A piezoelectric ceramic-based single droplet generation device

Abstract

This application discloses a single droplet generation device based on piezoelectric ceramics, including a microcavity liquid chamber, a piezoelectric driving component, a micro-orifice nozzle, a hydraulic adjustment system, and an electronically controlled driving module. The microcavity liquid chamber has a nozzle interface at its bottom, and its internal cavity volume is adapted to store a small amount of liquid and transmit pressure. The piezoelectric driving component includes 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 pulse pressure to the liquid in the liquid chamber. The micro-orifice nozzle is detachably connected to the bottom of the liquid chamber, and its nozzle diameter is adjustable to control the initial size of the droplet. The electronically controlled driving module includes a power supply, a driving circuit, and a controller, which outputs an adjustable electrical signal to coordinately control the voltage amplitude, pulse width, and trigger frequency of the piezoelectric driving component, and is linked with the hydraulic adjustment system to achieve multi-parameter control of the droplet size. This application achieves high-precision droplet control through the coordination of the piezoelectric driving component and the electronically controlled module.

Description

Technical Field

[0001] This application relates to the field of micro-liquid distribution technology, and in particular to a single droplet generation device based on piezoelectric ceramics. Background Technology

[0002] Droplet generation technology has important applications in micro-liquid distribution, biomedical detection, and microfluidic chips. Traditional droplet generation devices mostly rely on mechanical pumps or pneumatic drives, which have the following significant drawbacks: Insufficient precision: Mechanical drives are easily affected by mechanical wear and response delays when distributing small volumes of liquid, resulting in large droplet size deviations (especially for droplets in the 5-500μm range, which are difficult to control precisely); Complex parameter control: Droplet size is affected by multiple parameters such as nozzle diameter, driving pressure, and liquid viscosity. Existing devices lack a coordinated control mechanism, requiring repeated trial and error adjustments, resulting in low efficiency; Poor adaptability: Fixed nozzle designs are difficult to adapt to different liquid properties (such as high-viscosity, corrosive liquids), and are prone to nozzle clogging due to liquid residue or corrosion, leading to high maintenance costs; Low level of intelligence: Lacking real-time feedback and adaptive control capabilities, they cannot dynamically optimize parameters based on the droplet generation state, limiting applications in high-throughput or complex scenarios.

[0003] In recent years, piezoelectric ceramic drive technology has been introduced into the field of droplet generation due to its fast response and high precision. However, existing solutions still have the following problems: Insufficient sealing: The bonding process between the piezoelectric component and the liquid cavity is not mature, which can easily lead to liquid leakage or pressure transmission loss; Poor liquid surface stability: The balance control of hydrostatic pressure and surface tension is not precise, which can easily cause liquid to flow by itself or air to be sucked in; Lack of parameter coupling model: There is a lack of empirical formulas to guide the coordinated control of multiple parameters, which relies on human experience and has low repeatability.

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

[0005] To address the aforementioned problems, this application provides a single droplet generation device based on piezoelectric ceramics, which enables independent control of voltage amplitude, pulse width, and trigger frequency. Combined with dynamic balance of liquid level, it reduces droplet size error and achieves high-precision droplet control. The technical solution is as follows:

[0006] This application provides a single droplet generation device based on piezoelectric ceramics, including a microcavity liquid chamber, a piezoelectric driving component, a micro-orifice nozzle, a hydraulic adjustment system, and an electronically controlled driving module. The microcavity liquid chamber has a nozzle interface at its bottom, and its internal volume is adapted to store and transmit a small amount of liquid. The piezoelectric driving component includes a piezoelectric ceramic element, which is bonded to the microcavity liquid chamber and deforms under electrical signal drive to apply pulse pressure to the liquid within the chamber. The micro-orifice nozzle is detachably connected to the bottom of the liquid chamber, and its orifice diameter is adjustable to control the initial size of the droplet. The hydraulic adjustment system includes a liquid supply system and a liquid level adjustment device. The system includes a pressure balancing component, wherein: the liquid supply system comprises an adjustable liquid storage tank and fluid pipelines for continuously supplying liquid to the microcavity liquid chamber; the liquid level adjustment device includes a precision lifting mechanism to drive the liquid storage tank or microcavity liquid chamber to move vertically, thereby controlling the liquid level height difference Δh; the pressure balancing 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, drive circuit, and controller for outputting adjustable electrical signals to collaboratively control the voltage amplitude, pulse width, and trigger frequency of the piezoelectric drive component, and to link with the hydraulic adjustment system to achieve multi-parameter control of the droplet size.

[0007] For example, in one embodiment of the single droplet generating device based on piezoelectric ceramics, 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 one embodiment of the single droplet generating device based on piezoelectric ceramics, 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 to control the liquid chamber pressure in conjunction with the liquid level adjustment device.

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

[0010] For example, in one embodiment of the single droplet generating device based on piezoelectric ceramics, the liquid level 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.

[0011] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the droplet diameter D is determined by the nozzle diameter d. n The combined effect of voltage amplitude V, pulse width τ, and liquid level difference Δh determines the following relationship:

[0012] D = f(d) n (v, τ, Δh)

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

[0014] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the nozzle diameter d n The linear relationship with the droplet diameter D is:

[0015] D≈α·d n

[0016] Where α∈[0.9,1.3], the value of α is modified by adjusting the voltage amplitude V and the pulse width τ.

[0017] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the voltage amplitude V and the driving pressure ΔP inside the liquid chamber are positively correlated:

[0018] ΔP∝V

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

[0020] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the pulse width τ is related to the droplet volume V. drop Satisfies the power law relationship:

[0021] V drop ∝τ β

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

[0023] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the liquid level difference Δh is related to the hydrostatic pressure P at the nozzle. static satisfy:

[0024] P static =ρgΔh

[0025] Furthermore, the adjustment range of Δh is adapted to the equilibrium condition between the liquid surface tension σ and capillary pressure:

[0026]

[0027] The beneficial effects of the single droplet generation device based on piezoelectric ceramics provided in some embodiments of this application are as follows: This application achieves independent control of voltage amplitude, pulse width, and trigger frequency through the collaboration of piezoelectric drive components and electronic control modules. Combined with dynamic balance of liquid level, it reduces droplet size error, achieves high-precision droplet control, and meets the requirements of micro-dispensing and high-precision experiments. This application quantifies the coupling relationship of parameters such as nozzle diameter, voltage, and pulse width based on empirical models, simplifies the control process, improves repeatability, reduces manual trial and error costs, and improves production efficiency. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the overall structure of the single droplet generation device based on piezoelectric ceramics in this application.

[0030] Figure 2 The graph shows the relationship between the input voltage of the piezoelectric ceramic and the size of the generated droplets. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0033] This application provides a single droplet generation device based on piezoelectric ceramics, such as... Figure 1 As shown, the system includes a microcavity liquid chamber 1, a piezoelectric drive assembly 2, a micro-orifice nozzle 3, a hydraulic adjustment system 4, and an electronically controlled drive module. The microcavity liquid chamber 1 has a nozzle interface at its bottom, and its internal cavity volume is adapted to store and transmit a small amount of liquid. The piezoelectric drive assembly 2 includes a piezoelectric ceramic element, which is connected to the microcavity liquid chamber 1 by bonding. It is used to generate deformation under the drive of an electrical signal to apply pulse pressure to the liquid in the liquid chamber. The micro-orifice nozzle 3 is detachably connected to the bottom of the liquid chamber, and its nozzle diameter is adjustable to control the initial size of the droplets. The hydraulic adjustment system 4 includes a liquid supply system 41, a liquid level adjustment device 42, and a pressure balancer. The components include: a liquid supply system 41 comprising an adjustable liquid storage tank and fluid pipelines for continuously supplying liquid to the microcavity liquid chamber; a liquid level adjustment device 42 comprising a precision lifting mechanism for driving the liquid storage tank or microcavity liquid chamber to move vertically to control the liquid level height difference Δh; a pressure balancing component for maintaining a stable liquid level at the nozzle through the combined action of hydrostatic pressure and surface tension; and an electronically controlled drive module comprising a power supply, a drive circuit, and a controller for outputting adjustable electrical signals to collaboratively control the voltage amplitude, pulse width, and trigger frequency of the piezoelectric drive component, and for linkage with the hydraulic adjustment system to achieve multi-parameter control of the droplet size.

[0034] This application achieves precise control of liquid level through the collaboration of a hydraulic adjustment system and an electronic control module, ensuring the stability and repeatability of droplet generation.

[0035] For example, in one embodiment of the single droplet generating device based on piezoelectric ceramics, 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, thereby improving driving efficiency and sealing performance and ensuring stable transmission of pulse pressure.

[0036] Specifically, the piezoelectric drive assembly uses a metal-based piezoelectric ceramic disc with an outer diameter of 25 mm or less (such as the CUI CEB-25 series), a thickness of approximately 0.3–0.5 mm, and a drive frequency response up to 30 kHz. The piezoelectric ceramic disc is bonded to the upper surface of the liquid cavity using high-modulus RTV adhesive and secured with micro-screw clamping rings to form an airtight cavity. The brass side of the piezoelectric disc faces the liquid side, and its deformation can directly apply pulse pressure to the liquid inside the cavity under drive.

[0037] The microcavity liquid chamber is a monolithic metal structure with an internal cavity diameter of approximately 5–8 mm and a depth of less than 3 mm, with a volume controlled within 100 μL to improve instantaneous pressure response efficiency. The bottom of the cavity houses a micro-orifice nozzle interface, which connects to various micro-nozzles of different diameters via threaded engagement or a Luer-lock quick-change structure.

[0038] The nozzle assembly is a microporous component fabricated by laser processing or MEMS etching, with orifice diameters ranging from 5 μm to 500 μm. Metal diaphragms, glass capillaries, or Parylene coatings are preferred to improve liquid compatibility. The nozzle tip surface has a 45° chamfer to reduce liquid adhesion to the nozzle walls, and the rear end features a micron-level O-ring or solder seal. The nozzle length is preferably 2–5 mm to ensure sufficient flow velocity development.

[0039] The control module includes an adjustable DC power supply (0–150V), a high-frequency H-bridge driver circuit, and an STM32 / Arduino-like microcontroller. The piezoelectric element driving waveform is a bipolar square wave with the following adjustable 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 one embodiment of the single droplet generating device based on piezoelectric ceramics, 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 to control the liquid chamber pressure in conjunction with the liquid level adjustment device.

[0045] The liquid supply system employs a height-adjustable glass injector system, utilizing a miniature lifting platform (0.01 mm resolution) for liquid level control. The liquid level height Δh determines the hydrostatic pressure at the nozzle outlet, with a preferred adjustment range of ±10 mm and an actual hydrostatic pressure variation of ±98 Pa. This allows for the formation of a stable meniscus with liquids exhibiting a surface tension of 10–30 mN / m. According to the aforementioned embodiment, high-precision liquid level adjustment ensures a dynamic balance between hydrostatic pressure and surface tension, preventing liquid flow or air intake. A miniature water pump enhances the stability of the liquid supply, adapting to high-viscosity liquids or rapid response requirements, thus improving system flexibility.

[0046] For example, in one embodiment of the single droplet generating device based on piezoelectric ceramics, the front end of the microporous 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 adhesion to the wall and improving the stability and consistency of droplet generation.

[0047] For example, in one embodiment of the single droplet generating device based on piezoelectric ceramics, the liquid level 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.

[0048] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the droplet diameter D is determined by the nozzle diameter d. n The combined effect of voltage amplitude V, pulse width τ, and liquid level difference Δh determines the following relationship:

[0049] D = f(d) n (V, τ, Δh)

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

[0051] This application achieves wide-range, high-precision droplet control by overcoming the size limitations of traditional droplet generation technology through multi-parameter coordinated control.

[0052] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the nozzle diameter d n The geometry of droplet formation determines the basic limit of droplet size. The droplet size D is strongly constrained by the nozzle exit size, namely the nozzle diameter d. n The linear relationship with the droplet diameter D is:

[0053] D≈α·d n

[0054] Where α∈[0.9,1.3], the value of α is modified by adjusting the voltage amplitude V and pulse width τ. For smaller nozzles, the droplet volume is more susceptible to interference from surface tension and hydrostatic pressure fluctuations, requiring enhanced voltage and waveform control.

[0055] Based on the above embodiments, the basic constraint of nozzle diameter on droplet size is clarified, simplifying the parameter matching process.

[0056] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the voltage amplitude V affects the instantaneous pressure inside the liquid chamber, determining whether the liquid is ejected and raising or lowering the ejection threshold. The voltage amplitude V and the driving pressure ΔP inside the liquid chamber are positively correlated.

[0057] ΔP∝v

[0058] Droplet ejection is triggered when ΔP exceeds the sum of the hydrostatic pressure and capillary pressure at the nozzle. Droplets can only form when the driving pressure ΔP is sufficient to overcome the hydrostatic pressure and capillary pressure at the nozzle surface. If the voltage is insufficient, no droplets will be ejected; if it is too high, it may cause the trail to break or multiple droplets to form.

[0059] According to the above embodiments, the injection start-stop is controlled by a voltage threshold to avoid ineffective drive and improve energy utilization efficiency.

[0060] For example, in one embodiment of the single droplet generation device based on piezoelectric ceramics, the driving pulse width τ controls the liquid ejection volume, affecting the linear distribution range of the droplet volume. The pulse width τ is related to the droplet volume V. drop Satisfies the power law relationship:

[0061] V drop ∝τ β

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

[0063] Once the voltage determines the driving intensity, the pulse width τ determines the duration of the pressure application.

[0064] Experiments show that:

[0065] A shorter τ value will result in insufficient liquid propulsion, smaller droplet volume, or no droplet formation.

[0066] A longer τ value may lead to a "tail stretching" phenomenon, resulting in satellite droplets or unstable deformation.

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

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

[0069] P static =ρgΔh

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

[0071]

[0072] When Δh is too large (excessive static pressure), the liquid may automatically seep out and form droplets; when Δh is too low, the liquid surface will sink, or even draw in air, blocking the transmission of the driving pulse. A suitable Δh can stabilize the liquid surface into a meniscus shape, serving as an effective boundary condition for subsequent piezoelectric actuation.

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

[0074] Based on the experimental fitting results, for a specific nozzle size, the droplet diameter D can be fitted with 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 The horizontal axis represents the input voltage of the piezoelectric ceramic, and the vertical axis represents the size of the generated droplet. Figure 2 The three sets of lines represent different nozzle sizes, through... Figure 2 It can be seen that the droplet size is affected by the synergistic effect of multiple parameters.

[0078] Although the embodiments of this application have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this application. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A single droplet generation device based on piezoelectric ceramics, characterized in that, include: The micro-cavity fluid chamber is equipped with a nozzle interface at the bottom, and the internal cavity volume is adapted to the storage of trace amounts of liquid and pressure transmission. A piezoelectric drive assembly, including a piezoelectric ceramic element, is connected to a microcavity liquid chamber by adhesive bonding and is used to generate deformation under the drive of an electrical signal to apply pulse pressure to the liquid in the liquid chamber; A micro-orifice nozzle is detachably connected to the bottom of the liquid chamber, and the orifice diameter is adjustable to control the initial size of the droplets; The hydraulic adjustment system includes a liquid supply system, a liquid level adjustment device, and a pressure balancing component. The liquid supply system includes an adjustable liquid tank and fluid pipelines for continuously supplying liquid to the microcavity liquid chamber. The liquid level adjustment device includes a precision lifting mechanism that drives the liquid tank or microcavity liquid chamber to move vertically, thereby controlling the liquid level difference Δh. The pressure balancing component maintains a stable liquid level at the nozzle through the combined action of hydrostatic pressure and surface tension. The electronically controlled drive module includes a power supply, drive circuit, and controller. It is used to output adjustable electrical signals to coordinately control the voltage amplitude, pulse width, and trigger frequency of the piezoelectric drive component, and to link with the hydraulic adjustment system to achieve multi-parameter control of droplet size. 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. The micro-orifice nozzle has a chamfered structure at the front end and is connected to the rear end through a sealing component. The nozzle length is adapted to the droplet flow rate optimization requirements. The hydraulic adjustment system's liquid level difference adjustment range is adapted to the liquid surface tension and static pressure balance requirements to form a stable meniscus; The droplet diameter D is determined by the nozzle diameter d. n The combined effect of voltage amplitude V, pulse width τ, and liquid level difference Δh determines the following relationship: By adjusting the four parameters, continuous and repeatable generation of droplets in the range of 5-500μm can be achieved. The liquid level difference Δh and the hydrostatic pressure P at the nozzle are related. static satisfy: Furthermore, the adjustment range of Δh is adapted to the equilibrium condition between the liquid surface tension σ and capillary pressure: 。 2. 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 miniature lifting platform. A miniature water pump is integrated in the fluid pipeline to actively adjust the liquid supply flow rate and to control the liquid chamber pressure in conjunction with the liquid level adjustment device.

3. The single droplet generation device based on piezoelectric ceramics according to claim 1, characterized in that, The nozzle diameter d n The linear relationship with the droplet diameter D is as follows: Where α∈[0.9, 1.3], the value of α is modified by adjusting the voltage amplitude V and the pulse width τ.

4. The single droplet generation device based on piezoelectric ceramics according to claim 3, characterized in that, The voltage amplitude V and the driving pressure ΔP inside the liquid cavity are positively correlated: Droplet ejection is triggered when ΔP exceeds the sum of the hydrostatic pressure and capillary pressure at the nozzle.

5. The single droplet generation device based on piezoelectric ceramics according to claim 3, characterized in that, The pulse width τ and the droplet volume V drop Satisfies the power law relationship: Where β∈[0.5, 1.0], the specific value is determined by the nozzle impedance and the liquid viscosity.

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