Liquid lens driven by electrofluid and application and focusing method thereof

Abstract

The invention discloses an electrofluid-driven liquid lens and application and a focusing method thereof. The liquid lens comprises a first PDMS film, an electrode structure, a second PDMS film and a flexible shell in the middle of the electrode structure which are sequentially stacked, arranged and connected. The flexible shell is of a hollow square-frame-shaped structure, the middle of the electrode structure is provided with a circular hole communicated with the hollow portion of the flexible shell, the first PDMS thin film and the second PDMS thin film are fixedly connected to the two sides of the electrode structure respectively and cover the circular hole, and therefore the liquid lens forms a closed inner cavity in the middle of the flexible shell and the middle of the electrode structure. An electrofluid medium is arranged in the closed inner cavity, the electrode structure is electrified to enable the electrofluid medium to flow towards the center of the inner cavity, and the first PDMS film and the second PDMS film are driven by the electrofluid medium to protrude towards the direction away from the electrode structure to form a liquid lens. The liquid lens driven by the electrofluid has a great application prospect in the fields of wearable and embedded optical systems, medical treatment and diagnosis, machine vision, industrial detection and the like.

Description

Technical Field

[0001] This invention relates to a focusable optical element, particularly a liquid lens based on an electrofluid driving mechanism, its application, and focusing method, belonging to the technical fields of adaptive optics, microfluidic optical devices, and flexible electro-optical systems. Background Technology

[0002] With the widespread application of tunable optical elements in autofocus imaging, wearable devices, miniature vision systems, and biomimetic optical devices, liquid lenses, as optical elements with variable focal length and simple structure, have attracted much attention in recent years. Existing liquid lenses mostly rely on mechanisms such as electrowetting, electromagnetic coils, piezoelectricity, or thermodynamic actuation to adjust the liquid interface shape to achieve focal length control. However, these actuation methods often suffer from problems such as complex structure, high energy consumption, slow response, poor integrability, or insufficient flexibility and compatibility, limiting their application in miniaturized, flexible, low-power, or integrated optical systems.

[0003] Electrohydrodynamic (EHD) is a driving method that uses electrostatic forces to induce flow and interface deformation of ions within a liquid. It offers advantages such as low driving voltage, low power consumption, compact structure, and fast response. In recent years, electrohydrodynamic technology has been increasingly incorporated into liquid lens design to replace traditional driving methods. However, existing electrohydrodynamic liquid lenses still suffer from limitations such as limited control precision, small lens deformation range, high material rigidity, and unsuitability for flexible integration, making it difficult to meet the demands of emerging applications such as flexible electronic devices, wearable vision systems, and bionic organs.

[0004] Therefore, there is an urgent need to provide a liquid lens structure and its control method based on electrofluid drive. This device not only has good lens focusing capability, but also can be compatible with flexible materials and has high integration and low power consumption characteristics to meet the development needs of various new optical systems. Summary of the Invention

[0005] The technical problem solved by this invention is to provide an electrofluid-driven liquid lens, which provides a lightweight, highly integrated, and reliable solution for next-generation "bionic sensing systems", "wearable vision devices", and "micro-optical modules".

[0006] The technical solution to achieve the purpose of this invention is as follows: I. Electrofluid-driven liquid lens The device includes a first PDMS film, an electrode structure, a second PDMS film, and a flexible shell disposed in the middle of the electrode structure, which are sequentially stacked and fixedly connected. The flexible shell is a square frame structure with a certain thickness and a hollow structure. The electrode structure has circular holes in the middle and at the four corners, which are interconnected with the hollow structure of the flexible shell. The first and second PDMS films are fixedly connected to both sides of the electrode structure and cover the circular holes, so that the liquid lens forms a closed cavity in the middle of the flexible shell and the electrode structure. The cavity is filled with a current-carrying medium. The electrode structure is connected to an external power source and energized, causing the current-carrying medium to flow towards the center of the closed cavity. As a result, the first and second PDMS films bulge away from the electrode structure under the drive of the current-carrying medium after it is energized, forming a liquid lens.

[0007] The first PDMS film, the second PDMS film, the electrode structure, and the flexible shell are all square structures with consistent outer contours.

[0008] The electrode structure includes a first flexible FPC plate and a second flexible FPC plate, both connected to an external power source. When the first and second flexible FPC plates are energized, a high voltage is applied, causing the fluid medium inside the liquid lens to flow. The high voltage is typically 3-12 kV, and the higher the voltage, the greater the internal flow intensity. The first flexible FPC plate is fixedly connected to the second flexible FPC plate via a flexible outer shell.

[0009] The first flexible FPC board has a first central circular hole at its center. Multiple annular first negative electrodes and first positive electrodes are coaxially arranged along the first central circular hole. The number of first negative electrodes and first positive electrodes are equal and they are arranged alternately from the direction towards the center to away from the center. The electrode closest to the center is the first negative electrode. Each of the four corners of the first flexible FPC board has an edge circular hole. Each first edge circular hole and the first central circular hole are used to store current.

[0010] The second flexible FPC board has a second central circular hole at its center. Multiple annular second negative electrodes and second positive electrodes are coaxially arranged along the second central circular hole. The number of second negative electrodes and second positive electrodes are equal and they are arranged alternately. The electrode closest to the center is the second negative electrode. A second edge circular hole is provided at each of the four corners of the second flexible FPC board. Each second edge circular hole and the second central circular hole are used for the passage of current.

[0011] The first flexible FPC board and the second flexible FPC board have electrodes on their surfaces facing the flexible shell.

[0012] The first PDMS film, the first flexible FPC board, the flexible shell, the second flexible FPC board, and the second PDMS film are all flexible materials.

[0013] The current-carrying dielectric is one or more of the following: dibutyl sebacate, glyceryl triacetate, linaloyl acetate, electronic fluorinated liquid, etc.

[0014] II. Application of a Fluid-Driven Liquid Lens Applications in biomimetic sensing systems, wearable and embedded optical systems, micro-optical modules, medical and diagnostic applications, machine vision, and industrial inspection.

[0015] III. Focusing Method of Electrofluid-Driven Liquid Lenses The liquid lens described is an adjustable liquid lens. Its driving principle is that when a certain high voltage is applied to the positive and negative electrodes in the flexible FPC board, a strong electric field is formed in space. Under the action of the electric field, the fluid medium generates a net volume force and flows towards the center, causing the outer first and second PDMS films to bulge outward, thus forming a liquid lens. More specifically, the fluid medium generates directional flow along the direction of the net electric field force. The electrodes on the first and second flexible FPC boards are annular, and the direction of the net electric field force of the liquid around the annular electrodes is always towards the center. Therefore, the effect is that the fluid moves towards the center, that is, it converges towards the center.

[0016] When the first and second flexible FPC boards are energized, a force pointing towards the center is generated, causing the current-carrying medium to experience this force. The current-carrying medium inside the liquid lens flows towards the center of the inner cavity. The current converges at the center of the inner cavity, causing the first and second PDMS films at the locations of the first and second edge holes to concave towards the electrode structure. The centers of the first and second PDMS films bulge away from the electrode structure under the drive of the current-carrying medium after energization, forming a liquid lens. The liquid lens maintains an energized state during operation, thereby maintaining its bulging state. By adjusting the energizing voltage, the net force on the current-carrying medium is changed, thereby changing the pressure in the inner cavity, thus adjusting the degree of bulging of the first and second PDMS films, and consequently adjusting the focal length of the liquid lens, thereby adjusting the magnification of the liquid lens.

[0017] Compared with the prior art, the present invention has the following significant advantages: (1) The electrofluid driven liquid lens of the present invention is an adjustable liquid lens. The magnification of the lens can be adjusted by adjusting the voltage. The operation is simple.

[0018] (2) The liquid lens driven by the electrofluid of the present invention has the characteristics of small size, simple structure, fast response, no noise and good integration.

[0019] (3) The electrofluid-driven liquid lens of the present invention adopts a fully flexible design. Compared with the traditional rigid liquid lens, it has a series of unique advantages and is particularly suitable for the development needs of future wearable, bionic and micro optical systems. Attached Figure Description

[0020] Figure 1 This is a structural outline diagram of the electrofluid-driven liquid lens of the present invention; Figure 2 This is an exploded view of the structure of the electrofluid-driven liquid lens of the present invention; Figure 3 This is a structural diagram of the FPC board for the electrofluid-driven liquid lens of the present invention. Figure 4 This is a cross-sectional view of the FPC board of the electrofluid-driven liquid lens of the present invention. Figure 5 The diagram shows the current-driven principle of the present invention ((a) is a schematic diagram when the current-driven body is stationary, and (b) is a schematic diagram of the current-driven body flowing after being energized). Figure 6 This is a schematic diagram illustrating the working principle of the electrofluid-driven liquid lens of the present invention.

[0021] In the figure: 1. First PDMS film, 2. First flexible FPC board, 3. Flexible shell, 4. Second flexible FPC board, 5. Second PDMS film. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] To illustrate the technical solution and objectives of this invention, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0024] Combination Figure 1 and Figure 2The device includes a first PDMS film 1, an electrode structure, a second PDMS film 5, and a flexible shell 3 disposed in the middle of the electrode structure, which are arranged and fixedly connected in sequence. The flexible shell 3 is a square frame structure with a certain thickness and a hollow structure. The electrode structure has circular holes in the middle and four corners that are connected to the hollow structure of the flexible shell 3. The first PDMS film 1 and the second PDMS film 5 are fixedly connected to both sides of the electrode structure and cover the circular holes, so that the liquid lens forms a closed cavity in the middle of the flexible shell 3 and the electrode structure. The cavity is filled with a current-carrying medium. The electrode structure is connected to an external power source and energized, so that the current flows towards the center of the closed cavity. As a result, the first PDMS film 1 and the second PDMS film 5 bulge away from the electrode structure under the drive of the current-carrying medium after being energized, forming a liquid lens.

[0025] The first PDMS film 1, the second PDMS film 5, the electrode structure, and the flexible shell 3 are all square structures with consistent outer contours.

[0026] The electrode structure includes a first flexible FPC plate 2 and a second flexible FPC plate 4, both connected to an external power source. When the first flexible FPC plate 2 and the second flexible FPC plate 4 are energized, a current-carrying fluid flows inside the liquid lens under high voltage. The high voltage is typically 3~12 kV.

[0027] The first flexible FPC board 2 is fixedly connected to the second flexible FPC board 4 through the flexible shell 3. More specifically, one side of the first flexible FPC board 2 is in contact with and fixedly connected to the first PDMS film 1, and the other side is in contact with and fixedly connected to the flexible shell 3; one side of the second flexible FPC board 4 is in contact with and fixedly connected to the second PDMS film 5, and the other side is in contact with and fixedly connected to the flexible shell 3.

[0028] A first flexible FPC board 2 has a central circular hole at its center. Multiple annular first negative electrodes and first positive electrodes are coaxially arranged along this central circular hole. The number of first negative electrodes and first positive electrodes are equal, and they are arranged alternately from the direction towards the center to the direction away from the center. The electrode closest to the center is the first negative electrode. More specifically, multiple pairs of annular first electrodes are coaxially arranged along the central circular hole in the first flexible FPC board 2. Each pair of annular first electrodes consists of one annular first negative electrode and one annular first positive electrode, both coaxially arranged. The first negative electrode is closer to the center than the first positive electrode, thus forming a positive and negative electrode pair on the first flexible FPC board 2. An edge circular hole is provided at each of the four corners of the first flexible FPC board 2. Each first edge circular hole and each first central circular hole are used to store current.

[0029] The second flexible FPC board 4 has a second central circular hole at its center. Multiple annular second negative electrodes and second positive electrodes are coaxially arranged along the second central circular hole on the second flexible FPC board 4. The number of second negative electrodes and second positive electrodes are equal and alternately arranged, with the electrode closest to the center being the second negative electrode. More specifically, the second flexible FPC board 2 has multiple pairs of annular second electrodes coaxially arranged along the central circular hole. Each pair of second annular electrodes consists of one annular second negative electrode and one annular second positive electrode, both coaxially arranged. The first negative electrode is closer to the center than the first positive electrode, so that multiple pairs of annular electrodes form a positive and negative electrode pair on the second flexible FPC board 4. A second edge circular hole is provided at each of the four corners of the second flexible FPC board 4. Each second edge circular hole and the second central circular hole are used for the passage of current.

[0030] The first flexible FPC plate 2 and the second flexible FPC plate 4 have electrodes on their surfaces facing the flexible outer shell 3. The first PDMS film 1, the first flexible FPC plate 2, the flexible outer shell 3, the second flexible FPC plate 4, and the second PDMS film 5 are all flexible materials.

[0031] The current-sensitive dielectric can be composed of various electrically sensitive dielectric liquids such as dibutyl sebacate, glyceryl triacetate, linaloate acetate, or electronic fluorinated liquid. Dibutyl sebacate was chosen as the optimal working medium because it has good compatibility with PDMS, which can prevent wrinkles from forming in the first PDMS film 1 and the second PDMS film 5, thus preventing the formation of a liquid lens.

[0032] Applications in biomimetic sensing systems, wearable and embedded optical systems, micro-optical modules, medical and diagnostic applications, machine vision, and industrial inspection.

[0033] The electrofluid-driven focusing method for electrofluid-driven liquid lenses is as follows: A liquid lens is an adjustable liquid lens. Its driving principle is that the electrodes in the flexible FPC board drive the liquid to flow towards the center under a high voltage, causing the outer first PDMS film 1 and the second PDMS film 5 to bulge outward, thus becoming a liquid lens. More specifically, the current-carrying medium will generate directional flow along the direction of the net electric field force. The electrodes on the first flexible FPC plate 2 and the second flexible FPC plate 4 are annular. The direction of the net electric field force of the liquid around the annular electrode is pointing towards the center of the circle. Therefore, the effect is that the fluid moves towards the center, that is, it gathers towards the center. After the first flexible FPC plate 2 and the second flexible FPC plate 4 are energized, an electric field force pointing towards the center is generated. The current-carrying medium inside the liquid lens, including the current-carrying medium stored in the edge circular holes at the four corners of the first flexible FPC plate 2 and the second flexible FPC plate 4, generates directional flow along the direction of the net electric field force, that is, it flows towards the center of the inner cavity. The current-carrying medium gathers at the center of the inner cavity, causing the first PDMS film 1 and the second PDMS film 5 at the locations of the first edge circular holes and the second edge circular holes to be recessed towards the electrode structure. After the current-carrying medium is energized, the center of the first PDMS film 1 and the second PDMS film 5 bulges away from the electrode structure under the drive of the current-carrying medium to form a liquid lens. The liquid lens is kept energized during operation, thereby maintaining the bulging state of the liquid lens.

[0034] By adjusting the energizing voltage, the net force on the fluid medium is changed, thereby altering the internal pressure. This allows for adjustment of the degree of protrusion of the first PDMS film 1 and the second PDMS film 5, which in turn adjusts the focal length of the liquid lens and thus the magnification. Furthermore, when the contact areas between the first PDMS film 1, the second PDMS film 5, and the fluid (i.e., the central circle) are equal and the film materials are identical, the degree of film protrusion is related to the film thickness. If the upper and lower PDMS films have equal thickness, the degree of protrusion is consistent; similarly, if the thicknesses are different, the thinner film will protrude more.

[0035] Liquid lenses are driven by electrofluids and are characterized by small size, simple structure, fast response, no noise, and good integration.

[0036] The liquid lens features a fully flexible design. The first PDMS film 1 and the second PDMS film 5 possess strong elasticity and tensile strength; the first flexible FPC board 2 and the second flexible FPC board 4 are bendable circuit boards made of flexible PI (polyimide) material, enabling bending, folding, and even twisting; the flexible shell 3 is constructed using silicone rubber material with a hardness of 30A. This fully flexible design allows the liquid lens to integrate "optical focusing capability" with "flexible adaptability," providing a lightweight, highly integrated, and reliable solution for next-generation "bionic sensing systems," "wearable vision devices," and "micro-optical modules."

[0037] Combination Figure 3 and Figure 4 The structure of the first flexible FPC plate 2 and the second flexible FPC plate 4 for driving a liquid lens of the present invention includes 6 pairs of annular electrodes.

[0038] Combination Figure 5 and Figure 6 The liquid lens can be driven by applying a high voltage to the first flexible FPC plate 2 and the second flexible FPC plate 4. After the high voltage is applied, the working medium inside the lens flows from the positive electrode of the first flexible FPC plate 2 and the second flexible FPC plate 4 to the negative electrode. Since the positive electrode of the annular electrode is on the outside and the negative electrode is on the inside, the working medium accumulates inside the lens, causing the first PDMS film 1 and the second PDMS film 5 to bulge, forming the lens. The higher the voltage, the higher the bulge of the first PDMS film 1 and the second PDMS film 5, and the greater the magnification of the lens.

[0039] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. An electrofluidically driven liquid lens, characterized in that, comprising a first PDMS film (1), an electrode structure, a second PDMS film (5) and a flexible shell (3) arranged in sequence and fixedly connected, the flexible shell (3) is a square frame structure with a hollow structure, the middle and four corners of the electrode structure are respectively provided with circular holes which are mutually penetrated with the hollow structure of the flexible shell (3), the first PDMS film (1) and the second PDMS film (5) are respectively fixedly connected on both sides of the electrode structure and cover the circular holes, so that the liquid lens forms a closed inner cavity in the middle of the flexible shell (3) and the electrode structure; the inner cavity is provided with an electrofluidic medium which fills the inner cavity, the electrode structure is connected with an external power supply and is electrified so that the electrofluidic medium flows to the center of the closed inner cavity, thereby causing the first PDMS film (1) and the second PDMS film (5) to protrude in the direction away from the electrode structure after the electrofluidic medium is electrified to form a liquid lens.

2. The electrofluidically driven liquid lens according to claim 1, characterized in that, the first PDMS film (1), the second PDMS film (5), the electrode structure and the flexible shell (3) are all square structures and have consistent outer contours.

3. The electrofluidically driven liquid lens according to claim 2, characterized in that, the electrode structure comprises a first flexible FPC board (2) and a second flexible FPC board (4) which are both connected with an external power supply, and the first flexible FPC board (2) is fixedly connected with the second flexible FPC board (4) through the flexible shell (3).

4. The electrofluidically driven liquid lens according to claim 3, characterized in that, the first flexible FPC board (2) is provided with a first center circular hole in the center, a plurality of annular first negative electrodes and first positive electrodes are coaxially arranged along the first center circular hole, the number of the first negative electrodes and the first positive electrodes is equal and they are alternately arranged from the direction towards the center to the direction away from the center, and the electrode closest to the center is the first negative electrode; the four corners of the first flexible FPC board (2) are respectively provided with an edge circular hole, and each first edge circular hole and the first center circular hole are used to store electrofluid.

5. The electrofluidically driven liquid lens according to claim 4, characterized in that, the second flexible FPC board (4) is provided with a second center circular hole in the center, a plurality of annular second negative electrodes and second positive electrodes are coaxially arranged along the second center circular hole, the number of the second negative electrodes and the second positive electrodes is equal and they are alternately arranged, and the electrode closest to the center is the second negative electrode; the four corners of the second flexible FPC board (4) are respectively provided with a second edge circular hole, and each second edge circular hole and the second center circular hole are used for the passage of electrofluid.

6. The electrofluidically driven liquid lens according to claim 5, characterized in that, The first flexible FPC board (2) and the second flexible FPC board (4) are provided with electrodes on the surfaces thereof facing the flexible shell (3).

7. The liquid lens driven by electrofluidics according to claim 3, wherein, The first PDMS film (1), the first flexible FPC board (2), the flexible shell (3), the second flexible FPC board (4) and the second PDMS film (5) are all flexible materials.

8. The liquid lens driven by electrofluidics according to claim 1, wherein, The electrofluidic medium is a combination of one or more of dibutyl sebacate, glyceryl triacetate, linalyl acetate and electronic fluorinated liquid.

9. Use of an electrofluidically driven liquid lens according to any of claims 1 to 8, characterized in that, Applications in biomimetic sensing systems, wearable and embedded optical systems, micro-optical modules, medical and diagnostic, machine vision and industrial detection.

10. A focusing method applied to the liquid lens driven by electrofluidics according to any one of claims 1-8, wherein, After the first flexible FPC board (2) and the second flexible FPC board (4) are powered, a force directed to the center of the circle is generated to make the electrofluidic medium subjected to the force directed to the center of the circle, the electrofluidic medium in the liquid lens flows to the center of the inner cavity, the electrofluidic medium is gathered at the center of the inner cavity, the first PDMS film (1) and the second PDMS film (5) at the positions of the first edge circular hole and the second edge circular hole are recessed in the direction of the electrode structure, the centers of the first PDMS film (1) and the second PDMS film (5) are protruded in the direction away from the electrode structure to form the liquid lens after the electrofluidic medium is powered, and the liquid lens maintains the powered state in the working state to maintain the protruded state of the liquid lens. By adjusting the voltage value, the net force on the electrofluidic medium is changed to change the inner cavity pressure, thereby adjusting the protrusion degree of the first PDMS film (1) and the second PDMS film (5), and further adjusting the focal length of the liquid lens, thereby adjusting the magnification of the liquid lens.

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