Single liquid drop generation device based on piezoelectric ceramics

Abstract

The invention discloses a piezoelectric ceramic-based single droplet generation device, which comprises a microcavity liquid chamber, a piezoelectric driving assembly, a micropore nozzle, a hydraulic adjusting system and an electric control driving module, the bottom of the microcavity liquid chamber is provided with a nozzle interface, and the volume of the internal cavity is adaptive to trace liquid storage and pressure transmission; the piezoelectric driving assembly comprises a piezoelectric ceramic element which is connected with the micro-cavity liquid chamber in a bonding manner and is used for generating deformation under the driving of an electric signal so as to apply pulse pressure to liquid in the liquid cavity; the micropore nozzle is detachably connected to the bottom of the liquid chamber, the diameter of a spraying hole is adjustable, and the micropore nozzle is used for controlling the initial size of liquid drops; the electric control driving module comprises a power supply, a driving circuit and a controller, is used for outputting an adjustable electric signal to cooperatively control the voltage amplitude, the pulse width and the trigger frequency of the piezoelectric driving assembly, and is linked with the hydraulic adjusting system to realize multi-parameter regulation and control of the droplet size; according to the invention, through cooperation of the piezoelectric driving assembly and the electric control module, high-precision liquid drop control is realized.

Description

Technical Field

[0001] This application relates to the technical field of micro liquid dispensing, and particularly to a single droplet generation device based on piezoelectric ceramics. Background Art

[0002] Droplet generation technology has important applications in fields such as micro liquid dispensing, biomedical detection, and microfluidic chips. Traditional droplet generation devices mostly rely on mechanical pumps or pneumatic drives, and have the following significant defects: insufficient precision: The mechanical drive method is easily affected by factors such as mechanical wear and response delay during the dispensing of small volumes of liquid, resulting in large deviations in droplet size (especially difficult to precisely control droplets in the range of 5 - 500 μm); complex parameter regulation: The droplet size is affected by the coupling of multiple parameters such as nozzle diameter, driving pressure, and liquid viscosity. Existing devices lack a coordinated control mechanism and require repeated trial-and-error adjustments, resulting in low efficiency; poor adaptability: The fixed nozzle design is difficult to adapt to different liquid physical properties (such as high-viscosity and corrosive liquids), and is prone to nozzle blockage due to liquid residue or corrosion, resulting in high maintenance costs; low intelligence level: Lack of real-time feedback and adaptive control capabilities, unable to dynamically optimize parameters according to the droplet generation state, restricting applications in high-throughput or complex scenarios.

[0003] In recent years, piezoelectric ceramic drive technology has been introduced into the droplet generation field due to its fast response and high precision. However, the existing solutions still have the following problems: insufficient sealing: The bonding process between the piezoelectric component and the liquid chamber is not mature, easily leading to liquid leakage or pressure transmission loss; poor liquid surface stability: The balance control of hydrostatic pressure and surface tension is inaccurate, easily causing liquid self-flow or air inhalation; lack of parameter coupling model: Lack of empirical formulas to guide the coordinated regulation of multiple parameters, relying on manual experience, with low repeatability.

[0004] Therefore, there is an urgent need for a highly precise, intelligent, and adaptable droplet generation device to solve problems such as complex parameter coupling, high maintenance costs, and insufficient scalability in traditional technologies. Summary of the Invention

[0005] To solve the above problems, this application provides a single droplet generation device based on piezoelectric ceramics, which realizes independent regulation of voltage amplitude, pulse width, and trigger frequency, combines with the dynamic balance of liquid surface height, reduces droplet size error, and realizes high-precision droplet control. The technical solution is as follows:

[0006] The present application provides a single-droplet generation device based on piezoelectric ceramics, which includes a microcavity liquid chamber, a piezoelectric drive assembly, a microporous nozzle, a hydraulic regulation system, and an electric control drive module. The bottom of the microcavity liquid chamber is provided with a nozzle interface, and the internal cavity volume is adapted to the storage and pressure transmission of trace liquids. The piezoelectric drive assembly includes a piezoelectric ceramic element, which is connected to the microcavity liquid chamber by an adhesive bonding method and is used to generate deformation under the drive of an electrical signal to apply a pulsed pressure to the liquid in the liquid chamber. The microporous nozzle is detachably connected to the bottom of the liquid chamber, and the diameter of the spray hole is adjustable and is used to control the initial size of the droplets. The hydraulic regulation system includes a liquid supply system, a liquid level height adjustment device, and a pressure balance assembly, where: the liquid supply system includes an adjustable liquid storage tank and a fluid pipeline, which are used to continuously supply liquid to the microcavity liquid chamber; the liquid level height adjustment device includes a precision lifting mechanism that drives the liquid storage tank or the microcavity liquid chamber to move vertically to control the liquid level height difference Δh; the pressure balance assembly maintains the stability of the liquid level at the nozzle through the combined action of hydrostatic pressure and surface tension; the electric control drive module includes a power supply, a drive circuit, and a controller, which are used to output an adjustable electrical signal to jointly control the voltage amplitude, pulse width, and trigger frequency of the piezoelectric drive assembly, and are linked with the hydraulic regulation system to achieve multi-parameter regulation of the droplet size.

[0007] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the piezoelectric ceramic element is a metal-based piezoelectric disk, which is fixed to the upper surface of the liquid chamber by a high-modulus adhesive to form an airtight cavity.

[0008] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the liquid supply system includes a glass syringe and a water tank. The height of the glass syringe is adjusted by a micro-lifting platform, and a micro water pump is integrated in the fluid pipeline, which is used to actively adjust the liquid supply flow rate and is linked with the liquid level height adjustment device to control the pressure in the liquid chamber.

[0009] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, a chamfer structure is provided at the front end of the microporous nozzle, and the rear end is connected through a sealing component. The length of the nozzle is adapted to the optimization requirements of the droplet flow rate.

[0010] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the adjustment range of the liquid level height difference of the hydraulic regulation system is adapted to the requirements of the liquid surface tension and static pressure balance to form a stable meniscus.

[0011] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the droplet diameter D is determined by the combined action of the nozzle diameter d n , the voltage amplitude V, the pulse width τ, and the liquid level height difference Δh, and satisfies the following relational expression:

[0012] D = f(d n , v, τ, Δh)

[0013] By adjusting the four parameters, continuous and reproducible generation of droplets in the range of 5 - 500 μm is achieved.

[0014] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the linear relationship between the nozzle diameter d n and the droplet diameter D is:

[0015] D ≈ α·d n

[0016] where α ∈ [0.9, 1.3], and the value of α is corrected by the regulation of the voltage amplitude V and the pulse width τ.

[0017] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the voltage amplitude V and the driving pressure ΔP in the liquid cavity satisfy a positive correlation:

[0018] ΔP ∝ V

[0019] where droplet ejection is triggered when ΔP exceeds the sum of the hydrostatic pressure and the capillary pressure at the nozzle.

[0020] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the pulse width τ and the droplet volume V drop satisfy a power-law relationship:

[0021] V drop ∝ τ β

[0022] where β ∈ [0.5, 1.0], and the specific value is determined by the nozzle impedance and the liquid viscosity.

[0023] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the liquid level height difference Δh and the hydrostatic pressure P at the nozzle static satisfy:

[0024] P static = ρgΔh

[0025] and the adjustment range of Δh adapts to the equilibrium condition of the liquid surface tension σ and the capillary pressure:

[0026]

[0027] The beneficial effects brought by a single-droplet generation device based on piezoelectric ceramics provided by some embodiments of the present application are as follows: Through the cooperation of the piezoelectric drive component and the electronic control module, the present application realizes independent regulation of voltage amplitude, pulse width, and trigger frequency. Combined with the dynamic balance of the liquid level height, it reduces the droplet size error, realizes high-precision droplet control, and meets the requirements of micro-dispensing and high-precision experiments. The present application quantifies the coupling relationship between parameters such as nozzle diameter, voltage, and pulse width based on an empirical model, simplifies the regulation process, improves repeatability, reduces the cost of manual trial and error, and improves production efficiency. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic diagram of the overall structure of the single-droplet generation device based on piezoelectric ceramics of the present application;

[0030] Figure 2 It is a diagram showing the relationship between the input voltage of the piezoelectric ceramic and the size of the generated droplets. Detailed Embodiments

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application belong to the scope of protection of the present application.

[0032] Unless otherwise defined, the technical terms or scientific terms used in this disclosure should have the ordinary meaning understood by those of ordinary skill in the art in the field to which this disclosure belongs. The "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "including" or "comprising" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. "Connection" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0033] The present application provides a single-droplet generation device based on piezoelectric ceramics, as Figure 1 shown, which includes a microchamber liquid chamber 1, a piezoelectric driving assembly 2, a microporous nozzle 3, a hydraulic regulation system 4 and an electric control driving module. The bottom of the microchamber liquid chamber 1 is provided with a nozzle interface, and the internal cavity volume is adapted to the storage and pressure transmission of a small amount of liquid. The piezoelectric driving assembly 2 includes a piezoelectric ceramic element, which is connected to the microchamber liquid chamber 1 by an adhesive bonding method and is used to generate deformation under the drive of an electrical signal to apply a pulsed pressure to the liquid in the liquid chamber. The microporous nozzle 3 is detachably connected to the bottom of the liquid chamber, and the diameter of the spray hole is adjustable and is used to control the initial size of the droplet. The hydraulic regulation system 4 includes a liquid supply system 41, a liquid level height adjustment device 42 and a pressure balance assembly. Among them: the liquid supply system 41 includes an adjustable liquid storage tank and a fluid pipeline and is used to continuously supply liquid to the microchamber liquid chamber; the liquid level height adjustment device 42 includes a precision lifting mechanism that drives the liquid storage tank or the microchamber liquid chamber to move vertically to control the liquid level height difference Δh; the pressure balance assembly maintains the stability of the liquid level at the nozzle through the combined action of hydrostatic pressure and surface tension; the electric control driving module includes a power supply, a driving circuit and a controller and is used to output an adjustable electrical signal to jointly control the voltage amplitude, pulse width and trigger frequency of the piezoelectric driving assembly and is linked with the hydraulic regulation system to realize multi-parameter regulation of the droplet size.

[0034] Through the cooperation of the hydraulic regulation system and the electric control module, the present application realizes precise control of the liquid level height and ensures the stability and repeatability of droplet generation.

[0035] For example, in the single-droplet generation device based on piezoelectric ceramics provided in an embodiment, the piezoelectric ceramic element is a metal-based piezoelectric disk, which is fixed to the upper surface of the liquid chamber by a high-modulus adhesive to form an airtight cavity, improve the driving efficiency and sealing performance, and ensure the stable transmission of the pulsed pressure.

[0036] Specifically, the piezoelectric driving assembly selects a metal-based piezoelectric ceramic disk with an outer diameter of 25 mm or less (such as the CUI CEB-25 series), the sheet thickness is about 0.3–0.5 mm, and the driving frequency response is as high as 30 kHz. The piezoelectric ceramic sheet is bonded to the upper surface of the liquid cavity by a high-modulus RTV adhesive and fixed by a micro-screw compression ring to form an airtight cavity. The brass surface of the piezoelectric sheet faces the liquid side, and its deformation can directly apply a pulsed pressure to the liquid in the liquid cavity under drive.

[0037] The microchamber liquid chamber is an integral metal structure, the internal cavity diameter is about 5–8 mm, the depth is less than 3 mm, and the volume is controlled within 100 μL to improve the instantaneous pressure response efficiency. The bottom of the cavity is a microporous nozzle interface, which is connected to various caliber micro-nozzles through a threaded fit or a Luer-lock quick-change structure.

[0038] The nozzle assembly is a microporous component made by laser processing or MEMS etching, with a nozzle diameter ranging from 5μm to 500μm. It is preferred to use a metal diaphragm, glass capillary or Parylene coating structure to improve liquid adaptability. The front surface of the nozzle has a 45° chamfer structure to reduce liquid wall hanging, and the rear end is provided with a micron-level O-ring or welding seal connection. The nozzle length is preferably 2-5mm to ensure that the flow rate is fully developed.

[0039] The control module includes an adjustable DC power supply (0–150V), a high-frequency H-bridge drive circuit, and an STM32 / Arduino-type microcontroller. The piezoelectric drive waveform is a bipolar square wave with the following control parameters:

[0040] 1. Voltage amplitude range: ±10–120V;

[0041] 2. Pulse width range: 10–1000μs;

[0042] 3. Trigger frequency range: 1–500Hz;

[0043] 4. Rising / falling edge: <5μs.

[0044] For example, in the piezoelectric ceramic-based single droplet generation device provided in one embodiment, the liquid supply system includes a glass syringe and a water tank. The height of the glass syringe is adjusted by a micro-lifting platform. A micro water pump 423 is integrated in the fluid pipeline to actively adjust the liquid supply flow rate and control the liquid chamber pressure in conjunction with the liquid level adjustment device.

[0045] Among them, the liquid supply system adopts a height-adjustable glass syringe system, and uses a micro-lifting platform (resolution 0.01mm) to achieve liquid level control. The liquid level height Δh determines the hydrostatic pressure at the nozzle outlet, and the adjustment range is preferably ±10mm. The actual static pressure change is ±98Pa, which can form a stable meniscus with a liquid with a surface tension of 10-30mN / m. According to the above embodiment, the liquid level is adjusted with high precision to ensure the dynamic balance between the hydrostatic pressure and the surface tension, and to avoid liquid self-flow or air inhalation; the stability of the liquid supply is enhanced by a micro-water pump, which is suitable for high-viscosity liquids or rapid response requirements, and improves the flexibility of the system.

[0046] For example, in the piezoelectric ceramic-based single droplet generation device provided in one embodiment, the front end of the micropore nozzle 3 is provided with a chamfered structure, and the rear end is connected by a sealing component. The nozzle length is adapted to the droplet flow rate optimization requirements, reducing liquid wall adhesion and improving the stability and consistency of droplet generation.

[0047] For example, in the piezoelectric ceramic-based single-droplet generation device provided in one embodiment, the adjustment range of the liquid level height difference of the hydraulic regulation system is adapted to the requirements of the balance between liquid surface tension and static pressure to form a stable meniscus.

[0048] For example, in the piezoelectric ceramic-based single-droplet generation device provided in one embodiment, the droplet diameter D is determined by the nozzle diameter d n , the voltage amplitude V, the pulse width τ, and the combined effect of the liquid level height difference Δh, and satisfies the following relational expression:

[0049] D = f(d n , V, τ, Δh)

[0050] By adjusting the four parameters, continuous and repeatable generation of droplets in the range of 5 - 500 μm is achieved.

[0051] This application breaks through the size limitation of traditional droplet generation technology through multi-parameter collaborative regulation, and realizes wide-range and high-precision droplet control.

[0052] For example, in the piezoelectric ceramic-based single-droplet generation device provided in one embodiment, the nozzle diameter d n is the geometric basis for droplet formation, determines the basic upper limit of droplet size, the droplet size D is strongly restricted by the nozzle outlet size, and the linear relationship between the nozzle diameter d n and the droplet diameter D is:

[0053] D ≈ α·d n

[0054] where α ∈ [0.9, 1.3], and the value of α is corrected by the regulation of the voltage amplitude V and the pulse width τ. For smaller nozzles, the droplet volume is more susceptible to interference from surface tension and static pressure fluctuations, and voltage and waveform control need to be strengthened.

[0055] According to the above embodiment, the basic constraint of the nozzle diameter on the droplet size is clarified, and the parameter matching process is simplified.

[0056] For example, in the piezoelectric ceramic-based single-droplet generation device provided in one embodiment, the voltage amplitude V affects the instantaneous pressure in the liquid cavity, determines whether the liquid is ejected, raises or lowers the ejection threshold, and the voltage amplitude V and the driving pressure ΔP in the liquid cavity satisfy a positive correlation:

[0057] ΔP ∝ v

[0058] where droplet ejection is triggered when ΔP exceeds the sum of the hydrostatic pressure and the capillary pressure at the nozzle. When the driving pressure ΔP is sufficient to overcome the hydrostatic pressure and the capillary pressure at the nozzle liquid surface, droplets can be formed. If the voltage is insufficient, no droplets will be ejected; if it is too high, it may cause tail breakage or multi-droplet generation.

[0059] According to the above embodiments, by controlling the start and stop of injection through the voltage threshold, ineffective driving is avoided and the energy utilization efficiency is improved.

[0060] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the driving pulse width τ controls the volume of the ejected liquid and affects the linear distribution range of the droplet volume. The pulse width τ and the droplet volume V drop satisfy a power-law relationship:

[0061] V drop ∝τ β

[0062] where β ∈ [0.5, 1.0], and the specific value is determined by the nozzle impedance and the liquid viscosity.

[0063] When the voltage determines the driving strength, the pulse width τ determines the time length of the action of this pressure.

[0064] Experiments show that:

[0065] Shorter τ values will result in insufficient liquid propulsion, smaller droplet volumes or no droplet formation;

[0066] Longer τ values may lead to the "tail stretching" phenomenon, generating satellite droplets or unstable deformations.

[0067] According to the above embodiments, by quantifying the control law of the pulse width on the droplet volume, the predictability of the regulation is improved.

[0068] For example, in the single-droplet generation device based on piezoelectric ceramics provided in one embodiment, the liquid level height difference Δh affects the static interface morphology and the threshold of the minimum drivable liquid volume. The liquid level height difference Δh and the hydrostatic pressure P at the nozzle static satisfy:

[0069] P static = ρgΔh

[0070] and the adjustment range of Δh is adapted to the balance condition of the liquid surface tension σ and the capillary pressure:

[0071]

[0072] When Δh is too large (too high static pressure), the liquid may seep out automatically to form static droplets; when Δh is too low, the liquid level will be concave, and even air may be inhaled, blocking the transmission of the driving pulse. An appropriate Δh can stabilize the liquid level to form a meniscus shape, serving as an effective boundary condition for subsequent piezoelectric driving.

[0073] According to the above embodiments, by precisely controlling the liquid level stability, injection failure caused by liquid self-flow or air inhalation is avoided.

[0074] From the experimental fitting results, for a specific nozzle size, the droplet diameter D can be fitted to the following empirical formula:

[0075]

[0076] where γ ∈ [0.8, 1.1], is the reference voltage / time, and δ, η are usually positive values (0.3–1.0).

[0077] Figure 2 where the abscissa is the input voltage of the piezoelectric ceramic and the ordinate is the size of the generated droplets, Figure 2 and the three sets of lines in are for different nozzle sizes. By Figure 2 it can be seen that the combined action of multiple parameters affects the droplet size.

[0078] Although the embodiments of the present application have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present application. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present application is not limited to the specific details and the examples shown and described herein.

Claims

1. A single droplet generation device based on piezoelectric ceramics, characterized in that: include: The micro-cavity liquid chamber has a nozzle interface at the bottom, and the internal cavity volume is suitable for micro-liquid storage and pressure transmission; A piezoelectric drive assembly, including a piezoelectric ceramic element, which is connected to the microcavity liquid chamber by bonding, and is used to generate deformation under the drive of an electrical signal to apply a pulse pressure to the liquid in the liquid chamber; A micro-pore nozzle, detachably connected to the bottom of the liquid chamber, with an adjustable nozzle diameter, for controlling the initial size of the droplets; A hydraulic adjustment system, comprising a liquid supply system, a liquid level adjustment device and a pressure balance component, wherein: the liquid supply system comprises an adjustable liquid storage tank and a fluid pipeline for continuously supplying liquid to a micro-cavity liquid chamber; the liquid level adjustment device comprises a precision lifting mechanism for driving the liquid storage tank or the micro-cavity liquid chamber to move vertically to control the liquid level difference Δh; the pressure balance component maintains the stability of the liquid level at the nozzle through the synergistic effect of hydrostatic pressure and surface tension; The electronically controlled drive module includes a power supply, a drive circuit and a controller, which is used to output an adjustable electrical signal to coordinately control the voltage amplitude, pulse width and trigger frequency of the piezoelectric drive component, and to work with the hydraulic adjustment system to achieve multi-parameter control of the droplet size.

2. The single droplet generation device based on piezoelectric ceramics according to claim 1, characterized in that: The piezoelectric ceramic element is a metal-based piezoelectric disk, which is fixed to the upper surface of the liquid chamber by a high modulus adhesive to form an airtight cavity.

3. The single droplet generation device based on piezoelectric ceramics according to claim 1, characterized in that: The liquid supply system includes a glass syringe and a water tank. The height of the glass syringe is adjusted by a micro-lifting platform. A micro water pump is integrated in the fluid pipeline to actively adjust the liquid supply flow rate and control the liquid cavity pressure in conjunction with the liquid level adjustment device.

4. The single droplet generation device based on piezoelectric ceramics according to claim 1, characterized in that: The front end of the micropore nozzle is provided with a chamfered structure, and the rear end is connected via a sealing component, and the nozzle length is adapted to the requirements for optimizing the droplet flow rate.

5. The single droplet generation device based on piezoelectric ceramics according to claim 1, characterized in that: The liquid level height difference adjustment range of the hydraulic adjustment system is adapted to the liquid surface tension and static pressure balance requirements to form a stable meniscus.

6. The single droplet generation device based on piezoelectric ceramics according to claim 1, characterized in that: The droplet diameter D is determined by the nozzle diameter d n , voltage amplitude V, pulse width τ and liquid level height difference Δh, satisfying the following relationship: D=f(d n ,V,τ,Δh) By adjusting the four parameters, continuous and repeatable generation of droplets in the range of 5-500 μm can be achieved.

7. The single droplet generation device based on piezoelectric ceramics according to claim 6, characterized in that: The nozzle diameter d n The linear relationship with the droplet diameter D is: D≈α·d n Among them, α∈[0.9,1.3], and the α value is modified by the regulation of the voltage amplitude V and the pulse width τ.

8. The single droplet generation device based on piezoelectric ceramics according to claim 6, characterized in that: The voltage amplitude V and the driving pressure ΔP in the liquid cavity satisfy a positive correlation: ΔP∝V When ΔP exceeds the sum of the hydrostatic pressure and the capillary pressure at the nozzle, droplet ejection is triggered.

9. The single droplet generation device based on piezoelectric ceramics according to claim 6, characterized in that: The pulse width τ is related to the droplet volume V drop Satisfies the power law relationship: In drop ∝τ β Among them, β∈[0.5,1.0], the specific value is determined by the nozzle impedance and liquid viscosity.

10. The single droplet generation device based on piezoelectric ceramics according to claim 6, characterized in that: The liquid level height difference Δh and the hydrostatic pressure P at the nozzle static satisfy: P static =ρgΔh And the adjustment range of Δh is adapted to the equilibrium condition between the liquid surface tension σ and the capillary pressure:

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