Implantable dynamic pressure sensor system and preparation method thereof

Abstract

The invention discloses an implantable dynamic pressure sensor system and a preparation method thereof, and belongs to the field of medical instrument and sensor cross fusion. In the system, a packaging shell is used for accommodating a pressure sensing unit and a temperature sensing unit which are integrated on a Si substrate, the packaging shell comprises a groove gap, and a sensing end of the pressure sensing unit is opposite to the groove gap; one end of the pressure sensing unit is connected with one end of the temperature sensing unit, the other end of the pressure sensing unit and the other end of the temperature sensing unit are respectively connected with a positive input end and a negative input end of the detection circuit unit, and the temperature sensing unit performs temperature compensation on the pressure sensing unit; and the Si substrate at the position of the pressure sensing unit is thinned to a preset thickness. According to the invention, the miniaturization design of the sensing unit is realized, the sensitivity of the sensor is improved, and the detection requirement in a complex environment is met.

Description

Technical Field

[0001] The present invention belongs to the field of cross-integration of medical devices and sensors, and in particular relates to an implantable dynamic pressure sensor system and a preparation method thereof. Background Art

[0002] With the continuous development of medical technology, implantable medical devices play an increasingly important role in disease diagnosis and treatment. Among them, dynamic pressure sensors, as one of the key components, have shown significant potential in monitoring instantaneous pressure changes in the body and are widely used in various medical fields such as cardiovascular system monitoring, intracranial pressure monitoring, and respiratory system pressure observation. When working for a long time in a complex in vivo environment, implantable dynamic pressure sensing systems must have the characteristics of high sensitivity, long-term stability, low power consumption, and miniaturization. However, traditional implantable pressure sensors are usually based on capacitance or piezoresistance principles, and still have many shortcomings in dealing with temperature changes, sensitivity, and long-term stability, and cannot meet the requirements for detecting tissue pressure in the body. For example, capacitive sensors are highly sensitive to temperature changes, and temperature fluctuations will cause their capacitance values ​​to change, thereby affecting the accuracy of pressure measurement. Temperature changes in the in vivo environment are inevitable, which limits the application of capacitive sensors in implantable devices. Piezoresistive sensors face the problems of insufficient sensitivity and poor long-term stability, making it difficult to ensure continuous high-precision pressure monitoring. In addition, sensors implanted in the body for a long time must also solve challenges such as biocompatibility, volume, and power consumption, which largely limits their application in implantable medical devices.

[0003] In recent years, with the rapid development of materials science and micro-electromechanical systems (MEMS) technology, piezoelectric pressure sensors have attracted widespread attention due to their excellent dynamic pressure response capabilities. Piezoelectric materials such as lead zirconate titanate (PZT) and polyvinylidene fluoride (PVDF) generate charge signals when subjected to mechanical pressure. This property makes piezoelectric sensors have many advantages in pressure detection, such as high sensitivity, long-term stability, low power consumption, miniaturization and multifunctional integration. Piezoelectric materials have high piezoelectric coefficients and are extremely sensitive to small pressure changes. They can detect very small pressure fluctuations, so they are very suitable for monitoring pressure changes in the body. For example, in cardiovascular monitoring, subtle changes in blood pressure may indicate potential health problems, and piezoelectric sensors can capture these subtle changes to provide support for clinical diagnosis. Piezoelectric materials can maintain stable performance in mechanical fatigue and environmental changes, which is suitable for long-term pressure monitoring and meets the strict requirements of implantable devices for long-term reliability. Piezoelectric sensors do not require external continuous energy supply when generating electrical signals, and have extremely low power consumption, which is conducive to the management of power supply in implantable medical devices. In addition, the development of MEMS technology has enabled piezoelectric sensors to be made into miniaturized devices, which are easy to implant in the body without causing damage to surrounding tissues. At the same time, other functional modules, such as temperature sensors, can be integrated. This integrated feature gives piezoelectric sensors unique advantages in monitoring complex physiological signals. Therefore, piezoelectric pressure sensors have important application potential in implantable medical devices. However, existing piezoelectric pressure sensors are insufficient in terms of temperature changes, dynamic pressure response, and long-term stability. Especially when implanted in the body for a long time, it is difficult to accurately respond to complex physiological environmental changes, which significantly limits their application in implantable medical devices. Summary of the invention

[0004] To solve the above technical problems, the present invention proposes an implantable dynamic pressure sensor system based on MEMS technology. The pressure sensing unit and temperature sensing unit prepared by using the unique piezoelectric and thermal properties of piezoelectric materials can monitor the ambient temperature in real time and compensate the pressure sensor output according to the temperature change, thereby improving the accuracy and stability of the pressure sensor under different temperature conditions, and has important application prospects in implantable medical devices. The preparation method of the sensor is simple and feasible, suitable for large-scale production, and has low cost and high reliability.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: An implantable dynamic pressure sensor system comprises a packaging shell, a pressure sensing unit, a temperature sensing unit, and a detection circuit unit, wherein the packaging shell is used to accommodate the pressure sensing unit and the temperature sensing unit integrated on a Si substrate, wherein the packaging shell comprises a groove notch, and a sensing end of the pressure sensing unit faces the groove notch, and is used to directly contact with a biological tissue to be tested, and convert the detected pressure signal into an electrical signal; One end of the pressure sensing unit and one end of the temperature sensing unit are connected to each other through wiring inside the Si substrate, and the other end of the pressure sensing unit and the other end of the temperature sensing unit are connected to the positive input end and the negative input end of the detection circuit unit respectively, and the temperature sensing unit detects the temperature in the biological tissue in real time and performs temperature compensation on the pressure sensing unit; The Si substrate at the location of the pressure sensing unit is thinned to a preset thickness.

[0006] Furthermore, it is characterized in that the pressure sensing unit and the temperature sensing unit both include a Si substrate, a SiO2 insulating layer, a bottom electrode, a sensitive layer, a top electrode, and a lead electrode connected to a detection circuit unit.

[0007] Furthermore, the pressure sensing unit and the temperature sensing unit are both connected to the detection circuit unit via Au leads.

[0008] Furthermore, the pressure sensing unit is fixed to the groove notch of the packaging shell by means of biological glue.

[0009] Furthermore, the sensitive layers of the pressure sensing unit and the temperature sensing unit are made of any one of the piezoelectric materials BaTiO3, PVDF, and PZT.

[0010] Furthermore, the detection circuit unit includes an amplifier circuit composed of a field effect transistor, a diode and a resistor.

[0011] Furthermore, the detection circuit unit includes: a negative electrode of the pressure sensing unit is connected to a negative electrode of the temperature sensing unit, a positive electrode of the pressure sensing unit is connected to a positive input terminal of the detection circuit unit as an input terminal, a positive electrode of the temperature sensing unit is connected to a negative input terminal of the detection circuit unit, a resistor is connected to a gate of a field effect transistor, an input and an output terminal of a first diode are respectively connected to a negative input terminal of the detection circuit unit and a positive input terminal of the detection circuit unit, a source of the field effect transistor is connected to a second output port, a drain is connected to the first output port and is grounded, and an input and an output terminal of a second diode are respectively connected to the second output port and the first output port.

[0012] In another aspect, the present invention provides a method for preparing an implantable dynamic pressure sensor, the method comprising the following steps: A SiO2 layer is grown on the surface of the Si substrate using a plasma enhanced chemical vapor deposition process as an isolation layer; The bottom electrodes of the integrated pressure sensing unit and the temperature sensing unit are prepared on the SiO2 layer by photolithography and magnetron sputtering technology; preparing a piezoelectric film on a bottom electrode; The piezoelectric film is patterned by photolithography and etching processes, and the patterned piezoelectric film is used as a sensitive layer of a pressure sensing unit and a temperature sensing unit respectively; A top electrode and a lead electrode are prepared on the upper layer of the piezoelectric film and the SiO2 layer respectively as a positive terminal electrode of the pressure sensing unit and a positive terminal electrode of the temperature sensing unit by photolithography and sputtering processes; The piezoelectric film of the sensitive layer is polarized by thermal polarization method and electric field polarization method; The back Si substrate of the pressure sensing unit is thinned by using silicon back lithography and deep silicon etching process; The sensor chip with integrated pressure sensing unit and temperature sensing unit is released by photolithography and deep silicon etching on the front side of the wafer.

[0013] The beneficial effects of the present invention are: The present invention realizes the integration of the pressure sensing unit and the temperature sensing unit through the MEMS process, integrates the two sensing units on the same substrate, realizes the miniaturized design of the sensing unit, and is suitable for the application of implantable medical devices; utilizes the excellent piezoelectric and thermal sensitive properties of piezoelectric materials to realize high-sensitivity pressure signal detection, and monitors and compensates the influence of temperature on the output of the pressure sensor in real time. The temperature compensation technology ensures that the pressure sensor still has high precision and stability under different temperature conditions; the pressure sensing unit adopts a suspended structure, which reduces the mechanical constraints of the substrate on the piezoelectric material, improves the sensitivity of the sensor, and meets the detection needs in complex environments in the body. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a structural diagram of an implantable dynamic pressure sensor system of the present invention; Figure 2 This is a schematic diagram of an implantable dynamic pressure sensor system of the present invention; Figure 3 Schematic diagram of the sensor chip structure; Figure 4 This is the schematic diagram of the detection circuit.

[0015] Reference numerals: 1. Package shell; 2. Pressure sensing unit; 3. Temperature sensing unit; 4. Bio-glue; 5. Au lead; 6. Detection circuit unit; 7. Positive electrode of pressure sensing unit; 8. Positive electrode of temperature sensing unit; 9. Negative input terminal of detection circuit unit; 10. Positive input terminal of detection circuit unit; 11. Si substrate; 12. First diode; 13. Resistor; 14. Second diode; 15. Field effect transistor; 16. First output port; 17. Second output port. DETAILED DESCRIPTION

[0016] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0017] The present invention provides an implantable dynamic pressure sensor system, the structure of which is shown in FIG. Figure 1 The system includes a packaging shell 1, a pressure sensing unit 2, a temperature sensing unit 3, a biological glue 4, an Au lead 5, a detection circuit unit 6, and a Si substrate 11. The packaging shell 1 is in the shape of a capsule and can be made of a titanium alloy with good biocompatibility. The pressure sensing unit 2 and the temperature sensing unit 3 are integrated on the Si substrate 11 through a MEMS process. The back Si of the Si substrate 11 corresponding to the position of the pressure sensing unit 2 is thinned to make the pressure sensing unit 2 more sensitive. A groove notch is prepared in the middle of the packaging shell 1. The integrated pressure sensing unit 2 and the temperature sensing unit 3 are connected through the biological glue 4. The Si substrate 11 of the package shell 1 is bonded and packaged in the groove gap of the package shell 1, wherein the pressure sensing unit 2 and the temperature sensing unit 3 are connected to each other through the wiring inside the Si substrate 11, and both are electrically connected to the detection circuit unit 6. Specifically, the front side of the pressure sensing unit 2 faces upward and is directly opposite to the groove gap, so as to directly contact the biological tissue to be tested, convert the pressure signal into an electrical signal, and the positive terminal electrode 7 of the pressure sensing unit is connected to the positive input terminal 10 of the detection circuit unit through the Au lead 5, and the positive terminal electrode 8 of the temperature sensing unit is connected to the negative input terminal 9 of the detection circuit unit to realize signal transmission and amplification.

[0018] like Figure 2 As shown, the principle of the implantable dynamic pressure sensor system is: since piezoelectric materials have excellent piezoelectric and thermal sensitive properties, the present invention adopts piezoelectric materials as the sensitive layers of the pressure sensing unit 2 and the temperature sensing unit 3. The pressure sensing unit 2 is very sensitive to the local temperature. The piezoelectric sensing unit 2 is easily affected by the temperature while detecting the local pressure. The local temperature of the biological tissue environment is monitored in real time by the temperature sensing unit 3, and the output of the pressure sensing unit 2 is compensated according to the temperature change, thereby improving the accuracy and stability of the pressure sensing system under different temperature conditions, and obtaining a high-quality pressure signal through the detection circuit unit 6, which is suitable for long-term implantation.

[0019] like Figure 3 As shown, regarding the preparation of the chip integrating the pressure sensing unit 2 and the temperature sensor unit 3: the substrate of the present invention is made of insulating material, and a 4-inch 300mm thick double-polished Si substrate 11 (crystal direction 100) is selected. The SiO2 layer is grown on the surface of the Si substrate 11 by plasma enhanced chemical vapor deposition (PECVD) for 500nm as an isolation layer. The bottom electrodes of the pressure sensing unit 2 and the temperature sensing unit 3 are prepared on the substrate by photolithography and magnetron sputtering. In order to compensate for the influence of temperature on the output of the pressure sensing unit 2, the bottom electrodes of the pressure sensing unit 2 and the temperature sensing unit 3 are integrated together; a high-quality piezoelectric film is prepared on the bottom electrode by a gel-gel method, a sputtering method, a chemical vapor deposition (CVD) or a pulsed laser deposition (PLD) method; the piezoelectric film is patterned by photolithography and etching processes, and the patterned piezoelectric film is used as the sensitive layer of the pressure sensing unit 2 and the temperature sensing unit 3 respectively; the upper layer of the piezoelectric film and the Si are formed by photolithography and sputtering processes. A top electrode and a lead electrode are respectively prepared on the O2 layer as the positive electrode 7 of the pressure sensing unit and the positive electrode 8 of the temperature sensing unit; the piezoelectric film is polarized by means of thermal polarization and electric field polarization; in order to reduce the mechanical constraints of the substrate on the piezoelectric material and improve the sensitivity of the sensor, the back Si substrate 11 of the pressure sensing unit 2 is thinned by silicon back lithography and deep silicon etching process to obtain a quasi-suspended structure of the pressure sensing unit 2, and the thickness of the quasi-suspended part of the pressure sensing unit 2 can be controlled by setting etching parameters (gas, time, etc.); the sensor chip is released by wafer front lithography and deep silicon etching.

[0020] like Figure 4As shown, the detection circuit unit 6 includes a first diode 12, a second diode 14, a resistor 13, a field effect transistor 15 and a first and a second output port 16, 17. The piezoelectric pressure sensing unit 2 and the temperature sensing unit 3 provide signal input. The first diode 12 is used to prevent reverse current from entering the circuit, and the second diode 14 is used to stabilize the voltage of the pressure sensing unit 2 and the temperature sensing unit 3 to prevent excessive voltage from damaging the device. The resistor 13 is used as a current limiting resistor to protect the subsequent circuit from being affected by excessive current. The field effect transistor 15 is used to amplify the signal and output a high-quality and stable pressure signal. The negative end of the pressure sensing unit 2 is connected to the negative end of the temperature sensing unit 3, the positive electrode 7 of the pressure sensing unit is connected to the positive input end 10 of the detection circuit unit as the input end, the positive electrode 8 of the temperature sensing unit is connected to the negative input end 9 of the detection circuit unit, the resistor 13 is connected to the gate of the field effect tube 15, the input and output ends of the first diode 12 are respectively connected to the negative input end 9 of the detection circuit unit and the positive input end 10 of the detection circuit unit, the source of the field effect tube 15 is connected to the second output port 17, and the drain is connected to the first output port 16, that is, grounded, the input and output ends of the second diode 14 are respectively connected to the second output port 17 and the first output port 16, the electrical signal generated by the sensor regulates the current flowing through the field effect tube 15, and provides a signal that changes with pressure at the first and second output ports 16 and 17.

[0021] Preferably, the packaging shell 1 of the sensor can also be replaced by biocompatible materials such as stainless steel, polyetheretherketone, polyetherimide, polycarbonate, etc.; Preferably, the sensing unit can integrate blood oxygen, pH, ion sensors, etc. in addition to pressure and temperature through MEMS technology; Preferably, the sensitive layers of the pressure and temperature sensing units are made of piezoelectric materials (BaTiO3, PVDF, PZT, etc.) to monitor pressure and temperature, and have the advantages of high sensitivity and durability, and are suitable for long-term implantation.

[0022] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An implantable dynamic pressure sensor system, comprising a packaging shell, a pressure sensing unit, a temperature sensing unit, and a detection circuit unit, characterized in that: The package shell is used to accommodate the pressure sensing unit and the temperature sensing unit integrated on the Si substrate, wherein the package shell includes a groove notch, and the sensing end of the pressure sensing unit is directly opposite to the groove notch, and is used to directly contact with the biological tissue to be tested, and convert the detected pressure signal into an electrical signal; One end of the pressure sensing unit and one end of the temperature sensing unit are connected to each other through wiring inside the Si substrate, and the other end of the pressure sensing unit and the other end of the temperature sensing unit are connected to the positive input end and the negative input end of the detection circuit unit respectively, and the temperature sensing unit detects the temperature in the biological tissue in real time and performs temperature compensation on the pressure sensing unit; The Si substrate at the location of the pressure sensing unit is thinned to a preset thickness.

2. An implantable dynamic pressure sensor system according to claim 1, characterized in that: The pressure sensing unit and the temperature sensing unit both include a Si substrate, a SiO2 insulating layer, a bottom electrode, a sensitive layer, a top electrode, and a lead electrode connected to a detection circuit unit.

3. An implantable dynamic pressure sensor system according to claim 2, characterized in that: The pressure sensing unit and the temperature sensing unit are both connected to the detection circuit unit through Au leads.

4. An implantable dynamic pressure sensor system according to claim 2, characterized in that: The pressure sensing unit is fixed at the groove notch of the packaging shell by biological glue.

5. The implantable dynamic pressure sensor system according to claim 2, characterized in that: The sensitive layers of the pressure sensing unit and the temperature sensing unit are made of any one of the piezoelectric materials BaTiO3, PVDF and PZT.

6. The implantable dynamic pressure sensor system according to claim 1, characterized in that: The detection circuit unit comprises an amplifier circuit composed of a field effect tube, a diode and a resistor.

7. An implantable dynamic pressure sensor system according to claim 6, characterized in that: The detection circuit unit includes: the negative electrode of the pressure sensing unit is connected to the negative electrode of the temperature sensing unit, the positive electrode of the pressure sensing unit is connected to the positive input terminal of the detection circuit unit as an input terminal, the positive electrode of the temperature sensing unit is connected to the negative input terminal of the detection circuit unit, the resistor is connected to the gate of the field effect tube, the input and output terminals of the first diode are respectively connected to the negative input terminal of the detection circuit unit and the positive input terminal of the detection circuit unit, the source of the field effect tube is connected to the second output port, the drain is connected to the first output port and is grounded, and the input and output terminals of the second diode are respectively connected to the second output port and the first output port.

8. A method for preparing an implantable dynamic pressure sensor, characterized in that: The method comprises the following steps: A SiO2 layer is grown on the surface of the Si substrate using a plasma enhanced chemical vapor deposition process as an isolation layer; The bottom electrodes of the integrated pressure sensing unit and the temperature sensing unit are prepared on the SiO2 layer by photolithography and magnetron sputtering technology; preparing a piezoelectric film on a bottom electrode; The piezoelectric film is patterned by photolithography and etching processes, and the patterned piezoelectric film is used as a sensitive layer of a pressure sensing unit and a temperature sensing unit respectively; A top electrode and a lead electrode are prepared on the upper layer of the piezoelectric film and the SiO2 layer respectively as a positive terminal electrode of the pressure sensing unit and a positive terminal electrode of the temperature sensing unit by photolithography and sputtering processes; The piezoelectric film of the sensitive layer is polarized by thermal polarization method and electric field polarization method; The back Si substrate of the pressure sensing unit is thinned by using silicon back lithography and deep silicon etching process; The sensor chip with integrated pressure sensing unit and temperature sensing unit is released by photolithography and deep silicon etching on the front side of the wafer.

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