To make the above objects, features, and advantages of the present invention more obvious and understandable, the technical solutions of the present invention will be further described below in conjunction with specific embodiments. However, the present invention is not limited to the listed embodiments, and should also include any other well-known changes within the scope of the rights required by the present invention.

[0044] As used herein, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in an embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selectively exclusive embodiment from other embodiments.

[0045] Example 1

[0046] The following examples demonstrate an on-line preparation method of flexible strain sensing fibers, and the specific steps are as follows:

[0047] Dissolve polyurethane particles in the organic solvent N,N-dimethylformamide, seal and stir magnetically until completely dissolved to obtain a polyurethane spinning solution with a concentration of 8 wt.%. At the same time, prepare a hydrochloric acid-aniline doping solution containing 0.1 M aniline monomer and 0.5 M hydrochloric acid and a 0.5 M ammonium persulfate solution. Extrude the polyurethane solution, hydrochloric acid-aniline doping solution and ammonium persulfate solution respectively from channels I, II, and III of the microfluidic chip through a microfluidic pump syringe. The solution flow rates of channels I, II, and III are 1 ml / h, 2 ml / h, and 2 ml / h respectively. The distance from the outlet end of channel I to the outlet end of channel II is 10 mm, and the distance from the outlet end of channel II to the outlet end of channel III is 10 mm. The fiber gradually forms in the spinning channel and in-situ polymerization reaction occurs synchronously on the surface, and then is extruded from the needle and received in a glass dish. Let the obtained fiber stand for 6 h to allow the polymerization reaction to proceed fully. The spinning and reaction environment temperature is 25°C. Finally, wash the fiber with deionized water, dry it, and wind and collect it.

[0048] Please refer to Figure 3 and Figure 5 , Figure 3 is the on-line morphology electron micrograph of a flexible strain sensing fiber prepared in Example 1 by the on-line preparation method of a flexible strain sensing fiber described in the present invention;

[0049] Figure 5 is the strain sensing performance test chart of the flexible strain sensing fiber prepared by the on-line preparation method of a flexible strain sensing fiber described in the present invention. As Figure 3 shown, on the surface of the polyaniline / polyurethane flexible strain sensing fiber obtained by the above preparation method and process parameters, polyaniline exists in the form of particles. The diameter of the prepared flexible strain sensing fiber is 218±12 μm, and the conductivity is 0.37 S / m. As Figure 5 shown, the maximum strain that the flexible strain sensing fiber can sense is 200%, the sensitivity coefficient in the linear region is 12, and the linearity is 0.986.

[0050] Example 2

[0051] The following examples demonstrate an on-line preparation method of flexible strain sensing fibers, and the specific steps are as follows:

[0052] The polyurethane particles were dissolved in the organic solvent N,N-dimethylformamide and sealed with magnetic stirring until completely dissolved to obtain a polyurethane spinning solution with a concentration of 10 wt.%. At the same time, an acidic aniline doping solution containing 0.1 M aniline monomer and 0.3 M hydrochloric acid and a 0.3 M ammonium persulfate solution were prepared. The polyurethane solution, the acidic aniline doping solution, and the ammonium persulfate solution were respectively extruded from channels I, II, and III of the microfluidic chip through a microfluidic pump syringe. The solution flow rates of channels I, II, and III were 1 ml / h, 4 ml / h, and 4 ml / h, respectively. The distance from the outlet end of channel I to the outlet end of channel II was 15 mm, and the distance from the outlet end of channel II to the outlet end of channel III was 15 mm. The fibers were gradually formed in the spinning channel and an in-situ polymerization reaction occurred synchronously on the surface, and then were extruded from the needle and received in a glass dish. The obtained fibers were left standing for 2 h to allow the polymerization reaction to proceed fully. The temperature of the spinning and reaction environment was 5 °C. Finally, the fibers were washed with deionized water, dried, and wound up for collection.

[0053] Please refer to Figure 4 and Figure 5 , Figure 4 is the SEM image of the morphology of a flexible strain sensing fiber prepared in Example 2 by the on-line preparation method of a flexible strain sensing fiber described in the present invention; Figure 5 is the test chart of the strain sensing performance of the flexible strain sensing fiber prepared by the on-line preparation method of a flexible strain sensing fiber described in the present invention. As Figure 4 shown, the polyaniline on the surface of the polyaniline / polyurethane flexible strain sensing fiber obtained by the above preparation method and process parameters exists in the form of nanowires. The diameter of the prepared flexible strain sensing fiber is 227 ± 16 μm, and the conductivity is 17.9 S / m. As Figure 5 shown, the maximum strain that the flexible strain sensing fiber can sense is 300%, the sensitivity coefficient in the linear region is 24.2, and the linearity is 0.961.

[0054] In summary, the on-line preparation method of a flexible strain sensing fiber described in the present invention has a short process flow, is easy to operate, saves energy, and can realize the large-scale batch preparation of sensing fibers, and has good economic and social benefits.

[0055] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. An on-line preparation method of a flexible strain sensing fiber, characterized in that, It includes the following steps: (1) Set up a coaxial microfluidic chip with three channels. The three channels are set as the first channel, the second channel, and the third channel from the inside to the outside. The outlet end of the first channel extends into the outlet end of the second channel, and the outlet end of the second channel extends into the outlet end of the third channel. (2) Dissolve the fiber-forming polymer polyurethane in the organic solvent N,N-dimethylformamide, seal it and stir magnetically until completely dissolved to obtain a polyurethane spinning solution. (3) Prepare a protonic acid doping solution containing aniline monomers. (4) Prepare an oxidant solution. (5) Conduct microfluidic spinning: Put the polyurethane spinning solution, the protonic acid doping solution containing aniline monomers, and the oxidant solution into the first syringe, the second syringe, and the third syringe respectively. The first syringe, the second syringe, and the third syringe are respectively connected to the first microfluidic pump, the second microfluidic pump, and the third microfluidic pump. The first syringe is connected to the first channel of the microfluidic chip through the first spinning catheter, the second syringe is connected to the second channel of the microfluidic chip through the second spinning catheter, and the third syringe is connected to the third channel of the microfluidic chip through the third spinning catheter. The polyurethane spinning solution, the protonic acid doping solution containing aniline monomers, and the oxidant solution are respectively extruded from the first spinning catheter, the second spinning catheter, and the third spinning catheter, and enter the first channel, the second channel, and the third channel respectively. The polyurethane spinning solution gradually forms after successively contacting the protonic acid doping solution containing aniline monomers and the oxidant solution in the spinning channel, and in-situ polymerization reaction occurs synchronously on the surface to obtain initial fibers, which are then extruded from the needle into a glass dish. (6) Let the initial fibers stand still to allow the polymerization reaction to proceed fully, and finally wash them with deionized water, dry them to obtain flexible strain-sensing fibers, and wind and collect them.

2. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (1), the distance from the outlet end of the first channel to the outlet end of the second channel is 10 - 20 mm, and the distance from the outlet end of the second channel to the outlet end of the third channel is 10 - 20 mm.

3. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (2), the concentration of the polyurethane spinning solution is 8 - 12 wt.%.

4. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (3), the content of aniline monomers is 0.01 - 0.5 M, and the protonic acid is any one of hydrochloric acid, sulfuric acid, perchloric acid, camphorsulfonic acid, and dodecylbenzenesulfonic acid. When the protonic acid is hydrochloric acid, the concentration of hydrochloric acid is 0.1 - 1 M.

5. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (4), the oxidant is any one of ammonium persulfate, potassium dichromate, ferric chloride, hydrogen peroxide, sodium hypochlorite, and vanadium pentoxide. When the oxidant is ammonium persulfate, the concentration of ammonium persulfate is 0.1 - 1 M.

6. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (5), the flow rate of the polyurethane spinning solution in the first channel is 1 - 2 ml / h, the flow rate of the protonic acid doping solution containing aniline monomers in the second channel is 2 - 8 ml / h, and the flow rate of the oxidant solution in the third channel is 2 - 8 ml / h.

7. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (5), the temperature of the microfluidic spinning is 5 - 25 °C.

8. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (6), the standing time is 2 - 6 h.

9. The on-line preparation method of a flexible strain sensing fiber according to claim 1, characterized in that: In step (6), the diameter of the flexible strain sensing fiber is 180 - 240 μm, the conductivity is 0.3 - 20 S / m, the maximum strain response is 100% - 300%, the sensitivity coefficient in the linear region is 10 - 54, and the linearity is 0.918 - 0.996.

Images