CN201007826Y - A radio frequency tag - Google Patents

Abstract

The utility model relates to a wireless radio frequency tag and its reading system. The radio frequency tag includes a radio frequency wave signal source, an antenna matching circuit and a radio frequency antenna. Bulk acoustic wave resonant cavity, acoustic coupling layer, bottom electrode, piezoelectric film, insulating layer and top electrode distributed in sequence; the reading system includes a reader and a reader antenna, and the reader is a radio frequency tag query signal The transmitting and receiving radar transceiver equipment. The utility model has the advantages that it can directly respond to the query signal of the reader, can work in the working range of 300MHz-10GHz, and is easy to be integrated.

Description

A radio frequency tag

technical field

The utility model belongs to the technical field of radio frequency identification, in particular, the utility model relates to a radio frequency tag and a reading system thereof.

Background technique

Radio Frequency Identification (RFID, Radio Frequency Identification) is a non-contact automatic identification technology. Its basic principle is to use the transmission characteristics of radio frequency signals and space coupling (electromagnetic coupling or electromagnetic propagation) to realize automatic identification of identified objects.

Electromagnetic propagation or electromagnetic backscatter coupling is the so-called radar principle model. The emitted electromagnetic waves are reflected after hitting the target, and at the same time carry back the target information, based on the spatial propagation law of electromagnetic waves. The electromagnetic backscatter coupling method is generally suitable for long-distance radio frequency identification systems that work at high frequencies and microwaves. Typical working frequency bands include: 430~460MHz, 865~928MHz, 2.35~2.45GHz, 5.4~6.8GHz. The recognition range is 0.1 to 1 meter, and the typical range is 3 to 10 meters.

A radio frequency tag system generally consists of two parts, namely an electronic tag (transponder, Tag) and a reader (also called a reading head, or Reader). In the practical application of RFID, the electronic tag is attached to the identified object (surface or inside), when the identified item with the electronic tag passes through the identifiable area of the reader, the reader automatically sends the electronic The agreed identification information in the label is taken out, so as to realize the function of automatically identifying items or automatically collecting item identification information.

Currently existing radio frequency tags (RFID) are generally composed of integrated circuit IC chips and related antennas. The reader antenna transmits a radio signal to the tag, and the radio frequency tag (RFID) receives the signal through its own dedicated antenna, and uses the energy it gets from the signal (some RFID tags are equipped with a power supply) to start the integrated circuit chip on the tag to work. The reader is also composed of an antenna, a signal transceiver and a decoder. Once the chip on the RFID tag is activated and started, the required read and write operations are performed, and the reader can decode the data in the tag chip obtained through the antenna and send it to the host computer for processing.

This kind of passive radio frequency tag composed of integrated circuit IC chips must first obtain enough energy from the reader when it is working. When the received energy reaches a certain threshold, the IC in the tag will start to work. Therefore, the recognition time is long, and the scope of application is limited to a certain extent. When working in a higher frequency band (such as 430-460MHz, 865-928MHz, 2.35-2.45GHz, 5.4-6.8GHz frequency band), since there is no radio frequency oscillator inside, the frequency of the radio frequency signal carrier reflected back to the reader The stability is relatively poor, which brings certain difficulties to the reader's rapid and accurate identification.

Contents of the invention

The purpose of this utility model is to overcome the deficiencies of the prior art, adopt the bulk acoustic wave multimode resonator itself as the radio frequency or microwave signal source, thereby provide a kind of can directly respond to the inquiry signal of the reader, can work in 300MHz～10GHz Working range, and easy to integrate radio frequency tags and reading systems.

In order to achieve the purpose of the above-mentioned utility model, the wireless radio frequency tag provided by the utility model includes a radio frequency wave signal source and a radio frequency antenna 301. It is characterized in that the radio frequency signal source adopts a bulk acoustic wave multi-mode resonant structure, including sequentially distributed from bottom to top Bulk acoustic wave resonant cavity 310, bottom electrode 330, piezoelectric film 340, and top electrode 360; the bulk acoustic wave resonant cavity 310 is a solid medium for bulk acoustic wave propagation, and its solid medium material is sapphire single crystal, yttrium aluminum garnet or fused silica; the bottom electrode 330 and the top electrode 360 are both metal electrodes, and the bottom electrode 330 and the top electrode 360 are connected to the radio frequency antenna 301 .

In the above technical solution, the radio frequency signal source further includes an acoustic coupling layer 320 located between the bulk acoustic wave resonant cavity 310 and the bottom electrode 330; the acoustic coupling layer 320 is one or more layers of acoustic coupling layer for acoustic impedance matching. Propagation medium: the acoustic impedance of the acoustic coupling layer 320 is close to the square root of the product of the acoustic impedance of the piezoelectric film 340 and the acoustic impedance of the bulk acoustic wave resonant cavity 310 .

In the above technical solution, the radio frequency signal source further includes an insulating layer 350 located between the piezoelectric film 340 and the top electrode 360 .

In the above technical solution, the piezoelectric film 340 is a piezoelectric film produced by a magnetron sputtering method, or a piezoelectric single crystal film produced by a chemical micromachining method, or a piezoelectric film produced by a sol method.

In the above technical solution, it also includes an antenna matching circuit 302 for impedance matching between the radio frequency antenna 301 and the radio frequency signal source; one port of the antenna matching circuit 302 is connected to the bottom electrode 330 and the top electrode 360, and the other The port is connected to the radio frequency antenna 301 .

In the above technical solution, the radio frequency antenna 301 adopts a whip antenna or a composite dielectric antenna, or adopts a microstrip antenna integrated with the radio frequency signal source, or adopts a wire antenna made of conductive ink.

In order to achieve the purpose of the above invention, the wireless radio frequency tag reading system provided by the utility model includes a reader 400 and a reader antenna 401. The reader 400 is a radar transceiver device responsible for transmitting and receiving radio frequency tag query signals. It is characterized in that the reader 400 includes a voice prompt unit, a query signal generator, an external interface control unit, a radio frequency transceiver switch, a display unit, a signal detection and decoding circuit, and an embedded computer unit that controls the above-mentioned units; The power amplifier between the query signal generator and the radio frequency transceiver switch, and the low noise amplifier connected between the radio frequency transceiver switch and the signal detection decoding circuit; the radio frequency transceiver switch is connected with the reader antenna 401 .

The utility model has the advantage that since the bulk acoustic wave multimode resonator itself is a radio frequency (or microwave) resonator, it can be used as a radio frequency or microwave signal source, and it can directly convert the radio frequency signal received by the tag antenna into a bulk acoustic wave, thereby Responds directly to the interrogation signal from the reader. This kind of radio frequency tag can work in the working range of 300MHz-10GHz, therefore, both the tag and the antenna can be made very small and easy to be integrated. In terms of application, it can be used as an independent radio frequency tag, widely used in item identification or security personnel identification. It can also work with the existing radio frequency tag system with integrated circuit IC chip to form a dual-frequency radio frequency tag, and the functions complement each other. The utility model is especially suitable for working in ultra-high frequency and above frequency bands (such as 430-460MHz, 865-928MHz, 2.35-2.45GHz, 5.4-6.8GHz frequency bands).

Description of drawings

Figure 1 The schematic block diagram of the radio frequency tag (RFID) and system composed of bulk acoustic wave multimode resonators

Figure 2 A radio frequency tag (RFID) composed of a bulk acoustic wave multimode resonator, an antenna matching circuit and an antenna

Figure 3 Schematic block diagram of radio frequency tag (RFID) reader system

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the utility model is described in further detail.

Example:

Fig. 1 shows a schematic block diagram of two parts of the present invention, namely a radio frequency tag (RFID) and a corresponding radio frequency tag (RFID) reader system.

The radio frequency tag (RFID) is composed of a bulk acoustic wave multimode resonator 300 , an antenna matching circuit 302 and a radio frequency antenna 301 . The bulk acoustic wave multimode resonator 103 mainly includes a bulk acoustic wave resonator cavity and a piezoelectric film transducer. The thickness of the bulk acoustic wave resonator determines the interval between two adjacent resonance frequencies of the bulk acoustic wave multimode resonator 103 or the time interval between two adjacent reflection pulses in the time domain; The thickness of the piezoelectric film in the transducer determines the working center frequency of the bulk acoustic wave multimode resonator 103 . In the present invention, the working center frequency of the bulk acoustic wave multimode resonator 103 may be in the range of 300 MHz to 10 GHz, and the thickness of the bulk acoustic wave resonator may be in the range of 20 microns to 20 mm. Different radio frequency tags can be produced by adjusting the center frequency of the bulk acoustic wave multimode resonator 103 and the thickness of its resonant cavity.

Further, as shown in FIG. 2, the bulk acoustic wave multimode resonator 300 described in this embodiment includes a bulk acoustic wave resonator body 310, an acoustic coupling layer 320, a bottom electrode 330, a piezoelectric film 340, an insulating layer 350 and The top electrode 360 is formed. One port of the antenna matching circuit 302 is connected to the bottom electrode 330 and the top electrode 360 , and the other port is connected to the radio frequency antenna 301 .

The bulk acoustic wave resonant cavity 310 in the bulk acoustic wave multimode resonator 300 is located in the lowermost layer, which is generally used as a substrate, on which the acoustic coupling layer 320 is sequentially grown or deposited, vacuum evaporated or sputtered, and photoetched. Bottom electrode 330 , direct current or radio frequency magnetron sputtering piezoelectric film 340 , radio frequency sputtering or depositing insulating layer 350 , and top electrode 360 formed by vacuum evaporation or sputtering and photoetching. Generally speaking, the bulk acoustic wave multimode resonator 300 can be cut into any shape, as long as the cutting does not affect the performance of the device. Preference is given to cutting into cuboids or cubes. Only the bottom electrode 330 and the top electrode 360 are etched, and other layers are generally not etched. The shapes of the bottom electrode 330 and the top electrode 360 are generally circular, and may also be square or polygonal. Generally, the top electrode 360 is smaller than the bottom electrode 330 .

The radio frequency tag (RFID) reader system is composed of a reader 400 and a reader antenna 401 . As shown in Figure 3, the reader 400 includes a voice prompt unit 410, a query signal generator 420, a power amplifier 430, an external interface control unit 440, an embedded computer unit 450, a radio frequency transceiver switch 460, a display unit 470, a signal The detection and decoding circuit 480 and the low noise amplifier 490 are composed. The RF transceiver switch 460 is connected to the reader antenna 401 .

The embedded computer unit 450 is the heart of the reader 400, and it is connected with each important part of the reader 400 to realize the control of the whole system. Described embedded computer unit 450 is connected with described inquiry signal generator 420, makes it produce required inquiry pulse signal, the output of this inquiry signal generator 420 is connected the input of described power amplifier 430, and this The output of the power amplifier 430 is connected to the transmitting end of the RF transceiver switch 460 . The embedded computer unit 450 is connected with the radio frequency transceiver switch 460 to control whether the reader antenna 401 is used for transmitting or receiving, and the common end of the radio frequency transceiver switch 460 is connected with the The reader antenna 401 is connected. The embedded computer unit 450 is connected with the signal detection and decoding circuit 480, through the communication between them, the identification information of the radio frequency tag is obtained, and the signal detection and decoding circuit 480 is connected with the low noise amplifier 490 The output of the low noise amplifier 490 is connected to the input end of the low noise amplifier 490 and the receiving end of the RF transceiver switch 460 is connected. The embedded computer unit 450 is connected to the display unit 470 and the voice prompt unit 410, and outputs the radio frequency identification results through the display unit 410 and the voice prompt unit 410 to provide visual and auditory information. The embedded computer unit 450 establishes a connection with the remote device through the external interface control unit 440, and can also output the radio frequency identification result to the remote device at the same time.

The working process of radio frequency tag (RFID) and its reading system is like this: after the reader system is powered on, the embedded computer unit 450 of the reader system 400 runs its own firmware monitoring program to carry out system initialization, and then sends the inquiry signal generator 420 issues an instruction to make it send out a query pulse signal. After the pulse signal is amplified by the power amplifier 430, it is radiated in the form of electromagnetic waves through the radio frequency transceiver switch 460 and the reader antenna 401 in the transmitting state. When the radio frequency tag is within the inquiry range of the reader system 400, it uses the pulse signal received by the radio frequency antenna 301 as an excitation signal, and the excitation signal passes through the antenna matching circuit 302 in the bulk acoustic wave multimode resonator 300 A voltage is generated between the top electrode 360 and the metal bottom electrode 330, so that the bulk acoustic wave is excited in the resonant cavity 310 through the piezoelectric film 340, and the bulk acoustic wave propagates in the resonant cavity 310 and travels on both sides of the resonant cavity. But when the bulk acoustic wave passes through the piezoelectric film 340 each time, an electrical signal is generated on the top electrode 360 and the bottom electrode 330 of the piezoelectric film 340 through the piezoelectric effect, and the electrical signal passes through the piezoelectric film 340. The antenna matching circuit 302 and the radio frequency antenna 301 transmit out. After the reader 400 transmits the query pulse, the radio frequency transceiving switch 460 enters the receiving state and starts to receive the response signal from the radio frequency tag. The response signal of the radio frequency tag is transmitted to the embedded computer unit 450 through the reader antenna 401 , the low noise amplifier 490 and the signal detection and decoding circuit 480 . If within a given time, the embedded computer unit 450 can receive the expected response signal, then confirm the existence of the radio frequency tag, and display the recognition result by the display unit 470, and generate corresponding voice prompts by the voice prompt unit 410 simultaneously, The identification result can also be transmitted to a remote device through the external interface control unit, such as transmitting the identification result to a remote monitoring device through a public telephone network or the Internet. If within a given time, the embedded computer unit 450 can receive the expected response signal, it indicates that the existence of the radio frequency tag is not found, and the embedded computer unit 450 will make corresponding processing.

Further, in this embodiment, the radio frequency antenna 301 is a generalized antenna or an antenna system composed of multiple antenna elements, and its function is to effectively receive and radiate electromagnetic waves in a certain frequency range. It can also be a common whip antenna or a composite dielectric antenna; it can also be a microstrip antenna integrated with the bulk acoustic wave multimode resonator 300; it can also be a wire antenna made of conductive ink.

The antenna matching circuit 302 is a generalized impedance transformation circuit, and its function is to achieve impedance matching between the bulk acoustic wave multimode resonator 300 and the radio frequency antenna 301, so as to receive and radiate electromagnetic waves more effectively . Usually, it can be completed with several inductors and capacitors, and can also be integrated with the bulk acoustic wave multimode resonator 300 and the radio frequency antenna 301 on the same substrate or integrated in the bulk acoustic wave resonant cavity 310 superior. When the impedance of the piezoelectric transducer in the working frequency band is relatively close to the antenna impedance, or when the antenna matching circuit 302 has little effect on improving the performance of the tag, the antenna matching circuit 302 can be omitted.

The bulk acoustic wave resonant cavity 310 is a generalized bulk acoustic wave propagation solid medium. Its function is to allow the bulk acoustic wave to propagate sound waves in it while attenuating as little as possible. Because the sound waves are reflected back and forth therein, it is required that the parallelism of the two surfaces used for sound wave reflection is as good as possible. Commonly used materials for the BAW cavity 310 include sapphire single crystal (Al2O3), yttrium aluminum garnet (YAG), fused silica, and the like. The thickness of the BAW resonator body 310 determines the frequency interval between two adjacent frequency points of the BAW multimode resonator 300 . For short pulse signals, the thickness of the bulk acoustic wave resonant cavity 310 determines the interval of reflected pulses. For example, for a resonant cavity made of fused silica (the longitudinal sound velocity is 6000 m/s), if the thickness is 0.3 mm, the time interval between two adjacent reflected pulses is 100 nanoseconds (calculation method, time interval=2 *0.3*10e-3/6000=100 nanoseconds), and the interval between two adjacent resonant frequencies is 10MHz. (note: these two parameters of central frequency and adjacent two resonant frequency intervals are two indexes of the uniqueness of the indicated label of the present utility model. That is to say, different labels, just transform these two parameters.)

The acoustic coupling layer 320 is one or more layers of acoustic propagation medium. Its function is to couple the sound waves generated by the piezoelectric film 340 into the resonant cavity 310 as much as possible, so as to play the role of acoustic impedance matching. Generally, the material and thickness of the acoustic coupling layer 320 are determined by the materials of the piezoelectric film 340 and the bulk acoustic wave resonant cavity 310 . The thickness of the acoustic coupling layer 320 is generally a quarter of the wavelength of the bulk acoustic wave at the central frequency, and its acoustic impedance is generally close to the square root of the product of the acoustic impedance of the piezoelectric film 340 and the acoustic impedance of the resonant cavity 310 . Just like the quarter impedance matcher usually used in microwave communication. In the case where the acoustic impedance of the piezoelectric film 340 is relatively close to the acoustic impedance of the resonant cavity 310 , the acoustic coupling layer 320 may also be omitted.

The bottom electrode 330 can be a metal electrode (such as aluminum, gold, etc.), an aluminum/titanium (Al/Ti) composite layer metal electrode, or a gold-chromium composite layer (Au/Cr) electrode. Lead wires from the bottom electrode 330 are connected to the antenna matching circuit 302 .

The piezoelectric film 340 can be a piezoelectric film (such as ZnO, AlN) produced by a magnetron sputtering method, or a piezoelectric single crystal film (such as LiNbO ₃ , LiTaO ₃ ) made by a chemical micromachining method (CMP). ), it can also be a piezoelectric film made by sol method (Sol-gel) (such as PZT piezoelectric film made by Sol-gel method). The thickness of the piezoelectric film 340 determines the operating frequency of the bulk acoustic wave multimode resonator 300 . As far as the current process conditions are concerned, the manufactured piezoelectric film can work in the working range of 300MHz to 10GHz. Under the current technological conditions, the thickness of the piezoelectric film that can be produced is generally on the order of 0.5 microns to 10 microns.

Described insulating layer 350 can be the silicon dioxide (SiO2) that magnetron sputtering method is produced, also can be the insulating layer (as LTO) etc. that other methods make, and the effect of described insulating layer 350 is to avoid all The above-mentioned small defect or pinhole on the piezoelectric film 340 causes a DC short circuit or breakdown. When the thickness of the piezoelectric film 340 is relatively thick, for example, when the thickness is greater than 2 microns, the insulating layer 350 can also be omitted.

The top electrode 360 can be a metal electrode (such as aluminum, gold, etc.), can be an aluminum/titanium (Al/Ti) composite layer metal electrode, can also be a gold-chromium composite layer (Au/Cr) electrode, or There may be electrodes made from conductive ink. Lead wires from the top electrode 360 are connected to the antenna matching circuit 302 .

Further, in this embodiment, the reader antenna 401 is a generalized antenna or an antenna system composed of multiple antenna elements, and its function is to effectively receive and radiate electromagnetic waves in a certain frequency range. It can also be a common whip antenna, a composite dielectric antenna; it can also be a high-gain, highly directional antenna array composed of multiple antennas. The reader antenna 401 is connected to the output end of the radio frequency transceiving switch 460 .

The voice prompt unit 410 is a generalized voice generating device, and its function is to give voice prompts to the recognition results of the reader 400 . It can be a simple buzzer; it can also be a loudspeaker (or horn); it can also be a complex speech synthesis device, etc. The voice prompt unit 410 is connected to the embedded computer unit 450, which is equivalent to an external device unit thereof.

The query signal generator 420 is a generalized radar signal generating unit. Its function is to generate the interrogation signal required by the reader 400 . The inquiry signal generator 420 is controlled by the embedded computer unit 450 , and its output is connected to the input terminal of the power amplifier 430 . According to the characteristics of bulk acoustic wave multimode resonators, one or a combination of the following four signals is better as a query signal:

a) a short pulse signal (such as a delta pulse signal) comprising the spectrum component of the high-frequency signal in the working bandwidth of the bulk acoustic wave multimode resonator 300;

b) a pulse signal with a certain width modulated by a single high-frequency signal including the resonant frequency point (or non-resonant point) of the bulk acoustic wave multimode resonator 300;

c) a pulse signal with a certain width modulated by a frequency sweep signal comprising the operating bandwidth of the bulk acoustic wave multimode resonator 300;

d) a high-frequency code-modulated signal including the resonant frequency point (or non-resonant point) of the bulk acoustic wave multimode resonator 300;

The power amplifier 430 is a wide-band power amplification unit in a broad sense, and its function is to amplify the power of the signal generated by the query signal generator 420, and pass the amplified signal through the radio frequency transceiver switch 460 , radiate out in the form of electromagnetic waves through the reader antenna 401 . The output of the power amplifier 430 is connected to the transmit input end of the radio frequency transceiving switch 460 .

The external interface control unit 440 is a generalized peripheral communication interface controller, and its function is to establish communication with the embedded computer unit 450 and the outside as a bridge, mainly to transmit the recognition result to a distant place. Equipment or monitoring system, the interface of the remote equipment can be the Internet, the public telephone network or the adapter of Wi-Fi, WiMax, GPRS wireless network. The embedded computer unit 450 establishes a bidirectional connection with the external interface control unit 440 through multiple lines, and realizes control, programming and data transmission.

The embedded computer unit 450 is a complete computer system, including corresponding hardware and system monitoring software. It is the heart part of the reader 400, it is connected with each of the readers, and its function is to control the whole system. It generates the required query pulse signal by controlling the query signal generator 420, and controls the transmitting or receiving state of the reader antenna 401 by controlling the radio frequency transceiver switch 460; With the communication of the decoding circuit 480, the identification information of the radio frequency tag is obtained; it outputs the result of the radio frequency identification through the display device and the voice device through the display unit 470 and the voice prompt unit 410 respectively; it passes the external interface control unit The 440 establishes a connection with the remote device, and can also output the radio frequency identification result to the remote device at the same time.

The radio frequency transceiving switch 460 is a generalized single pole double throw (SPDT) broadband radio frequency switch. Its function is to switch the position of the antenna when transmitting and receiving. When transmitting, the RF transceiver switch 460 connects the reader antenna 401 and the power amplifier 430; when receiving, the RF transceiver switch 460 connects the reader antenna 401 and the low noise amplifier 490. Switching of the RF transceiver switch 460 is controlled by the embedded computer unit 450 . The transmitting input end of described radio frequency transceiving switch 460 is connected with the output end of described power amplifier 430, and its receiving output end is connected with the input end of described low noise amplifier, and the common end of its radio frequency switch is connected with the described The reader antenna 401 is connected, and its control terminal is connected with the embedded computer unit.

The display unit 470 is a display device or device in a broad sense. Its function is to give the results of the RFID system visually. Common display units are CRT monitors, display screens, liquid crystal display screens, and the like.

The signal detection and decoding circuit 480 is a generalized signal detection and processing circuit. Its function is to further amplify, shape, demodulate, and peak detect the signal output by the low noise amplifier 490 to obtain the desired identification signal. The signal detection and decoding circuit 480 is controlled by the embedded computer unit 450 , but its input is connected with the output of the low noise amplifier 490 .

The low-noise amplifier 490 is a wide-band radio-frequency low-noise amplifying circuit in a broad sense, which may include one-stage or multi-stage radio-frequency amplifiers, and may also include a band-pass filter. Its function is to perform low-noise amplification on the weak response signal of the radio frequency tag 300 received by the reader antenna 401 . The input terminal of the low noise amplifier 490 is connected to the RF receiving terminal of the RF transceiving switch 460 , and its output terminal is connected to the signal detection and decoding circuit 480 .

Claims (5)

1. radio frequency label, comprise rf wave signal source and radio-frequency antenna (301), it is characterized in that, described radio-frequency signal source adopts bulk acoustic wave multimode resonance structure, comprises the bulk acoustic wave resonant cavity (310), hearth electrode (330), piezoelectric membrane (340) and the top electrode (360) that distribute successively from the bottom to top; Described hearth electrode (330) and top electrode (360) are metal electrode, and described hearth electrode (330) is connected with described radio-frequency antenna (301) with top electrode (360).

2. by the described radio frequency label of claim 1, it is characterized in that described radio-frequency signal source also comprises the acoustics coupling layer (320) that is positioned between bulk acoustic wave resonant cavity (310) and the hearth electrode (330).

3. by the described radio frequency label of claim 1, it is characterized in that described radio-frequency signal source also comprises the insulation course (350) that is positioned between piezoelectric membrane (340) and the top electrode (360).

4. by the described radio frequency label of claim 1, it is characterized in that, comprise that also one realizes the antenna-matching circuit (302) of impedance matching between radio-frequency antenna (301) and radio-frequency signal source; Described antenna-matching circuit (302) one ports are connected with top electrode (360) with described hearth electrode (330), and the another port is connected with described radio-frequency antenna (301).

5. by the described radio frequency label of claim 1, it is characterized in that, described radio-frequency antenna (301) adopts whip antenna or complex media antenna, perhaps adopts the microstrip antenna that integrates with described radio-frequency signal source, the wire antenna that perhaps adopts electrically conductive ink to make.

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