A device and method for measuring the charge amount of contact-separation friction power generation

Abstract

The present invention relates to a charge measurement device and method for contact-separation friction power generation, the charge measurement device comprises a friction nanogenerator body and a digital oscilloscope, the friction nanogenerator body comprises a left electrode, a film to be measured, a right electrode and a reciprocating linear mechanism, the right electrode drives the film to be measured to contact and move away from the left electrode under the drive of the reciprocating linear mechanism; the digital oscilloscope is connected between the left electrode and the right electrode through a wire, and comprises an equivalent circuit for measuring the instantaneous voltage between the two electrodes, and a calculation module for calculating the charge based on the instantaneous voltage. The present invention replaces the expensive linear motor and 6514 electrometer with a crankshaft reciprocating motor and a digital oscilloscope respectively, and can quantitatively obtain the charge when different materials are in contact, and can also be used to measure the electrical output characteristics of the generator under different load resistances, and the entire instrument has low cost.

Description

Technical Field

[0001] The invention belongs to the field of charge measurement, and in particular relates to a device and method for measuring the charge amount of contact-separation friction power generation. Background Art

[0002] The phenomenon that after two different substances rub or touch each other, the surface of one object becomes positively charged and the surface of the other object becomes negatively charged is called triboelectric charging. Its essence is the transfer of charge between the rubbing (or touching) substances. It took thousands of years from the discovery of triboelectric charging to its direct application.

[0003] In 2012, Professor Wang Zhonglin's research group invented the friction nanogenerator. This technology not only has many advantages in collecting low-frequency mechanical energy, such as light weight, diverse structure and material selection, but also can infer the movement of an object through the change of its electrical signal, thereby realizing self-powered sensing. Therefore, in the past decade, the friction nanogenerator has received widespread attention from scientific researchers and has become one of the research hotspots in the scientific and energy communities.

[0004] When two materials rub against each other (or come into contact), electric charges are generated, and the amount of electric charges generated is related to the type of materials. The amount of frictional charge has a crucial impact on the performance of triboelectric nanogenerators, so quantitative measurement of the amount of frictional charge is an important part of the field of triboelectric power generation. Arranging the amount of charge generated by friction of different materials in order can provide effective guidance for the selection of materials for triboelectric nanogenerators.

[0005] In scientific research, the device that drives the linear motion of the friction generator is a linear motor, and the electrical quantity test requires a Keithley 6514 electrometer. However, these two devices are relatively expensive, which brings a great financial burden to some small enterprises or laboratories. Summary of the invention

[0006] The object of the present invention is to provide a device and method for measuring the charge amount of contact-separation friction power generation in order to solve the above-mentioned problems.

[0007] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0008] A contact-separation type friction power generation charge quantity measuring device, comprising:

[0009] The friction nanogenerator body comprises a left electrode, a film to be tested, a right electrode and a reciprocating linear mechanism, wherein the right electrode drives the film to be tested to contact and move away from the left electrode under the drive of the reciprocating linear mechanism;

[0010] The digital oscilloscope is connected between the left electrode and the right electrode through a wire, and comprises an equivalent circuit for measuring the instantaneous voltage between the two electrodes and a calculation module for calculating the charge amount based on the instantaneous voltage.

[0011] As a further optimization scheme of the present invention, sample holders are provided on the side of the left electrode and the right electrode away from each other, and sample card slots are clamped on the outside of the two sample holders. The sample card slot on the left electrode side is slidably set in the guide rail, and the sample card slot on the right electrode side is connected to the reciprocating linear mechanism.

[0012] As a further optimization solution of the present invention, a buffer structure is provided on the opposite surfaces of the two sample card slots, and the buffer structure adopts a sponge or a spring.

[0013] As a further optimization scheme of the present invention, the reciprocating linear mechanism adopts a reciprocating crank-connecting rod mechanism, including a linear motor, a speed regulator, a crank connecting rod, a push rod and a linear bearing. The linear motor drives the crank connecting rod and the push rod under the control of the speed regulator. The push rod passes through the linear bearing and drives the right electrode to contact the film to be tested and away from the left electrode.

[0014] As a further optimization scheme of the present invention, the equivalent circuit of the digital oscilloscope includes an internal resistance R of the digital oscilloscope connected in parallel with the friction nanogenerator body, an equivalent capacitor C' and a voltmeter, wherein the impedance corresponding to the equivalent capacitor C' is ignored.

[0015] A method for measuring the amount of charge in contact-separation friction power generation, the method using the above-mentioned charge amount measuring device, the method comprising:

[0016] S101. Start the reciprocating linear mechanism so that the right electrode drives the film to be tested to contact and move away from the left electrode to generate friction power;

[0017] S102. Using the equivalent circuit of a digital oscilloscope to measure the instantaneous voltage u(t) output by the triboelectric nanogenerator body;

[0018] S103. Calculating the charge using a calculation module of a digital oscilloscope, comprising the following steps:

[0019] The maximum distance h between the left and right electrodes is h(t) max and the peak value u of the instantaneous voltage u(t) max Substitute into the following formula to calculate the surface charge density σ0 of the film to be tested:

[0020]

[0021] Where h1 is the thickness of the film to be measured, A is the electrode area, ε ris the vacuum dielectric constant, h0 is the right electrode motion amplitude, f is the vibration frequency, R is the internal resistance of the digital oscilloscope, h 1r =h1 / ε r , h(t)=h0(1-cosωt), ω=2πf;

[0022] The friction charge q0 on the surface of the film to be tested is calculated based on the charge density σ0:

[0023] q0=Aσ0;

[0024] The electrode surface charge density σ(t) and its corresponding friction charge q(t) are calculated based on the following formula:

[0025]

[0026] A method for measuring the electrical output characteristics of a triboelectric nanogenerator, which adopts the above-mentioned charge quantity measuring device and can measure the electrical output characteristics under different load resistances, comprising:

[0027] S201. Connect a load resistor R in parallel or in series in the equivalent circuit of a digital oscilloscope X , so that the load resistance R X The total load of the digital oscilloscope internal resistance R is equal to the external load R L ;

[0028] S202. Use a digital oscilloscope to measure the load resistance R X The voltage corresponding to the total load of the digital oscilloscope internal resistance R, that is, the external load R L The corresponding voltage u L , then based on the load resistance R X , digital oscilloscope internal resistance R and voltage u L Calculate i L and P L .

[0029] As a further optimization solution of the present invention, when the external load R L When the resistance is less than the internal resistance R of the digital oscilloscope, R X and the internal resistance R of the digital oscilloscope in parallel, so that R X The total load of R is equal to the external load R L , at this time R L =R·R X / (R+R X ), and then calculate i according to Ohm's law L and P L ;

[0030] When the external load R L When it is greater than the internal resistance R of the digital oscilloscope, R X Connected in series with the internal resistance R of the digital oscilloscope, making RX The total load in series with R is equal to the external load R L , at this time R L =R+R X , and then calculate i according to Ohm's law L and P L .

[0031] The beneficial effects of the present invention are:

[0032] 1) The present invention utilizes the equivalent circuit of an oscilloscope to theoretically derive the relationship between the charge amount and the voltage measured by the oscilloscope, thereby being able to quantitatively obtain the charge amount when different materials are in contact. In addition, it can also be used to measure the electrical output characteristics of a generator under different load resistances;

[0033] 2) The present invention replaces the expensive linear motor and 6514 electrometer with a crankshaft reciprocating motor and a digital oscilloscope respectively, and the cost of the whole set of instruments (excluding the digital oscilloscope) can be within one thousand yuan;

[0034] 3) The present invention solves the problem that a digital oscilloscope cannot directly measure the transferred charge and the problem that the internal resistance of the oscilloscope cannot be regarded as infinite. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0036] Figure 2 It is a schematic diagram of the structure of the reciprocating linear mechanism of the present invention.

[0037] Figure 3 It is a schematic diagram of the push rod moving stroke of the present invention.

[0038] Figure 4 It is a basic principle diagram of contact-separation friction power generation of the present invention; wherein, (I) is a charge transfer diagram when the generator is connected to an ideal voltmeter with infinite internal resistance, and (II) is a charge transfer diagram when the generator is connected to an ammeter or an external load.

[0039] Figure 5 The present invention is a schematic diagram of using an oscilloscope to measure the voltage of a friction generator; wherein (I) is an ideal voltmeter circuit diagram, (II) is an oscilloscope equivalent circuit diagram, and (III) is an oscilloscope simplified circuit diagram.

[0040] Figure 6 1 is a graph showing the relationship between voltage and time at a frequency of 2 Hz and a stroke of 8 cm according to the present invention; wherein (I) is a graph showing the theoretical relationship between voltage and time when measured using an oscilloscope and an ideal voltmeter respectively; and (II) is an experimental measurement curve.

[0041] Figure 7The present invention is a circuit diagram for measuring the power of a friction nanogenerator under different loads using an oscilloscope; wherein (I) is an ideal ammeter circuit diagram, (II) is an oscilloscope equivalent circuit diagram, and (III) is an oscilloscope simplified circuit diagram.

[0042] Figure 8 The amplitude of the present invention is 4cm, the frequency is 2Hz, and the load R L The corresponding peak power P Lmax Experimental value graph.

[0043] Fig. 9 The amplitude of the present invention is 4cm, the frequency is 2Hz, and the load R L The corresponding peak power P Lmax Theoretical value curve graph.

[0044] In the figure: 1. Friction nanogenerator body; 11. Left electrode; 12. Film to be tested; 13. Right electrode; 14. Reciprocating linear mechanism; 141. Linear motor; 142. Curved connecting rod; 143. Push rod; 144. Linear bearing; 15. Sample holder; 16. Sample slot; 17. Slider; 18. Buffer structure; 19. Guide rail; 2. Digital oscilloscope. DETAILED DESCRIPTION

[0045] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0046] Example 1

[0047] like Figure 1-3 As shown, a contact-separation type friction power generation charge measurement device comprises a friction nanogenerator body 1 and a digital oscilloscope 2;

[0048] The triboelectric nanogenerator body 1 includes a left electrode 11, a film to be tested 12, a right electrode 13, a reciprocating linear mechanism 14, a sample holder 15, a sample slot 16, a slider 17, a fastening screw and a guide rail 19;

[0049] in,

[0050] First, the left electrode 11 and the right electrode 13 are fixed on the sample holder 15 respectively, and then the film 12 to be tested is covered and fixed on the surface of the right electrode 13. Then, the left electrode 11 and the right electrode 13 are symmetrically clamped in two sample clamping grooves 16 through the sample holder 15, so that the electrodes and the film 12 to be tested can be easily replaced. The sample clamping groove 16 at the bottom of the left electrode 11 is slidably set in the guide rail 19 through the slider 17 and the fastening screw. The slider 17 can be adjusted to a suitable position on the guide rail 19 and fastened. The sample clamping groove 16 at the bottom of the right electrode 13 is connected to the reciprocating linear mechanism 14. The right electrode 13 drives the film 12 to contact and move away from the left electrode 11 under the drive of the reciprocating linear mechanism 14, so as to perform friction power generation;

[0051] By arranging a buffer structure 18 in the sample slot 16, the buffer structure 18 is a sponge or a spring. The advantage is that on the one hand, it provides a certain buffer, and on the other hand, it can ensure sufficient contact between the electrode and the film 12 to be tested.

[0052] In addition, the reciprocating linear mechanism 14 adopts a reciprocating crank-connecting rod mechanism, including a linear motor 141, a speed regulator, a crank connecting rod 142, a push rod 143 and a linear bearing 144. The crank connecting rod 142 is composed of two hinged connecting rods, one of which is connected to the output shaft of the linear motor 141, and the other connecting rod is hinged to the push rod 143. The linear motor 141 drives the crank connecting rod 142 and the push rod 143 under the control of the speed regulator. The push rod 143 passes through the linear bearing 144 and drives the right electrode 13 to contact the film 12 to be tested and away from the left electrode 11.

[0053] The maximum amplitude of the left-right movement of the push rod 143 is the rotation radius of one of the connecting rods, the total stroke of the push rod 143 is twice the rotation radius, and the horizontal movement stroke of the push rod 143 is the movement amplitude h0 of the right electrode 13.

[0054] The digital oscilloscope 2 is connected between the left electrode 11 and the right electrode 13 through a wire, and includes an equivalent circuit for measuring the instantaneous voltage between the two electrodes, and a calculation module for calculating the charge amount based on the instantaneous voltage;

[0055] The equivalent circuit of the digital oscilloscope 2 includes an internal resistance R of the digital oscilloscope 2 connected in parallel with the friction nanogenerator body 1 , an equivalent capacitor C′ and a voltmeter.

[0056] The present invention measures the triboelectric properties of different types of thin film materials based on the above-mentioned contact-separation friction nanogenerator. Specifically, the generator is driven by a curved link 142 reciprocating motor, and the output voltage of the generator is measured by a digital oscilloscope 2. Due to the high impedance characteristics of the friction nanogenerator, the internal resistance of the digital oscilloscope 2 cannot be regarded as infinite. Therefore, the present invention needs to use the equivalent circuit of the digital oscilloscope 2 to theoretically derive the relationship between the charge amount and the test result of the digital oscilloscope 2, and then indirectly measure the charge amount of different materials when they are in contact. The specific principle analysis is as follows:

[0057] The core principle of triboelectric power generation is the well-known triboelectric charging and electrostatic induction. Here we introduce the basic principle of contact-separation triboelectric nanogenerator. Figure 4 As shown in (I), the film 12 to be tested is an insulating dielectric film, and its thickness and relative dielectric constant are set to h1 and ε respectively. r , the left electrode 11 and the right electrode 13 are metal electrodes, and the gap between them changes periodically with time, which is set as h(t);

[0058] Assuming that the electrode area A is infinite, if the two electrodes are connected to an ideal voltmeter (infinite internal resistance), there is no charge transfer between the electrodes. After the electrode contacts the film 12 to be tested, the surface will carry opposite charges. After several contacts, the charge will stabilize. The charge surface density is set to ±σ0, and the electric field strength between the electrode and the medium is E=σ0 / ε0, where ε0 is the vacuum dielectric constant. Therefore, the voltage between the two plates is:

[0059]

[0060] If the left electrode is grounded at 0 potential, then the potential of the right electrode is:

[0061]

[0062] The absolute value of the charge density on the surface of the film 12 to be tested by triboelectric charging |σ0| is generally between 1 and 100 μC / m 2 , the maximum value of h(t) is generally in the centimeter range, so the theoretical voltage peak is 1~100KV, which shows that the friction nanogenerator has high voltage characteristics. The two electrodes are regarded as parallel plate capacitors, and their capacitance is:

[0063]

[0064] In the above formula, A is the electrode area, the thickness h1 of the film to be measured is generally below 50 μm, and the relative dielectric constant ε r Generally, it is about 2, and area A is generally 20 to 100 cm 2 , then the capacitance C is in the order of pico-farads. Since the generator frequency is generally below 3 Hz, the impedance R of the capacitor C=1 / ωC is 10 4 It is near the MΩ level. It can be seen that the friction nanogenerator has high impedance characteristics;

[0065] As the two electrodes come into contact and separate, a voltage will be generated between them. If the two electrodes are short-circuited or connected to a load, an AC current will flow through the external circuit. Figure 4 (II). Since |σ0| is generally between 1 and 100 μC / m 2 , if area A is 25cm 2 , the amount of charge transferred in half a cycle is 2.5 to 250 nC. Combined with the current definition i = dq / dt, it can be seen that the output current of the friction nanogenerator is very small and has low current characteristics.

[0066] Using professional scientific research instruments, such as the 6514 electrometer, the amount of charge transferred between the two electrodes during the contact (or separation) process can be directly measured, and the amount of charge on the surface of the medium can be obtained. In addition, the surface charge of the medium can also be inferred by measuring the voltage between the two electrodes (indirect measurement). From formula (1), it is known that u(t) and h(t) are linearly related. In the experiment, the peak value of u(t) and the maximum value of h(t) can be substituted into formula (1) to calculate the surface charge density σ0 of the medium.

[0067] The voltage of the triboelectric nanogenerator is measured using a digital oscilloscope 2:

[0068] As mentioned in the previous discussion of equation (2), the impedance of the generator is very large, which is 10 4 If the voltage is measured by digital oscilloscope 2, the internal resistance (R = 1MΩ) of digital oscilloscope 2 cannot be regarded as infinite, so digital oscilloscope 2 cannot be equivalent to Figure 5 The ideal voltmeter in (I) has an equivalent circuit as shown in Figure 5 (II).

[0069] The internal resistance of digital oscilloscope 2 is R = 1MΩ, the equivalent capacitance C' = 16PF, and the frequency of the contact-separation friction nanogenerator is very low (less than 3Hz), so the impedance corresponding to C' is R C ≈10 4 MΩ, compared with the internal resistance R = 1MΩ of the digital oscilloscope 2, the capacitance impedance R C can be ignored, the corresponding simplified circuit diagram is as follows Figure 5 (III) as shown.

[0070] Assume that the electrode area is A, the charge density of the lower electrode is σ(t), and the charge is q(t) = Aσ(t). According to the Gaussian theorem of electrostatic field and the principle of superposition of electric field intensity, the charge distribution on the plane electrode can be obtained as follows: Figure 5 (III) As shown. At any time t when the two plates are in contact and separated, the current is i(t) and the instantaneous voltage is u(t), then:

[0071]

[0072] In the above formula, h is defined 1r =h1 / ε r , and u(t) is the potential difference between the upper electrode and the lower electrode. According to Ohm's law:

[0073]

[0074] Equation (3) is equal to equation (4), and the following differential equation can be obtained:

[0075]

[0076] where the definition Concurrently

[0077] h(t)=h0(1-cosωt) (6)

[0078] Formula (6) can be calculated based on the motion of the reciprocating motor of the curved connecting rod 142;

[0079] When the initial condition is t = 0, h(t) = 0, q(t) = 0, the solution of differential equation (5) can be obtained, and it can be substituted into (4) to obtain:

[0080]

[0081] Set parameter σ0 = 10 -5 C / m 2 , R = 10 6 Ω, A=25cm 2 , ε r =2, h1 = 50 μm, ω = 2πf = 4π, amplitude h0 = 4 cm, and we can get the value of (7) by plotting Figure 6 The solid line in (I) shows that the measurement result of the digital oscilloscope 2 should be a pulse voltage. Figure 6 The dotted line in (I) is the theoretical curve when measuring with an ideal voltmeter, corresponding to equation (1). Obviously, because the internal resistance of the digital oscilloscope 2 cannot be regarded as infinite, its voltage curve is very different from that of the ideal voltmeter. The measurement results of the experiment using the digital oscilloscope 2 are shown in Figure 6 (II) Comparison Figure 6 (II) and Figure 6 (I) It can be seen that the actual measurement curve using the digital oscilloscope 2 is completely consistent with the theoretical calculation curve.

[0082] It should be noted that Figure 5 The lower electrode is grounded, and the measured voltage is actually the potential of the upper electrode. Here we assume that σ0 = 10 - 5 C / m2 is a positive value, and the calculation results show that the voltage is greater than 0 when in contact and less than 0 when separated. Figure 6 (I); If σ0 is negative, the voltage is negative when in contact and positive when separated. Therefore, we can judge the positive or negative charge on the surface of the dielectric according to the positive or negative voltage when in contact. Experimental curve Figure 6 (II) is the case where the electrode is copper and the dielectric is Nylon film. It can be seen that the actual measured voltage is positive when in contact, so when Nylon rubs against copper, Nylon loses electrons and becomes positively charged.

[0083] Rewrite (7) as:

[0084]

[0085] It can be seen from formula (8) that the voltage u measured in the experiment can be used to calculate the surface charge density σ0 caused by friction. Since the voltage changes with time, the measured peak value can be used for calculation. In the experiment, only the peak voltage u at the time of contact is read. max By setting different frequency and stroke parameters to calculate equation (8), we can get u under different conditions. max The theoretical results of / σ0 are shown in Table 1. According to Table 1 and the actual measured voltage peak u max , we can calculate σ0.

[0086] Table 1. u under different conditions max / σ0, where u max is the peak voltage at contact

[0087]

[0088] For example, Figure 6 The test result of (II) is that nylon and copper are separated from each other with amplitude h0 = 4 cm and frequency f = 2 Hz. The peak voltage at contact is u max ≈+0.6V, from Table 1 we know Therefore, the surface charge density of nylon after friction with copper is:

[0089]

[0090] Experimental verification:

[0091] Copper (copper foil) was regarded as the comparative material in this experiment, and the charge surface density of FEP, PTFE, Kapton, Nylon, white paper, and PET film after contacting with copper was measured respectively.

[0092] 1. Select an amplitude of 4 cm and a frequency of 2 Hz; the materials in contact with copper are Nylon, white paper, PET, Kapton, PTFE, and FEP films, all of which have a thickness of about 50 μm. Record the peak voltages of the six materials when they are in contact with copper, and calculate their respective surface charge densities using formula (9) and Table 1. The calculation results are shown in Table 2.

[0093] Table 2. Peak voltage and charge density of 6 different materials in contact with copper

[0094] Material Nylon White paper PET Kapton PTFE FEP Voltage peak(V) 0.69 0 -0.50 -4.50 -7.89 -24.00 <![CDATA[Surface charge density (μC / m 2 )]]> 1.5 0 -1.1 -9.8 -17.1 -52.1

[0095] 2. Select FEP and copper for friction, with the amplitude fixed at 4 cm and the frequencies at 1.2, 1.4, 1.6, 1.8, and 2.0 Hz. Record the peak voltage during contact and calculate the respective charge surface densities. The calculation results are shown in Table 3.

[0096] Table 3. Peak voltage and charge surface density at different frequencies

[0097] Frequency (Hz) 1.2 1.4 1.6 1.8 2.0 Voltage peak(V) -15.64 -17.74 -20.06 -22.12 -24.00 <![CDATA[Surface charge density (μC / m 2 )]]> -51.8 -51.5 -52.1 -52.2 -52.1

[0098] 3. At a frequency of 2 Hz, FEP was in contact with copper, and the voltage peaks (when in contact) at different amplitudes (1, 2, 3, and 4 cm) were measured. The charge surface densities of each were calculated. The calculation results are shown in Table 4.

[0099] Table 4. Voltage peak (V) and charge surface density at different amplitudes (1, 2, 3, 4 cm)

[0100] Amplitude(cm) 1 2 3 4 Voltage peak(V) -18.54 -18.98 -20.18 -24.00 <![CDATA[Surface charge density (μC / m 2 )]]> -51.8 -54.6 -49.1 -52.1

[0101] Example 2

[0102] The present invention is based on the above-mentioned contact-separation type friction nanogenerator and can also be used to measure the electrical output characteristics of the friction nanogenerator such as current, voltage, power, etc. when the friction nanogenerator is connected to an external load. The specific principle analysis is as follows:

[0103] The electrical output characteristics of triboelectric nanogenerators are one of the important research contents in this field. It is usually necessary to test the current, voltage, and power of the generator when it is connected to different load resistances, and obtain the matching load value at the maximum power. In addition to the measurement of charge quantity introduced above, the present invention can also measure these quantities.

[0104] The 6514 electrometer used in scientific research can be regarded as Figure 7 (I) is an ideal ammeter and voltmeter. Now we only need to change the load R L The size of the current i can be directly tested L and voltage u L , then use the formula P L =uL 2 / R L or P L =i L 2 R L The calculation can be used to obtain the load power.

[0105] Here, using digital oscilloscope 2, we can only measure the voltage, and according to i L =u L / R L In addition, since the internal resistance R of the digital oscilloscope 2 cannot be ignored, when the external load R L When the equivalent resistance R of the digital oscilloscope is less than 1MΩ, it is necessary to use Figure 7 (II) circuit and choose the appropriate R x , so that R x The total load in parallel with R is equal to R L When the external load R L When it is greater than 1MΩ, you need to use Figure 7 (III) circuit and choose the appropriate R x , so that R x The total load in series with R is equal to R L .

[0106] for Figure 7 (II) The voltage u actually measured by the digital oscilloscope 2 is the total load R L =R·R x / (R+R x ) voltage u L .for Figure 7 (III), the actual measured u is only the voltage of the internal resistance R of the digital oscilloscope 2, and the total load R L =R+R x The voltage u L Should be

[0107]

[0108] Get u L Then, according to Ohm's law, we can easily get

[0109] i L =u L / R L (11)

[0110]

[0111] Experimental verification:

[0112] Select the amplitude of 4cm and the frequency of 2Hz; the material in contact with copper is FEP film. Connect resistors of different resistance values ​​in series and parallel, and measure the peak voltage u when in contactmax , and according to u max Calculate the corresponding u Lmax 、i Lmax and P Lmax The results are shown in Table 5 and Figure 8 .

[0113] Table 5. Different load R L The corresponding peak voltage u Lmax , peak current i Lmax , Power P Lmax

[0114]

[0115] Experimental conclusion:

[0116] The matched (optimal) load of the generator at 2 Hz frequency and 4 cm amplitude is around 10 MΩ.

[0117] Finally, different load resistance R L Substituting into equation (7), with other parameters unchanged, the peak power P can be theoretically obtained: Lmax ,See Fig. 9 ;

[0118] By comparison Fig. 9 and Figure 8 It is found that the electrical output characteristics of the generator under different load resistances can be measured by using the digital oscilloscope 2.

[0119] In scientific research, the device that drives the linear motion of the friction generator is a linear motor, and the Keithley 6514 electrometer is required for the power test. However, these two devices are relatively expensive and are not suitable for large-scale equipment in university physics laboratories.

[0120] Therefore, the invention replaces the expensive linear motor and 6514 electrometer with a crankshaft reciprocating motor and a digital oscilloscope, respectively, and can introduce the relevant content of the friction nanogenerator into the teaching of university physics experiments. Through this experiment, students can not only have a deeper understanding of friction electrification and its applications, understand the measurement method of friction charge and the output characteristics of the friction generator, master the relevant theories of capacitance, and become more familiar with the use of digital oscilloscopes, but also understand this cutting-edge topic in the energy and scientific communities.

[0121] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for measuring the charge amount of contact-separation friction power generation, characterized in that: The method is completed by using a charge measurement device, and the charge measurement device comprises: The friction nanogenerator body comprises a left electrode, a film to be tested, a right electrode and a reciprocating linear mechanism, wherein the right electrode drives the film to be tested to contact and move away from the left electrode under the drive of the reciprocating linear mechanism; A digital oscilloscope, connected between the left electrode and the right electrode through a wire, comprising an equivalent circuit for measuring the instantaneous voltage between the two electrodes, and a calculation module for calculating the charge amount based on the instantaneous voltage; The method comprises: S101. Start the reciprocating linear mechanism so that the right electrode drives the film to be tested to contact and move away from the left electrode to generate friction power; S102. Using the equivalent circuit of a digital oscilloscope to measure the instantaneous voltage output by the triboelectric nanogenerator u ( t ); S103. Calculating the charge using a calculation module of a digital oscilloscope, comprising the following steps: The distance between the left and right electrodes Maximum spacing And the instantaneous voltage Peak Substitute into the following formula to calculate the surface charge density of the film to be tested: : ； in, is the thickness of the film to be measured, is the electrode area, ε 0 is the dielectric constant of vacuum, is the right electrode motion amplitude, is the vibration frequency, is the internal resistance of the digital oscilloscope, , , ; Based on the charge density Calculate the triboelectric charge on the film surface to be tested : ； The electrode surface charge density was calculated based on the following formula And its corresponding friction charge : ； in, is the relative dielectric constant.

2. The method for measuring the charge amount of contact-separation friction power generation according to claim 1, characterized in that: Sample holders are provided on the side of the left electrode and the right electrode away from each other, and sample slots are clamped on the outside of the two sample holders. The sample slot on the left electrode side is slidably set in the guide rail, and the sample slot on the right electrode side is connected to the reciprocating linear mechanism.

3. The method for measuring the charge amount of contact-separation friction power generation according to claim 2, characterized in that: The opposite surfaces of the two sample slots are provided with a buffer structure, and the buffer structure adopts a sponge or a spring.

4. The method for measuring the charge amount of contact-separation friction power generation according to claim 3, characterized in that: The reciprocating linear mechanism adopts a reciprocating crank-connecting rod mechanism, including a linear motor, a speed regulator, a crank connecting rod, a push rod and a linear bearing. The linear motor drives the crank connecting rod and the push rod under the control of the speed regulator. The push rod passes through the linear bearing and drives the right electrode to contact the film to be tested and move away from the left electrode.

5. The method for measuring the charge amount of contact-separation friction power generation according to claim 4, characterized in that: The equivalent circuit of the digital oscilloscope includes an internal resistance R of the digital oscilloscope connected in parallel with the friction nanogenerator body, an equivalent capacitor C' and a voltmeter.

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