TW202346437A - Fabrication method of polycrystalline phase polyvinylidene fluoride film and wearable device using polycrystalline phase polyvinylidene fluoride film - Google Patents

Abstract

The present invention proposes a fabrication method of a polycrystalline phase polyvinylidene fluoride (PVDF) film. The polycrystalline phase PVDF film obtained by the fabrication method of the present invention has both a β crystal phase and a γ crystal phase, so the polycrystalline phase PVDF film of the present invention has a good piezoelectric effect to sense pressure or tension in different directions. At the same time, the polycrystalline phase PVDF film of the present invention also has a good pyroelectric effect for sensing the surrounding temperature.

Description

Method for producing polycrystalline polyvinylidene fluoride film and wearable device using polycrystalline polyvinylidene fluoride film

The invention relates to a method for making a polyvinylidene difluoride (PVDF) film, and in particular to a method for making a polycrystalline polyvinylidene fluoride film.

In addition to its good chemical resistance, high temperature resistance, oxidation resistance, weather resistance, and radiation resistance, polyvinylidene fluoride (PVDF) also has piezoelectric effect, pyroelectric effect, and dielectric effect. , so it is widely used in functional films such as piezoelectric films, solar backsheet films, and lithium battery separators. The piezoelectric effect means that when a piezoelectric crystal deforms under the action of external force, equal amounts of charges with different signs will appear on some corresponding surfaces. The pyroelectric effect refers to the phenomenon that the electrical polarization of a polar dielectric changes due to temperature changes. The pyroelectric effect can be used to measure ambient temperature or body temperature.

Compared with traditional piezoelectric materials (such as ceramic piezoelectric sheets), polyvinylidene fluoride has the characteristics of wide frequency response, large dynamic range, high force point conversion sensitivity, good mechanical properties, high mechanical strength, and easy matching of acoustic impedance. It also has the advantages of light weight, softness and non-brittleness, impact resistance, not easily contaminated by water and chemicals, and easy to be made into sheets or pipes of any shape and area. It is widely used in technical fields such as mechanics, acoustics, optics, electronics, measurement, infrared, security alarm, medical care, military, transportation, information engineering, office automation, ocean development, geological exploration and other technical fields.

The piezoelectric film formed of polyvinylidene fluoride has the advantages of thin thickness, light weight, very softness, and can work without power supply, so it is widely used in medical sensors and other devices. As a dynamic strain sensor, the piezoelectric film formed of polyvinylidene fluoride is very suitable for application on the surface of human skin or implanted inside the human body for physiological status monitoring, such as monitoring breathing and heartbeat.

Polyvinylidene fluoride is a polycrystalline polymer, and polyvinylidene fluoride films with different crystal phases can be obtained by using different methods such as additives. Its crystal phases mainly include α crystal phase, β crystal phase and γ crystal phase. Polyvinylidene fluoride in the alpha crystal phase has high thermodynamic stability, and the molecular chain conformation of TGTG' in its crystal lattice causes its molecular chain dipoles to be opposite in polarity without showing polarity. Polyvinylidene fluoride in the β crystal phase is an orthorhombic all-trans conformation TTT, which has spontaneous polarity and excellent piezoelectric properties. The molecular conformation of polyvinylidene fluoride in the γ crystal phase is TTTGTTTG'. The two molecular chains in the same unit cell are arranged in parallel and have polarity due to the same dipole moment direction. Figure 1, Figure 2 and Figure 3 respectively show the molecular structure of polyvinylidene fluoride in the α crystal phase, β crystal phase and γ crystal phase, in which C is a carbon atom, F is a fluorine atom and H is hydrogen. (Hydrogen) atoms.

The β crystal phase and γ crystal phase of polyvinylidene fluoride have high spontaneous polarization intensity and are important crystal phase structures of polyvinylidene fluoride. Polyvinylidene fluoride in the β crystal phase and γ crystal phase has excellent ferroelectricity, pyroelectricity and piezoelectric properties.

In recent years, polyvinylidene fluoride films have also begun to be used in wearable devices. However, current polyvinylidene fluoride films only use one of its crystal phases and have a single function, so their application in wearable devices with limited space is limited. To this end, the present invention proposes a polycrystalline polyvinylidene fluoride film to provide multiple functions at the same time.

One of the objects of the present invention is to provide a method for producing a polycrystalline polyvinylidene fluoride film.

One object of the present invention is to provide a wearable device using a polycrystalline polyvinylidene film.

According to the present invention, a method for making a polycrystalline polyvinylidene fluoride film includes: coating a polyvinylidene fluoride solution on a substrate to form a film, and heating the polyvinylidene fluoride solution on the substrate to its melting point Above, to produce a first polyvinylidene fluoride film; cooling the first polyvinylidene fluoride film to obtain a second polyvinylidene fluoride film in a semi-molten state, a supercooled state and having an α crystal phase; using electrospinning Preparing a plurality of polyvinylidene fluoride fibers with a β crystal phase; arranging the plurality of polyvinylidene fluoride fibers in parallel on the second polyvinylidene fluoride film to obtain a third polyvinylidene fluoride film; at a fixed temperature The third polyvinylidene fluoride film is heated and annealed to change the α phase crystal to the γ phase crystal, and finally obtain the polycrystalline phase polyvinylidene fluoride film having the β crystal phase and the γ crystal phase.

In one embodiment, a polyvinylidene fluoride material can be dissolved in a solvent to prepare the polyvinylidene fluoride material solution, where the solvent can be but is not limited to dimethylformamide (DMF).

In one embodiment, the step of producing the first polyvinylidene fluoride film includes heating the polyvinylidene fluoride solution on the substrate to above the melting point (eg, 200° C.) to produce the first polyvinylidene fluoride film.

In one embodiment, the fixed temperature may be 160°C.

In one embodiment, the step of producing the plurality of polyvinylidene fluoride fibers includes electrospinning a polyvinylidene fluoride material to produce the plurality of polyvinylidene fluoride fibers.

According to the present invention, a wearable device includes a polycrystalline polyvinylidene fluoride film, a switch device and a processor. The polycrystalline polyvinylidene fluoride film has a β crystal phase and a γ crystal phase. The polycrystalline polyvinylidene fluoride film can sense temperature and pressure to generate a temperature sensing signal and a pressure sensing signal. The processor is coupled to the polycrystalline polyvinylidene fluoride film and the switch device, controls the switch device to turn on or off the wearable device according to the temperature sensing signal, and generates an electrical signal according to the pressure sensing signal.

In one embodiment, when the polycrystalline polyvinylidene fluoride film senses human body temperature, the processor activates the wearable device according to the temperature sensing signal.

In one embodiment, when the polycrystalline polyvinylidene fluoride film does not sense human body temperature, the processor turns off the wearable device according to the temperature sensing signal.

In one embodiment, the electrical signal is used to determine physiological status or generate relevant information.

In one embodiment, the physiological state includes heartbeat, blood pressure, or respiration.

In one embodiment, the relevant information includes pressure, weight or distance.

In order to make the description of the present invention more detailed and complete, the following provides an illustrative description of the implementation modes and specific embodiments of the present invention, but this is not the only form of implementing or using the specific embodiments of the present invention. The present invention may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will enable those skilled in the art to fully understand the scope of the invention.

Numerical values or ranges mentioned herein are approximate unless otherwise expressly stated.

The terminology used herein is used only to describe specific embodiments and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to cover the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that when the terms "comprising" and "include" are used in the specification, the presence of the stated features, integers, steps, operations, elements and/or parts is specified but does not exclude one or more other features, integers. , steps, operations, components and/or parts.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It is further understood that terms such as those defined in commonly used dictionaries should be interpreted to have meanings consistent with their meaning in the context of the relevant field and should not be interpreted in an overly idealized or overly formal sense, Unless explicitly defined herein.

In this document, numerous specific details are set forth in detail to enable the reader to fully understand the following embodiments. However, embodiments of the invention may be practiced without these specific details. In other instances, well-known structures and devices are shown schematically in the drawings for the purpose of simplifying the drawings.

In various embodiments, one feature, element, or circuit is formed on, connected to, and/or coupled to another feature, element, or circuit, and may include connecting contacts of these features, elements, or circuits. Embodiments may also include embodiments in which another feature, component, or circuit may be incorporated between the features, components, or circuits such that the features, components, or circuits may not be in direct contact.

Figure 4 shows the process for producing a polycrystalline polyvinylidene fluoride film according to the present invention. In step S10 of Figure 4, a polyvinylidene fluoride solution is prepared, and the polyvinylidene fluoride solution is coated on a substrate to form a film, and then the polyvinylidene fluoride solution on the substrate is heated to above its melting point. To smooth the polyvinylidene fluoride solution into a first polyvinylidene fluoride film. The first polyvinylidene fluoride film produced in step S10 is a half melt film. Heating the polyvinylidene fluoride solution, in addition to producing the first polyvinylidene fluoride film, can also eliminate the thermal history of the polyvinylidene fluoride material in the polyvinylidene fluoride solution, so that subsequent crystallization is not affected by the previous The influence of the generation conditions. The thermal history includes the effects of temperature, shearing and stretching on the polyvinylidene fluoride material before it is molded and shipped from the factory. In one embodiment, the polyvinylidene fluoride solution on the substrate can be heated to about 200° C. to obtain the first polyvinylidene fluoride film. In one embodiment, the step of preparing the polyvinylidene fluoride solution includes dissolving a polyvinylidene fluoride material in a corresponding solvent to obtain the polyvinylidene fluoride solution, wherein the solvent includes but is not limited to dimethylformamide. (DMF).

After the first polyvinylidene fluoride film is produced in step S10, step S12 of FIG. 4 is performed. In step S12, the first polyvinylidene fluoride film is cooled to form a second polyvinylidene fluoride film in a semi-molten state. The second polyvinylidene fluoride film has an α crystal phase. In one embodiment, the first polyvinylidene fluoride film is cooled from a temperature of about 200°C to a temperature of about 160°C to obtain the second polyvinylidene fluoride film. The cooling method in step S12 includes but is not limited to natural cooling.

In step S14 of FIG. 4 , a polyvinylidene fluoride material is placed into an electrospinning device for electrospinning to produce a plurality of polyvinylidene fluoride fibers with a β crystal phase. During the electrospinning process, the polyvinylidene fluoride material will be melted to eliminate the thermal history of the polyvinylidene fluoride material to avoid affecting subsequent crystallization. Electrospinning is a technology for preparing fibers through high electric fields. The β crystal phase of polyvinylidene fluoride fibers produced by electrospinning is relatively stable and easy to prepare, mainly because electrospinning gives polyvinylidene fluoride materials Stretch curing occurs simultaneously with electropolarization. Electrospinning is a common technology, so its specific operations and principles will not be described again here. In the embodiment of FIG. 4 , electrospinning is used to produce multiple polyvinylidene fluoride fibers with β crystalline phase. However, the present invention is not limited to this. Other methods can be used to produce polyvinylidene fluoride fibers with β crystalline phase. Also applicable to the present invention.

In the embodiment of FIG. 4 , step S10 and step S14 may be performed simultaneously, or one step may be completed before the other. For example, steps S10 and S12 are performed first and then step S14 is performed, or step S14 is performed first and then steps S10 and S12 are performed.

In the embodiment of FIG. 4 , the polyvinylidene fluoride material in the polyvinylidene fluoride solution used in step S10 and the polyvinylidene fluoride material used in step S14 may be the same or different.

Step S16 is performed after obtaining the second polyvinylidene fluoride film and the plurality of polyvinylidene fluoride fibers. In step S16, the second polyvinylidene fluoride film is placed on a collection platform, and the plurality of polyvinylidene fluoride fibers are arranged in parallel on the second polyvinylidene fluoride film to obtain an α crystal phase. And the third polyvinylidene fluoride film with β crystal phase. In one embodiment, the collection station may be an electrospinning collection station.

In one embodiment, after step S10 is completed to obtain the first polyvinylidene fluoride film, the first polyvinylidene fluoride film can be transferred to the collection stage. During this transfer process, the first polyvinylidene fluoride film The vinyl fluoride film has sufficient time to naturally cool to form the second polyvinylidene fluoride film in a semi-molten state.

After obtaining the third polyvinylidene fluoride film, step S18 is performed. In step S18 of FIG. 4 , the third polyvinylidene fluoride film is placed on the heating stage, and the third polyvinylidene fluoride film is heated and annealed at a fixed temperature. During the heating annealing process in step S18, since the third polyvinylidene fluoride film has polyvinylidene fluoride fibers in the β crystal phase, the α phase crystals in the third polyvinylidene fluoride film will change phase into γ phase crystals, and then A polycrystalline polyvinylidene fluoride film having a β crystal phase and a γ crystal phase is produced. In one embodiment, the fixed temperature used in step S18 is about 160°C, and the continuous heating time is about 48 hours.

The polycrystalline polyvinylidene fluoride film of the present invention has both a β crystal phase and a γ crystal phase. Since the β crystal phase and the γ crystal phase are arranged at an included angle of 90°C, the polycrystalline phase polyvinylidene fluoride film can move in different directions (such as d31 and d33) all have good piezoelectric effects. In other words, when the polycrystalline polyvinylidene fluoride film of the present invention is applied to a ring-shaped wearable device, pressure or tension in various directions can be sensed. In addition, since both the β crystal phase and the γ crystal phase have pyroelectric effects, the polycrystalline polyvinylidene fluoride film of the present invention can also achieve temperature sensing. In wearable devices, the temperature sensing function of the polycrystalline polyvinylidene fluoride film can be used to sense human body temperature. When the polycrystalline polyvinylidene fluoride film senses body temperature or the sensed temperature is higher than a preset value , the wearable device will be activated. On the contrary, when the polycrystalline polyvinylidene fluoride film does not sense body temperature or the sensed temperature is lower than a preset value, the wearable device will be turned off. This function of automatically turning on and off the wearable device can prevent users from forgetting to turn off the wearable device, resulting in a waste of power, and can also extend the service life of the wearable device.

Figure 5 shows a wearable device 10 using the polycrystalline polyvinylidene fluoride film 12 of the present invention. In the embodiment of FIG. 5 , the wearable device 10 includes a polycrystalline polyvinylidene fluoride film 12 , a processor 14 and a switching device 16 . The polycrystalline polyvinylidene fluoride film 12 has both a β crystal phase and a γ crystal phase. The processor 14 connects the polycrystalline polyvinylidene fluoride film 12 and the switching device 16 . The switch device 16 is used to control the startup and shutdown of the wearable device 10 . The wearable device 10 may be, but is not limited to, a pulse sensor.

The processor 14 of FIG. 5 may be a machine using hardware, firmware and/or software, and is physically adapted to operate on a plurality of logic gates forming a specific physical circuit through Boolean logic. Perform specific tasks defined by executable machine instructions. The processor may utilize mechanical, pneumatic, hydraulic, electrical, magnetic, optical, information, chemical, and/or biological principles, mechanisms, adaptations, signals, inputs, and/or outputs to perform tasks. The processor may be a general-purpose device, such as a microcontroller and/or a microprocessor. In some embodiments, the processor may be a special purpose device, such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

The switching device 16 of Figure 5 is an opening/closing circuit for cutting off or conducting a current path. In one embodiment, the switching device 16 may be, but is not limited to, a switch formed by a transistor.

Figure 6 shows a first embodiment of the operation of the wearable device 10 of Figure 5 . As shown in steps S20 and S22 of FIG. 6 , when the user wears the wearable device 10 on the wrist, the polycrystalline polyvinylidene fluoride film 12 of the wearable device 10 senses the user's body temperature, and the polycrystalline phase polymerizes The vinylidene fluoride film 12 thus outputs a temperature sensing signal to the processor 14 . After the processor 14 receives the temperature sensing signal from the polycrystalline polyvinylidene fluoride film 12 , the processor 14 controls the switch device 16 to start the wearable device 10 , as shown in step S24 of FIG. 6 . When the user takes off the wearable device 10 , the polycrystalline polyvinylidene fluoride film 12 of the wearable device 10 cannot sense the user's body temperature, so the polycrystalline polyvinylidene fluoride film 12 stops outputting the temperature sensing signal to The processor 14 is shown in steps S26 and S28 of FIG. 6 . After the polycrystalline polyvinylidene fluoride film 12 stops outputting the temperature sensing signal, the processor 14 controls the switch device 16 to turn off the wearable device 10 , as shown in step S29 of FIG. 6 .

Figure 7 shows a second embodiment of the operation of the wearable device 10 of Figure 5 . When the user wears the wearable device 10 on the wrist, the polycrystalline polyvinylidene fluoride film 12 of the wearable device 10 can sense the pressure or tension on the wrist, as shown in step S30 of FIG. 7 . Pressure or tension on the wrist comes from the beating of the pulse or the swing of the arm. Based on the sensed pressure or tension, the polycrystalline polyvinylidene fluoride film 12 generates a pressure sensing signal to the processor 14 . The processor 14 determines an electrical signal according to the pressure sensing signal, as shown in step S32. The wearable device 10 determines the user's physiological state or generates relevant information based on the electrical signal. Finally, the wearable device 10 can feed back the obtained physiological state or related information to the user, as shown in step S34. Methods of feedback to the user include but are not limited to displaying physiological status or related information on a display, where the display can be provided on the wearable device 10 or externally connected. Depending on the type of the wearable device 10 , the physiological state obtained by the wearable device 10 will be different. For example, when the wearable device 10 is a pulse sensor, the physiological state may be the user's heartbeat or blood pressure. When the wearable device 10 is a breathing sensor, the physiological state may be the user's breathing. Similarly, depending on the type of the wearable device 10 , the relevant information obtained by the wearable device 10 may be but is not limited to pressure, weight or distance.

The above are only embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed in the embodiments above, they are not used to limit the present invention. Anyone with ordinary knowledge in the technical field, Without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make some changes or modifications to equivalent embodiments with equivalent changes. Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solution of the present invention.

10: Wearable devices 12: Polycrystalline polyvinylidene fluoride film 14: Processor 16: Switching device S10: Steps S12: Steps S14: Steps S16: Steps S18: Steps S20: Steps S22: Steps S24: Steps S26: Steps S28: Steps S29: Steps S30: Steps S32: Steps S34: Steps C: carbon atom F: fluorine atom H: Hydrogen atom

Figure 1 shows the molecular structure of polyvinylidene fluoride in the alpha crystal phase. Figure 2 shows the molecular structure of polyvinylidene fluoride in the β crystal phase. Figure 3 shows the molecular structure of polyvinylidene fluoride in the gamma crystal phase. Figure 4 shows the process for producing a polycrystalline polyvinylidene fluoride film according to the present invention. Figure 5 shows a wearable device using the polycrystalline polyvinylidene fluoride film of the present invention. Figure 6 shows a first embodiment of the operation of the wearable device of Figure 5. Figure 7 shows a second embodiment of the operation of the wearable device of Figure 5.

S10: Steps

S12: Steps

S14: Steps

S16: Steps

S18: Steps

Claims (11)

A method for making a polycrystalline polyvinylidene fluoride film, including the following steps: Coating a polyvinylidene fluoride solution on a substrate to form a film, and heating the polyvinylidene fluoride solution on the substrate to above its melting point to produce a first polyvinylidene fluoride film; Cooling the first polyvinylidene fluoride film to obtain a second polyvinylidene fluoride film in a semi-molten state, a supercooled state and having an α crystal phase; Produce multiple polyvinylidene fluoride fibers with β crystalline phase; Arranging the plurality of polyvinylidene fluoride fibers in parallel on the second polyvinylidene fluoride film to obtain a third polyvinylidene fluoride film having an α crystal phase and a β crystal phase; and The third polyvinylidene fluoride film is heated and annealed at a fixed temperature to produce the polycrystalline polyvinylidene fluoride film having a β crystal phase and a γ crystal phase. The manufacturing method as described in claim 1 further includes dissolving a polyvinylidene fluoride material in a solvent to prepare the polyvinylidene fluoride solution. The production method of claim 1, wherein the step of producing the first polyvinylidene fluoride film includes heating the polyvinylidene fluoride solution on the substrate to 200° C. to produce the first polyvinylidene fluoride film. The production method as described in claim 1, wherein the fixed temperature is 160°C. The production method of claim 1, wherein the step of producing the plurality of polyvinylidene fluoride fibers includes electrospinning a polyvinylidene fluoride material to produce the plurality of polyvinylidene fluoride fibers. A wearable device including: A polycrystalline polyvinylidene fluoride film has a beta crystal phase and a gamma crystal phase. The polycrystalline polyvinylidene fluoride film senses temperature and pressure to generate a temperature sensing signal and a pressure sensing signal; a switching device; and A processor is coupled to the polycrystalline polyvinylidene fluoride film and the switch device, controls the switch device to activate or deactivate the wearable device according to the temperature sensing signal, and generates an electrical signal according to the pressure sensing signal. The wearable device of claim 6, wherein when the polycrystalline polyvinylidene fluoride film senses human body temperature, the processor activates the wearable device according to the temperature sensing signal. The wearable device of claim 6, wherein when the polycrystalline polyvinylidene fluoride film does not sense human body temperature, the processor turns off the wearable device according to the temperature sensing signal. The wearable device of claim 6, wherein the electrical signal is used to determine physiological status or generate relevant information. The wearable device of claim 9, wherein the physiological state includes heartbeat, blood pressure or respiration. The wearable device of claim 9, wherein the relevant information includes pressure, weight or distance.

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