CN109793516B - Skin electrical impedance flexible detection device and skin electrical impedance detection method - Google Patents
Skin electrical impedance flexible detection device and skin electrical impedance detection method Download PDFInfo
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- CN109793516B CN109793516B CN201910053755.0A CN201910053755A CN109793516B CN 109793516 B CN109793516 B CN 109793516B CN 201910053755 A CN201910053755 A CN 201910053755A CN 109793516 B CN109793516 B CN 109793516B
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Abstract
The invention discloses a skin electrical impedance flexible detection device and a skin electrical impedance detection method, wherein the skin electrical impedance flexible detection device comprises: the micro-electrode module is in contact with skin to be measured and used for collecting electrical impedance information, and the micro-processor module controls the impedance measuring module to send voltage excitation signals with different frequencies to the micro-electrode module and analyzes and transmits an impedance response signal received and processed by the impedance measuring module; the microelectrode module is arranged on the lower surface of the flexible circuit substrate, and the upper surface of the flexible circuit substrate is provided with a transparent thin film layer. By using the method, the bioelectrical impedance of the surface can be accurately monitored and analyzed in real time under the condition of multiple frequencies.
Description
Technical Field
The invention belongs to the field of biomedical engineering, and particularly relates to a skin electrical impedance flexible detection device and a skin electrical impedance detection method.
Background
The number of surgical patients is about 6500 ten thousand per year in China, and the bandage technology for wound treatment is very common in application. For surgical patients, one of the important problems faced is the problem of wound healing after surgery. The method is simple and easy to implement, but once the wound is wrapped, a doctor cannot monitor the growth state of the wound in situ in real time and cannot treat inflammation and the like in real time, the wound healing is a long time, the wound cannot be accurately observed and diagnosed in the long time, the skin healing is about 10-20 days even though the operation is performed on the surface of the skin, and the wound cannot be treated in time if early inflammation or other problems of the wound occur in the long time. For example, infection of a wound surface not only results in delayed healing of the wound surface, but also seriously endangers the life of the patient. In clinical diagnosis, invasive gold standard method is adopted in early stage, although the measurement is accurate, the gauze needs to be uncovered continuously to detect the wound surface state, the secondary injury of the wound is caused, the risk of secondary infection is increased, and the method has the defects of high price, time consumption, incapability of continuous measurement and the like. Therefore, the biosensor sensitive to the wound infection marker (such as impedance) is used for detecting the wound condition, and has important clinical guiding significance.
Based on this, electronic bandage technology has been proposed. Currently, impedance biosensors generally consist of an impedance biochip and an impedance analyzer, which is generally performed by a large-scale analysis instrument. Impedance analysis instruments or electrochemical workstations have been developed by Agilent, Zahner, germany, Solartron, united kingdom. In addition, some small impedance analysis devices have been reported, for example, a handheld impedance detection device (publication No. CN203310795) is proposed by an inventor and others, and pre-processing such as noise filtering and signal amplification is added between an object to be measured and a detection electrode, so as to improve the accuracy and stability of impedance measurement. The device proposed by kularhua et al can realize multi-target measurement and has an alarm mechanism (publication No. CN 203241371).
The existing small-sized impedance detection device has the following problems: (1) real-time in-situ measurement cannot be realized, the measurement frequency range is mostly limited to one or more frequencies, the measurement frequency cannot be adjusted according to actual conditions, and the characteristic of skin impedance can be better reflected by broadband measurement; (2) the whole system integrating the measuring electrode, the impedance measurement, the preprocessing, the data processing, the microprocessor and the graphical interface of the mobile phone end does not exist, the application depends on other auxiliary equipment, and the application scene is not clear; (3) the measuring device is large and hard, no equipment which is nontoxic, harmless and free of foreign body sensation to the skin exists, and the contact with the skin is unstable.
Disclosure of Invention
The invention provides a skin electrical impedance flexible detection device and a skin electrical impedance detection method, which can realize real-time accurate monitoring and analysis of the bioelectrical impedance on the surface under the condition of multiple frequencies.
The technical scheme of the invention is as follows:
a skin electrical impedance flexible detection device, comprising: the micro-electrode module is in contact with skin to be measured and used for collecting electrical impedance information, and the micro-processor module controls the impedance measuring module to send voltage excitation signals with different frequencies to the micro-electrode module and analyzes and transmits an impedance response signal received and processed by the impedance measuring module;
the microelectrode module is arranged on the lower surface of the flexible circuit substrate, and the upper surface of the flexible circuit substrate is provided with a transparent thin film layer.
The impedance measurement module includes: a frequency generator for generating a voltage excitation signal; an analog-to-digital converter for outputting a voltage excitation signal and receiving an impedance response signal; and the signal processing module is used for processing the impedance response signal. The signal processing module is used for carrying out discrete Fourier transform processing on the received impedance response signal.
Preferably, the impedance measuring module further comprises a front-end processing circuit, the front-end processing circuit comprising a first emitter follower and a first voltage amplifier for amplifying and low-pass filtering the impedance response signal before the analog-to-digital converter receives the impedance response signal.
The microelectrode modules are connected to different channels of the data selector, impedance response signals generated by the microelectrode modules are transmitted to the impedance measuring module after passing through the data selector, and the data selector controls the on-off of each signal path through the microprocessor module. The data selector is adopted to select the signal path of the microelectrode module, so that the measurement error can be reduced in a small range.
Preferably, the number of the microelectrode modules is 5, the microelectrode modules are in the shape of circular rings, the inner diameter of each circular ring is 1.35-1.45cm, and the outer diameter of each circular ring is 1.55-1.65 cm. The bioelectrical impedance values of five points are repeatedly measured for a plurality of times in the adjacent range, and accidental errors caused by measuring a single point are reduced.
Preferably, the material of the flexible circuit substrate is Polyimide (PI).
Preferably, the transparent isolation layer film is a transparent film with light transmittance of more than 70% and biocompatibility, further, the material of the transparent film layer is polydimethylsiloxane PDMS or polylactic acid PLA, and the thickness of the transparent isolation layer is 90-110 μm. The transparent film layer prevents the wound surface liquid from corroding the reflective photoelectric detection module and has a ventilation effect.
The microprocessor module adopts a low-power consumption Bluetooth BLE chip which passes through I2The interface C exchanges instructions and data with the impedance measurement module, the on-off of each microelectrode module is controlled by outputting a control signal through the I/O port, and the Bluetooth result is sent to an interactive interface on the mobile equipment through the antenna.
The low-power consumption Bluetooth BLE chip is provided with a single chip microcomputer module, the single chip microcomputer module is used for on-off control of an access between an impedance measurement module and a microelectrode module and a data selector, and the module comprises a data analysis processing unit and is responsible for collecting and processing data and converting the data into a data format capable of being processed through a Bluetooth module.
The invention also provides a skin electrical impedance detection method, which comprises the following steps:
(1) contacting the microelectrode module with the surface of the skin to be measured, and covering the transparent film layer;
(2) the microprocessor module configures the impedance measurement module and sends an instruction for starting frequency sweep measurement impedance, and a frequency generator in the impedance measurement module generates a voltage signal to excite external impedance through the microelectrode module;
(3) the generated impedance response signal is processed by a front-end processing circuit, then is sampled by an analog-to-digital converter in the impedance measuring module, is subjected to discrete Fourier transform processing, returns an imaginary part and a real part, and is transmitted to the microprocessor module;
(4) the microprocessor module performs algorithm calculation and sends the result to a human-computer interaction interface on the mobile device through Bluetooth.
In the detection method, the impedance measurement module obtains the real part and imaginary part data of hexadecimal measured impedance after the discrete Fourier transform processing of the signal processing module, and the data is processed through I2C is transmitted to a microprocessor module for subsequent algorithm, and the following formula is utilized to obtain the specific amplitude and phase of the bioelectrical impedance:
in the formula, R is a real part of the obtained measured impedance, I is an imaginary part of the measured impedance, the amplitude is the amplitude calculated by using the real part and the imaginary part, and the gain coefficient is calculated by using a resistor with a known size when the system is calibrated by using the calibration impedance;
phase tan-1(I/R)
The phase is calculated by using a real part and an imaginary part. The calculated value of the amplitude and the phase is sent to a human-computer interaction APP of the mobile terminal through a low-power Bluetooth BLE chip to be displayed and processed.
Compared with the prior art, the invention has the following beneficial effects: (whether or not there is a supplement)
1. The flexible skin electrical impedance detection device disclosed by the invention realizes the flexibility of the whole module by adding the coated transparent film on the flexible circuit board substrate, can ensure that the flexible circuit board substrate is in close contact with the surface to be detected of the skin, increases the repeatability and accuracy of measurement, is non-toxic and harmless to the applied surface, does not bring discomfort, and meets the feasibility requirement of a future medical biosensor.
2. The invention integrates the measuring electrode, the impedance measurement, the preprocessing, the data processing, the microprocessor and the mobile phone end graphical interface system on a tiny flexible circuit board substrate, and accords with the development direction of miniaturization and multiple functions of the future biosensor.
3. The invention realizes real-time in-situ measurement of the skin electrical impedance under multiple frequencies, can acquire real-time impedance amplitude and phase data and graphic information through an App graphical interface at a mobile phone end, and can judge the current stage condition of the surface to be detected, such as skin or wound, by setting a threshold value.
4. The device for measuring the skin electrical impedance under multiple frequencies can set the measured frequency according to the actual situation, can measure the impedance to be measured such as skin and the like under a wider frequency band, and better reflects the characteristics of complex impedance.
Drawings
FIG. 1 is a system block diagram of a flexible skin electrical impedance detection device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a flexible skin electrical impedance detection device according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating a bio-impedance equivalent model established by the microprocessor module of the flexible skin electrical impedance detection device through the conversion of measured values according to the embodiment of the invention;
FIG. 4 is a graph of a standard impedance measurement profile of a flexible electrical impedance skin test apparatus according to an embodiment of the present invention;
FIG. 5 is a diagram showing the skin impedance test result of the flexible skin impedance detection apparatus according to the embodiment of the present invention.
Detailed Description
The invention will be described in further detail below with reference to the drawings and examples, which are intended to facilitate the understanding of the invention without limiting it in any way.
As shown in FIG. 1, the skin electrical impedance flexible detection device comprises a microprocessor module, an impedance measurement module and a microelectrode module.
The impedance measurement module is internally integrated with a 12-bit 1MSPS analog-to-digital converter ADC, a frequency generator, a front-end processing circuit and a signal processing module. The frequency generator is used for generating voltage excitation signals with different frequencies; the analog-to-digital converter is used for outputting a voltage excitation signal and receiving an impedance response signal; the signal processing module is used for carrying out discrete Fourier transform processing on the impedance response signal; the front-end processing circuit comprises a first-stage emitter follower and a first-stage voltage amplifier and is used for performing simple preprocessing on the impedance analog signals collected by the 8-to-1 data selector and performing signal amplification and low-pass filtering processing.
The timing sequence of the impedance measurement module adopts 16.766MHz clock signal generated by an internal crystal oscillator as the working frequency. During measurement, a direct-current stable voltage signal generated by an internal frequency generator is output from a Vout port by an analog-to-digital converter (ADC) to excite external impedance, a response signal is sampled from a Vin port by the analog-to-digital converter (ADC), discrete Fourier transform processing is carried out through a signal processing module, an imaginary part and a real part are returned, reading can be carried out through serial ports SCL and SDA, and RFB is used as a feedback resistor.
The microprocessor module adopts a low-power consumption Bluetooth (BLE) chip, and Bluetooth data transmission with lower power consumption is realized while the working requirement of the single chip microcomputer is met. The clock of the low-power consumption Bluetooth chip is provided by an external crystal oscillator, a 32MHz active crystal oscillator provides a working clock, and a sleep clock is provided by a passive crystal oscillator with the frequency of 32.768 kHz; the low power consumption Bluetooth chip and the impedance measurement module pass through I2C are connected with each other to realize the interaction of time sequence and data; the low-power-consumption Bluetooth chip outputs a control signal through the I/O port to control the on-off of each microelectrode module on the 1-out-of-8 data selector, and can control the on-off of each data channel by programming.
The device is also provided with a DC-DC power circuit module which is used for carrying out voltage reduction processing on a 3.7V direct current signal fed by the lithium battery into 3.3V and supplying power supply voltage requirements of each module.
As shown in fig. 2, the microelectrode module 1 is placed on the skin or wound to be measured and contacted with the surface, and then the microelectrode module and the impedance measuring module are connected by a circumscribed bending wire. The surface of the whole device is coated with the transparent film layer 2, the material is polydimethylsiloxane PDMS or polylactic acid PLA, the light transmittance is more than 70%, and the device has biocompatibility. The flexible circuit substrate 3 is Polyimide (PI), and the surface 4 to be measured such as skin or wound is in direct contact with the microelectrode module 1.
As shown in fig. 3, the micro processor module of the skin electrical impedance flexible detection device comprises a data processing and analyzing unit and is used for establishing a biological impedance equivalent model by converting measured values. When the biological tissue (including the skin surface) passes through direct current or low-frequency current, the direct current or low-frequency current can be allowed to pass due to the capacitance characteristic of the cell membrane, and the current cannot enter the intracellular fluid and directly bypasses the cell membrane to flow from the extracellular fluid; when the frequency rises to a certain extent, the cell membrane cannot block the passage of current because the capacitance allows the passage of alternating current, and the current flows from the intracellular fluid. Therefore, the frequency is a very important loop in the bio-impedance measurement, and has a great influence on the electrical impedance characteristics of the biological tissue. Therefore, the three-element measurement model of the bioelectrical impedance on the skin surface can be established by carrying out basic algorithm processing on the gain coefficient obtained by calculating the calibration impedance and the amplitude obtained by measurement. Wherein, Re, Ri and Cm are respectively extracellular fluid resistance, intracellular fluid resistance and cell membrane capacitance.
As shown in FIG. 4, the results of the frequency sweep of commercial standard resistances (10k, 20k, 30k, 50k, 100k) (error 0.01%) were tested by using the flexible electrical impedance skin impedance detection device of the present invention to verify the measurement accuracy of the device. The test frequency band is selected to be set between 100Hz and 40kHz, and the average result obtained by multiple detections shows that the general errors of the amplitude and the phase can be controlled within 0.1 percent under the condition that the skin electrical impedance flexible detection device measures complex impedance in a wider frequency range. Therefore, the flexible skin electrical impedance detection device can realize accurate multi-frequency detection of the bioelectrical impedance.
As shown in FIG. 5, tests specific to the skin surface and the muscle surface were tested using the flexible skin electrical impedance measuring apparatus of the present invention to verify the experimental feasibility of the apparatus in measuring the skin waiting for the measurement of the biological complex impedance. The overall test frequency is set at 30kHz, the step frequency is 2Hz, 100 test points are measured, and the multi-frequency complex impedance frequency sweep test is carried out on the epidermis layer and the muscle layer respectively. Test results show that different skin layers exhibit different amplitude and phase conditions when measuring the skin impedance. Experiments prove that the flexible skin electrical impedance detection device can be embodied on the surface of living body impedance such as skin and the like and has good working operation condition.
The embodiments described above are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions and equivalents made within the scope of the principles of the present invention should be included in the scope of the present invention.
Claims (1)
1. A skin electrical impedance detection method is characterized in that a skin electrical impedance flexible detection device is adopted, and the skin electrical impedance flexible detection device comprises: the system comprises a microprocessor module, an impedance measuring module and at least one microelectrode module, wherein the microelectrode module is in contact with the wound surface of skin to be measured and is used for collecting electrical impedance information, the microprocessor module controls the impedance measuring module to send voltage excitation signals with different frequencies to the microelectrode module, and the impedance measuring module receives and processes impedance response signals to analyze and transmit;
the microelectrode modules are connected to different channels of the data selector, impedance response signals generated by the microelectrode modules are transmitted to the impedance measurement module after passing through the data selector, and the data selector controls the on-off of each signal path through the microprocessor module; the microprocessor module adopts a low-power consumption Bluetooth BLE chip which passes through I2The interface C exchanges instructions and data with the impedance measurement module, outputs control signals through the I/O port to control the on-off of each signal path in the data selector, and transmits Bluetooth data to an interactive interface on the mobile equipment through an antenna;
the impedance measuring module comprises: the device comprises a frequency generator for generating a voltage excitation signal, an analog-to-digital converter for outputting the voltage excitation signal and receiving an impedance response signal, a signal processing module for processing the received impedance response signal, and a front-end processing circuit; the front-end processing circuit comprises a first-stage emitter follower and a first-stage voltage amplifier, and is used for amplifying and low-pass filtering the signals before the analog-to-digital converter receives the impedance response signals;
the microelectrode module is arranged on the lower surface of the flexible circuit substrate, is placed on the surface of a wound to be contacted with the wound, and is connected with the microelectrode module and the impedance measuring module by an external bending wire; the upper surface of the flexible circuit substrate is provided with a transparent thin film layer; the flexible circuit substrate is made of polyimide; the transparent film layer is made of polydimethylsiloxane or polylactic acid, is 90-110 mu m thick and is used for ventilating and preventing the wound liquid from corroding the reflective photoelectric detection module; the number of the microelectrode modules is 5, the microelectrode modules are circular rings, the inner diameter of each circular ring is 1.35-1.45cm, and the outer diameter of each circular ring is 1.55-1.65 cm;
the skin electrical impedance detection method comprises the following steps:
(1) contacting the microelectrode module with the surface of the skin to be measured, and covering the transparent film layer;
(2) the microprocessor module configures the impedance measurement module and sends an instruction for starting frequency sweep measurement impedance, and a frequency generator in the impedance measurement module generates a voltage signal to excite external impedance through the microelectrode module;
(3) the generated impedance response signal is processed by a front-end processing circuit, then is sampled by an analog-to-digital converter in the impedance measuring module, is subjected to discrete Fourier transform processing, returns an imaginary part and a real part, and is transmitted to the microprocessor module;
(4) the microprocessor module performs algorithm calculation and sends the result to a human-computer interaction interface on the mobile device through Bluetooth.
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| CN211934041U (en) * | 2019-07-08 | 2020-11-17 | 奥佳华智能健康科技集团股份有限公司 | Ache detection device and massage armchair |
| CN110687180B (en) * | 2019-10-16 | 2021-12-14 | 深圳市刷新智能电子有限公司 | Miniature assembled layered biosensor structure |
| CN111938639A (en) * | 2020-07-07 | 2020-11-17 | 四川大学华西医院 | Device for detecting injury degree and range of organism soft tissue based on electrical impedance method |
| CN112802615A (en) * | 2021-01-30 | 2021-05-14 | 上海大学 | Non-inductive wearable wound physiological parameter intelligent monitoring and rehabilitation system |
| CN113425305A (en) * | 2021-06-09 | 2021-09-24 | 上海交通大学 | Self-adaptive active electrode for non-invasive biological signal acquisition |
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