A miniature low-power MEMS pressure or pressure sensor suitable for endoscopic and minimally invasive surgical instruments

Abstract

The application discloses a micro low-power MEMS pressure / pressure sensor suitable for endoscopes and minimally invasive surgical instruments and a packaging method thereof, and belongs to the technical field of micro-electro-mechanical systems and medical instruments. The sensor comprises a pressure sensing film, a sensing piezoelectric resonator, a reference piezoelectric resonator and a CMOS integrated processing circuit, adopts an on-demand reading mode, and standby power consumption is extremely low. The sensing resonator is rigidly coupled to the edge of the film and resonates frequency drift occurs with the deformation of the film; the same environment reference resonator is not mechanically coupled, and real-time temperature drift, humidity and common mode interference are eliminated through hardware differential demodulation. The sensor can be vertically integrated and vacuum packaged, supports pressure / pressure dual-mode measurement and three-dimensional force calculation, outputs direct current or digital signals, and is resistant to electromagnetic interference and miniaturized. The application effectively solves the defects of high power consumption, large temperature drift, poor anti-interference and large volume of traditional sensors, and meets the clinical monitoring requirements of high precision, low power consumption and high reliability of minimally invasive endoscopes and surgical robots.

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems and medical device technology, specifically relating to a miniature low-power MEMS pressure / pressure sensor based on piezoelectric resonant frequency response, with reference resonator temperature drift compensation, and supporting on-demand reading, suitable for integration at the front end of endoscopes and precision measurement of gas / liquid pressure in small spaces. Background Technology

[0002] In the field of modern medicine, minimally invasive laparoscopic surgery, with its advantages of less trauma, less bleeding, and faster postoperative recovery, has become a core diagnostic and treatment technology in clinical departments such as general surgery, urology, obstetrics and gynecology, and thoracic surgery. It is widely used for exploration, resection, suturing, and reconstruction of various sites, including the abdominal cavity, thoracic cavity, and joint cavity. Throughout the minimally invasive surgical procedure, the magnitude of the force exerted by the surgical instruments when contacting, clamping, pulling, and cutting human tissue directly determines the safety and precision of the surgery. Real-time, accurate, and stable sensing of the contact pressure and interface pressure between the instruments and tissue can effectively avoid tissue tearing, blood vessel rupture, and nerve damage caused by excessive clamping, significantly improving the controllability and success rate of complex surgeries. This is a key core technology for achieving intelligent and precise advanced minimally invasive instruments and surgical robots.

[0003] Currently, MEMS pressure sensors have seen some development in the medical field. For example, the "Implantable External Chamber Pressure Sensor" (CN110520031A) proposed by Caltech uses a MEMS pressure-sensitive membrane structure. Pressure is transmitted to the sensor through an oil-filled chamber and a catheter, enabling wireless monitoring of chamber pressures such as intraocular pressure. This approach represents a valuable exploration in implantable pressure detection; however, its sensor operates in a continuously powered mode, resulting in high power consumption. Furthermore, its pressure transmission relies on a liquid-filled catheter structure, making its overall size relatively large and difficult to integrate into extremely small installation spaces such as the tip of endoscopic instruments.

[0004] In the field of resonant MEMS pressure sensors, the "Single-Chip Implementation Method of MEMS Silicon Resonant Pressure Sensor and Automatic Gain Control Circuit" (CN119363059A) proposed by the East China Institute of Optoelectronic Integrated Devices uses a silicon resonant pressure-sensitive structure and an AC-AGC automatic gain control circuit to form a closed-loop feedback, converting the detected pressure value into a frequency value output. This scheme achieves frequency signal output and has the advantage of strong anti-interference capability, but it relies on continuous closed-loop oscillation to maintain operation, resulting in high static power consumption; temperature drift compensation is implemented using board-level circuitry, limiting integration; and no specific design for the medical device field has been observed.

[0005] Regarding temperature drift compensation, Nanjing High-Tech Co., Ltd. proposed a "MEMS pressure sensor and its temperature drift compensation method and device" (CN117387811A), which uses a temperature drift compensation model based on a BP neural network to compensate for the temperature of the pressure output value through a software algorithm. Although this method can improve measurement accuracy, it relies on subsequent software calibration, resulting in a response delay. In scenarios with rapid temperature changes, such as fluctuations in patient body temperature during surgery and changes in the temperature difference of intraoperative irrigation fluid, it is difficult to achieve real-time and synchronous temperature drift suppression.

[0006] In the field of three-dimensional force detection, Xi'an Jiaotong University proposed a "piezoresistive integrated three-dimensional turning force sensor" (CN103471752B), which uses two mutually perpendicular octagonal ring structures in conjunction with a MEMS silicon micro-force-sensitive chip to achieve independent measurement of three-dimensional forces. This solution has good reference value in three-dimensional force decoupling, but its structural size is relatively large (suitable for turning force measurement scenarios), and it can only detect contact forces, unable to achieve isotropic pressure detection, making it difficult to meet the miniaturization and multi-functional integration requirements of minimally invasive surgical instruments.

[0007] In addition, regarding zero drift and temperature drift compensation of MEMS pressure sensors, existing solutions use the method of integrating compensation resistors in the Wheatstone bridge to achieve in-bridge hardware compensation. However, this compensation method is a one-time adjustment before leaving the factory and cannot respond to dynamic temperature changes during use in real time.

[0008] In summary, existing MEMS pressure sensor technologies suffer from the following common technical deficiencies in minimally invasive laparoscopic and surgical robot applications: Traditional sensors employ continuous power supply and continuous measurement modes, with resonators and conditioning circuits operating continuously. Solutions such as CN119363059A rely on closed-loop continuous oscillation, resulting in persistently high power consumption. The limited heat dissipation space at the front end of micro-laparoscopic instruments poses a risk of tissue burns due to excessive power consumption. Solutions such as CN117387811A, which use software algorithm compensation, rely on backend digital processing, leading to response lag; and solutions such as CN110520031A lack effective temperature drift suppression structures. Measurement accuracy is difficult to guarantee under rapid temperature changes during surgery, such as patient temperature fluctuations, intraoperative irrigation fluid temperature differences, and postoperative high-temperature and high-pressure sterilization.

[0009] Traditional solutions output analog voltage signals, which are highly susceptible to interference from strong electromagnetic equipment such as electrosurgical units, ultrasonic scalpels, and high-frequency electrocoagulation devices in the operating room during transmission through the slender wires of minimally invasive instruments. Three-dimensional force sensors such as CN103471752B have complex structures and large sizes; while CN119363059A uses a single-chip solution, its peripheral circuitry remains complex, making it difficult to pass through the Φ3mm-Φ8mm miniature endoscope clamp channels. Existing solutions either only detect contact pressure (e.g., CN103471752B) or only detect ambient pressure (e.g., CN110520031A), failing to achieve pressure / intensity dual-mode switching and simultaneous three-dimensional force calculation on a single chip.

[0010] To address the aforementioned technical deficiencies, this invention provides a miniature, low-power MEMS pressure / pressure sensor based on piezoelectric resonant frequency response, with real-time hardware differential temperature drift compensation for a reference resonator, and supporting on-demand readout mode, thereby achieving a miniaturized, low-power, temperature drift resistant, interference resistant, and multifunctional sensing solution. Summary of the Invention

[0011] To address the technical shortcomings of existing pressure sensors used in laparoscopic and minimally invasive surgical instruments, such as high power consumption during continuous power supply, large temperature drift, poor resistance to electromagnetic interference during long-distance transmission, large overall size, and limited functionality, this invention provides a miniature, low-power MEMS pressure / pressure sensor and its packaging method suitable for laparoscopic and minimally invasive surgical instruments. This sensor achieves miniaturization, low power consumption, resistance to temperature drift, interference resistance, and high-precision pressure / pressure detection, meeting the integration and clinical application requirements of minimally invasive laparoscopy, surgical robots, and precision diagnostic and therapeutic instruments.

[0012] To achieve the above objectives, the present invention adopts the following technical solution: The miniature low-power MEMS pressure / pressure sensor of the present invention includes a pressure sensing thin film structure, at least two sensing piezoelectric resonators, at least one reference piezoelectric resonator, and a CMOS integrated processing circuit; the sensor adopts an on-demand readout working mode, supports dual-mode pressure / pressure measurement, and can realize three-dimensional force calculation.

[0013] The pressure-sensing thin-film structure is rigidly coupled at its edges to the underlying silicon substrate, while the surrounding sensing and reference cantilever beams are similarly fixed to the side-protruding silicon substrate. The other end of the sensing resonator is connected to the thin-film structure for force sensing, while both ends of the reference resonator are fixed to the substrate in the same manner.

[0014] A pressure-conducting medium layer is provided below or around the pressure-sensing thin film structure. The medium layer is a solid flexible material, a liquid, or a sealed gas, used to transmit external concentrated pressure or isotropic pressure to the thin film structure, causing the thin film to undergo corresponding mechanical deformation.

[0015] The sensing piezoelectric resonators are rigidly coupled to the edge of the pressure-sensing thin-film structure. Their equivalent stiffness changes with the deformation of the pressure-sensing thin-film structure, resulting in a resonant frequency drift. There are 2-8 sensing piezoelectric resonators, symmetrically arranged around the pressure-sensing thin-film structure. Both the sensing and reference piezoelectric resonators are cantilever beam structures with PZT or AlN piezoelectric thin film material attached to their surfaces. These are used to achieve resonant excitation and amplitude-frequency response reading. When the film pressure changes, causing deformation, this deformation is transmitted to the resonant beam through mechanical coupling, thereby changing the resonant frequency of the beam, typically from 1 kHz to 1000 kHz. The amount of this frequency change reflects the magnitude of the received pressure.

[0016] The reference piezoelectric resonator is located in the same environment as the sensing piezoelectric resonator and is not mechanically coupled to the pressure sensing film structure. It is used to provide a reference signal for environmental disturbances. The cantilever beam of the sensing piezoelectric resonator has a length ranging from 100 μm to 600 μm and a width ranging from 10 μm to 50 μm. The pressure sensing film structure can be a circular or polygonal closed film, with the longest side-to-side distance greater than 60 μm to 1000 μm and a thickness ranging from 2 μm to 60 μm.

[0017] The sensor is configured for on-demand reading: the pressure sensor described in this patent employs real-time recording and on-demand reading technology to ensure low power consumption and low heat generation. The specific implementation method is as follows: In this case, the pressure recording film essentially bears the force deformation caused by the internal and external pressure difference. The internal pressure is approximately zero after vacuum sealing, while the external pressure is transmitted to the film through the pressure sensing material (PDMS, etc.). Therefore, the film continuously receives the internal and external pressure difference, causing deformation and simultaneously changing the stress and deformation of the sensing resonator in real time. Under these conditions, when pressure needs to be read, the external signal excites the sensing cantilever beam, calculates the resonant frequency, and performs subsequent calculations.

[0018] Traditional piezoelectric thin-film pressure sensors record the dynamic deformation of the thin film. That is, the piezoelectric layer attached to the surface of the thin film only releases charge when the film is under pressure and deforming. When the thin film reaches a steady state and is stationary, it does not release charge. Therefore, traditional pressure sensors must read data over a long period of time and rely on integration to estimate the real-time pressure.

[0019] Furthermore, the sensing piezoelectric resonators are symmetrically arranged around the pressure sensing thin film structure; both the sensing piezoelectric resonators and the reference piezoelectric resonators adopt a cantilever beam structure, with PZT (lead zirconate titanate) or AlN (aluminum nitride) piezoelectric thin film material attached to the surface, which is used to realize resonant excitation and amplitude-frequency response signal reading.

[0020] Furthermore, the sensor also includes a three-dimensional pressure demodulation module, which calculates... The frequency difference of multiple sensing piezoelectric resonators in a direction is used to calculate and output three-dimensional data of external pressure, shear force or torque.

[0021] When three-dimensional force sensing is required, the system utilizes four sensing cantilever beams (denoted as ) arranged around the MEMS thin film. , , , (These are located at four orthogonal positions along the +x, +y, -x, and -y axes, respectively). The module decouples the three-dimensional pressure vector using the following spatial difference algorithm: Z-axis normal pressure (vertical downward pressure): X-axis tangential shear force (or torque about the Y-axis): Y-axis tangential shear force (or torque about the X-axis):

[0022] Furthermore, when the pressure transmission medium layer is a sealed gas, medical silicone oil, or saline solution, the sensor acts as a pressure sensor. The pressure sensing film receives the external isotropic pressure and calculates the external pressure value by sensing the frequency drift of the piezoelectric resonator.

[0023] Furthermore, the overall dimensions of the sensor are no greater than 500 μm × 500 μm × 300 μm, and the size of the entire system after packaging is less than 1 mm × 1 mm × 0.5 mm. It only requires metal wires for external connection and can be used for installation in laparoscopic clamp channels with a diameter of 3 mm or larger.

[0024] This invention also provides two MEMS pressure sensor packaging methods: The first packaging method is wafer-level packaging. The MEMS sensor body structure is fabricated on a silicon substrate (lower layer) wafer. An upper cover plate is bonded to the lower wafer to form a sealed cavity, sealing the sensing piezoelectric resonator and the reference piezoelectric resonator in a vacuum environment to prevent air damping and ensure a high mechanical quality factor (Q value). PDMS or air is filled under or around the pressure-bearing film to buffer and transmit external pressure. A glass or silicon upper cover plate is placed on top for isolation. Electrical signals are led out through pads, gold connectors, and leads using bonding technology to connect to external medical system wires.

[0025] The second packaging method is leadless chip carrier (LCC) package packaging. The MEMS sensor body and CMOS circuit are fixed inside a standard LCC package; the inside of the LCC package is evacuated to a vacuum state to provide an undamped oscillation environment for the resonator; the lower part of the package is sealed with vacuum adhesive, and the external pressure signal is conducted to the central thin film area through flexible PDMS or air medium, realizing vacuum protection and isolation from external pressure transmission.

[0026] The CMOS integrated processing circuit is electrically connected to the sensing piezoelectric resonator and the reference piezoelectric resonator. It receives frequency signals, performs differential demodulation, and outputs an electrical signal corresponding to pressure or stress. The CMOS integrated processing circuit is vertically integrated below the MEMS resonator structure and electrically connected via vertical interconnect technology. The CMOS integrated processing circuit includes a piezoelectric signal processing and demodulation module, an environmental disturbance elimination module, a phase-locked loop module, and a DC signal output module. Specifically, the piezoelectric signal processing and demodulation module amplifies the charge signal generated by the vibration of the piezoelectric material and demodulates the signal into a frequency domain spectrum to acquire the resonant peak frequency. The environmental disturbance elimination module compares the frequency changes of the sensing piezoelectric resonator and the reference piezoelectric resonator to eliminate the effects of temperature drift and humidity at the hardware level. The phase-locked loop module locks the phase of the resonant peak and adjusts the excitation frequency in real time to maintain the resonant state. The DC signal output module converts the frequency difference signal into a DC voltage signal or a digital signal and transmits it to the endoscope monitoring system.

[0027] The piezoelectric signal processing and demodulation module in the CMOS integrated processing circuit is used to amplify the charge signal generated by the vibration of the piezoelectric material and demodulate the signal into a frequency domain spectrum to acquire the resonant peak frequency. Its working principle is as follows: The initial resonant frequency of the piezoelectric resonator is sensed using the resonant frequency demodulation principle; the initial resonant frequency of the inductive cantilever beam is set to... ,in For the initial equivalent stiffness, For equivalent quality.

[0028] When a MEMS thin film is subjected to compressive deformation and tension on a cantilever beam, it causes a change in stiffness. The piezoelectric signal processing module locks the phase of the piezoelectric feedback signal through a phase-locked loop (PLL) and demodulates the actual resonant frequency after compression in real time. And calculate the frequency offset. .

[0029] The environmental disturbance cancellation module compares the frequency changes of the sensing piezoelectric resonator with those of a reference piezoelectric resonator, eliminating the effects of temperature drift and humidity at the hardware level. Let the temperature change of the system's environment be... The induction cantilever beam is subjected to pressure simultaneously. and temperature change Due to the influence of [the factor], its total frequency output is: in The pressure sensitivity coefficient, This is the temperature drift coefficient. This is common-mode random noise. Since the MEMS reference cantilever beam is not under pressure... The effect of this is that its frequency output is: The environmental disturbance elimination module performs a difference subtraction algorithm: This eliminates temperature drift at the hardware level. and common-mode noise .

[0030] The phase-locked loop (PLL) module is used to lock the resonant peak phase and adjust the excitation frequency in real time to maintain the resonator's resonant state. The DC signal output module then outputs the frequency difference signal processed by the environmental disturbance cancellation module. It is converted into a DC voltage signal or a digital signal and transmitted to the endoscope monitoring system.

[0031] Dual working modes: On-demand read mode: Zero power consumption in standby mode, short-term excitation read triggered by command, suitable for static tissue palpation and low power consumption scenarios; Continuous output mode: Phase-locked loop tracks the resonant frequency in real time, suitable for high dynamic force feedback and precision operation scenarios.

[0032] When the pressure / pressure dual-mode switching medium is a flexible solid such as PDMS, it realizes contact pressure measurement; when the medium is a sealed gas / liquid, it realizes isotropic pressure measurement, which can be used for monitoring abdominal pneumoperitoneum pressure.

[0033] Compared with existing piezoresistive and capacitive pressure sensors and conventional MEMS pressure sensing technologies, this invention has outstanding technical advantages and significant beneficial effects in extreme minimally invasive medical applications, as detailed below:

[0034] This invention employs a pressure-state mechanical storage and on-demand excitation and reading mechanism. During non-reading periods, the sensor is in a zero-power or extremely low-power standby state, recording real-time pressure using only a thin film; the resonator and circuitry consume no electrical energy. Only upon receiving a read command does it perform a short-duration high-frequency excitation and signal acquisition, immediately returning to sleep mode after completion. Compared to traditional continuously powered, continuously measured sensors, the average power consumption is reduced by more than an order of magnitude, significantly reducing chip heat generation and avoiding thermal damage to human tissue. It is fully compatible with medical devices highly sensitive to power consumption and heat generation, such as endoscopic instruments, interventional devices, and wireless sensing modules.

[0035] This invention employs a sensing mechanism that ensures independent sensing of three-dimensional pressure / intensity. When the pressure diaphragm is subjected to a normal force along the z-axis, the left and right sensing resonators undergo identical deformation, resulting in identical frequency changes; when the pressure diaphragm is subjected to a normal force along the z-axis, the left and right sensing resonators undergo identical deformation, resulting in identical frequency changes. When a lateral force is applied in the axial direction, the sensing resonators on both sides will produce different deformations, resulting in different frequency changes. Therefore, the differential frequency can be used as a measure of the force magnitude.

[0036] This invention establishes a reference piezoelectric resonator with the same environment, size, and initial stiffness as the sensing piezoelectric resonator, and without mechanical coupling. Differential demodulation is performed in real-time at the hardware level via CMOS circuitry, synchronously and with zero delay eliminating common-mode disturbances such as temperature changes, material stress relaxation, electromagnetic noise, and humidity variations, without requiring subsequent software lookup tables or external temperature sensor compensation. This physically eliminates the influence of temperature drift, maintaining ultra-high measurement accuracy and stability even under extreme conditions such as surgical temperature fluctuations, high-temperature and high-pressure sterilization, and strong electromagnetic interference.

[0037] This invention employs a parallel arrangement of a MEMS resonant structure and a CMOS processing circuit, achieving electrical connection through LCC internal wire bonding, significantly reducing the chip's footprint. Combined with wafer-level vacuum packaging, the sensor can achieve sub-millimeter to millimeter-level miniature dimensions (the sensor structure itself can be as small as 500 μm * 500 μm * 300 μm in side length, and the packaged system size can be less than 1 mm * 1 mm * 0.5 mm, requiring only metal wires for external connection). It can be easily integrated into extremely small installation spaces such as laparoscopic forceps, minimally invasive instrument tips, puncture needles, and interventional catheters, overcoming the technical limitations of traditional sensors that cannot be applied to high-end minimally invasive medical devices due to their large size and complex peripheral circuits.

[0038] This invention employs wafer-level vacuum packaging to seal the resonator in a vacuum environment, eliminating air damping and maintaining an ultra-high mechanical quality factor (Q value) (above 5k at 0.01 mbar pressure), significantly improving pressure detection sensitivity and resolution. Simultaneously, the packaging structure possesses biocompatibility, resistance to bodily fluid corrosion, resistance to high-temperature and high-pressure sterilization, and resistance to mechanical shock, enabling it to withstand the harsh operating environments of minimally invasive surgery and repeated sterilization, ensuring long-term stable operation of the sensor and extending the lifespan of the device. Attached Figure Description

[0039] Figure 1 : Overall structural hierarchy and module interaction diagram of a multi-mode low-power MEMS pressure sensor system.

[0040] Figure 2 : A top view of the physical sensing layer (MEMS layer).

[0041] Figure 3Flowchart of signal processing logic and algorithm demodulation.

[0042] Figure 4 : A spatial force vector diagram of the 3D Force Decoupling module.

[0043] Figure 5 The first packaging example in the embodiment is used to ensure the cross-sectional structure of the resonant Q value.

[0044] Figure 6 The embodiment uses the second packaging method to ensure the cross-sectional structure of the resonant Q value. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0046] Example 1

[0047] This embodiment utilizes wafer-level vacuum packaging to fabricate a miniature, low-power MEMS pressure sensor. The pressure-sensing thin film structure is square, with a longest side-to-side spacing of 600 μm and a thickness of 2 μm. The pressure-conducting medium layer is made of PDMS flexible solid material. Both the sensing piezoelectric resonator and the reference piezoelectric resonator are cantilever beam structures, with a cantilever beam length of 100 μm and a width of 10 μm. The piezoelectric layer material is AlN. Two sensing piezoelectric resonators are symmetrically arranged around the thin film. The reference piezoelectric resonator shares the same environment, size, and initial stiffness as the sensing resonators and is not mechanically coupled to the thin film. The CMOS integrated processing circuitry is vertically integrated below the MEMS structure and electrically connected via vertical interconnects. The sensor employs an on-demand readout mode, with an excitation signal of a 10 MHz to 15 MHz wideband pulse, and the vacuum level of the sealed cavity is less than 1 Pa.

[0048] Example 2

[0049] This embodiment utilizes wafer-level vacuum packaging to fabricate a miniature, low-power MEMS pressure sensor. The pressure-sensing thin film structure is square, with a longest side-to-side spacing of 1000 μm and a thickness of 60 μm. The pressure-conducting medium layer is made of PDMS flexible solid material. Both the sensing piezoelectric resonator and the reference piezoelectric resonator are cantilever beam structures, with a cantilever beam length of 600 μm and a width of 50 μm. PZT is used as the piezoelectric layer material. Eight sensing piezoelectric resonators are symmetrically arranged around the thin film. The reference piezoelectric resonator shares the same environment, size, and initial stiffness as the sensing resonators and is not mechanically coupled to the thin film. The CMOS integrated processing circuitry is vertically integrated below the MEMS structure and electrically connected via vertical interconnects. The sensor employs an on-demand readout mode, with an excitation signal of a 10MHz to 15MHz wideband pulse, and the vacuum level of the sealed cavity is less than 1 Pa.

[0050] Example 3

[0051] This embodiment employs an LCC-cased vacuum encapsulation to fabricate a MEMS pressure sensor. The pressure-sensing thin-film structure is circular, with a diameter of 800 μm and a thickness of 30 μm. A sealed gas is used as the pressure transmission medium. Both the sensing piezoelectric resonator and the reference piezoelectric resonator are cantilever beam structures, with a length of 350 μm and a width of 30 μm. AlN is used as the piezoelectric layer material. Four sensing piezoelectric resonators are symmetrically arranged around the thin film. The reference piezoelectric resonator shares the same environment, size, and initial stiffness as the sensing resonators and is not mechanically coupled to the thin film. The CMOS integrated processing circuitry is vertically integrated beneath the MEMS structure and electrically connected via vertical interconnects. The sensor incorporates a three-dimensional pressure demodulation module, supporting continuous real-time reading. The LCC casing is evacuated, and the bottom is sealed with vacuum adhesive.

[0052] Example 4

[0053] This embodiment utilizes an LCC-cased vacuum encapsulation system to fabricate a dual-mode MEMS pressure / pressure sensor. The pressure-sensing thin-film structure is circular, with a diameter of 800 μm and a thickness of 30 μm. Medical-grade silicone oil is used as the pressure transmission medium. Both the sensing and reference piezoelectric resonators are cantilever beam structures, with a length of 350 μm and a width of 30 μm. PZT is used as the piezoelectric layer material. Four sensing piezoelectric resonators are symmetrically arranged around the thin film, while two reference piezoelectric resonators share the same environment, size, and initial stiffness as the sensing resonators and are not mechanically coupled to the thin film. The CMOS integrated processing circuitry is vertically integrated below the MEMS structure and electrically connected via vertical interconnects. The sensor supports automatic switching between intermittent reading and continuous output. The LCC casing is evacuated, and the bottom is sealed with vacuum adhesive.

[0054] Comparative Example 1

[0055] This comparative example uses a traditional piezoresistive pressure sensor. The sensing structure is a silicon piezoresistive strip directly fabricated on the thin film surface, without a reference resonator or hardware differential temperature drift compensation. The sensor operates in continuous power supply mode, outputting an analog voltage signal, with temperature correction relying solely on backend software. The package uses a conventional plastic surface mount structure, lacking vacuum protection and air damping elimination design.

[0056] Comparative Example 2

[0057] This comparative example uses a standard capacitive MEMS pressure sensor. It does not employ piezoelectric resonance or differential modulation structures, and operates on a continuous excitation and continuous acquisition mode, lacking a low-power on-demand readout mode. The packaging is not vacuum-sealed, and the resonator is significantly affected by air damping, resulting in a low mechanical quality factor. The sensor can only detect single-axis normal pressure and does not support X / Y-axis shear force or three-dimensional torque calculation.

[0058] Table 1. Specific embodiments and comparative example data. standby current <1μA <1μA <1μA <1μA >1mA >500μA Average power consumption <3μW <5μW <20μW <30μW >1mW >500μW Temperature drift (37℃-65℃) <0.1%FS <0.2%FS <0.2%FS <0.2%FS >3.5%FS >4%FS Mechanical quality factor Q ＞10000 ＞15000 ＞8000 ＞10000 ＜1000 ＜500 Sterilization tolerance ≥20 times ≥20 times ≥20 times ≥20 times <5 times <3 times Adaptor for laparoscopic forceps Φ3mm and above Φ3mm and above Φ3mm and above Φ3mm and above not applicable not applicable

Claims

1. A miniature, low-power MEMS pressure or pressure sensor suitable for laparoscopic and minimally invasive surgical instruments, characterized in that, include: A pressure-sensing thin film structure has a pressure-conducting medium layer below or around it. The pressure-conducting medium layer is used to transmit external pressure or stress to the thin film structure and cause it to undergo mechanical deformation. At least two sensing piezoelectric resonators are rigidly coupled to the edge or near the pressure-sensing thin film structure. Their equivalent stiffness changes with the deformation of the thin film structure and causes the resonant frequency to drift. At least one reference piezoelectric resonator is located in the same environment as the sensing piezoelectric resonator and is not mechanically coupled to the pressure sensing thin film structure; a CMOS integrated processing circuit is electrically connected to the sensing piezoelectric resonator and the reference piezoelectric resonator to receive frequency signals and perform differential demodulation; the sensor adopts an on-demand reading mode, in which the resonator remains stationary or in low-power standby mode when no reading command is received, and after receiving the reading command, it is driven to resonate by the excitation source and the frequency difference is read.

2. A miniature low-power MEMS pressure or pressure sensor suitable for laparoscopic and minimally invasive surgical instruments according to claim 1, characterized in that, The sensing piezoelectric resonators consist of 2-8 units, symmetrically arranged around the pressure-sensing thin-film structure. Both the sensing and reference piezoelectric resonators are cantilever beam structures with PZT (lead zirconate titanate) or AlN (aluminum nitride) piezoelectric thin-film material attached to their surfaces. These are used to achieve resonant excitation and amplitude-frequency response reading. When the pressure on the thin film changes, causing deformation, this deformation is transmitted to the resonant beam through mechanical coupling, thereby changing the resonant frequency of the beam, typically from 1 kHz to 1000 kHz. The amount of this frequency change reflects the magnitude of the received pressure.

3. A miniature low-power MEMS pressure or pressure sensor suitable for laparoscopic and minimally invasive surgical instruments according to claim 1, characterized in that, The cantilever beam of the sensing piezoelectric resonator has a length range of 100 μm to 600 μm and a width range of 10 μm to 50 μm; the pressure sensing film structure can be a circular or polygonal closed film, with the longest side-to-side distance greater than 60 μm to 1000 μm and a thickness range of 2 μm to 60 μm.

4. A miniature low-power MEMS pressure or pressure sensor suitable for laparoscopic and minimally invasive surgical instruments according to claim 1, characterized in that, The CMOS integrated processing circuit is vertically integrated below the MEMS resonator structure and connected via a vertical interconnect process. The CMOS integrated processing circuit includes a piezoelectric signal processing and demodulation module, an environmental disturbance elimination module, a phase-locked loop (PLL) module, and a DC signal output module. The piezoelectric signal processing and demodulation module amplifies the charge signal generated by the vibration of the piezoelectric material and demodulates the signal into a frequency domain spectrum to acquire the resonant peak frequency. The environmental disturbance elimination module is used to compare the frequency changes of the sensing piezoelectric resonator with a reference piezoelectric resonator, eliminating the effects of temperature drift and humidity at the hardware level. The PLL module locks the resonant peak phase and adjusts the excitation frequency in real time to maintain the resonant state. The DC signal output module converts the frequency difference signal into a DC voltage signal or a digital signal and transmits it to the endoscope monitoring system.

5. A miniature low-power MEMS pressure or pressure sensor suitable for laparoscopic and minimally invasive surgical instruments according to claim 1, characterized in that, It also includes a three-dimensional pressure demodulation module, which calculates and outputs three-dimensional external pressure data by calculating the resonant frequency difference of multiple sensing piezoelectric resonators in the X, Y, and Z directions.

6. A packaging method for a MEMS pressure sensor according to any one of claims 1-4, characterized in that, The wafer-level packaging process includes: constructing a MEMS sensor body structure on a silicon substrate; forming a sealed cavity between the upper and lower wafers to seal the sensing and reference piezoelectric resonators in a vacuum environment, improving the mechanical quality factor to the 10k to 100k range; filling the pressure-bearing film with PDMS or air medium to achieve pressure buffering and conduction; and providing isolation with a glass or silicon cover plate on top, and leading out electrical signals and connecting them to external medical system wires through pads, gold connectors, and wire bonding.

7. A packaging method for a MEMS pressure sensor according to any one of claims 1-4, characterized in that, The process involves using a leadless chip carrier LCC housing for encapsulation. The steps include: fixing the MEMS sensor body and CMOS circuit inside the LCC housing; evacuating the LCC housing to a vacuum state to provide an undamped oscillation environment for the resonator; sealing the lower part of the housing with vacuum adhesive; and transmitting the external pressure signal at the bottom of the sensor to the central thin film area through PDMS or air medium to achieve vacuum protection and pressure transmission isolation.

8. A miniature low-power MEMS pressure or pressure sensor suitable for laparoscopic and minimally invasive surgical instruments according to claim 1, characterized in that, When the pressure transmission medium layer is a sealed gas, medical silicone oil, or saline solution, the sensor acts as a pressure sensor. The pressure sensing film receives the external isotropic pressure and calculates the external pressure value by sensing the frequency drift of the piezoelectric resonator.

9. A miniature low-power MEMS pressure or pressure sensor suitable for laparoscopic and minimally invasive surgical instruments according to claim 1, characterized in that, The sensor's overall dimensions are no greater than 500 μm × 500 μm × 300 μm. After packaging, the entire system size can be less than 1 mm × 1 mm × 0.5 mm. It only requires metal wires for external connection and can be used with laparoscopic clamp channels of Φ3 mm and above.

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