KR20210051201A - Flexible nanogenerator using mesh-shaped electrodes - Google Patents

Abstract

A flexible nanogenerator and a wearable energy device including the same are provided. According to embodiments of the present invention, the flexible nanogenerator comprises: a first nanogenerator comprising a first fabric and a first material pattern and a second material pattern alternately disposed on the first fabric; and a second nanogenerator including a second fabric and a third material pattern and a fourth material pattern alternately disposed on the second fabric. The first material pattern, the second material pattern, the third material pattern, and the fourth material pattern may have different surface roughness. The wearable energy device comprises: the flexible nanogenerator disposed on a commercial fabric; and a supercapacitor disposed on the commercial fabric and electrically coupled to the flexible nanogenerator.

Description

Flexible nanogenerator using mesh-shaped electrode{omitted}

The present invention relates to a flexible nanogenerator using a mesh-type electrode.

Wearable electronic devices are receiving great attention along with the rapid spread of mobile devices as well as flexible and flexible electronic devices. The flexible electronic device includes, for example, an inorganic semiconductor-based epidermal electronic device, an organic electronic device, an organic electronic device bonded to the skin, highly sensitive pressure and pressure sensors capable of imitating human skin, and active electronic skin. There is a great interest in collecting physiological and electrophysiological information from the human body, such as being applied to a matrix mechanical sensor and a multifunctional electronic patch for diagnosis and treatment of movement disorders.

However, most flexible electronic devices have limitations in their application to mobile devices because they rely on connection with an external power source through a long wire. Accordingly, there is a need to develop an integrated electricity generation and storage device included in a wearable device.

Nanogenerators are energy devices that can be used in wearable devices. Nanogenerators can convert mechanical friction such as contact/release and sliding motions into electrical energy. Contact/release friction occurs most during vertical motion. In the contact state, electrons move at the interface between two different materials. In the process of changing to the release state, the air gap formed at the two interfaces maintains the electric potential balance, and generates a current through the external wire by induction of static electricity. On the other hand, the friction occurs more commonly during horizontal motion. Recent efforts to exploit horizontal friction have focused on forming undulating structures by patterning polymer arrays to form empty air gaps. However, it is necessary to use a hard material to maintain the structure (air gap), which cannot be applied to a flexible device. In order to use horizontal friction as an energy source for wearable electronic devices, a new type of triboelectric generator that is flexible and does not depend on an air gap is required. In addition, in order to operate independently, electricity generated by the triboelectric generator must be stored in the wearable system.

In order to solve the above problems, the present invention provides a flexible nanogenerator.

The present invention provides a wearable energy device including the flexible nanogenerator.

Other objects of the present invention will become apparent from the following detailed description and accompanying drawings.

The flexible nanogenerator according to the embodiments of the present invention includes a first nanogenerator and a second fabric including a first material pattern and a second material pattern alternately disposed on the first fabric and the first fabric, and the second fabric. 2 It includes a second nanogenerator including a third material pattern and a fourth material pattern alternately disposed on the fabric. The first material pattern, the second material pattern, the third material pattern, and the fourth material pattern may have different surface roughnesses.

The first fabric and the second fabric may be conductive carbon fabrics.

The first material pattern may include polyurethane, the second material pattern may include polyimide, the third material pattern may include polydimethylsiloxane, and the fourth material pattern is aluminum It may include.

The first material pattern and the second material pattern may have the same thickness, and the third material pattern and the fourth material pattern may have the same thickness.

A wearable energy device according to embodiments of the present invention includes the flexible nanogenerator disposed on a commercial fabric and a supercapacitor disposed on the commercial fabric and electrically connected to the flexible nanogenerator.

Each of the first nanogenerator and the second nanogenerator may be included in plurality, and the first nanogenerator and the second nanogenerator may be connected in parallel.

The commercial fabric may include clothing, the first nanogenerator may be disposed on the arm portion of the clothing, and the second nanogenerator may be disposed on the body portion of the clothing. The first nanogenerator and the second nanogenerator may generate electricity by rubbing against each other. The supercapacitor may be disposed on the chest of the clothing to store the electricity.

The flexible nanogenerator and the flexible supercapacitor may be sewn and bonded to the commercial fabric, and may be connected to each other by conductive threads that are sewn and bonded to the commercial fabric.

The wearable energy device according to embodiments of the present invention includes a flexible nanogenerator and a flexible supercapacitor. The wearable energy device may harvest and store energy generated through human activities. The wearable energy device can be used to supply power to external sensors or devices as well as to monitor the activity.

Since the flexible nanogenerator is formed of four different materials and does not require an air gap, it may have flexibility and elasticity. Thereby, the flexible nanogenerator may be attached to commercial fabrics such as clothing, and may have durability against frequent bending. The flexible nanogenerator may generate electricity by horizontal and vertical friction.

The performance of the flexible supercapacitor may be improved by using a vertical carbon nanotube (CNT)/RuO2 nanoparticle electrode formed on a carbon fabric. In addition, it can have excellent durability, which is stable even after 4000 charge-discharge cycles.

1 schematically shows the structure and operating principle of a wearable energy device according to an embodiment of the present invention.
2 schematically shows the structure and mechanism of an electric friction generator.
3 is a diagram for explaining a short circuit current generated by continuous friction or separation friction of a nanogenerator.
4 schematically shows the structure and electrochemical properties of a supercapacitor.
5 is a view for explaining the operation and measurement of an electrical signal of a wearable energy device according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail through examples. Objects, features, and advantages of the present invention will be easily understood through the following embodiments. The present invention is not limited to the embodiments described herein, and may be embodied in other forms.

The embodiments introduced herein are provided so that the disclosed contents may be thorough and complete, and the spirit of the present invention may be sufficiently transmitted to those of ordinary skill in the art to which the present invention pertains. Therefore, the present invention should not be limited by the following examples.

In the drawings, the sizes of elements, or the relative sizes between elements, may be somewhat exaggerated for a clearer understanding of the present invention. In addition, the shape of the elements shown in the drawings may be slightly changed due to variations in the manufacturing process. Accordingly, the embodiments disclosed in the present specification should not be limited to the shapes shown in the drawings unless otherwise specified, and should be understood as including some degree of modification.

As used herein, the term commercial fabric means a fabric including clothing that can be worn by humans.

1 schematically shows the structure and operating principle of a wearable energy device according to an embodiment of the present invention. The wearable energy device is fabricated on a conductive carbon fabric, which allows the wearable energy device to be woven at a specific location on a garment and connected by a conductive thread.

As shown in FIG. 1A, the nanogenerator (TEG) may be disposed in the armpit area to maximize friction, and the super capacitor (SC) is safe from friction damage and disposed in the chest area, which is an area adjacent to the nanogenerator (TEG). I can. Electricity can be generated and stored by swing movements made while walking.

A circuit diagram of an integrated energy device is shown in FIG. 1B. A plurality of nanogenerators (TEG) are connected in parallel to generate sufficient electricity to charge the supercapacitor (SC). A rectifier disposed between the nanogenerator (TEG) and the supercapacitor (SC) converts the generated alternating current (AC) into direct current (DC) to charge the supercapacitor (SC).

1C to 1E, the design of a nanogenerator (TEG) can be made according to a controlled arrangement of four complementary materials so that both horizontal and vertical friction generated between the arm and the body can be used. have. On the inside of the arm, polyurethane (PU, mean square roughness (Rq) = 158 nm) and polyimide (PI, Rq = 23.5 nm) are alternately patterned on the carbon fabric to form the first nanogenerator (TEG I). On the opposite side, polydimethylsiloxane (PDMS, Rq=49.4nm) and aluminum (Al, Rq=200nm) are alternately patterned on the carbon fabric to form a second nanogenerator (TEG II). Each material has its own relative triboelectric polarity, and aluminum (Al) is a conductive material that moves electrons to the polymer surface and is connected to the circuit. The generated electricity is stored in an integrated fabric-based supercapacitor (SC). The supercapacitor (SC) has a structure in which a carbon fabric, a carbon nanotube (CNT)/RuO2 electrode, a polyvinyl alcohol (PVA)/H3PO4 gel electrolyte, a carbon nanotube (CNT)/RuO2 electrode, and a carbon fabric are sequentially stacked. I can.

2 schematically shows the structure and mechanism of an electric friction generator.

2A to 2D, the polarity of the induced current is determined by the relative position of each material. For example, positive and negative peaks appear when aluminum (Al) is aligned with polyurethane (PU) and polyimide (PI). Since the aluminum (Al) conductive layer moves electrons to the electrode, it acts as a charge storage. The current is monitored by connecting the first nanogenerator (TEG I) and the second nanogenerator (TEG II) to ground and signal lines, respectively. As shown in FIG. 2B, when aluminum (Al) is dragged toward the polyurethane (PU), the surface of the polyurethane (PU) charged with a positive charge is neutralized by supplying electrons. This is indicated by the upper peak in Fig. 2c. When aluminum (Al) is dragged toward the polyimide (PI), electrons are extracted from the negatively charged polyimide (PI) layer. This appears as a lower peak in Fig. 2c. The surfaces of positively charged polyurethane (PU) and negatively charged polyimide (PI) are formed through frictional contact with polydimethylsiloxane (PDMS), and because of the triboelectric series, polydimethylsiloxane (PDMS) And polyurethane (PU) are filled with electrons and holes, respectively. When electron-filled polydimethylsiloxane (PDMS) slides toward polyimide (PI), electrons move from polydimethylsiloxane (PDMS) to polyimide (PI), and polydimethylsiloxane and polyimide share electrons. As shown in FIG. 2D, the amount of transferred charges is almost the same regardless of the flow direction.

Fig. 2e shows a schematic diagram of the principle that a nanogenerator converts vertical friction into electrical energy in a contact/release mode.

2F and 2G, a rubbing speed of 3 cm/s similar to the swing speed of a human arm at a normal walking speed using a friction distance of 5 mm to confirm the performance of a nanogenerator (TEG) Isc (short-circuit current) and Voc (open-circuit voltage) were measured at (rubbing speed). Isc is a relationship proportional to the number of repetitive lines (length: 1.5cm, width: 0.5cm, area: 0.75cm2) of the material used in the manufacture of a nanogenerator (TEG) (6 lines: 23nA, 12 lines: 43nA, 18 line: 55nA). In addition, even if Voc increases to 6V, it appears to stagnate as the area increases by more than 12 lines due to the input impedance of the measurement system.

2H and 2I, nanogenerators having the same surface area under contact/release friction generate a current of 130nA and a voltage output of 15V.

2j to 2m, an alternating current (AC) output is converted to direct current (DC) through a rectifier diode. Fig. 2J shows the accumulated current during rubbing, and Fig. 2K shows the accumulated current during contact/release. The peak value of Isc induced by rubbing (see Fig. 2L) is not as regular as the peak value due to contact/release friction (see Fig. 2m), but since the integrated area of each peak is similar, the accumulated current is applied to the rubbing friction and the contact. All show a linear increase in /release friction.

3 is a diagram for explaining a short circuit current generated by continuous friction or separation friction of a nanogenerator. In FIG. 3, the drawings in the first row indicate the case of continuous friction, and the drawings in the second row indicate the case of separation friction. In addition, FIG. 3A shows the case where the thickness of the aluminum layer is 0.4 mm, FIG. 3B shows the case where the thickness of the aluminum layer is 0.1 mm, and FIG. 3C shows the case where the thickness of the aluminum layer is 0.2 mm. The thickness of all other polymer (polydimethylsiloxane, polyurethane, and polyimide) layers is constant at 0.2 mm. The nanogenerator disposed above and comprising a polyurethane layer and a polyimide layer is a first nanogenerator, and the nanogenerator disposed below and comprising a polydimethylsiloxane layer and an aluminum layer is a second nanogenerator.

Referring to FIG. 3A, during rubbing, only aluminum contacts the polymers of the first nanogenerator, and aluminum moves or withdraws electrons for each of the polyimide and polyurethane by a triboelectric effect. The area covered by polydimethylsiloxane in the carbon fabric transfers electrons back and forth by electrostatic induction with the electrification of aluminum. The free electrons in the aluminum often produce a peculiar current output at both the positive and negative peaks. Aluminum can induce triboelectric charges and give or receive electrons in the polymer of the first nanogenerator.

Referring to FIG. 3B, only polydimethylsiloxane contacts the polymers of the first nanogenerator, and the polarity of the current output is inverse. This can be explained by the sum of the two kinds of current induction: static induction and dynamic induction. Electrostatic induction is induced by the contact/release behavior of polydimethylsiloxane during rubbing. When negatively charged polydimethylsiloxane is dragged from the polyurethane to the polyimide, the polyurethane exposed to the air loses the negative environment (release), and the polyimide acquires a negative environment (contact). Because of the contact/release induced by the same polydimethylsiloxane, the amount of induced current is the same and the direction of the induced current is opposite to each other, forming a total zero output current. The dynamic conversion is induced by friction between the polydimethylsiloxane and the polymers of the first nanogenerator. Polydimethylsiloxane converted by polyurethane allows electrons to flow to the lower fabric, and polydimethylsiloxane converted by polyimide allows electrons to flow to the upper fabric.

Referring to FIG. 3C, when both polydimethylsiloxane and aluminum are in contact with the polymers of the first nanogenerator, the current peak shows the same flow regardless of the direction.

4 schematically shows the structure and electrochemical properties of a supercapacitor.

4A to 4D illustrate a manufacturing process for forming a supercapacitor and scanning electron microscopy (SEM) images at each process step. 4A to 4D, single-walled carbon nanotubes (CNTs) are synthesized into fabrics of carbon fibers through chemical vapor deposition using an electron-beam-evaporated iron catalyst layer. Vertical growth of carbon nanotubes (CNTs) forms a 30-40㎛ high carbon nanotube forest that maximizes the surface area for an electrical double layer. Subsequently, electrochemical deposition is performed to form RuO2 nanoparticles on the carbon nanotubes (CNT).

4E, CV curves obtained at scan rates between 5 and 100 mV/s represent a similar rectangular shape of a typical supercapacitor. Referring to FIG. 4F, area capacitances at current densities of 10, 5, 2, and 1mA/cm2 are shown as 74.6, 80.0, 85.2, and 87.9mF/cm2, respectively, from galvanostatic charge-discharge curves. .

4G and 4H, since the gel electrolyte used is water-based, the potential window is limited to 0.8V to prevent damage caused by H2 generation. The potential window in series connection and the total capacitance in parallel connection can be easily adjusted by connecting a plurality of supercapacitors. Two supercapacitors connected in series or parallel each have double the potential limit or capacitance compared to a single supercapacitor.

4I to 4L, the performance of the supercapacitor can be maintained unchanged even when bent up to 135°, which is due to the high flexibility of each component. In addition, there is little difference in area capacitance even after 4000 charge-discharge cycles are performed.

5 is a view for explaining the operation and measurement of an electrical signal of a wearable energy device according to an embodiment of the present invention.

5A, a fabric-based nanogenerator (TEG) (5cm×9cm, 18 lines) and a supercapacitor (SC) can be easily sewn and pasted onto clothing such as a shirt, and can be connected by a conductive carbon thread.

5B and 5C, energy harvesting through regular and routine activities such as running or walking is accumulated by rubbing the nanogenerator (TEG) at various speeds. At 1.5Hz rate, the average output voltage and rectified current are measured as 33V and 0.25µA, respectively. The current generated in this way and stored in the supercapacitor is strong enough to illuminate the LED.

Referring to FIG. 5D, the rubbing period shows a proportional relationship within the range of 0.67 to 4 Hz, and determines the slope of charge accumulation. This allows the wearable energy device to function as a wearable self-powered human activity monitor.

5E shows the rectified output current (black, left vertical axis) and charge accumulation (red, right vertical axis) recorded from stretching, walking, running, sprinting, and cooldown walking, which are general jogging processes. When the slope of the charge accumulation is monitored, the activity of the test subject wearing the wearable energy device may be tracked. The slopes associated with stretching, walking, running, sprinting, and cooldown were 0.48, 8.4, 22, 53, and 9.6 nC/s, respectively.

Figure 5f shows a graph of voltage versus time for three different capacitors with capacitances of 1, 10, and 100nF. A fast charge/discharge capacitor (1nF) provides better sensitivity for human activity monitoring, while a high capacitance capacitor (100nF) is suitable for long-term monitoring.

5G and 5H, a supercapacitor charged by a nanogenerator may supply power to other sensors. For example, a supercapacitor charged by a nanogenerator can provide the required current to a pressure sensor.

The pressure sensor may be composed of a porous pressure-sensitive rubber (PPSR) sandwiched between carbon fabrics.

5I and 5J, the resistance of the porous pressure-sensitive rubber PPSR changes linearly with respect to the applied pressure.

5K, it is possible to determine the applied pressure by measuring the change in current. This can be confirmed by placing objects weighing 20, 50, 100, and 200 g, respectively, on the sensor.

The wearable energy device according to embodiments of the present invention may harvest and store energy generated through human activities. The wearable energy device can be used to supply power to external sensors or devices as well as to monitor the activity.

The nanogenerator according to the embodiments of the present invention is formed of four different materials and has a unique structure that does not require an air gap. The nanogenerator may generate electricity by horizontal and vertical friction, and may have an average output power density of 0.18㎼/cm2 at 1.5Hz, which is a typical condition of running.

The supercapacitor according to the embodiments of the present invention can improve its performance by using a vertical carbon nanotube (CNT)/RuO2 nanoparticle electrode formed on a carbon fabric, and 85.2mF/ at a discharge current of 1mA/cm2. It can have a capacitance of cm2. In addition, it has excellent durability that is stable even after 4000 charge-discharge cycles, so it is suitable for generating wearable power through the triboelectric friction machine.

Fabrication of flexible nanogenerators on carbon fabrics

On the carbon fabric, 5 mm wide polyimide (PI) tapes were placed at intervals of 5 mm. Polyurethane acrylate (PUA) is poured onto the carbon fabric, a PET film is placed thereon, and pressed to form a polyurethane acrylate (PUA) film having a uniform thickness. The polyurethane acrylate (PUA) is placed under an ultraviolet lamp for 12 hours to harden, and then the polyimide (PI) tape is removed. A polyimide (PI) tape is laminated on the exposed areas of the carbon fabric until the surface is flat. Thereby, the first nanogenerator is formed.

On the carbon fabric, 5mm wide aluminum (Al) tapes are placed at 5mm intervals. The aluminum (Al) tape is covered with a polyimide (PI) tape, and polydimethylsiloxane (PDMS) (a 10:1 mixture of prepolymer and curing agent) is poured onto the carbon fabric. A PET film covered with polyimide is placed on the polydimethylsiloxane (PDMS), pressed with a 3 kg stainless-steel plate, and then a polydimethylsiloxane (PDMS) film having a uniform thickness is formed. After curing the polydimethylsiloxane in a convection oven at 90° C. for 12 hours or more, the polyimide (PI) tape is removed. An aluminum (Al) tape is laminated on the aluminum (Al) tape until the surface is flat. Thereby, a second nanogenerator is formed.

The first nanogenerator and the second nanogenerator are attached to a commercial fabric by a fabric binder and then sewn with a conductive thread to form a parallel connected nanogenerator.

Preparation of supercapacitors on carbon fabrics

A 10 nm-thick aluminum layer is deposited on the carbon fabric using a thermal evaporator, and a 3.5 nm-thick iron layer is deposited thereon using an electron beam evaporator to form a catalyst. After placing a carbon fabric coated with a catalyst on a quartz plate, it is loaded into a 1 inch diameter CVD quartz cylinder to form carbon nanotubes at atmospheric pressure. The temperature was increased to 730°C under a 100 sccm flow of 99.999% pure argon and a 50 sccm flow of argon containing water. When this temperature is reached, 75 sccm of ethylene and 100 sccm of hydrogen are introduced into the reactor for 10 minutes as precursors and carrier gases, respectively.

A RuO2 electroplating solution was prepared using 5mM ruthenium(III) chloride hydrate, 0.1M KCl, and 0.01M HCl in deionized water. 3M NaOH solution is slowly added until the pH of the electroplating solution reaches 2.0. Prior to plating, the carbon nanotubes are hydrophilized by O2 plasma using a reactive ion etcher.

The plating solution was heated to 50° C. in a water bath, and between -0.2 V and 1.0 V at a scan rate of 0.05 mV/s using a potentiostat having a Pt counter electrode and an Ag/AgCl reference electrode in NaCl. Apply cyclic voltammetry.

An electrolyte for a supercapacitor was prepared by adding 6 g of polyvinyl alcohol (PVA) (MW: 146000 to 186000 g/mol) to 60 mL of deionized water containing 9 g of H3PO4. The mixture is heated to 104° C. while continuously stirring in a mineral oil bath to obtain a clear solution. The solution is poured into a Petri dish and dried at room temperature to form a gel electrolyte film.

A supercapacitor is formed by disposing a polyvinyl alcohol (PVA)/H3PO4 gel electrolyte between carbon fabrics with carbon nanotubes (CNT)/RuO2 electrodes formed thereon.

So far, specific examples of the present invention have been looked at. Those of ordinary skill in the art to which the present invention pertains will be able to understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative interest rather than a limiting point of view.

The scope of the present invention is shown in the claims rather than the above description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims (8)

A first nanogenerator including a first fabric and a first material pattern and a second material pattern alternately disposed on the first fabric; And
A second fabric and a second nanogenerator including a third material pattern and a fourth material pattern alternately disposed on the second fabric,
The first material pattern, the second material pattern, the third material pattern, and the fourth material pattern have different surface roughnesses. The method of claim 1,
The first fabric and the second fabric is a flexible nanogenerator, characterized in that the conductive carbon fabric. The method of claim 1,
The first material pattern includes polyurethane,
The second material pattern includes polyimide,
The third material pattern includes polydimethylsiloxane,
The fourth material pattern is a flexible nanogenerator, characterized in that comprising aluminum. The method of claim 1,
The first material pattern and the second material pattern have the same thickness,
The flexible nanogenerator, characterized in that the third material pattern and the fourth material pattern have the same thickness. The flexible nanogenerator of any one of claims 1 to 4 disposed on a commercial fabric; And
A wearable energy device comprising a supercapacitor disposed on the commercial fabric and electrically connected to the flexible nanogenerator. The method of claim 5,
Each of the first nanogenerator and the second nanogenerator is included in plurality,
The wearable energy device, characterized in that the first nanogenerator and the second nanogenerator are connected in parallel. The method of claim 5,
The commercial fabric comprises apparel,
The first nanogenerator is disposed on the arm of the clothing,
The second nanogenerator is disposed on the body portion of the clothing,
The first nanogenerator and the second nanogenerator generate electricity by rubbing against each other,
The supercapacitor is disposed on a chest of the clothing to store the electricity. The method of claim 5,
The flexible nanogenerator and the supercapacitor are sewn and bonded to the commercial fabric, and are connected to each other by conductive threads that are sewn and bonded to the commercial fabric.

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