A low-power sweat information collection and perception system based on backscattering technology

Abstract

The present invention discloses a low-power sweat information collection and perception system based on backscattering technology, including a reader and multiple sensors; the sensor includes a communication module, a control module, a power module and an electrochemical module connected to each other, and the communication module and the reader communicate wirelessly through backscattering; the electrochemical module includes a driving circuit, an electrochemical electrode, a current signal conversion circuit, a voltage signal amplification circuit, a voltage-controlled oscillator and a control switch. The present invention realizes the detection of uric acid, ascorbic acid and Na + The monitoring of ion concentration effectively reduces power consumption by using voltage-frequency conversion and backscattering technology, enables continuous collection and ensures detection accuracy and working range.

Description

Technical Field

[0001] The present invention belongs to the field of Internet of Things, and in particular relates to a low-power sweat information collection and perception system based on backscattering technology. Background Art

[0002] In recent years, the concept of smart healthcare has attracted widespread attention from researchers, and wearable sweat sensing technology has gradually developed and progressed. By placing sensors on the user's skin, the concentration changes of various components in sweat can be continuously monitored, providing convenient, invasive, long-term, and continuous physical health monitoring.

[0003] Wearable sweat sensors can monitor Na + We can use wearable sweat sensors to monitor the sweating of athletes in real time and remind them to replenish water and electrolytes in time, which can effectively avoid this dangerous situation. In addition, for some people with underlying diseases, by monitoring the changes in sweat composition in real time, we can also judge the condition and remind users to go to the hospital in time to prevent the condition from worsening.

[0004] In the past, a lot of research work has focused on designing wireless wearable sweat sensing systems. The usual approach is to use various biosensors to convert sweat information into electrical signals. The communication methods can be divided into two categories, one using WiFi or Bluetooth modules to send sensor readings to mobile devices (such as smartphones), and the other type of system uses passive near-field communication (NFC) to passively send its sensing data to a reader device.

[0005] Using WiFi or Bluetooth, sweat information can be transmitted to a remote monitoring device (such as a mobile phone), but this solution has bottlenecks. One of the main bottlenecks hindering the adoption of wearable devices is the problem of continuous power supply. The power consumption of such systems is usually very high, requiring a large-capacity battery to be powered. However, large-capacity batteries increase the size and weight of these devices, making them unsightly and causing discomfort to users.

[0006] Passively sending its sensor data to a reader device using passive near-field communication (NFC) can achieve lower power consumption than WiFi or Bluetooth. However, one disadvantage of existing passive NFC-based wireless and battery-free wearable devices is that their operating range is limited, usually less than 10 cm. Such an operating range severely limits the convenience of use, especially in mobile scenarios. For example, when a user is running, cycling, or doing other types of sports, it is impossible to place the reader 10 cm away from the sensor to obtain sensor data. Therefore, in actual usage scenarios, NFC-based wearable sensor systems cannot achieve real-time and continuous monitoring. Summary of the invention

[0007] The purpose of the present invention is to provide a low-power sweat information collection and perception system based on backscattering technology to solve the problems of high power consumption and inability to achieve real-time continuous monitoring in the prior art.

[0008] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0009] On the one hand, the present invention provides a low-power sweat information collection system based on backscattering technology, including a reader and multiple sensors; the sensor includes a communication module, a control module, a power module and an electrochemical module connected to each other, and the communication module and the reader perform wireless communication by backscattering;

[0010] The electrochemical module comprises a driving circuit, an electrochemical electrode, a current signal conversion circuit, a voltage signal amplifying circuit, a voltage-controlled oscillator and a control switch; wherein the electrochemical electrode comprises two pairs of electrodes and an electrode interface, each pair of electrodes comprises a working electrode and a counter electrode, the electrode interface comprises ports 1 to 4, ports 1 and 2 of the electrode interface are used when sweat is collected by the chronoamperometry method, port 1 is connected to the working electrode, and port 2 is connected to the counter electrode; when sweat is collected by the open circuit voltage method, ports 3 and 4 of the electrode interface are used, port 3 is connected to the working electrode, and port 4 is connected to the counter electrode; ports 1, 2, 3 and 4 of the electrode interface are respectively connected to the driving circuit, the current signal conversion circuit, the common ground and the voltage signal amplifying circuit; the current signal conversion circuit and the voltage signal amplifying circuit are respectively connected to the voltage-controlled oscillator; the voltage-controlled oscillator is connected to the communication module; the source of the control switch is connected to the driving circuit, the current signal conversion circuit, the voltage signal amplifying circuit and the voltage-controlled oscillator, the drain is connected to the power supply VCC, and the gate is connected to the control module.

[0011] Furthermore, the driving circuit includes a voltage regulating circuit and a voltage follower connected thereto.

[0012] Furthermore, the voltage regulating circuit uses a 1M ohm potentiometer, and the voltage follower uses an operational amplifier OPA313.

[0013] Furthermore, the communication module includes an antenna, an impedance matching circuit, a radio frequency switch and a signal monitoring circuit; wherein the antenna and the reader perform wireless communication through backscattering; the impedance matching circuit is an LC circuit, and the radio frequency switch is respectively connected to the antenna, the electrochemical module and the control module; the signal monitoring circuit is composed of a voltage doubler rectifier circuit and a comparison circuit, the output end of the voltage doubler rectifier circuit is connected to the in-phase input end of the comparator in the comparison circuit, the inverse input end of the comparator is grounded, and the output end of the comparator is connected to the control module.

[0014] Furthermore, the radio frequency switch adopts an N-channel enhancement type field effect transistor, the source and drain of the field effect transistor are directly connected to the two poles of the antenna, and the gate is connected to the electrochemical module and the control module.

[0015] Furthermore, the comparison circuit adopts NCS2200.

[0016] Furthermore, the power module includes a power control circuit and a power supply interface connected to the power control circuit, a solar thin-film battery and a lithium battery, wherein the power control circuit is also connected to the control module.

[0017] Furthermore, the power control circuit includes a buck-boost chip BQ25570 and its peripheral circuits; the capacity of the lithium battery is 200mAh.

[0018] Furthermore, the control module adopts the ultra-low power consumption microcontroller MSP430FR5996.

[0019] On the other hand, the present invention provides a low-power sweat sensing system based on backscattering technology, characterized in that it includes an information processing system and the above-mentioned low-power sweat information collection system based on backscattering technology, wherein the information processing system is used to perform short-time Fourier transform processing on the data obtained by the sweat information collection system to obtain sweat sensing results.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] 1. Using voltage-frequency conversion and low-power backscattering, the concentrations of different analytes in sweat are directly converted into backscattered signals of different frequencies, which are captured and identified by the remote reader. This meets the key needs of sweat information sensing in sports scenarios, especially in user sports and low-power operation scenarios.

[0022] 2. Avoid using high-power hardware components (such as ADC, DAC, Bluetooth communication module and WiFi communication module). The core function of the present invention uses only a small number of ultra-low-power operational amplifiers. In such application scenarios, microcontrollers are indispensable. Since the design of the present invention avoids the need for high-performance microcontrollers or processors, the system power consumption can be reduced by adopting ultra-low-power and low-performance microcontrollers. In terms of system design, the present invention further optimizes the system structure and adopts a variety of energy supply solutions, which significantly reduces power consumption and increases the continuous working time of the system.

[0023] 3. Compared with the NFC-based solution, the present invention extends the working range to the normal range of body activities, which can reach 200 cm after experiments, while the NFC-based solution is usually less than 10 cm. Therefore, the present invention can transmit the sensor signal to the reader with ultra-low power consumption when the sensor is in motion, and can work continuously relying on solar energy.

[0024] 4. The sensor is designed on a flexible PCB, which can be attached to the human skin to collect information on the concentration of sweat analytes. It is small in size and easy to promote.

[0025] In summary, the present invention senses the concentrations of different analytes in sweat in a wireless manner, and by using voltage-frequency conversion and backscattering technology, it ensures the sensing accuracy while effectively reducing the power consumption of the sensor, thereby achieving real-time and continuous sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the application scenario;

[0027] Figure 2 It is the system structure diagram;

[0028] Figure 3 Example diagram for encoding sensor identity information;

[0029] Figure 4 is the system state diagram;

[0030] Figure 5(a) is a circuit diagram of a communication module; Figure 5(b) is an example diagram of backscattering;

[0031] Figure 6 This is the circuit diagram of the power module;

[0032] Figure 7(a) is a schematic diagram of the chronoamperometry method; Figure 7(b) is a schematic diagram of the open circuit voltage method; Figure 7(c) is a circuit diagram of the electrochemical module;

[0033] Figure 8 This is the circuit diagram of the control module;

[0034] Fig. 9 It is the ID waveform diagram;

[0035] Fig.10 is the SNR and standard deviation at different working distances;

[0036] Figure 11(a) shows the charging time of a 200mAh lithium battery; Figure 11(b) shows the power consumption and standby time of the sensor in different states;

[0037] Fig.12 The results of sensing different concentrations of uric acid;

[0038] Fig.13 The results of ascorbic acid perception for different concentrations;

[0039] Fig.14 For different concentrations of Na + Ion sensing results. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings.

[0041] Example 1

[0042] The low-power sweat information collection system based on backscattering technology provided by the present invention includes a reader and multiple sensors. The application scenarios of the present invention are as follows: Figure 1 As shown. The reader is used to send wireless signals to the sensor and receive the backscattered signals of the sensor, and is set within 2 meters of the sensor. The sensor includes a communication module, a control module, a power module and an electrochemical module connected to each other. The communication module communicates wirelessly with the reader through backscattering;

[0043] The sensor is made of flexible PCB and can be attached to the skin surface of different parts of the human body; the power module is used to provide power to other modules, the control module is used to control the electrochemical module to collect analyte concentration information in sweat, and the communication module is used to send the information to the reader by backscattering. Figure 2 shown.

[0044] The sensor identity information (ID) is 8 bits in total and is stored in the control module. It is used to identify the unique identity of the sensor and uses Manchester encoding, such as Figure 3 As shown. In Manchester encoding, there is a transition in the middle of each bit. The transition in the middle of the bit serves as both a clock signal and a data signal. The clock and data are included in the signal stream. While transmitting the code information, the clock synchronization signal is also sent to the reader.

[0045] The whole system has three states: sleep state, waiting state and working state. The specific operation process of the system is as follows: Figure 4As shown. When the antenna in the sensor does not receive the wireless signal sent by the reader or the power module is underpowered, each sensor is in a sleep state; when the reader sends a wireless signal, the antenna in the sensor receives the wireless signal and the power module is not underpowered, the sensor enters a waiting state, and each sensor waits for a different time to avoid signal collision caused by working at the same time. After the waiting time is reached, the sensor enters the working state. First, the control module sends the sensor identity information (ID) to the reader through the communication module, and then enters the sensing stage. The control module controls the electrochemical module to start working and sends the analyte concentration information collected from the sweat by the electrochemical module to the reader through the communication module. When working, if the power supply is underpowered or the wireless signal sent by the reader disappears, the sensor re-enters the sleep state; since the chronoamperometry and open circuit voltage methods can obtain an accurate concentration information of the analyte in sweat in only 5 seconds, the sensor will re-enter the waiting state after working for 5 seconds, and will automatically enter the working state after waiting for a period of time.

[0046] The communication module includes an antenna, an impedance matching circuit, a radio frequency switch, and a signal monitoring circuit, as shown in Figure 5(a). The communication method uses backscattering, and the wireless signal sent by the reader is modulated by the switch and backscattered to the reader, as shown in Figure 5(b). The antenna is used to receive and reflect the wireless signal sent by the reader; the impedance matching circuit is an LC circuit, which is used to connect the antenna and the signal monitoring circuit to ensure that the wireless signal received by the antenna can be transmitted to the subsequent circuit to the maximum extent and prevent the signal from being reflected back to the antenna. The RF switch Q1 adopts an N-channel enhancement type field effect transistor. The source and drain of the field effect transistor are directly connected to the two poles of the antenna, and the gate is connected to the signal output line of the electrochemical module and the control module. When the gate of the field effect transistor is input with a high level, it is turned on, the two poles of the antenna are short-circuited, and the impedance matching circuit is short-circuited, resulting in impedance mismatch. At this time, the wireless signal received by the antenna cannot be transmitted to the subsequent circuit. The signal is reflected back to the antenna and then reflected back to the reader through the antenna. The signal received at one end of the reader is reflected as a high level. When the gate of the field effect transistor is input with a low level, it is turned off. The wireless signal received by the antenna is transmitted to the subsequent circuit through the impedance matching circuit. Only a small part of the signal is reflected. The signal received at one end of the reader is reflected as a low level. The RF switch Q1 works in a switching state, and controls the antenna and circuit to switch between impedance mismatch and matching states according to the input signal to reflect or receive wireless signals, thereby realizing switch modulation of the backscattered signal. The signal monitoring circuit consists of a voltage doubling rectifier circuit and a comparison circuit. The output end of the voltage doubling rectifier circuit is connected to the in-phase input end of the comparator in the comparison circuit, the inverting input end of the comparator is grounded, and the output end of the comparator is connected to the control module. The wireless signal input by the impedance matching circuit is amplified and input into the control module to activate the control module, thereby switching the working state; the voltage doubling rectifier circuit is used to increase the input signal voltage; the voltage comparison circuit adopts the NCS2200 low-power comparator, and when the input voltage is greater than the reference voltage, it outputs a high level to the microcontroller.

[0047] The power module includes a power control circuit and a power supply interface connected to the power control circuit, a solar thin film battery and a lithium battery, wherein the power control circuit is connected to the control module, such as Figure 6As shown. In order to reduce power consumption, the power supply voltage VCC provided by the power module to other modules is set at 2.0V. The power control circuit includes a buck-boost chip and its peripheral circuits. The buck-boost chip model is BQ25570. When there is light, it can collect the electric energy provided by the solar thin-film battery. First, the input voltage is boosted to 5.0V to charge the lithium battery. The lithium battery is a small battery with a capacity of 200mAh. Then the output voltage VCC of the lithium battery is stepped down and stabilized at 2.0V to provide power for other modules. The power supply interface can directly power the sensor through an external power supply, and is also connected to the power control circuit, which can quickly charge the lithium battery at the same time. In addition, BQ25570 monitors the output voltage VCC in real time. When the voltage is lower than 1.9V, it will output an undervoltage signal to the control module through the power status line connected to the control module.

[0048] The electrochemical module uses a dual-electrode system, and uses the chronoamperometry and open circuit voltage method to detect the concentration of different analytes in sweat. The chronoamperometry is used to detect the concentration of uric acid and ascorbic acid in sweat. The working electrode material is carbon cloth, and the counter electrode material is carbon powder. By applying a voltage of 0.4V to the working electrode and the counter electrode of the electrochemical electrode, the relationship between the current response and time can be obtained. Different concentrations of analytes will result in different current response characteristic curves, which can reflect the concentration of uric acid and ascorbic acid. The higher the concentration, the slower the current decreases over time, as shown in Figure 7(a); the open circuit voltage method is used to detect Na in sweat. + The concentration of ions, the working electrode is Na + Ion selective electrode, Ag / AgCl is used as the counter electrode. Different concentrations of analytes will lead to different open circuit voltages between the working electrode and the counter electrode. The voltage across the electrodes can be directly measured to obtain the Na in sweat. + The higher the concentration, the higher the open circuit voltage, as shown in Figure 7(b).

[0049] The electrochemical module includes a driving circuit, an electrochemical electrode, a current signal conversion circuit, a voltage signal amplification circuit, a voltage-controlled oscillator and a control switch, as shown in FIG7( c ).

[0050] The electrochemical electrode includes two pairs of electrodes and an electrode interface. The two pairs of electrodes are used for the chronoamperometry and the open circuit voltage method, respectively. Each pair of electrodes includes a working electrode and a counter electrode. The electrode interface includes ports 1-4. When the chronoamperometry is used, ports 1 and 2 of the electrode interface are used, port 1 is connected to the working electrode, and port 2 is connected to the counter electrode; when the open circuit voltage method is used, ports 3 and 4 of the electrode interface are used, port 3 is connected to the working electrode, and port 4 is connected to the counter electrode. Ports 1, 2, 3, and 4 of the electrode interface are connected to the drive circuit, the current signal conversion circuit, the common ground, and the voltage signal amplification circuit, respectively.

[0051] The current signal conversion circuit and the voltage signal amplification circuit are respectively connected to the voltage-controlled oscillator; the voltage-controlled oscillator is connected to the RF switch Q1 of the communication module through the output line of the electrochemical module. The source of the control switch Q2 is connected to the drive circuit, the current signal conversion circuit, the voltage signal amplification circuit and the voltage-controlled oscillator, the drain is connected to the power supply VCC, and the gate is connected to the electrochemical control line of the control module, which is used to decide whether to provide power to the electrochemical module according to the instructions of the control module.

[0052] Based on the above design, the working principle of the electrochemical module is as follows:

[0053] The chronoamperometry method is used to detect uric acid and ascorbic acid. The detection circuit is composed of a driving circuit, an electrochemical electrode, and a current signal conversion circuit. At this time, ports 1 and 2 of the electrode interface are used, with port 1 connected to the working electrode and port 2 connected to the counter electrode. After connecting the corresponding electrodes to the sensor, the sensor with the electrode side is attached to the skin surface of the person being tested.

[0054] The driving circuit includes a voltage regulator circuit and a voltage follower. The driving circuit is used to provide working voltage for the electrode part. The voltage regulator circuit uses a 1M ohm potentiometer, which divides the 2.0V power supply voltage and outputs it to the voltage follower. The output voltage can be easily adjusted by the potentiometer. The voltage follower uses an ultra-low power operational amplifier OPA313 to isolate the impact of the subsequent load on the voltage and improve the output capacity; the current signal conversion circuit is a current-voltage converter composed of OPA313; when working, the driving circuit applies a voltage of 0.4V to the working electrode, and the current signal conversion circuit extracts the weak current signal flowing out of the counter electrode and converts it into a voltage signal and amplifies it, and outputs it to the voltage-controlled oscillator.

[0055] To Na + When ions are detected, the open circuit voltage method is used, and its circuit consists of an electrochemical electrode and a voltage signal amplification circuit. At this time, ports 3 and 4 of the electrode interface are used, with port 3 connected to the working electrode and port 4 connected to the counter electrode.

[0056] The voltage signal amplification circuit uses a common-mode proportional amplifier with OPA313 as the core. When working, the corresponding working electrode is grounded, and the voltage signal amplification circuit amplifies the weak voltage signal output by the electrode and outputs it to the voltage-controlled oscillator.

[0057] Finally, the voltage signal controls the voltage-controlled oscillator to generate a square wave signal. When the signal output by the electrode changes, voltages of different magnitudes can drive the voltage-controlled oscillator to generate square wave signals of different frequencies. The square wave signal is output to the RF switch Q1 of the communication module through the signal output line.

[0058] The control module uses the ultra-low power microcontroller MSP430FR5996, which is connected to the communication module, power module, and electrochemical module. Figure 8 As shown. The microcontroller is responsible for wireless signal monitoring, power status monitoring, status control, sensor identity information transmission and collision avoidance protocol when multiple sensors work simultaneously. MSP430FR5996 has 7 working modes, namely active mode (AM), low power mode 0 to 4 (LPM0 to 4), low power mode 3.5 (LPM3.5) and low power mode 4.5 (LPM4.5). Among them, AM mode has the highest power consumption and LPM4.5 has the lowest power consumption.

[0059] According to the system operation process, such as Figure 3 As shown, the microcontroller works in low power modes LPM3 and LPM4.5 almost all the time, which significantly reduces its own power consumption. In order to further optimize the power consumption of the microcontroller, combined with the application scenario, the present invention does not use any high-precision and high-frequency oscillator to provide the clock for the microcontroller, but uses the ultra-low power low-frequency oscillator VLO with an internal frequency of 10kHz of the microcontroller as the clock of the microcontroller CPU and peripheral timer, and turns off the ferroelectric memory FRAM. When in AM mode, only the CPU is turned on; when in LPM3, only the timer and external interrupt are turned on; when in LPM4.5, only the external interrupt is turned on. When the signal monitoring circuit does not detect the wireless signal or the power module is under-powered, the sensor is in sleep state, corresponding to LPM4.5 of the microcontroller; the reader sends a wireless signal, when the power module is not under-powered and the signal monitoring circuit detects the signal, the microcontroller is activated, and the microcontroller waits according to the collision avoidance protocol, and the waiting state corresponds to LPM3; when working, the sensor identity information (ID) is first sent to the RF switch Q1, and then the electrochemical module is controlled to start working. At this time, the square wave signal output by the electrochemical module is further output to the RF switch Q1 through the signal output line. The ID sending stage of the working state corresponds to AM, and the perception stage of the microcontroller controlling the electrochemical module to send sweat analyte data corresponds to LPM3.

[0060] On the one hand, the control module can control the entire sensor to work through the wireless signal monitoring line, power status line and electrochemical control line, and on the other hand, it can control the communication module to send the switch-modulated backscattered signal to the reader through the control module data line connected to the RF switch Q1.

[0061] Example 2

[0062] This embodiment is a low-power sweat sensing system based on backscattering technology, including an information processing system and the above-mentioned sweat information collection system, wherein the information processing system is used to perform short-time Fourier transform processing on the data obtained by the sweat information collection system to obtain sweat sensing results.

[0063] Experimental example

[0064] Experiment I: Sensor backscattering function verification

[0065] The goal of this experiment is to verify whether the sensor backscatter function is good by demodulating the sensor identity information (ID). First, deploy the experimental equipment and place the sensor 40 cm in front of the reader. Then start the system, the reader sends a 900MHz sine wave signal, and the sensor sends a backscattered ID signal to the reader, setting the ID to 01000001.

[0066] Test results of Experiment I:

[0067] The experimental results are as follows Fig. 9 As shown, we can see that the ID waveform is clear and can be decoded normally to get the sensor ID as 01000001. The experiment proves that the sensor backscatter function can work normally.

[0068] Experiment II: Sensor working distance test

[0069] The goal of this experiment is to verify the effective working distance of the sensor. A 20μmol / L uric acid solution was prepared and the chronoamperometry method was used to test the received backscattered signal signal-to-noise ratio (SNR) and standard deviation every 20 cm from 20 cm to 200 cm in front of the reader. Each test lasted 30 seconds.

[0070] Test results of Experiment II:

[0071] The experimental results are as follows Fig.10 As shown in the figure, the backscattered signal of the sensor still has a good signal-to-noise ratio at 200 cm, indicating that the effective working distance of the sensor can reach 200 cm.

[0072] Experiment III: Sensor power supply and power consumption verification

[0073] The goal of this experiment is to test the sensor power module and measure whether the power consumption in the actual application scenario can meet the application scenario. When the external 5.0V power supply is directly powered through the power supply interface, the charging time of the lithium battery is tested; when the light intensity is about 8*10 4 Under the sunlight condition of Lux, the power control circuit of the solar thin-film battery and the power module is tested to see if they can work properly, and the charging time of the lithium battery is calculated. The output voltage VCC of the power module is 2.0V, and the EnergyTrace++ technology provided by TI is used to test the average power consumption of the sensor in each state, and the standby time of each state is calculated under the condition of power supply of a fully charged 200mAh lithium battery.

[0074] Test results of Experiment III:

[0075] The experimental results are shown in Figure 11(a) and Figure 11(b). As shown in Figure 11(a), the power module can charge the lithium battery normally. As shown in Figure 11(b), the sensor power consumption is low. Combined with Figure 11(a), it can be seen that in daily life, intermittent charging can be achieved by relying only on solar energy, thereby realizing passive sensing.

[0076] Experiment IV: Verification of Uric Acid Sensing at Different Concentrations

[0077] The purpose of this experiment is to verify whether the sensor can sense different concentrations of uric acid in sweat. The concentration of uric acid in human sweat ranges from 0 to 50 μmol / L. Uric acid solutions of 10 μmol / L, 20 μmol / L, 30 μmol / L, 40 μmol / L, and 50 μmol / L are prepared and detected by chronoamperometry.

[0078] Test results of Experiment IV:

[0079] The experimental results are as follows Fig.12 As shown in the figure, by performing short-time Fourier transform on the received data, the concentration information of uric acid can be obtained. The results show that the sensor can sense different concentrations of uric acid in sweat.

[0080] Experiment V: Verification of the perception of ascorbic acid at different concentrations

[0081] The purpose of this experiment is to verify whether the sensor can sense different concentrations of ascorbic acid in sweat. The concentration of ascorbic acid in human sweat ranges from 0 to 50 μmol / L. Ascorbic acid solutions of 10 μmol / L, 20 μmol / L, 30 μmol / L, 40 μmol / L, and 50 μmol / L were prepared and detected by chronoamperometry.

[0082] Test results of Experiment V:

[0083] The experimental results are as follows Fig.13 As shown in the figure, by performing short-time Fourier transform on the received data, the concentration information of ascorbic acid can be obtained. The results show that the sensor can sense different concentrations of ascorbic acid in sweat.

[0084] Experiment VI: Different concentrations of Na + Ion perception verification

[0085] The purpose of this experiment is to verify whether the sensor can sense different concentrations of Na in sweat. + Ions. Na in human sweat +The ion concentration range was 0-100 μmol / L, and 20 μmol / L, 40 μmol / L, 60 μmol / L, 80 μmol / L, and 100 μmol / L NaCl solutions were prepared respectively, and detection was performed by the open circuit voltage method.

[0086] Test results of Experiment VI:

[0087] The experimental results are as follows Fig.14 As shown, by performing short-time Fourier transform on the received data, Na can be obtained. + The results show that the sensor can sense different concentrations of Na ions in sweat. + ion.

Claims

1. A low-power sweat information collection system based on backscattering technology, characterized in that: It includes a reader and multiple sensors; the sensor includes a communication module, a control module, a power module and an electrochemical module connected to each other, and the communication module communicates wirelessly with the reader by backscattering; The electrochemical module comprises a driving circuit, an electrochemical electrode, a current signal conversion circuit, a voltage signal amplifying circuit, a voltage-controlled oscillator and a control switch; wherein the electrochemical electrode comprises two pairs of electrodes and an electrode interface, each pair of electrodes comprises a working electrode and a counter electrode, the electrode interface comprises ports 1 to 4, ports 1 and 2 of the electrode interface are used when sweat is collected by the chronoamperometry method, port 1 is connected to the working electrode, and port 2 is connected to the counter electrode; when sweat is collected by the open circuit voltage method, ports 3 and 4 of the electrode interface are used, port 3 is connected to the working electrode, and port 4 is connected to the counter electrode; ports 1, 2, 3 and 4 of the electrode interface are respectively connected to the driving circuit, the current signal conversion circuit, the common ground and the voltage signal amplifying circuit; the current signal conversion circuit and the voltage signal amplifying circuit are respectively connected to the voltage-controlled oscillator; the voltage-controlled oscillator is connected to the communication module; the source of the control switch is connected to the driving circuit, the current signal conversion circuit, the voltage signal amplifying circuit and the voltage-controlled oscillator, the drain is connected to the power supply VCC, and the gate is connected to the control module.

2. The low-power sweat information collection system based on backscattering technology as claimed in claim 1, characterized in that: The driving circuit comprises a voltage regulating circuit and a voltage follower connected thereto.

3. The low-power sweat information collection system based on backscattering technology as claimed in claim 2, characterized in that: The voltage regulating circuit uses a 1M ohm potentiometer, and the voltage follower uses an operational amplifier OPA313.

4. The low-power sweat information collection system based on backscattering technology as claimed in claim 1, characterized in that: The communication module includes an antenna, an impedance matching circuit, a radio frequency switch and a signal monitoring circuit; wherein the antenna and the reader perform wireless communication by backscattering; the impedance matching circuit is an LC circuit, and the radio frequency switch is connected to the antenna, the electrochemical module and the control module respectively; the signal monitoring circuit is composed of a voltage doubling rectifier circuit and a comparison circuit, wherein the output end of the voltage doubling rectifier circuit is connected to the in-phase input end of the comparator in the comparison circuit, the inverting input end of the comparator is grounded, and the output end of the comparator is connected to the control module.

5. The low-power sweat information collection system based on backscattering technology as claimed in claim 4, characterized in that: The radio frequency switch adopts an N-channel enhanced field effect transistor, the source and drain of the field effect transistor are directly connected to the two poles of the antenna, and the gate is connected to the electrochemical module and the control module.

6. The low-power sweat information collection system based on backscattering technology as claimed in claim 4, characterized in that: The comparison circuit adopts NCS2200.

7. The low-power sweat information collection system based on backscattering technology as claimed in claim 1, characterized in that: The power module includes a power control circuit and a power supply interface connected to the power control circuit, a solar film battery and a lithium battery, wherein the power control circuit is also connected to the control module.

8. The low-power sweat information collection system based on backscattering technology as claimed in claim 7, characterized in that: The power control circuit includes a buck-boost chip BQ25570 and its peripheral circuits; the capacity of the lithium battery is 200mAh.

9. The low-power sweat information collection system based on backscattering technology as claimed in claim 1, characterized in that: The control module adopts the ultra-low power consumption microcontroller MSP430FR5996.

10. A low-power sweat sensing system based on backscattering technology, characterized in that: It comprises an information processing system and the low-power sweat information collection system based on backscattering technology as described in any one of claims 1 to 9, wherein the information processing system is used to perform short-time Fourier transform processing on the data obtained by the sweat information collection system to obtain sweat sensing results.

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