Valveless piezoelectric micropump based on lead-free piezoelectric ceramics

Abstract

The present invention provides a valveless piezoelectric micropump based on lead-free piezoelectric ceramics, which includes a fluid excitation unit and a first substrate and a second substrate respectively arranged on both sides of the fluid excitation unit. The fluid excitation unit includes a cavity plate, and the liquid channel of the cavity plate includes a variable diameter section, and the variable diameter section has a shape with different widths at both ends, the end with a larger width is the large diameter end, and the end with a smaller width is the small diameter end. The kinetic energy loss of the liquid flowing from the small diameter end to the large diameter end is smaller than the loss of the liquid flowing from the large diameter end to the small diameter end, and a net flow rate in a single direction can be achieved under the drive of a lead-free piezoelectric oscillator. A stepped structure is nested in the variable diameter section, with the highest platform of the step at the small diameter end and gradually descending towards the large diameter end. The stepped structure uses gravitational potential energy and asymmetric geometric structure to further enhance the suppression of fluid backflow by the variable diameter section, thereby improving the liquid delivery efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of piezoelectric micropumps, and in particular relates to a valveless piezoelectric micropump having lead-free piezoelectric ceramics. Background Art

[0002] With the rapid development of microelectronics technology, the demand for miniaturized, high-performance fluid delivery devices is growing. Microelectromechanical systems (MEMS) technology, a key technology for miniaturizing devices, has been widely used in fields such as biomedicine, consumer electronics, automotive manufacturing, and aerospace. Traditional mechanical pumps, due to their large size, high energy consumption, high heat generation, and low infusion accuracy, are unable to meet the requirements of microfluidic systems. In contrast, micropumps based on MEMS technology offer advantages such as small size, low energy consumption, low heat generation, and high infusion accuracy, making them an ideal alternative to traditional mechanical pumps.

[0003] There are various ways to drive micropumps. Among them, piezoelectric micropumps driven by the piezoelectric effect are considered to be the most suitable driving method for microfluidic systems such as transdermal drug delivery and liquid cooling of 3C products due to their simple structure, low energy consumption, high output flow and pressure, and high flow control accuracy. According to the structure of the piezoelectric actuator, piezoelectric micropumps can be divided into stacked type and thin film type. Stacked micropumps increase the driving force by stacking thicker piezoelectric ceramic blocks, while thin film micropumps use thinner piezoelectric ceramic films to achieve higher vibration displacement. Although stacked micropumps have certain advantages in output pressure and flow, thin film micropumps may have a higher maximum output flow under no back pressure or low back pressure conditions, and their uniformity and consistency are better, making them more suitable for large-scale production and cost control.

[0004] Regarding the valve structure of piezoelectric micropumps, traditional valve-type piezoelectric micropumps control unidirectional fluid flow through mechanical or flexible valves. While these offer high output flow and low backflow, mechanical losses in the valves reduce device reliability and service life, and they are prone to clogging in narrow locations. Consequently, valveless piezoelectric micropumps are attracting increasing attention due to their simpler structure and maintenance-free operation. While valveless micropumps achieve unidirectional fluid flow by modifying the geometry of the pump body or flow channel, current valveless micropumps suffer from relatively high backflow, making them incapable of achieving stable and constant flow output.

[0005] In addition, with increasingly stringent environmental protection requirements, traditional lead-containing piezoelectric ceramics (such as lead zirconate titanate, PZT) are restricted due to the risk of environmental pollution.

[0006] Therefore, there is an urgent need for a piezoelectric micropump that is environmentally friendly, can suppress reflux and improve infusion efficiency. Summary of the Invention

[0007] The object of the present invention is to provide a valveless piezoelectric micropump with lead-free piezoelectric ceramics, which is environmentally friendly and safe, and can also suppress reflux and improve infusion efficiency.

[0008] The above-mentioned object of the present invention is achieved through the following technical solutions.

[0009] In the context of the present invention, the term "diffusion angle" refers to twice the angle θ between the side of the cross section of the variable diameter section in the horizontal direction of the cavity plate and the horizontal line, that is, the diffusion angle is 2θ. Figure 9 As shown, the figure shows the angle θ between the side and the horizontal line.

[0010] The present invention provides a valveless piezoelectric micropump based on a lead-free piezoelectric ceramic sheet, which comprises a fluid excitation unit and a first substrate and a second substrate respectively arranged on both sides of the fluid excitation unit;

[0011] The fluid excitation unit includes: a lead-free piezoelectric ceramic sheet, a vibration sheet, and a cavity plate. The cavity plate has a central through hole in the thickness direction. The cavity plate is sealed with the first substrate and the vibration sheet at both sides to form a pump cavity at the central through hole.

[0012] The cavity plate is further provided with a first channel and a second channel extending in different directions toward the pump cavity in the thickness direction, and a first through hole serving as a liquid input cavity and a second through hole serving as a liquid output cavity located at the ends of the first channel and the second channel respectively;

[0013] wherein at least a portion of the first channel is configured as a first diameter-reducing section, with its large diameter end facing the pump cavity and its small diameter end facing the first through hole; and at least a portion of the second channel is configured as a second diameter-reducing section, with its large diameter end facing the second through hole and its small diameter end facing the pump cavity;

[0014] Wherein, the first diameter-changing section and the second diameter-changing section are respectively provided with a first step structure and a second step structure which gradually descends from the small diameter end to the large diameter end;

[0015] Through holes are respectively formed on the second substrate and the vibration plate at positions corresponding to the first through holes and the second through holes.

[0016] The inventors of this application unexpectedly discovered that the stepped structure of the present invention, when incorporated within the variable diameter section, significantly suppresses backflow in piezoelectric micropumps, improving the micropump's delivery efficiency. This is likely due to the fact that the highest platform of the steps is located at the small diameter end, descending gradually toward the large diameter end. Liquid moving from the small diameter end to the large diameter end follows the steps downward, while liquid moving from the large diameter end to the small diameter end moves against the steps upward. This structure leverages gravitational potential energy and asymmetric geometry to further enhance the variable diameter section's suppression of fluid backflow, thereby improving the micropump's delivery efficiency.

[0017] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, a through hole is formed on the second substrate at a position corresponding to the central through hole to accommodate the lead-free piezoelectric ceramic sheet.

[0018] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramic sheets described in the present invention, the first channel includes a first cylindrical section, a first diameter-reducing section and a first buffer section arranged along the direction from the first through hole to the central through hole; the second channel includes a second buffer section, a second diameter-reducing section and a second cylindrical section arranged along the direction from the central through hole to the second through hole.

[0019] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet described in the present invention, the first column segment, the second column segment, the first buffer segment and the second buffer segment are each independently a cylinder or a square column.

[0020] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramic sheets described in the present invention, the cross-sections of the first variable diameter section and the second variable diameter section in the horizontal plane direction of the cavity plate are isosceles trapezoidal, and the cross-sections in the direction perpendicular to the horizontal plane of the cavity plate are rectangular.

[0021] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, in the first channel, the opening width of the small diameter end of the first diameter-changing section is smaller than the inner diameter or width of the first cylindrical section.

[0022] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramics of the present invention, in the first channel, the opening width of the large diameter end of the first diameter-changing section is less than or equal to the inner diameter or width of the first buffer section.

[0023] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, in the second channel, the opening width of the small diameter end of the second diameter-changing section is smaller than the inner diameter or width of the second buffer section.

[0024] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramics of the present invention, in the second channel, the opening width of the large diameter end of the second diameter-varying section is less than or equal to the inner diameter or width of the second cylindrical section.

[0025] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramic sheets described in the present invention, the bottom surfaces of the first cylindrical section, the first diameter-reducing section and the first buffer section are on the same horizontal plane; the bottom surfaces of the second cylindrical section, the second diameter-reducing section and the second buffer section are on the same horizontal plane.

[0026] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramics described in the present invention, the first diameter-changing section is a cylinder with an expanded diameter from the first through hole to the central through hole; the second diameter-changing section is a cylinder with an expanded diameter from the central through hole to the second through hole.

[0027] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, in the first channel, the inner diameter of the small diameter end of the first diameter-changing section is smaller than the inner diameter or width of the first cylindrical section.

[0028] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramics of the present invention, in the first channel, the inner diameter of the large diameter end of the first diameter-changing section is smaller than or equal to the inner diameter or width of the first buffer section.

[0029] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, in the second channel, the inner diameter of the small diameter end of the second diameter-changing section is smaller than the inner diameter or width of the second buffer section.

[0030] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramics of the present invention, in the second channel, the inner diameter of the large diameter end of the second diameter-changing section is less than or equal to the inner diameter or width of the second cylindrical section.

[0031] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, the diameters of the first through hole and the second through hole are respectively smaller than or equal to the diameter of the central through hole.

[0032] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, the diameter of the lead-free piezoelectric ceramic sheet is smaller than the diameter of the central through hole.

[0033] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramics described in the present invention, the length of the first buffer segment is smaller than the length of the first diameter-changing segment; the length of the second buffer segment is smaller than the length of the second diameter-changing segment.

[0034] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, the sum of the lengths of the first cylindrical section and the first buffer section is 2-3 times that of the first diameter-changing section.

[0035] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, the sum of the lengths of the second cylindrical segment and the second buffer segment is 2-3 times that of the second diameter-varying segment.

[0036] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, the diffusion angles of the first diameter-changing section and the second diameter-changing section are 10-30°, preferably 12-20°, and more preferably 16°.

[0037] Preferably, in the valveless piezoelectric micropump based on the lead-free piezoelectric ceramic sheet of the present invention, the lead-free piezoelectric ceramic sheet is a potassium sodium niobate-based lead-free piezoelectric ceramic sheet.

[0038] Preferably, in the valveless piezoelectric micropump based on a lead-free piezoelectric ceramic described herein, the lead-free piezoelectric ceramic is a potassium sodium niobate-based lead-free piezoelectric ceramic with a thickness between 0.1 and 0.2 mm and a diameter of approximately 8 mm, for example. It can be produced by a tape casting process. Potassium sodium niobate-based (KNN) lead-free piezoelectric ceramics exhibit high piezoelectricity and excellent temperature stability. This material not only meets environmental requirements but also exhibits excellent biocompatibility, making it suitable for microfluidic systems in fields such as biomedicine and consumer electronics.

[0039] Preferably, in the valveless piezoelectric micropump based on lead-free piezoelectric ceramics of the present invention, the thickness of the pump cavity is greater than the thickness of the vibrating plate. For example, the thickness of the pump cavity is 0.3-0.5 mm, and the thickness of the vibrating plate is 0.1 mm.

[0040] In a specific embodiment of the present invention, the cavity plate of the present invention can be manufactured by 3D printing technology.

[0041] In a specific embodiment of the present invention, both the variable diameter section and the nested stepped structure of the present invention can be manufactured by 3D printing technology.

[0042] The present invention has the following beneficial effects:

[0043] 1. Environmental protection and biocompatibility

[0044] Applications of lead-free piezoelectric ceramics: Potassium sodium niobate (KNN)-based lead-free piezoelectric ceramic films with excellent biocompatibility replace traditional lead-containing piezoelectric ceramics (such as lead zirconate titanate, PZT). This lead-free piezoelectric ceramic not only meets environmental requirements and avoids lead contamination, but also passes biocompatibility testing, making it suitable for microfluidic systems in fields such as biomedicine and consumer electronics.

[0045] This improves the applicability of micropumps in environmental and biomedical applications, meeting the strict global requirements for environmental protection and biosafety.

[0046] 2. Efficient fluid delivery performance

[0047] Variable diameter sections and stepped structure: By designing variable diameter sections with varying widths on both sides and nesting stepped structures within them, the ability to suppress fluid backflow is significantly enhanced by utilizing the principles of fluid mechanics and gravitational potential energy. The kinetic energy loss is minimal when the liquid flows from the smaller diameter end to the larger diameter end, while the kinetic energy loss is greater when flowing from the larger diameter end to the smaller diameter end, thus achieving a net flow in a single direction.

[0048] This reduces the reflux rate, improves the infusion efficiency of the micropump, ensures stable flow output, and solves the problem of large reflux in traditional valveless micropumps.

[0049] 3. Optimized structural design

[0050] Piezoelectric actuator design: Lead-free piezoelectric ceramic discs with a thickness of 0.1-0.2mm are manufactured through a tape-casting process, resulting in high piezoelectricity and excellent temperature stability. This design not only improves vibration efficiency but also enhances the reliability and stability of the micropump.

[0051] Integrated structural design: The pump chamber, vibrating plate, liquid inlet and outlet channels, and liquid inlet and outlet chambers are manufactured in an integrated manner using 3D printing technology, ensuring precise fit and a tight seal. This design simplifies the manufacturing process, reduces production costs, and improves the precision and consistency of the micropump's manufacturing.

[0052] 4. Wide application applicability

[0053] Versatility: This lead-free, valveless piezoelectric micropump is suitable for a variety of applications, including transdermal drug delivery in the biomedical field and liquid cooling systems for consumer electronics. Its excellent biocompatibility and environmental friendliness give it significant advantages in these areas. This expands the application range of micropumps and meets the demand for miniaturized, high-performance fluid delivery devices across various industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

[0055] Figure 1 A schematic diagram of a piezoelectric micropump according to a specific embodiment of the present invention;

[0056] Figure 2 Schematic cross-sectional view of a cavity plate of a piezoelectric micropump according to a specific embodiment of the present invention;

[0057] Figure 3 A schematic longitudinal section of a piezoelectric micropump according to a specific embodiment of the present invention;

[0058] Figure 4 An enlarged view of a schematic cross-sectional and longitudinal section of a stepped structure according to a specific embodiment of the present invention;

[0059] Figure 5 A cross-sectional schematic diagram of a working state of pumping liquid according to a specific embodiment of the present invention;

[0060] Figure 6 A longitudinal sectional schematic diagram of a working state of pumping liquid according to a specific embodiment of the present invention;

[0061] Figure 7 A cross-sectional schematic diagram of a working state of pumping out liquid according to a specific embodiment of the present invention;

[0062] Figure 8 A longitudinal sectional schematic diagram of a working state of pumping out liquid according to a specific embodiment of the present invention;

[0063] Figure 9 Schematic diagram of the angle θ between the side of the variable diameter section and the horizontal line in the cross section in the horizontal direction of the cavity plate according to a specific embodiment of the present invention;

[0064] Wherein, the reference numerals:

[0065] 100-lead-free piezoelectric ceramic sheet; 200-second substrate; 300-vibration plate; 400-cavity plate; 500-step structure; 600-first substrate; 401-center through hole; 402-second column section; 403-second through hole; 404-second diameter-reducing section; 405-second buffer section; 406-first through hole; 407-first column section; 408-first diameter-reducing section; 409-first buffer section; 501-first step structure; 502-second step structure. DETAILED DESCRIPTION

[0066] With reference to the accompanying drawings, a schematic diagram of a valveless piezoelectric micropump using lead-free piezoelectric ceramics disclosed herein is described in detail. While the drawings are provided to illustrate some embodiments of the present invention, they are not necessarily drawn to the dimensions of a specific embodiment. Certain components in the drawings may be repositioned as needed without affecting the technical effect. The phrase "in the accompanying drawings" or similar terms appearing in this specification do not necessarily refer to all figures or examples.

[0067] Certain directional terms used in the following description of the drawings, such as "upper," "upper," and other directional terms, should be understood to have their normal meanings and refer to those directions when the drawings are normally viewed. Unless otherwise indicated, the directional terms used in this specification are generally in accordance with conventional directions understood by those skilled in the art.

[0068] Reference Figures 1 to 3The present invention provides a valveless piezoelectric micropump based on a lead-free piezoelectric ceramic sheet, which includes a fluid excitation unit and a first substrate 600 and a second substrate 200 respectively arranged on both sides of the fluid excitation unit;

[0069] The fluid excitation unit includes: a lead-free piezoelectric ceramic sheet 100, a vibration plate 300, and a cavity plate 400. The cavity plate 400 has a central through-hole 401 formed in the thickness direction. The cavity plate 400 is sealed with the first substrate 600 and the vibration plate 300 on both sides to form a pump cavity at the central through-hole 401.

[0070] The cavity plate 400 is further provided with a first channel and a second channel extending in different directions toward the pump cavity in the thickness direction, as well as a first through hole 406 serving as a liquid input cavity and a second through hole 403 serving as a liquid output cavity located at the ends of the first channel and the second channel, respectively.

[0071] At least a portion of the first channel is configured as a first diameter-reducing section 408, with its large diameter end facing the pump cavity and its small diameter end facing the first through hole 406; at least a portion of the second channel is configured as a second diameter-reducing section 404, with its large diameter end facing the second through hole 403 and its small diameter end facing the pump cavity;

[0072] The first diameter-changing section 408 and the second diameter-changing section 404 are respectively provided with a first step structure 501 and a second step structure 502 which gradually descends from the small diameter end to the large diameter end.

[0073] Through holes are respectively formed on the second substrate 200 and the vibration plate 300 at positions corresponding to the first through hole 406 and the second through hole 403 .

[0074] The buffer section is designed to facilitate connections between the pump chamber, the reducer, and the inlet and outlet channels, avoiding asymmetric connections between the small and large diameter ends of the reducer and the pump chamber. This asymmetric connection causes the flow rate entering the large diameter end to be consistently greater than the flow rate entering the small diameter end, potentially reducing or even destroying the flow-rectifying effect of the structure and should be avoided.

[0075] When the stepped structure of the present invention is incorporated within the variable diameter section, it significantly suppresses backflow in piezoelectric micropumps, improving the micropump's delivery efficiency. This is likely due to the fact that the highest platform of the steps is located at the small diameter end, descending gradually toward the large diameter end. Liquid moving from the small diameter end to the large diameter end follows the steps downward, while liquid moving from the large diameter end to the small diameter end moves upward against the steps. This structure leverages gravitational potential energy and asymmetric geometry to further enhance the variable diameter section's suppression of fluid backflow, improving the micropump's delivery efficiency.

[0076] In this embodiment, a through hole is opened at a position of the second substrate 200 corresponding to the central through hole 401 to accommodate the lead-free piezoelectric ceramic sheet 100 .

[0077] In this embodiment, the first channel includes a first cylindrical section 407, a first diameter-reducing section 408 and a first buffer section 409 arranged along the direction of the first through hole 406 toward the central through hole 401; the second channel includes a second buffer section 405, a second diameter-reducing section 404 and a second cylindrical section 402 arranged along the direction of the central through hole 401 toward the second through hole 403.

[0078] In this embodiment, the first column segment 407, the second column segment 402, the first buffer segment 409, and the second buffer segment 405 are square columns. The first and second diameter-reducing segments 408 and 404 have isosceles trapezoidal cross-sections in the horizontal direction of the cavity plate and rectangular cross-sections in the direction perpendicular to the horizontal plane of the cavity plate.

[0079] In this embodiment, in the first channel, the opening width of the small diameter end of the first reducing section 408 is smaller than the width of the first cylindrical section 407, with the opening width of the small diameter end being 0.2 mm. In the first channel, the opening width of the large diameter end of the first reducing section 408 is smaller than the width of the first buffer section 409. In the second channel, the opening width of the small diameter end of the second reducing section 404 is smaller than the width of the second buffer section 405, with the opening width of the small diameter end being 0.2 mm. In the second channel, the opening width of the large diameter end of the second reducing section 404 is smaller than the width of the second cylindrical section 402. The bottom surfaces of the first cylindrical section 407, the first reducing section 408, and the first buffer section 409 are on the same horizontal plane; the bottom surfaces of the second cylindrical section 402, the second reducing section 404, and the second buffer section 405 are on the same horizontal plane.

[0080] In this embodiment, it can be understood that the first column segment 407, the first diameter-reducing segment 408 and the first buffer segment 409 are connected from top to bottom on the cavity plate; the second column segment 402, the second diameter-reducing segment 404 and the second buffer segment 405 are also connected from top to bottom on the cavity plate.

[0081] In this embodiment, the diameters of the first through hole 406 and the second through hole 403 are respectively smaller than the diameter of the central through hole 401. The diameter of the central through hole is 12 mm, and the thickness is 0.5 mm. The diameter of the lead-free piezoelectric ceramic sheet 100 is 8 mm. The length of the first buffer section 409 is smaller than the length of the first reducing section 408; the length of the second buffer section 405 is smaller than the length of the second reducing section 404. The lengths of the first reducing section 408 and the second reducing section 404 are 1.0 mm. The combined lengths of the first cylindrical section 407 and the first buffer section 409 are 2.5 times that of the first reducing section 408. The combined lengths of the second cylindrical section 402 and the second buffer section 405 are 2.5 times that of the second reducing section 404. The divergence angles of the first reducing section 408 and the second reducing section 404 are 16°.

[0082] In this embodiment, the lead-free piezoelectric ceramic sheet is a potassium sodium niobate-based lead-free piezoelectric ceramic sheet with a thickness of 0.2 mm and a diameter of 8 mm, which is manufactured by a tape casting process. The upper and lower surfaces of the ceramic sheet are coated with silver electrode layers, which are connected to the positive and negative electrodes of the power supply through wires. It can exceed 300 pC / N, and its performance is close to that of mature PZT-4 products on the market.

[0083] In this embodiment, the second substrate 200 and the first substrate 600 are manufactured using photosensitive resin 3D printing technology, which has good waterproofness and vibration conduction efficiency. The first substrate 600 and the cavity plate 400 are integrally formed using 3D printing technology to ensure structural integrity and sealing.

[0084] In this embodiment, the vibrating plate 300 is made of brass or beryllium copper, which has a good effect of amplifying piezoelectric vibrations and has a thickness of 0.1 mm. The vibrating plate 300 is bonded to the lead-free piezoelectric ceramic plate 100 at room temperature using epoxy resin to form a piezoelectric vibrator. The second substrate 200 is bonded to the piezoelectric vibrator at room temperature using a highly viscous waterproof adhesive, forming a complete package of the upper layer of the pump body, ensuring liquid sealing and improving the efficiency of vibration conduction. When the lead-free piezoelectric ceramic plate 100 vibrates under the power drive, the vibrating plate 300 vibrates accordingly and amplifies the amplitude, generating a pressure change in the pump chamber, thereby driving the liquid to flow.

[0085] In this embodiment, the highest platform of the steps is located at the smaller diameter end, with the steps gradually descending toward the larger diameter end. Liquid moving from the smaller diameter end to the larger diameter end will follow the steps downward, while liquid moving from the larger diameter end to the smaller diameter end will move against the steps upward. This structure utilizes gravitational potential energy and asymmetric geometry to further enhance the ability of the variable diameter section to suppress fluid backflow, thereby improving the micropump's infusion efficiency.

[0086] In this embodiment, the entire pump structure is fabricated using 3D printing technology, ensuring precise fit of all components and a leak-tight overall structure. 3D printing not only simplifies the manufacturing process but also improves the precision and consistency of the micropump's manufacturing. To ensure biocompatibility, enhance the pump's viscoelasticity, and improve vibration transmission efficiency, the pump body can also be fabricated using PDMS soft lithography. Both 3D printing and PDMS soft lithography offer advantages such as low cost, high yield, short production cycles, and excellent overall sealing.

[0087] The overall working principle of the piezoelectric micropump of the present invention is as follows:

[0088] When the power is turned on, the lead-free piezoelectric ceramic sheet 100 vibrates under the action of the electric field. The vibration is transmitted to the pump chamber through the vibrating sheet 300, causing the pressure in the pump chamber to change. When the pressure in the pump chamber decreases, the liquid flows into the liquid input chamber through the external pipe, and enters the pump chamber from the liquid input channel through the small diameter end of the first reducing section 408; at this time, a very small amount of liquid is also sucked into the liquid output channel side and enters the pump chamber through the second reducing section 404. Because the second stepped structure 502 is provided in the second reducing section 404 of the present invention, the amount of liquid entering the pump chamber from the liquid output channel side can be suppressed. In general, the amount of liquid sucked into the liquid input channel side far exceeds the amount of liquid sucked into the liquid output channel side.

[0089] When the pressure within the pump chamber increases, liquid flows from the pump chamber through the larger diameter end of the second reducing section 404 into the liquid output chamber and is then discharged through the external pipe. At this point, a very small amount of liquid is also discharged from the liquid input channel, passing through the first reducing section 408 and into the liquid input chamber. Because the first reducing section 408 of the present invention includes a built-in first stepped structure 501, the amount of liquid discharged from the liquid input channel is suppressed. Overall, the amount of liquid discharged from the liquid output channel far exceeds that discharged from the liquid input channel.

[0090] The working principle of the variable diameter section and stepped structure of the present invention, which generates a single-directional net flow, is that when liquid flows from the small-diameter end (narrower end) to the large-diameter end (wider end), the liquid flow rate decreases while the static pressure increases, allowing the liquid to flow smoothly into the pump chamber. Conversely, when liquid flows from the large-diameter end to the small-diameter end, the liquid flow rate increases but the static pressure decreases, making it difficult for the liquid to flow out of the pump chamber normally. Therefore, the flow rate of liquid flowing from the small-diameter end to the large-diameter end is greater than the flow rate from the large-diameter end to the small-diameter end, thereby achieving a single-directional net flow. In addition, when the fluid flows from the small-diameter end to the large-diameter end, it will follow the steps downward, while when it moves from the large-diameter end to the small-diameter end, it will move against the steps upward. This utilizes gravitational potential energy and the asymmetric geometry to further enhance the variable diameter section's suppression of fluid backflow, thereby improving the micropump's infusion efficiency.

Claims

1. A valveless piezoelectric micropump based on a lead-free piezoelectric ceramic sheet, comprising a fluid excitation unit and a first substrate and a second substrate respectively disposed on both sides of the fluid excitation unit. The fluid excitation unit includes: A lead-free piezoelectric ceramic sheet, a vibrating sheet, and a cavity plate, wherein the cavity plate has a central through hole formed in the thickness direction, and the cavity plate is sealedly connected to the first substrate and the vibrating sheet at both sides to form a pump cavity at the central through hole; The cavity plate is further provided with a first channel and a second channel extending in different directions toward the pump cavity in the thickness direction, and a first through hole serving as a liquid input cavity and a second through hole serving as a liquid output cavity located at the ends of the first channel and the second channel respectively; wherein at least a portion of the first channel is configured as a first diameter-reducing section, with its large diameter end facing the pump cavity and its small diameter end facing the first through hole; and at least a portion of the second channel is configured as a second diameter-reducing section, with its large diameter end facing the second through hole and its small diameter end facing the pump cavity; Wherein, the first diameter-changing section and the second diameter-changing section are respectively provided with a first step structure and a second step structure which gradually descends from the small diameter end to the large diameter end; The second substrate and the vibration plate are respectively provided with through holes at positions corresponding to the first through holes and the second through holes; The first channel includes a first cylindrical section, a first diameter-reducing section, and a first buffer section arranged along the direction from the first through hole to the central through hole; the second channel includes a second buffer section, a second diameter-reducing section, and a second cylindrical section arranged along the direction from the central through hole to the second through hole; The second substrate is provided with a through hole at a position corresponding to the central through hole to accommodate the lead-free piezoelectric ceramic sheet; The lead-free piezoelectric ceramic sheet is a potassium sodium niobate-based lead-free piezoelectric ceramic sheet.

2. The valveless piezoelectric micropump based on lead-free piezoelectric ceramics according to claim 1, wherein: The first column segment, the second column segment, the first buffer segment and the second buffer segment are each independently a cylinder or a square cylinder.

3. The valveless piezoelectric micropump based on lead-free piezoelectric ceramics according to claim 2, wherein: The cross-sections of the first diameter-changing section and the second diameter-changing section in the horizontal plane direction of the cavity plate are isosceles trapezoidal, and the cross-sections in the direction perpendicular to the horizontal plane of the cavity plate are rectangular.

4. The valveless piezoelectric micropump based on lead-free piezoelectric ceramics according to claim 3, wherein: In the first channel, the opening width of the small diameter end of the first diameter-changing section is smaller than the inner diameter or width of the first column section.

5. The valveless piezoelectric micropump based on lead-free piezoelectric ceramics according to claim 3, wherein: In the first channel, the opening width of the large-diameter end of the first diameter-changing section is smaller than or equal to the inner diameter or width of the first buffer section.

6. The valveless piezoelectric micropump based on lead-free piezoelectric ceramics according to claim 3, wherein: In the second channel, the opening width of the small-diameter end of the second diameter-changing section is smaller than the inner diameter or width of the second buffer section.

7. The valveless piezoelectric micropump based on lead-free piezoelectric ceramics according to claim 1, wherein: The first diameter-changing section is a cylinder with an expanding diameter from the first through hole to the central through hole; the second diameter-changing section is a cylinder with an expanding diameter from the central through hole to the second through hole.

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