Dental caries detection device based on MEMS ultrasonic transducer

Abstract

The invention relates to the technical field of ultrasonic decayed tooth detection, in particular to a decayed tooth detection device based on MEMS ultrasonic transducers, which comprises an ASIC circuit and a transceiving integrated MEMS ultrasonic transducer array which are connected with each other, and the ASIC circuit and the transceiving integrated MEMS ultrasonic transducer array are attached to the surface of a tooth to be detected after being wrapped by an external coupling layer; the ASIC circuit is connected with one end of a wire which penetrates through the external coupling layer and is composed of a polymer multi-cycle heterojunction thermoelectric material and a gold electrode, the other end of the wire is arranged outside the oral cavity, and after thermoelectric potential is generated by utilizing the Seebeck effect, the ASIC circuit generates an excitation signal according to the thermoelectric potential; the transmitting array of the transmitting-receiving integrated MEMS ultrasonic transducer array transmits ultrasonic waves outwards, so that the ultrasonic waves are transmitted through the external coupling layer to enter the interior of the tooth to be detected, and the receiving array receives ultrasonic echoes returned by the tooth to be detected so as to carry out decayed tooth detection on the tooth to be detected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultrasonic caries detection, and particularly relates to a caries detection device based on a MEMS ultrasonic transducer. BACKGROUND

[0002] Caries, commonly known as tooth decay or worm tooth, is a chronic, progressive and destructive disease occurring in the hard tissue of teeth, which is caused by bacteria as the main pathogen and multiple factors. It is one of the most common diseases after cold and has a significant impact on human health. If caries is not discovered and treated in time in the early stage, the tooth tissue will be further damaged, the carious cavity will become larger and deeper, and the dentin shallow layer will be invaded and developed to the dental pulp. If the bacterial infection reaches the dental pulp (dental nerve), it will cause spontaneous and severe pain, and if not treated in time, it will also cause apical periodontitis, tooth apex abscess, and even facial swelling. However, since the development of caries is a gradual process and there are no self-aware symptoms in the early stage of caries, patients are difficult to discover it by themselves, and it can only be discovered by careful examination by an oral medicine doctor in a hospital.

[0003] At present, the detection techniques based on the commonly used caries detection devices in the clinic mainly include visual exploration, X-ray imaging examination and laser fluorescence detection. However, these detection techniques all have obvious limitations. Visual and probe examination is highly dependent on the experience of the operator, has low sensitivity to early caries loss hidden in the sulcus or adjacent surface, and has the risk of damaging the tooth tissue in mechanical exploration. Although X-ray technology can detect some hidden caries, it has the harm of ionizing radiation and is not suitable for frequent screening of pregnant women and children, and it can only be identified when the mineral loss reaches a significant degree, and it is difficult to achieve early diagnosis. The laser fluorescence device is easily disturbed by the pollutants on the tooth surface, and has a high false positive rate.

[0004] High-frequency ultrasonic waves can penetrate the tooth to a certain extent. The demineralization and organic matter decomposition phenomenon of caries will cause the acoustic impedance of the caries position to be obviously different from the acoustic impedance of other normal parts in the tooth, which will change the state of ultrasonic wave propagation in caries and normal teeth. Therefore, the health status of the tooth can be judged by analyzing the time of flight, amplitude attenuation and scattering characteristics of the ultrasonic echo signal. However, the traditional piezoelectric ceramic ultrasonic transducer has a large physical size, which is difficult to adapt to the narrow and complex operation space in the oral cavity, and has high energy consumption, which is not conducive to the design of portable devices. SUMMARY

[0005] The present application aims to provide a caries detection device based on a MEMS ultrasonic transducer, which can solve the problem of large size and high energy consumption of the traditional piezoelectric ceramic ultrasonic transducer, which is not conducive to the design of portable devices.

[0006] To solve the above technical problems, the embodiment of the present application provides a caries detection device based on a MEMS ultrasonic transducer, comprising: an ASIC circuit and a transceiving integrated MEMS ultrasonic transducer array connected with each other, and the ASIC circuit and the transceiving integrated MEMS ultrasonic transducer array are attached to the surface of the tooth to be measured after being wrapped by an external coupling layer; wherein the transceiving integrated MEMS ultrasonic transducer array comprises a transmitting array and a receiving array respectively formed by a plurality of MEMS ultrasonic transducers; The ASIC circuit is connected to one end of a wire formed by a polymer multi-period heterojunction thermoelectric material and a gold electrode hinge passing through the external coupling layer, and the other end of the wire is placed outside the oral cavity to generate a temperature difference potential by using the Seebeck effect; The ASIC circuit generates an excitation signal according to the temperature difference potential, and each MEMS ultrasonic transducer in the transmitting array generates a driving bending moment due to the inverse piezoelectric effect of the piezoelectric layer under the action of the excitation signal, drives the structural layer to vibrate, and transmits ultrasonic waves outward, so that the ultrasonic waves are transmitted into the tooth to be measured through the external coupling layer; When each MEMS ultrasonic transducer in the receiving array receives the ultrasonic echo returned by the tooth to be measured, the structural layer vibrates, so that the piezoelectric layer generates an electric signal for caries detection of the tooth to be measured due to the piezoelectric effect.

[0007] Further, the ASIC circuit comprises a power level lifting module, a signal generator module, a power amplifier module, a data acquisition module and a low-noise preamplifier module; The power level lifting module is used for performing level lifting processing on the temperature difference potential generated by using the Seebeck effect, the signal generator module is used for generating an excitation signal according to the processed temperature difference potential, and the power amplifier module is used for power amplifying the generated excitation signal to send the amplified excitation signal to the transmitting array; The data acquisition module is used for acquiring the electric signal generated by the receiving array, and the low-noise preamplifier module is used for filtering and signal amplifying the acquired electric signal to perform caries detection of the tooth to be measured through the processed electric signal.

[0008] Further, the device further comprises a host computer, and the ASIC circuit further comprises a WiFi module or a Bluetooth module, both of which are used for transmitting the electric signal processed by the low-noise preamplifier module to the host computer for caries detection of the tooth to be measured.

[0009] Further, the transmitting array of the transceiving integrated MEMS ultrasonic transducer array is an internal solid circular array, and the receiving array is an external hollow annular array.

[0010] Furthermore, in the transmitting and receiving arrays of the integrated MEMS ultrasonic transceiver array, the piezoelectric layer of each MEMS ultrasonic transceiver is made of PZT, ZnO, AlN, KNN or PVDF thin film, and the structural layer is made of Si3N4 or SiO2 thin film.

[0011] Furthermore, the length and width of the device are both less than 6 mm.

[0012] Furthermore, the device is positioned on the labial or buccal surface of the tooth to be tested.

[0013] Furthermore, the external coupling layer is made of a hydrogel material with acoustic impedance matching function.

[0014] The dental caries detection device based on a MEMS ultrasonic transducer provided by this invention has at least the following beneficial effects: This invention employs a transceiver integrated MEMS ultrasonic transducer array based on a MEMS ultrasonic transducer design to transmit and receive ultrasonic waves for caries detection. The MEMS ultrasonic transducer uses a design distinct from traditional piezoelectric transducers. d 33 Thickness vibration mode d 31 Bending vibration mode typically requires only a lower driving voltage and consumes less energy. Furthermore, it employs semiconductor micro-nano fabrication technology, which can easily manufacture high-density two-dimensional arrays and facilitates monolithic integration with front-end integrated circuits (ASICs). Therefore, by integrating a transceiver-integrated MEMS ultrasonic transducer array based on MEMS ultrasonic transducers with ASIC circuits and then wrapping it with an external coupling layer, it can be attached to the surface of the tooth to be tested to achieve caries detection. Compared with traditional piezoelectric ceramic ultrasonic transducers, the device is smaller in size and consumes less energy.

[0015] The ASIC circuit driving the MEMS ultrasonic transducer employs a self-powered mode. It only requires connecting one end of a wire (placed inside the mouth on the tooth to be tested) made of polymer multi-periodic heterojunction thermoelectric material and gold electrodes, passing through the outer coupling layer, and placing the other end of the wire outside the mouth. This allows the Seebeck effect to generate a thermoelectric potential, which is then used to generate an excitation signal to drive the MEMS ultrasonic transducer. This approach offers greater operability without increasing device size or cost, making it beneficial for the design of portable devices. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 This is a schematic diagram of a dental caries detection device based on a MEMS ultrasonic transducer provided by the present invention; Figure 2 This invention provides a schematic diagram of a MEMS ultrasonic transducer unit and array structure design. Figure 3 A schematic diagram of an ASIC circuit design provided by the present invention; Figure 4 This is a schematic diagram comparing the ultrasonic echo signals of a normal tooth and a decayed tooth, as provided by the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] This invention addresses the significant limitations of existing caries detection devices in the early diagnosis of caries by proposing a device based on a transceiver integrated MEMS ultrasonic transducer array, which enables portable, non-self-adhesive caries detection.

[0020] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] One embodiment of the present invention relates to a dental caries detection device based on a MEMS ultrasonic transducer. The specific structure of the dental caries detection device based on a MEMS ultrasonic transducer in this embodiment can be as follows: Figure 1 As shown, the device includes an interconnected ASIC circuit 1 and a transceiver integrated MEMS ultrasonic transducer array 2. The connection between the two can be achieved using a through-silicon via (TSV) process. After being encased in an external coupling layer 3, the ASIC circuit and the transceiver integrated MEMS ultrasonic transducer array can be attached to the surface of the tooth 4 to be tested. Therefore, the length and width of this device are smaller than the length and width of a canine in a human tooth, generally less than 6 mm, allowing it to be placed on the labial or buccal surface of the tooth to be tested.

[0022] Among them, the ASIC circuit is connected to one end of a wire 5 formed by a polymer multi-periodic heterojunction thermoelectric material and a gold electrode hinged through the outer coupling layer. Figure 1(The reference numeral 6 indicates the hinge point). The other end of the wire is placed outside the oral cavity to generate a thermoelectric potential using the Seebeck effect. The ASIC circuit can then generate an excitation signal based on this thermoelectric potential to excite the MEMS ultrasonic transducer array to produce ultrasonic waves. In other words, the ASIC circuit adopts a self-powered design. It uses a polymer multi-periodic heterojunction (PMHJ) thermoelectric material with low thermal conductivity, high electrical conductivity, and a high Seebeck coefficient to form a closed loop with gold electrodes. The hot end is placed inside the oral cavity (approximately 36.5-37.5°C), while the cold end is exposed to room temperature (approximately 25°C). The Seebeck effect is used to generate a potential, thus forming a thermoelectric generator.

[0023] MEMS ultrasonic transceiver array with integrated transceiver, such as Figure 2 As shown, the array includes an internal circular array (transmitting array 8) for emitting ultrasonic waves and an external ring array (receiving array 9) for receiving ultrasonic echo signals. The two arrays are independent of each other and have no electrical connection. Each transmitting and receiving array consists of multiple MEMS ultrasonic transducers. In the transmitting array, under the action of an excitation signal, the piezoelectric layer of each MEMS ultrasonic transducer generates a driving moment due to the inverse piezoelectric effect, causing the structural layer to vibrate and emitting ultrasonic waves outward. These ultrasonic waves then penetrate the tooth under test through the external coupling layer. In the receiving array, when each MEMS ultrasonic transducer receives the ultrasonic echo returned from the tooth under test, the structural layer vibrates, causing the piezoelectric layer to generate an electrical signal for caries detection of the tooth under test due to the piezoelectric effect.

[0024] The external coupling layer uses a hydrogel material with acoustic impedance matching function. The hydrogel material in the coupling layer is used to prevent short circuits in the transducer due to contact with oral fluids, and also to achieve acoustic impedance matching. Hydrogel is a flexible material that is harmless to the human body and has a certain degree of deformability. It can fit precisely on the non-flat curved surfaces of teeth, enhance the effective signal, increase the signal-to-noise ratio, and provide a comfortable feel, improving the patient experience.

[0025] from Figure 1 As can be seen, the tooth decay detection device based on MEMS ultrasonic transducer has a sandwich structure, consisting of an outer coupling layer and a "chip" layer composed of an intermediate MEMS ultrasonic transducer chip and ASIC circuit. Then, the packaged MEMS ultrasonic transducer detection device is attached tightly to the surface of a tooth to be tested, and the wires wrapped with gold wires and thermoelectric materials with high Seebeck coefficient are extended to the outside of the oral cavity.

[0026] In a specific implementation, the structure of each MEMS ultrasonic transceiver unit in the transmitting and receiving arrays of the transceiver integrated MEMS ultrasonic transceiver array can also be found in [reference needed]. Figure 2 It includes an upper electrode 10, a piezoelectric layer 11, a lower electrode 12, a structural layer 13, an insulating layer 14, and a substrate 15.

[0027] Each MEMS ultrasonic transducer employs a method distinct from traditional piezoelectric transducers. d 33 Thickness vibration mode d 31 The bending vibration mode occurs when each MEMS ultrasonic transducer in the transmitting array generates an electric field under the action of alternating current between the upper and lower electrodes. The piezoelectric layer undergoes transverse strain due to the inverse piezoelectric effect, while the structural layer does not have a piezoelectric effect. Under the action of alternating stress within the piezoelectric layer, the in-plane stress of the multilayer composite film becomes mismatched, causing the film to warp. Under the action of alternating driving signal, it undergoes periodic warping vibration, thereby emitting ultrasound outward.

[0028] Each MEMS ultrasonic transducer uses a piezoelectric layer made of PZT, ZnO, AlN, KNN or PVDF thin film (a non-toxic and environmentally friendly material with good biocompatibility and meeting the environmentally friendly requirements of modern electronic products), and a structural layer made of Si3N4 or SiO2 thin film.

[0029] The specific structure of the ASIC circuit is as follows: Figure 3 As shown, it includes a power level boosting module, a signal generator module, a power amplifier module, a data acquisition module, and a low-noise preamplifier module.

[0030] The power level boosting module is used to boost the level of the thermoelectric potential (weak potential signal) generated by the Seebeck effect, and is responsible for the power supply of the entire ASIC circuit. The signal generator module is used to generate an excitation signal based on the boosted thermoelectric potential. The waveform parameters of the excitation signal include frequency, period, number of pulses, amplitude, and duration. The power amplifier module is used to amplify the generated excitation signal and send it to the transmitting array of the transceiver MEMS ultrasonic transducer array to excite the ultrasonic transducer to radiate a sufficiently strong sound wave signal.

[0031] The data acquisition module is used to acquire the electrical signals generated by the receiving array of the MEMS ultrasonic transceiver array (to acquire parameters such as flight time and amplitude attenuation). The low-noise preamplifier module is used to filter and amplify the acquired electrical signals to enhance the signal-to-noise ratio, so as to use the processed electrical signals for caries detection of the teeth to be tested.

[0032] It is understood that the tooth decay detection device based on MEMS ultrasonic transducer in this embodiment may also include a host computer 7. In this case, the ASIC circuit also includes a WiFi (or Bluetooth) module. The WiFi (or Bluetooth) module is used to receive parameters that need to change the waveform of the excitation signal generated by the signal generator module, and to wirelessly transmit the electrical signal processed by the low-noise preamplifier module to the host computer (external control device (computer or mobile phone)) for tooth decay detection of the tooth to be tested.

[0033] The ASIC circuit integrates a power level boosting module, a signal generator module, a power amplifier module, a low-noise preamplifier module, a data acquisition module, and a WiFi module, enabling wireless data transmission and miniaturized and convenient design of the detection device.

[0034] Based on the above structure, the dental caries detection process based on the MEMS ultrasonic transducer in this embodiment includes: a signal generator module receives and generates a sinusoidal pulse signal with a frequency equal to the resonant frequency of the transducer unit and a pulse width of three to five cycles, which is then applied to the upper electrode of the MEMS ultrasonic transducer transmitting array after amplitude amplification; under the excitation of alternating current, the piezoelectric layer in the MEMS ultrasonic transducer generates a driving moment due to the inverse piezoelectric effect, causing the structural layer to vibrate and emit ultrasonic waves outward; after passing through a coupling layer with acoustic impedance matching, the ultrasonic waves are transmitted into the tooth to be tested. When the ultrasonic waves encounter the tooth structure interface, tooth contour, or carious part during propagation within the tooth, they are reflected. These reflected ultrasonic echoes cause the structural layer of the MEMS ultrasonic transducer to vibrate when they reach the receiving array. At this time, the piezoelectric layer generates an electrical signal due to the piezoelectric effect. The signal processing module filters and amplifies these signals to eliminate background noise and enhance the useful echo signal; the acquisition module performs digital-to-analog conversion on the signal and stores it; the above process is repeated to sequentially traverse all the teeth to be tested. The data collected from each tooth are used to extract key features, such as the time delay, amplitude variation, and spectral characteristics of the reflected echo signal, and then compared with the key features obtained from normal teeth to determine whether the tooth under test has decay and the location and size of the decayed part.

[0035] One method for determining whether a tooth has decayed is to first determine the flight time of the ultrasonic echo signals from the cementoenamel interface, occlusal surface, and lingual / palatal surface in the ultrasonic echo signals of the same type of normal tooth. If an abnormal waveform appears in the ultrasonic echo signal of the tooth under test during this period, it is considered that decay has occurred, and the larger the waveform amplitude, the more severe the decay or demineralization. Figure 4 A comparison image of ultrasound echo signals between normal teeth and decayed teeth is provided.

[0036] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of the embodiments of the present invention. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the embodiments of the present invention; therefore, the scope of protection of the embodiments of the present invention should be determined by the scope defined in the claims.

Claims

1. A MEMS ultrasonic transducer based caries detection device, characterized in that, The device comprises an ASIC circuit and a transceiving integrated MEMS ultrasonic transducer array connected with each other, and the ASIC circuit and the transceiving integrated MEMS ultrasonic transducer array are attached to the surface of the tooth to be measured after being wrapped by an external coupling layer; wherein the transceiving integrated MEMS ultrasonic transducer array comprises a transmitting array and a receiving array respectively formed by a plurality of MEMS ultrasonic transducers; The ASIC circuit is connected to one end of a wire formed by a polymer multi-period heterojunction thermoelectric material and a gold electrode hinge, and the other end of the wire is placed outside the oral cavity to generate a temperature difference potential by using the Seebeck effect; The ASIC circuit generates an excitation signal according to the temperature difference potential, and each MEMS ultrasonic transducer in the transmitting array generates a driving bending moment due to the inverse piezoelectric effect of the piezoelectric layer under the action of the excitation signal, driving the structure layer to vibrate and emit ultrasonic waves outward, so that the ultrasonic waves are transmitted into the tooth to be measured through the external coupling layer; When each MEMS ultrasonic transducer in the receiving array receives the ultrasonic echo returned by the tooth to be measured, the structure layer vibrates, causing the piezoelectric layer to generate an electrical signal for caries detection of the tooth to be measured due to the piezoelectric effect.

2. The MEMS ultrasonic transducer based caries detection apparatus of claim 1, wherein, The ASIC circuit comprises a power level lifting module, a signal generator module, a power amplifier module, a data acquisition module and a low-noise preamplifier module; The power level lifting module is used for level lifting processing of the temperature difference potential generated by using the Seebeck effect, the signal generator module is used for generating an excitation signal according to the processed temperature difference potential, and the power amplifier module is used for power amplifying the generated excitation signal to send the amplified excitation signal to the transmitting array; The data acquisition module is used for acquiring the electrical signal generated by the receiving array, and the low-noise preamplifier module is used for filtering and signal amplifying processing of the acquired electrical signal to perform caries detection of the tooth to be measured through the processed electrical signal.

3. The MEMS ultrasonic transducer based caries detection apparatus of claim 2, wherein, The device further comprises a host computer, and the ASIC circuit further comprises a WiFi module or a Bluetooth module, both of which are used for transmitting the electrical signal processed by the low-noise preamplifier module to the host computer for caries detection of the tooth to be measured.

4. The MEMS ultrasonic transducer based caries detection apparatus of claim 1, wherein, The transmitting array of the transceiving integrated MEMS ultrasonic transducer array is an internal solid circular array, and the receiving array is an external hollow annular array.

5. The MEMS ultrasonic transducer based caries detection apparatus of claim 4, wherein, The piezoelectric layer of each MEMS ultrasonic transducer in the transmitting array and the receiving array of the transceiving integrated MEMS ultrasonic transducer array adopts a thin film of PZT material, ZnO material, AlN material, KNN material or PVDF material, and the structure layer adopts a thin film of Si3N4 material or SiO2 material.

6. The MEMS ultrasonic transducer based dental caries detection apparatus of claim 1, wherein, The length and width of the device are both less than 6 mm.

7. The MEMS ultrasonic transducer based caries detection apparatus of claim 6, wherein, The device is arranged on the labial surface or the buccal surface of the tooth to be measured.

8. The MEMS ultrasonic transducer based dental caries detection apparatus of claim 1, wherein, The external coupling layer adopts a hydrogel material with an acoustic impedance matching function.

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