MEMS technology-based miniature in-situ synchronous heart sound and electrocardiogram detection sensor
Technical Field
The invention belongs to a novel biomedical device, and particularly relates to a heart sound electrocardio miniature in-situ synchronous detection sensor based on an MEMS (micro-electromechanical systems) technology.
Background
Coronary heart disease, i.e. coronary atherosclerotic heart disease, is a heart disease in which atherosclerotic lesions occur in coronary vessels to cause stenosis or occlusion of the inner lumen of the vessel, resulting in myocardial ischemia, hypoxia or necrosis of patients. Coronary heart disease is a serious disease seriously threatening the life and health of human beings, and the prevention and treatment of the coronary heart disease are major public health problems facing the world. At present, the current situation of coronary heart disease prevention and treatment is not optimistic: coronary heart disease, which is growing rampant in recent 10 years, has become one of the most important diseases seriously harming people's health in many countries as an important cardiovascular disease, and is a relatively high disease type in heart disease. According to the statistics of the world health organization, about 1200 million people die of coronary heart disease every year and are generally recognized as worldwide 'number one killer'.
Cardiac auscultation is one of the oldest methods for diagnosing coronary heart disease and understanding cardiac function. To date, this technique remains a fundamental method for diagnosing cardiovascular disease, and the appearance of heart sound patterns further enhances the diagnosis of cardiovascular disease. Most of the existing high-precision medical equipment for diagnosing the coronary heart disease cannot solve the problem of early accurate diagnosis of the coronary heart disease, and meanwhile, certain misdiagnosis and missed diagnosis phenomena exist in single medical equipment when the coronary heart disease is diagnosed, so that the coronary heart disease cannot be comprehensively analyzed and diagnosed from multiple angles and multiple parameters in a combined manner, and the development and change process of the coronary heart disease cannot be known in time. Diastolic heart murmurs contain a large amount of pathological information of early coronary heart disease, and because traditional auscultation is limited by sensitivity of human ear hearing and subjective experience of doctors, the role of heart sounds in diagnosing coronary heart disease is greatly restricted. In view of the advantages of simplicity, no wound, reliability, low cost, good repeatability and the like of the heart sound and the electrocardio signals, the heart sound and the electrocardio signals can well reflect early symptoms of the coronary heart disease, and the electrocardio is the most common clinical noninvasive means for diagnosing the coronary heart disease. Therefore, a new type of device for detecting electrocardio and heart sound signals is urgently needed to be developed.
Disclosure of Invention
The invention aims to provide a brand-new micro in-situ synchronous detection sensor for heart sound and electrocardio based on the MEMS technology. The sensor can simultaneously detect electrocardiosignals and heart sound signals, an acoustic sensor microstructure is designed by utilizing the MEMS technology to detect the heart sound signals, an electrocardio-electrode is designed by utilizing the MEMS processing technology, and finally, the shell is packaged and fixed by adopting flexible materials. Realizing the synchronous acquisition of heart sound and electrocardiosignal.
The invention is realized by the following technical scheme:
a micro in-situ synchronous detection sensor for cardioelectric and electrocardio based on MEMS technology comprises a shell with an open top, a sound transmitting cap is hermetically fixed at the open end of the shell, an oil filling hole and a lead wire hole are arranged on the shell bottom of the shell, a support plate is arranged in the shell, an MEMS sound sensor microstructure is fixed on the support plate, the MEMS sound sensor microstructure is obtained by etching an SOI silicon wafer by ICP plasma etching technology, the piezoelectric ceramic comprises a support frame and a central mass block arranged in the central position of the support frame, wherein two ends of the central mass block are respectively connected and fixed with the support frame through cantilever beams, two ends of each cantilever beam are respectively implanted with boron ions by utilizing a plasma implantation technology to form piezoresistors, the prevention of the four piezoresistors is equal, the four piezoresistors are connected through metal leads to form a Wheatstone full-bridge differential circuit capable of detecting heart sound and breath sound signals; a lead wire at the output end of the MEMS acoustic sensor microstructure penetrates out of the lead hole, silicone oil is injected into the inner space of the shell through the oil injection hole, and the oil injection hole and the lead hole are sealed; a circle of electrocardio-electrode is sleeved on the periphery of the shell, and a circle of sucker is sleeved on the periphery of the electrocardio-electrode; the electrocardio-electrode comprises a flexible conductive substrate with the top surface designed as a pinpoint microarray, a metal seed layer is sputtered on the top surface of the flexible conductive substrate, a metal layer is sputtered on the metal seed layer, and a conductive silver glue layer is coated on the back surface of the flexible conductive substrate.
The MEMS acoustic sensor microstructure provided by the invention has the working principle that: the sound-transmitting cap is attached to the skin of a patient, lossless projection of heart sound signals can be achieved, namely when heart sounds are transmitted to a central mass block of the MEMS sound sensor microstructure, deformation of the cantilever beam can be caused, and the deformation of the cantilever beam can cause change of the resistance value of the piezoresistor, so that the output signal of the Wheatstone full-bridge differential circuit can be changed along with the change of the resistance value of the piezoresistor, and therefore when the heart sounds and the respiratory sound signals are changed, the voltage value output by the MEMS sound sensor microstructure can also be changed, and the waveform diagram of the heart and lung sounds can be drawn.
The electrocardio-electrode is a micro-electrode of a micro-needle array designed based on the MEMS technology, belongs to a flexible electrode, and is an electrocardio dry electrode prepared on a flexible conductive substrate by utilizing the flexible MEMS technology and the bioelectronic technology, does not need conductive adhesive, has good flexibility and ductility, and can be tightly attached to the skin. The micro-needle is manufactured by a micro-machining process, has a micro-scale size, is in a needle point-shaped structure, and has chemical stability and biocompatibility. In the electrocardio-electrode, the metal layer is used as the main body of the electrode, the metal seed layer is used as an adhesion layer between the flexible conductive substrate and the metal layer, the flexible conductive substrate is used for the lead of electrocardiosignals and is used for the lead of electrocardiosignals, and the conductive silver colloid layer is equivalent to the function of a lead and transmits the signals to the back-end circuit. The micro-needle has wide application in the biomedical field, not only has small volume, but also has the characteristics on the performance which are incomparable with the conventional method, namely accuracy, painlessness, high efficiency and convenience. When in use, the electrocardio-electrodes are placed at different parts of a body, and the potential differences of different points of the body can be measured. The micro-needle array electrode can pierce the stratum corneum of the skin, avoids the high-impedance characteristic of the stratum corneum of the skin, does not need skin preparation and electrolytic gel, and is beneficial to long-term measurement and use. The micro-needle array electrode is convenient and reliable, has the advantages of small impedance, small electrochemical noise and the like, generates a painless electrode-electrolyte interface on the stratum corneum and converts ion current caused by active cells into current.
The shell and the sucker both adopt flexible conformal structures, can be tightly attached to the skin, can reduce the discomfort of a patient, and can reduce the interference of noise signals such as joint bones and the like.
As a preferred technical scheme, a metal seed layer in the electrocardio-electrode adopts Cu, a metal layer adopts Au, and the Au has good biocompatibility and is a metal material which is relatively suitable for contacting the skin.
As the preferred technical scheme, the sound-transmitting cap is made of an ultrathin butyronitrile high polymer material. The ultrathin butyronitrile high-molecular sound-transmitting cap has good sound-transmitting performance on low-frequency sound signals, good oil resistance, water resistance, air tightness and good bonding performance, is matched with the characteristic impedance of internal coupling liquid insulating silicon oil, a shell made of flexible materials and organ characteristics of visceral organs, has a high sound-transmitting coefficient, is favorable for better transmitting heart sounds and lung sounds to the microstructure of the MEMS sound sensor, and is convenient for medical diagnosis.
The invention researches a novel sensor which is based on Micro-Electro-Mechanical System (MEMS) technology, has low cost, small volume, strong anti-interference performance and high sensitivity and can synchronously acquire heart sound and electrocardio parameters by utilizing the technical experience, test equipment and process flow of MEMS accumulated by the applicant for many years, thereby realizing multi-parameter combined analysis and diagnosis of the coronary heart disease. The quantitative relation between diastole heart murmurs and the coronary heart disease blockage degree is disclosed by comparing and analyzing the heart sound signals and the electrocardio signals, the pathogenesis of the coronary heart disease is disclosed and the development process of the coronary heart disease is monitored by analyzing the internal relation of the two signals, and the early discovery and early diagnosis of the coronary heart disease are finally realized, so that the problems of the misdiagnosis rate and the high death rate of the coronary heart disease are solved.
Compared with the traditional stethoscope or electrocardio sensor, the sensor integrates the heart sound and the electrocardio into a whole by utilizing the MEMS technology, further can realize multi-parameter combined analysis and diagnosis of the coronary heart disease, and has the advantages of high sensitivity, small volume, batch processing, low cost and the like. The concrete expression is as follows: (1) the acoustic sensor based on the MEMS technology has the advantages of small volume, high sensitivity, high integration level, multiple functions and batch production, the signal induction is sensitive, real and effective, and the second heart sound can be obviously induced; (2) the electrocardio-electrode is a flexible dry electrode, so that the electrocardio-electrode has small volume and no stimulation to patients, and is more accurate, efficient and convenient in performance than a common electrode; (3) the sensor integrally adopts a flexible conformal packaging structure, is tightly attached to the skin, and reduces the blocking effect of joint bones on acoustic signal detection. Part of the electrocardio-electrodes and the heart sound probe are integrated to realize the synchronous in-situ detection of the electrocardio and the heart sound. (4) The ultrathin butyronitrile polymer sound transmission cap has good sound transmission performance, is beneficial to the sound sensor to receive heart sound and lung sound signals, and is also beneficial to the processing of the heart sound signals and expert consultation.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate exemplary embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention.
FIG. 1 is a schematic diagram of the inner side of the sensor of the present invention.
Fig. 2 is a schematic structural diagram of the outer side surface of the sensor of the present invention.
Fig. 3 is a schematic diagram of an explosive structure of the sensor of the present invention.
FIG. 4 is a schematic structural diagram of a MEMS acoustic sensor microstructure in a sensor according to the present invention.
Fig. 5 is a schematic structural diagram of a center electrocardioelectrode of the sensor of the invention.
In the figure: the acoustic sensor comprises a shell 1, an acoustic cap 2, a support plate 3, an MEMS acoustic sensor microstructure 4, a support frame 4, a central mass block 4, a cantilever beam 4, a piezoresistor 4, an electrocardio electrode 5, a flexible conductive substrate 5, a metal seed layer 5, a metal layer 3, a conductive silver adhesive layer 5, a conductive silver adhesive layer 4, a needle point type microarray 5, and a sucker 6.
Detailed Description
In order that those skilled in the art will better understand the present invention, a more complete and complete description of the present invention is provided below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
As shown in fig. 1 to 5, a miniature normal position synchronous detection sensor of heart sound electrocardio based on MEMS technique, casing 1 for open design including the top, the open end of casing 1 is sealed through polyurethane glue and is fixed with sound-transmitting cap 2, sound-transmitting cap 2 adopts ultra-thin butyronitrile macromolecular material to make and forms, oil filler point and pin hole have been seted up on the shell bottom of casing 1, install backup pad 3 in the casing 1, be fixed with MEMS sound sensor microstructure 4 through polyurethane glue on the backup pad 3, backup pad 3 plays the fixed effect of support to MEMS sound sensor microstructure 4.
The MEMS acoustic sensor microstructure 4 is processed by adopting an SOI silicon wafer as a processing material and adopting an MEMS semiconductor micromachining technology, and specifically comprises the following steps: etching on a silicon substrate by utilizing an ICP (inductively coupled plasma) plasma etching technology to obtain a support frame 4-1, a central mass block 4-2 and cantilever beams 4-3, wherein the central mass block 4-2 is positioned at the central position in the support frame 4-1, two ends of the central mass block 4-2 are respectively connected and fixed with the support frame 4-1 through the symmetrically arranged cantilever beams 4-3, boron ions are respectively injected into two ends of each cantilever beam 4-3 by utilizing a plasma injection technology to form a piezoresistor 4-4, the prevention of the four piezoresistors 4-4 is equal, and the four piezoresistors 4-4 are connected through metal leads to form a Wheatstone full-bridge differential circuit capable of detecting heart sounds and breath sound signals; after penetrating out of the lead hole, a lead at the output end of the MEMS sound sensor microstructure 4 is connected with circuit modules of voltage stabilization, amplification, filtering, impedance matching and the like of a subsequent circuit; the inner space of the shell 1 is filled with silicone oil through the oil injection hole, the MEMS acoustic sensor microstructure 4 is immersed in the silicone oil, the silicone oil and the water are close in density, acoustic coupling matching is good, the sensitivity of the sensor microstructure is improved, and finally the oil injection hole and the lead hole are sealed.
The periphery of the shell 1 is sleeved with a circle of electrocardio-electrodes 5, the periphery of the electrocardio-electrodes 5 is sleeved with a circle of suckers 6, and the suckers 6 are made of flexible materials.
The electrocardio-electrode 5 is a needle point type microarray based on MEMS technology and bioelectronics technology, a micro-needle-shaped dry electrode array with chemical stability and biocompatibility is prepared on a flexible substrate, the electrode adopts a flexible dry electrode, has good ductility and flexibility, can be tightly attached to the skin of a patient, and the main body of the electrode adopts a metal structure. The electrocardio-electrode 5 specifically comprises a flexible conductive substrate 5-1 with a needle point type microarray 5-5 designed top surface, a metal seed layer 5-2 is sputtered on the top surface of the flexible conductive substrate 5-1, a metal layer 5-3 is sputtered on the metal seed layer 5-2, and a conductive silver glue layer 5-4 is coated on the back surface of the flexible conductive substrate 5-1, wherein the metal seed layer 5-2 is made of Cu, and the metal layer 5-3 is made of Au.
The specific preparation process flow of the electrocardio-electrode 5 is as follows:
1) thermal oxidation of a layer of SiO on a silicon substrate2Used as a mask layer for subsequent wet etching and deep silicon etching (DRIE);
2) coating a positive photoresist, and performing prebaking, photoetching, developing and postbaking, wherein the photoetched pattern is used as a mask for subsequent Inductively Coupled Plasma (ICP);
3) ICP etching, SiO2Etching through the buried oxide layer;
4) wet etching, namely etching silicon under the buried oxide layer by using TMAH etching solution to form pits in the inverted pyramid row and stop etching;
5) deep silicon etching, namely etching a certain depth to form a groove needle tip array;
6) removing the glue solution, heating in water bath at 60 ℃, removing the photoresist, and completing the preparation of the groove needle point array silicon die
7) Preparing a Carbon Nano Tube (CNT) dispersion liquid, mixing carbon nano tube powder with an organic solvent, fully stirring, and performing ultrasonic treatment to prepare the CNT dispersion liquid;
8) adding the CNT dispersion into PDMS, magnetically stirring at a certain temperature, adding a curing agent after an organic solvent is evaporated, fully stirring and pumping out bubbles to prepare a mixture of CNT and PDMS;
9) pouring the prepared mixture on a groove needle point silicon mold, heating and curing, and uncovering the film to obtain a CNT-PDMS flexible conductive substrate with a needle point structure;
10) carrying out magnetron sputtering on a metal seed layer Cu and a metal layer Au on a flexible conductive substrate;
11) and coating a conductive silver adhesive layer on the back of the flexible conductive substrate to finally finish the preparation of the flexible electrocardio-electrode.
The technical solutions in the embodiments of the present invention are clearly and completely described above, and the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.