Micro material counting device based on piezoelectric sensor

Abstract

The invention discloses a micro material counting device based on a piezoelectric sensor. The micro material counting device comprises a material conveying device, a material collecting device and the piezoelectric sensor. The material conveying device conveys materials to the position above the material collecting device, the material conveying device is provided with a size-adjustable tiny material collecting rail, and transportation and screening of tiny materials of different sizes can be achieved by adjusting the size of the rail. The material collecting device is located on one side of the material conveying device, is lower than the material conveying device and is used for collecting materials falling from the conveying device; the piezoelectric sensor is embedded in the inclined surface of the material collecting device and can detect pressure signals generated when materials fall down and output voltage signals, the output voltage signals are analyzed and processed through the signal processing circuit, and accurate counting of the materials is achieved. The micro material counting device based on the piezoelectric sensor has the advantages of simple structure, low cost, high counting precision, wide application range and the like, and can effectively solve the problems in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of material counting, and in particular to a tiny material counting device based on a piezoelectric sensor, which is suitable for accurately counting tiny materials in health care, industrial production and agricultural production. Background Art

[0002] Counting tiny objects has widespread application in healthcare, industrial production, and agricultural production, for example, counting pills in pharmaceutical production, chips in electronic component production, and seeds in crop seed production. However, existing technologies for counting tiny objects still have some shortcomings in terms of cost, accuracy, and adaptability.

[0003] Traditional counting systems often rely on optical sensors or photoelectric sensing technologies. For example, while devices based on laser scanning or machine vision can achieve non-contact detection, they are susceptible to contamination or interference in dusty environments or when using transparent materials, resulting in increased false positives and high equipment installation and maintenance costs. Furthermore, some counting systems based on pressure sensors use weighing to indirectly infer material quantity, but their accuracy is limited by the minimum resolution of a single weighing, making them difficult to meet the dynamic and continuous counting requirements of small materials. Furthermore, they are only suitable for materials of consistent weight and cannot handle items with large weight variations (such as agricultural products). Piezoelectric technology is gaining attention in the field of particle detection due to its high sensitivity and dynamic response characteristics. For example, patent CN117589344A proposes a piezoelectric sensor device that reduces noise signals by providing an insulating layer between the metal body and the piezoelectric element. However, its design is primarily for static pressure detection and does not address counting scenarios involving dynamic material flows. Patent CN102608005A uses a collision-sensing probe to capture particle impact signals and, combined with a kinetic model, infers the particle size distribution. However, this requires complex calibration and is only applicable to gas-solid two-phase flow scenarios.

[0004] In summary, it is of great significance to develop a small material counting device with simple structure, low cost and high adaptability to solve the core problems of the existing technology, such as poor material size adaptability, insufficient dynamic detection accuracy and weak adaptability to complex environments. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a small material counting device with simple structure, low cost, high counting accuracy and wide application range, so as to meet the urgent demand for accurate counting of small materials in the fields of health care, industrial production, agricultural production, etc.

[0006] Technical solution: The micro-material counting device based on piezoelectric sensors described in the present invention includes a material transportation device, a material collecting device, and a piezoelectric sensor; the material transportation device transports the material to the top of the material collecting device; the material collecting device is located on one side of the material transportation device, and the height of the material collecting device is lower than the material transportation device, and is used to collect materials dropped from the transportation device; the piezoelectric sensor is embedded in the inclined surface of the material collecting device, can detect the pressure signal generated when the material falls, and output a voltage signal, and the output voltage signal is analyzed and processed by the signal processing circuit to achieve accurate counting of the material.

[0007] The material transport device includes a bracket, a baffle, a rotating shaft, a conveyor belt, and a size-adjustable micro-material collecting track.

[0008] The baffle can effectively limit the transportation position of the material and prevent the material from falling during transportation.

[0009] The size-adjustable micro-material collecting track is composed of two groups of chutes and one group of tracks.

[0010] The two sets of slide grooves can be moved left and right respectively to adjust the track size.

[0011] Among them, the track only allows single materials that are consistent with the track size to pass through. Materials that are larger than the track size cannot enter the track and are picked out by staff. Materials that are smaller than the track size will fall from the track gap. By adjusting the track size, the transportation and screening of small materials of different sizes can be achieved.

[0012] Among them, the material collection device consists of two collection boxes. The first collection box close to the transportation device is used to collect smaller materials falling from the track gap. A rectangular hollow is provided below the piezoelectric sensor embedded in the inclined surface of the second collection box. Materials that meet the size standards fall from the rectangular hollow into the second collection box after falling onto the surface of the piezoelectric sensor.

[0013] The piezoelectric sensor is composed of a piezoelectric sensing layer, an electrode layer, a PDMS wrinkled base layer, a Teflon tape packaging layer, and a copper wire.

[0014] The piezoelectric sensing layer is a piezoelectric polymer film. The piezoelectric polymer film material is PVDF and / or P(VDF-TrFE) or other polymer materials with piezoelectricity. The piezoelectric polymer film is prepared by blade coating or spin coating.

[0015] Wherein, the electrode layer is a metal plane electrode such as Pt, Au, Ag, etc. sputtered by a vacuum coating device.

[0016] Among them, the PDMS wrinkled base layer can effectively improve the sensitivity and sensing lower limit of the piezoelectric sensor by increasing the deformation of the piezoelectric sensing layer during the pressure process. At the same time, the presence of the wrinkled microstructure makes the contact area between the piezoelectric sensing layer and the PDMS substrate small and incompletely continuous, reducing the mutual interference between the pressure sensing points; the PDMS wrinkled base layer can be prepared by plasma, ultraviolet light irradiation or metal thin film deposition, combined with pre-stretching or heating and cooling.

[0017] The method for preparing the piezoelectric sensor comprises the following steps:

[0018] (1) Depositing a Pt electrode layer on the surface of the PDMS wrinkled base layer and leading out a copper wire on one side;

[0019] (2) Two PDMS wrinkled substrates with Pt electrode layers deposited thereon are placed opposite to each other with their wrinkled microstructures parallel to each other, a piezoelectric sensing layer is placed in the middle, and then they are packaged with Teflon tape to obtain a piezoelectric sensor.

[0020] Beneficial effects: Compared with the prior art, the present invention has achieved the following significant effects: 1. The present invention prepares a micron-scale PDMS wrinkle structure with good repeatability and controllability, low cost and high precision by pre-stretching combined with plasma surface treatment. 2. The piezoelectric sensor prepared by the present invention innovatively introduces a PDMS wrinkle substrate, which significantly improves the sensitivity of the piezoelectric sensor, and the piezoelectric sensor has a simple structure, is easy to prepare, low cost and has good stability. 3. The present invention proposes a tiny material counting device based on a piezoelectric sensor, which utilizes a piezoelectric sensor to detect the pressure signal generated when the material falls, and analyzes and processes the output voltage signal through a signal processing circuit to achieve accurate counting of the material. The device has the advantages of simple structure, low cost, high counting accuracy and a wide range of applications, and can effectively solve the problems existing in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a three-dimensional diagram of the main structure of a tiny material counting device based on a piezoelectric sensor according to the present invention;

[0022] Figure 2 This is a disassembled three-dimensional diagram of the structure of a micro-material collecting track with adjustable size of a micro-material counting device based on a piezoelectric sensor of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of a piezoelectric sensor of a tiny material counting device based on a piezoelectric sensor according to the present invention;

[0024] Figure 4 Schematic diagram of the PDMS wrinkled base layer prepared in the present invention;

[0025] Figure 5 are atomic force microscope height images, wherein (a) is an atomic force microscope height image of the PDMS wrinkled base layer prepared by the present invention (stretching rate is 20%, plasma treatment time is 10 min); (b) is a cross-sectional view at the white line in (a);

[0026] Figure 6 The output response voltage of the piezoelectric sensor of the present invention to different tiny materials;

[0027] In the figure, 1. material transport device, 2. material collecting device, 3. piezoelectric sensor, 4. bracket, 5. baffle, 6. rotating shaft, 7. conveyor belt, 8. size-adjustable micro-material collecting track, 9. chute, 10. track, 11. first collecting box, 12. second collecting box, 13. rectangular hollow, 14. piezoelectric sensing layer, 15. electrode layer, 16. PDMS wrinkled base layer, 17. Teflon tape packaging layer, 18. copper wire. DETAILED DESCRIPTION

[0028] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] This embodiment provides a small material counting device based on a piezoelectric sensor, such as Figure 1 As shown, the system includes a material transport device 1, a material collection device 2, and a piezoelectric sensor 3. The material transport device 1 transports materials to the top of the material collection device 2. The material collection device 2 is located on the side of the material transport device 1, at a lower height than the material transport device 1, and is used to collect materials that fall from the transport device 1. The piezoelectric sensor 3 is embedded in the inclined surface of the material collection device 2 and can detect the pressure signal generated by the falling material and output a voltage signal. The output voltage signal is analyzed and processed by the signal processing circuit to achieve accurate material counting.

[0030] The signal processing circuit comprises:

[0031] The signal input interface is fixedly connected to the copper wire 18 by welding;

[0032] Amplification module, the input end is directly connected to the signal input interface, and the instrument amplifier is used to realize the primary amplification of the signal;

[0033] The filter module is connected to the output of the amplifier module through PCB traces and includes a second-order Butterworth low-pass filter;

[0034] The counting module receives the output signal of the filtering module through the digital bus, including:

[0035] a voltage comparator to compare the signal with a threshold;

[0036] STM32 microcontroller, accumulates and counts the comparator output pulses;

[0037] The display module is connected to the microcontroller through the SPI interface and uses an OLED screen to display the counting results in real time.

[0038] The material transport device 1 includes a bracket 4, a baffle 5, a rotating shaft 6, a conveyor belt 7, and a size-adjustable micro-material collection track 8. The baffle 5 can effectively limit the transportation position of the material and prevent the material from falling during transportation. The baffle 5 is vertically fixed to the two side edges of the conveyor belt 7 by bolts to form a material transportation channel. The size-adjustable micro-material collection track 8 consists of two sets of chutes 9 and a set of tracks 10. The two sets of chutes 9 can move left and right to adjust the size of the track 10. The chutes 9 are synchronized to move toward or away from each other through a threaded screw mechanism to continuously adjust the width of the track 10. The track 10 only allows a single material that is consistent with the size of the track 10 to pass through. Materials larger than the size of the track 10 cannot enter the track 10 and are picked out by staff. Materials smaller than the size of the track 10 will fall through the gaps in the track 10. By adjusting the size of the track 10, the transportation and screening of micro-materials of different sizes can be achieved.

[0039] The material collection device 2 consists of two collection boxes. The first collection box 11, located near the material transport device 1, is used to collect smaller materials that fall from the gaps between the tracks 10. The second collection box 12 has a rectangular cutout 13 located below the piezoelectric sensor 3 embedded in the inclined surface. After materials that meet the size requirements fall onto the surface of the piezoelectric sensor 3, they fall through the rectangular cutout 13 into the second collection box 12. The opening area of the rectangular cutout 13 is larger than the maximum projected area of the materials, ensuring that the materials can fall freely after hitting the sensor.

[0040] The piezoelectric sensor 3 includes a piezoelectric sensing layer 14, an electrode layer 15, a PDMS corrugated base layer 16, a Teflon tape packaging layer 17, and a copper wire 18. Figure 3 As shown, in this embodiment, the piezoelectric sensing layer 14 is a P(VDF-TrFE) thin film prepared by spin coating, and the electrode layer 15 is a Pt planar electrode. The piezoelectric sensing layer 14 is bonded to the electrode layer 15 with a conductive adhesive, and the PDMS corrugated base layer 16 is bonded to the electrode layer 15 through plasma treatment.

[0041] The preparation method of the PDMS wrinkled base layer 16 comprises the following steps:

[0042] (1) The PDMS prepolymer and curing agent were mixed evenly in a certain mass ratio, vacuum degassed, and evenly coated on a clean glass plate with a doctor blade. After heating and curing, a flat PDMS film was obtained.

[0043] (2) The flat PDMS film obtained in step (1) is pre-stretched along a uniaxial direction at a stretching rate of 10% to 30%, and then placed in a plasma cleaning machine for O2 plasma surface treatment for 5 to 10 minutes. A dense hard layer of silicon oxide (SiOx) is formed on the surface of the PDMS film, forming a modulus difference with the soft PDMS substrate below, providing a driving force for wrinkle formation.

[0044] (3) After plasma surface treatment, the pre-stretching strain is gradually released, causing the surface oxide layer to become unstable under compressive stress, forming periodic one-dimensional wrinkles with the wrinkle direction perpendicular to the pre-stretching direction.

[0045] (4) After releasing the pre-stretching strain, the PDMS film is placed in an environment of 80-90°C for thermal annealing for 15-30 min. By thermally activating the movement of the PDMS molecular chains, the internal residual stress is reduced, and the wrinkle period and amplitude are made consistent, thus obtaining a PDMS base layer with a regular and uniform wrinkle structure, such as Figure 4 As shown. Figure 4 It is only for illustrating the wrinkled microstructure of the PDMS base layer and does not represent the actual state of the PDMS wrinkled base layer 16 , and should not be understood as limiting the present invention.

[0046] Figure 5 (a) is an atomic force microscope height image of the PDMS wrinkled base layer 16 prepared by the present invention (stretching rate is 20%, plasma treatment time is 10 minutes); Figure 5 Middle (b) is a cross-sectional view at the white line in the height map, where the wrinkle microstructure can be clearly seen. The wavelength of the wrinkles is 4.09 μm and the amplitude is 930.655 nm.

[0047] The preparation method of the piezoelectric sensor 3 includes the following steps:

[0048] (1) P(VDF-TrFE) powder was dissolved in DMF solvent (12 wt.%) and a film with controllable thickness was spin-coated using a spin coater. The film was dried at 70°C for 20-60 min and annealed at 140°C for 1-5 h to allow the excess solvent to evaporate completely, thereby obtaining a P(VDF-TrFE) piezoelectric film.

[0049] (2) Using a tool, the prepared PDMS wrinkled base layer 16 is cut into small base layers of 2.5 cm×2 cm. A Pt electrode layer 15 is deposited on the surface of the cut PDMS wrinkled base layer 16, and a copper wire 18 is led out from one of the short sides.

[0050] (3) Two PDMS wrinkled base layers 16 with Pt electrode layers 15 deposited thereon are placed opposite to each other, with the wrinkled microstructures of the two PDMS base layers being parallel to each other, and a P (VDF-TrFE) piezoelectric film is placed in the middle, and then they are packaged with Teflon tape to obtain a piezoelectric sensor 3.

[0051] Figure 6 The output response voltage of the piezoelectric sensor 3 prepared for the present invention for four kinds of tiny materials, namely rice seeds (0.020g), tablets (0.266g), paper clips (0.470g), and nuts (0.688g), can be seen from the figure. The piezoelectric sensor 3 can detect the pressure signal generated when the material falls, output a response voltage, and analyze and process the output voltage signal through the subsequent signal processing circuit to achieve accurate counting of the material. The minimum material weight that can be detected is as low as 0.02g, which can basically meet the counting needs of various tiny materials.

Claims

1. A micro material counting device based on a piezoelectric sensor, characterized in that: include: A material transport device (1) is used to transport materials to above the material collecting device (2); A material collecting device (2) is located on one side of the material transporting device (1) and is lower in height than the material transporting device (1), and is used to receive materials dropped from the material transporting device (1); A piezoelectric sensor (3) is embedded in the inclined surface of the material collecting device (2) and is used to detect a pressure signal generated when the material falls and output a voltage signal; The signal processing circuit is electrically connected to the piezoelectric sensor (3) and is used for analyzing and processing the output voltage signal to achieve accurate counting of materials.

2. The device according to claim 1, characterized in that: The material transport device (1) comprises a bracket (4), a baffle (5), a rotating shaft (6), a conveyor belt (7) and a size-adjustable micro-material collecting track (8); wherein the baffle (5) is fixed to both sides of the conveyor belt (7) for limiting the transport path of the material; and the size-adjustable micro-material collecting track (8) is arranged at the end of the conveyor belt (7) for screening materials of different sizes.

3. The device according to claim 2, characterized in that: The size-adjustable micro-material collecting track (8) is composed of two groups of chutes (9) that can move left and right and one group of tracks (10); the chutes (9) adjust the width of the tracks (10) by sliding, so that the tracks (10) only allow single materials that are consistent with the set size to pass through, while materials that do not meet the size are separated.

4. The device according to claim 1, characterized in that: The material collecting device (2) comprises a first collecting box (11) and a second collecting box (12); the first collecting box (11) is located below the material transport device (1) and is used to collect undersized materials that fall from the gap between the tracks (10); the piezoelectric sensor (3) is embedded in the inclined surface of the second collecting box (12), and a rectangular hollow (13) is provided below the second collecting box, so that materials that meet the size requirements fall into the box through the hollow (13) after hitting the piezoelectric sensor (3).

5. The device according to claim 1, characterized in that: The piezoelectric sensor (3) comprises a piezoelectric sensing layer (14), an electrode layer (15) and a PDMS wrinkled base layer (16) stacked in sequence, is externally wrapped by a Teflon tape packaging layer (17), and is connected to a signal processing circuit via a copper wire (18).

6. The device according to claim 5, characterized in that: The PDMS wrinkle base layer (16) forms a periodic wrinkle structure through pre-stretching and plasma treatment, and the wrinkle direction is perpendicular to the pre-stretching direction, which is used to increase the deformation of the piezoelectric sensing layer (14) and improve the sensitivity.

7. The device according to claim 5, characterized in that: The piezoelectric sensing layer (14) is a PVDF or P (VDF-TrFE) piezoelectric polymer film, which is prepared by a spin coating method or a blade coating method.

8. The device according to claim 5, characterized in that: The electrode layer (15) is a Pt, Au or Ag metal plane electrode sputtered by a vacuum coating apparatus and is used for collecting piezoelectric signals.

9. The device according to claim 1, characterized in that: The minimum detection weight of the piezoelectric sensor (3) is 0.02 g, which can meet the dynamic continuous counting requirements of tiny materials such as tablets, seeds, and electronic components.

10. The device according to any one of claims 1 to 9, characterized in that: The signal processing circuit comprises an amplifying module, a filtering module and a counting module. The input end of the amplifying module is directly connected to the copper wire (18) of the piezoelectric sensor (3) for amplifying weak piezoelectric signals; the input end of the filtering module is connected to the output end of the amplifying module for filtering out environmental noise and signal interference; the input end of the counting module is connected to the output end of the filtering module for identifying effective voltage pulses and counting the number of materials.

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