Highly sensitive linear circuit and design method for ion-electron polymer sensor

Abstract

The application discloses a high-sensitivity linear circuit suitable for an ion-electron polymer sensor and a design method, the circuit comprising an alternating current power supply, an inductor, an ion-electron polymer sensor, a reference alternating current and a lock-in amplification module; the application further discloses a design method of the circuit, through circuit equations combined with linear optimization, for different load-capacitance and resistance response ion-electron polymer sensors, by optimizing and changing the frequency of the alternating current power supply and the size of the fixed inductor, the linearization of the high-sensitivity circuit is realized; the external load changes the alternating current impedance of the ion-electron polymer sensor in the circuit, thereby outputting a voltage varying with the external load. Compared with a traditional series resistance voltage division sensor signal acquisition circuit, the application can provide a universal sensor circuit design method for different types of ion-electron polymer sensors, so that the ion-electron polymer sensors have good linearity and high sensitivity, and can be used in fields of human motion monitoring, flexible pressure, flexible strain and the like.

Description

Technical Field

[0001] This invention relates to the field of ion-electron polymer sensor technology, and specifically to a highly sensitive linear circuit and design method suitable for ion-electron polymer sensors. Background Technology

[0002] Ion-electron polymer sensors, due to their high sensitivity, interference resistance, low detection noise, and dynamic / static force response, have unique applications in environmental interaction, health monitoring, and motion recognition. Currently, ion-electron polymer sensors are being developed for medical and healthcare applications in wearable, implantable, or digestible forms. Furthermore, because most polymers are optically transparent, ion-electron polymer sensors also hold promise for use in transparent interactive products, such as endoscopes. During sensing, the sensor converts external loads into deformation of the ion-electron polymer or changes in the metal-polymer interface, thereby sensing changes in its electrical quantities. In practical applications, the changes in electrical quantities caused by the load must be processed by dedicated data acquisition and signal processing circuits to obtain a usable voltage signal. Utilizing specialized acquisition circuits in the aforementioned low-power electronic products to achieve high-performance operation of ion-electron polymer sensors is crucial for emerging wearable monitoring and disposable applications. Linearity and sensitivity are important indicators of the performance of a sensor's signal acquisition circuit, influenced by various factors such as the sensor's electromechanical characteristics, circuit type, and the values ​​of circuit components. Linearity refers to the degree of closeness or deviation between the actual input / output characteristic curve and the ideal input / output characteristic curve (called the fitted straight line) (linearity is also known as "nonlinear error"). A smaller value indicates better linearity and significantly reduces difficulties in practical data processing. Sensitivity refers to the ratio of the output signal of the acquisition circuit to the applied load on the sensor. At the same noise level, a larger value indicates a higher signal-to-noise ratio for the sensor.

[0003] Ion-electron polymer sensors have only been developed for a little over a decade, but they have attracted widespread attention from researchers due to their high sensitivity and high signal-to-noise ratio. They can generate huge changes in electrical quantities under small loads. However, because these changes are extremely nonlinear, the data collected is severely limited in practical applications. Existing sensor acquisition circuit technologies often use series resistor voltage dividers, high-sensitivity resistor bridges, and other methods such as capacitive / piezoresistive microphones and resistance strain gauges. Since the electrical quantity changes of traditional sensors under unit loads are small, existing sensor acquisition circuit technologies are sufficient to meet their requirements. However, for ion-electron polymer sensors, there is currently no suitable low-power, high-sensitivity linear voltage acquisition circuit, which is a significant disadvantage for the practical application of this emerging sensing technology. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a highly sensitive linear circuit and its design method suitable for ion-electron polymer sensors, thereby solving the problem of nonlinearity or inapplicability of existing voltage acquisition circuits for ion-electron polymer sensors and promoting the application of ion-electron polymer sensors from the laboratory to people's daily lives.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: A highly sensitive linear circuit suitable for ion-electron polymer sensors is disclosed. The highly sensitive linear circuit includes an AC power supply, an inductor, and an ion-electron polymer sensor, as well as a reference AC power supply and a lock-in amplifier module. In the LCR resonant circuit formed by the AC power supply, inductor, and ion-electron polymer sensor connected in series, the AC voltage divider across the inductor is connected to the lock-in amplifier module via a signal channel. Simultaneously, a reference AC power supply of the same frequency and phase is also connected to the lock-in amplifier module via a reference channel. The lock-in amplifier module amplifies the two AC signals through operational amplification to output a final DC voltage signal. The AC power supply, ion-electron polymer sensor, and inductor constitute the core circuit.

[0006] The amplitude of the AC power supply must not exceed the electrochemical window of the corresponding ion-electron polymer sensor to avoid electrochemical reactions causing sensor failure (usually less than 1 Vpp); the frequency of the AC power supply should be selected so that the ion-electron polymer sensor is in a frequency range that is mainly capacitive or mainly resistive. The ion-electron polymer sensor refers to a sensor composed of a metal and an ion-polymer in contact, such as a typical sandwich compression sensor structure with a metal upper layer, an ion-polymer middle layer, and a metal lower layer. Under alternating current, a double-layer capacitance is formed at the contact point between the metal and the ion-polymer, while the internal resistance of the ion-polymer is equivalent to a bulk resistance. The amplitude of the reference AC power supply is greater than the minimum voltage required by the reference channel of the lock-in amplifier module, and the frequency and phase are consistent with the AC power supply in the core circuit. The lock-in amplifier module has two functions: first, filtering: based on the orthogonality principle of sine functions, it calculates and outputs only the voltage divider signal changes that are consistent with the frequency of the AC power supply in the core circuit, converting the AC voltage divider output into a DC voltage divider output with amplitude, thereby improving the anti-interference capability of the inductor and ion-electron polymer sensor; second, amplification: under the premise of constant environmental noise, it amplifies the DC voltage divider output through the built-in operational amplifier to improve the signal-to-noise ratio of the ion-electron polymer sensor.

[0007] The sensor formed by the contact between the metal and the ionic polymer is a sandwich compression sensing structure with a metal upper layer, an ionic polymer middle layer, and a metal lower layer.

[0008] The frequency range for which the ion-electron polymer sensor operates in capacitive or predominantly capacitive with a secondary resistive bias is 10kHz to 200kHz.

[0009] The aforementioned design method for a high-sensitivity linear circuit suitable for ion-electron polymer sensors involves designing the high-sensitivity linear circuit using a combination of circuit equations and linear optimization. Specifically: First, the equivalent circuit elements of the ion-electron polymer sensor under AC power are determined (in most cases, a capacitor in series with a resistor). These equivalent circuit elements are then connected in series with an inductor to form an LCR circuit. Subsequently, a reference AC power supply is connected to the reference channel of the lock-in amplifier module, and the AC voltage divider across the inductor in the LCR circuit is connected to the signal channel of the lock-in amplifier module. Second, the final DC voltage output of the lock-in amplifier module is calculated using circuit equations. Finally, a difference function is defined, which is the difference between the voltage output of the ion-electron polymer sensor and the load ratio under different loads. By optimizing the AC power supply frequency and the inductor size to minimize the difference function, the output of the high-sensitivity linear circuit is linearized.

[0010] The design method described above uses an AC power supply. , in The voltage amplitude of the AC power supply is given by the fixed inductor. In AC circuits, ion-electron polymer sensors are equivalent to double-layer capacitors. Series resistor The AC voltage drop across the inductor is then... ,in It is high-frequency noise. The AC voltage drop across the inductor is the amplitude. The phase difference between the two ends; when the reference AC current is At that time, among them For reference, the voltage amplitude of alternating current, To reference the phase difference of the AC voltage, the voltage across the inductor is divided and then passed through a phase-locked loop amplifier module to output the voltage. Calculate using the following circuit equations; (1) When the phase difference of the reference AC voltage Phase difference with the inductor terminals When they are the same, the sensor voltage output is: (2) In the above formula, the double-layer capacitance and series resistance are both based on the AC power supply frequency. and load The function, i.e. , The basic electromechanical properties of the ion-electron polymer sensor were obtained through experiments. Then, optimize the AC frequency. and fixed inductance The size can make the load and output voltage Linearization, the sensitivity of its circuit, i.e. the output voltage under unit load, can be achieved by adjusting the electromechanical performance of the ion-electron polymer sensor and the amplification factor of the circuit.

[0011] The basic electromechanical properties of the ion-electropolymer sensor are capacitance. The data was obtained through experiments with controlled variables. The experimental procedure was as follows: First, the ion-electron polymer sensor was connected to an AC impedance analyzer to obtain the capacitance and resistance at a preset AC frequency; second, at a fixed AC frequency... Under different loads applied to the ion-electron polymer sensor Record the sensor capacitance at a single AC frequency and resistance Finally, by changing different AC frequencies and recording the sensor capacitance and resistance data relative to the load at different AC frequencies, the electromechanical performance of the ion-electron polymer sensor can be obtained through bivariate function fitting. and Compared with the prior art, the present invention has the following advantages and beneficial effects: (A) The design strategy of this invention is to utilize the fact that the ion-electron polymer sensor is equivalent to a capacitor and a resistor under alternating current. By introducing a fixed inductor to form an LCR AC resonant circuit, a large voltage output can be obtained by using circuit resonance with a small voltage power input, thereby realizing low power consumption of the acquisition circuit. (B) The circuit design of the present invention can optimize the output performance by adjusting the frequency of the AC power supply and the value of the fixed inductor, thereby achieving linearization of the voltage acquisition circuit applicable to most ion-electron polymer sensors; (C) In addition to the LCR resonance acquisition circuit, the circuit of the present invention can obtain a pure voltage divider signal by using a reference AC current with the same frequency and phase through a lock-in amplifier module, and then amplify it to obtain a voltage output, thereby improving the overall signal-to-noise ratio of the sensor. (D) The circuit elements of the present invention have a simple structure, are easy to implement, have low cost, and are easy to arrange in the structure of the acquisition circuit in sensor design. It is expected to truly bring ion electron polymer sensors to the application market. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the highly sensitive linear circuit for ion-electron polymer sensors proposed in this invention.

[0013] Figure 2a This describes the force-capacitance response of an ion-electron polymer sensor at different AC frequencies in a specific embodiment.

[0014] Figure 2b This describes the force-resistance response of an ion-electron polymer sensor at different AC frequencies in a specific embodiment.

[0015] Figure 3 This is a comparison of the output of the same ion-electron polymer sensor in one specific embodiment under the conditions of the present invention and a conventional series voltage divider resistor circuit. Detailed Implementation

[0016] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent transformations and modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0017] Following the above technical solutions, such as Figure 1 , Figure 2a , Figure 2b and Figure 3 As shown in the figure, this embodiment presents a highly sensitive linear circuit and design method suitable for ion electron polymer sensors.

[0018] like Figure 1 As shown, the present invention is applicable to a high-sensitivity linear circuit for ion electron polymer sensors, and has a simple structure, including an AC power supply. ,inductance Ion-electron polymer sensor, reference AC power supply The circuit consists of a lock-in amplifier module, in which an AC power supply, an inductor, and an ion-electron polymer sensor are connected in series to form an AC LCR resonant circuit. The AC voltage divider across the inductor is then connected to the lock-in amplifier module via a signal channel, and a reference AC power supply of the same frequency and phase is also connected to the lock-in amplifier module via a reference channel. The lock-in amplifier module amplifies the output DC voltage signal. Finally, the basic electromechanical properties of the ion-electron polymer sensor are obtained experimentally. Then, the AC frequency is optimized by substituting it into the circuit output expression obtained from the circuit equations. and inductor The size can make the load and output voltage Linearization, specifically the sensitivity of the circuit (i.e., the output voltage under unit load), can be achieved by adjusting the electromechanical properties of the ion-electron polymer sensor and the amplification factor of the circuit. This concludes the design concept and method for a high-sensitivity linear circuit applicable to ion-electron polymer sensors.

[0019] In one specific embodiment, an ion-electron polymer sensor with a "sandwich" compressed structure of "electrode-microstructure ion gel-electrode" fabricated in the laboratory was used as the test object of this invention. The specific experimental comparison procedure is described in detail below: like Figure 2a As shown in the figure, the data represents the load-capacitance response of this ion-electron polymer sensor, i.e. First, the sensor was placed on a micro-load loading test bench and fixed in its initial position, and the electrode leads were connected to an impedance analyzer. Second, the AC voltage amplitude of the impedance analyzer was set to 100 mV, with frequencies of 10 kHz, 30 kHz, 50 kHz, 70 kHz, 90 kHz, 110 kHz, 130 kHz, 150 kHz, and 170 kHz. Finally, a load was applied to the sensor using the micro-load loading bench at each AC frequency, and its capacitive response under different loads was recorded using the impedance analyzer. In the figure, the origin represents the experimental data, and the surface is the load-capacitance response surface of the sensor fitted using the least squares method. ; like Figure 2b As shown in the figure, the data represents the load-resistance response of this ion-electron polymer sensor, i.e. The experimental procedure remains the same as described above, except that the impedance analyzer is used to record the resistance response under different loads at the end. In the figure, the origin represents the experimental data, and the surface is the load-resistance response surface of the sensor fitted using the least squares method. ; like Figure 3 As shown, the load-capacitance and resistance response relationship of the ion-electron polymer sensor obtained by the above method is substituted into the sensor output voltage expression obtained by the circuit equation, i.e., equation (1). Then, by using linear optimization, the two parameters obtained are the AC frequency and the AC frequency, respectively. =10kHz and inductance =7.7mH, at the AC power supply amplitude When the voltage is 100mV and the circuit amplification factor is 1, the solid line in the figure represents the output curve of this invention. The dashed line represents the sensor connected to a traditional series resistor voltage divider circuit. It is easy to see from the figure that, compared with traditional voltage signal acquisition circuits, the output curve of this invention has high linearity, and the sensitivity remains around 678.36 mV / kPa under different loads. For ion-electron polymer sensors, this invention is significantly superior to existing data acquisition circuits.

[0020] This invention provides a reliable technical approach for data acquisition using high-performance ion-electron polymer sensors.

[0021] Application scope: The high-sensitivity linear circuit of this invention can be used in sensing fields such as human motion monitoring, flexible pressure, and flexible strain sensors for flexible ion-electron polymer sensors.

[0022] The potential economic benefits of this invention are: Ion-electron polymer sensors, due to their main advantages such as flexibility, extremely high sensitivity, anti-interference, low detection noise, and dynamic / static force response, have unique applications in environmental interaction, health monitoring, and motion recognition. This invention, as the technical guarantee for signal acquisition of ion-electron polymer sensors, has equally important aspects and value.

[0023] Impact of this invention on the future technology market in China: In the current technology market, sensor circuits based on series resistor voltage dividers and resistor bridges have limited applicability due to their inherent limitations, making them unsuitable for ion-electron polymer sensors with extremely high sensitivity. In recent years, emerging ion-electron polymer sensors have become a research hotspot due to their advantages such as flexibility, extremely high sensitivity, interference resistance, low detection noise, and dynamic / static force response. Because the electrical quantities of ion-electron polymer sensors change dramatically and nonlinearly under unit loads, traditional sensor circuits cannot meet their application requirements. According to literature reports in this field, traditional series resistor voltage divider circuits and resistor bridge circuits can only maintain the linearity of the output load-voltage within the very small load range of ion-electron polymer sensors, which cannot meet the needs of further development in this field. This invention technically solves the problems existing in this field and provides design ideas.

Claims

1. A highly sensitive linear circuit suitable for ion-electron polymer sensors, characterized in that: The high-sensitivity linear circuit includes an AC power supply, an inductor, an ion-electron polymer sensor, a reference AC power supply, and a lock-in amplifier module. In the LCR resonant circuit formed by the AC power supply, inductor, and ion-electron polymer sensor connected in series, the AC voltage divider across the inductor is connected to the lock-in amplifier module via a signal channel. Simultaneously, a reference AC power supply of the same frequency and phase is also connected to the lock-in amplifier module via a reference channel. The lock-in amplifier module amplifies the two AC signals through operational calculations, outputting the final DC voltage signal. The AC power supply, ion-electron polymer sensor, and inductor constitute the core circuit. The amplitude of the AC power supply cannot exceed the electrochemical window of the corresponding ion-electron polymer sensor to avoid electrochemical reactions causing sensor failure; the amplitude of the AC power supply is less than 1. Vpp; The frequency of the AC power supply should be selected so that the ion-electron polymer sensor is in a frequency range of capacitive or predominantly capacitive and secondarily resistive, wherein the frequency range is 10kHz~200kHz; The ion-electron polymer sensor is a sensor composed of metal and ion-type polymer in contact. Under AC power, the part in contact between the metal and ion-type polymer will form a double-layer capacitor, and the internal resistance of the ion-type polymer is equivalent to a bulk resistance; The sensor composed of metal and ion-type polymer in contact is a sandwich compression sensing structure with metal as the upper layer, ion-type polymer as the middle layer, and metal as the lower layer; The amplitude of the reference AC power supply is greater than the minimum voltage required by the reference channel of the lock-in amplifier module, and the frequency and phase are consistent with the AC power supply in the core circuit; The lock-in amplifier module is used to calculate and output only the voltage divider signal change with the same frequency as the AC power supply in the core circuit according to the orthogonality principle of the sine function, converting the AC voltage divider output into a DC voltage divider output with amplitude, and amplifying the DC voltage divider output through the built-in operational amplifier.

2. The design method for a highly sensitive linear circuit suitable for ion-electron polymer sensors as described in claim 1, characterized in that: The high-sensitivity linear circuit is designed using a combination of circuit equations and linear optimization. Specifically: First, the equivalent circuit elements of the ion-electron polymer sensor under AC power are determined, and these elements are connected in series with an inductor to form an LCR circuit. Then, a reference AC power is connected to the reference channel of the lock-in amplifier module, and the AC voltage divider across the inductor in the LCR circuit is connected to the signal channel of the lock-in amplifier module. Second, the DC voltage output of the final lock-in amplifier module is calculated using circuit equations. Finally, a difference function is defined, which is the difference between the voltage output of the ion-electron polymer sensor and the load ratio under different loads. By optimizing the AC power frequency and the inductor size, the difference function is minimized, thereby linearizing the output of the high-sensitivity linear circuit.

3. The design method according to claim 2, characterized in that: The AC power supply is , in The voltage amplitude of the AC power supply is given by the fixed inductor. In AC circuits, ion-electron polymer sensors are equivalent to double-layer capacitors. Series resistor The AC voltage drop across the inductor is then... ,in It is high-frequency noise. The AC voltage drop across the inductor is the amplitude. The phase difference between the two ends; when the reference AC current is At that time, among them For reference, the voltage amplitude of alternating current, To reference the phase difference of the AC voltage, the voltage across the inductor is divided and then passed through a phase-locked loop amplifier module to output the voltage. Calculate using the following circuit equations; （1） When the phase difference of the reference AC voltage Phase difference with the inductor terminals When they are the same, the sensor voltage output is: （2） In the above formula, the double-layer capacitance and series resistance are both based on the AC power supply frequency. and load The function, i.e. , ; The basic electromechanical properties of the ion-electron polymer sensor were obtained through experiments. Then, optimize the AC frequency. and fixed inductance The size can make the load and output voltage Linearization, the sensitivity of its circuit, i.e. the output voltage under unit load, can be achieved by adjusting the electromechanical performance of the ion-electron polymer sensor and the amplification factor of the circuit.

4. The design method according to claim 2, characterized in that: The basic electromechanical properties of the ion-electropolymer sensor are capacitance. The data was obtained through experiments with controlled variables. The experimental procedure was as follows: First, the ion-electron polymer sensor was connected to an AC impedance analyzer to obtain the capacitance and resistance at a preset AC frequency; second, at a fixed AC frequency... Under different loads applied to the ion-electron polymer sensor Record the sensor capacitance at a single AC frequency and resistance Finally, by changing different AC frequencies and recording the sensor capacitance and resistance data relative to the load at different AC frequencies, the electromechanical performance of the ion-electron polymer sensor can be obtained through bivariate function fitting. and .

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