Flexible ultra-low profile lightweight liquid metal antenna and method of making same

Abstract

The application provides a flexible ultra-low profile light liquid metal antenna and a preparation method thereof, comprising a flexible substrate, upper and lower surfaces of the flexible substrate being a substrate front surface and a substrate back surface respectively, comprising a first microstrip transmission line, an antisymmetric elliptical ring radiation structure, a second microstrip transmission line and a rectangular ground layer, the antisymmetric elliptical ring radiation structure comprising a first half elliptical ring and a second half elliptical ring, the substrate front surface being provided with the first microstrip transmission line and the first half elliptical ring, the substrate back surface being provided with the rectangular ground layer, the second microstrip transmission line and the second half elliptical ring, the first microstrip transmission line, the antisymmetric elliptical ring radiation structure, the second microstrip transmission line and the rectangular ground layer forming a liquid metal conductive layer; the application has the advantages of low profile, light weight, high gain and wide bandwidth characteristics, can realize a dense liquid metal conductive layer with high electrical conductivity, can effectively reduce dielectric loss and conductor loss, and has stable wireless communication capability in bending and extreme humidity scenes.

Description

Technical Field

[0001] This invention relates to a flexible, ultra-low profile, lightweight liquid metal antenna and its fabrication method, belonging to the field of liquid metal antennas. Background Technology

[0002] Low-profile, lightweight flexible antennas are characterized by their small size, light weight, and mechanical conformability, meeting the stringent requirements of wearable devices, spacecraft, and deep-sea submersibles for wireless communication devices. The structural design based on highly conductive materials is key to ensuring that flexible antennas possess ultra-low profile, light weight, and excellent radio frequency performance. Gallium-based liquid metal has a profile of 3.4 × 10⁻⁶. 6 Sm -1 Its high electrical conductivity and excellent flow flexibility, which distinguish it from the irreversible deformation of traditional metallic materials such as copper and silver, as well as the relatively low electrical conductivity of novel flexible materials such as graphene and conductive polymers, make it the most promising candidate material for flexible antennas.

[0003] However, flexible, ultra-low profile, lightweight liquid metal antennas still face multiple challenges. First, due to the high fluidity of liquid metal, conventional processes typically rely on thick polymer layers for encapsulation to restrict its flow. However, such thick encapsulation not only introduces significant dielectric losses but also limits the low-profile design of the antenna. Second, liquid metal itself has a high density, and flexible encapsulation structures usually require thick conductive channels to maintain continuity, making it difficult to simultaneously achieve lightweight design and mechanical flexibility. Summary of the Invention

[0004] This invention aims to propose a flexible, ultra-low profile, lightweight liquid metal antenna and its fabrication method. It addresses the problems of existing liquid metal antennas relying on thick encapsulation layers to suppress fluidity, resulting in large profile thickness and heavy overall weight. The invention provides a solution that combines low profile, light weight, and high performance.

[0005] The technical solution of this invention is:

[0006] A flexible, ultra-low profile, lightweight liquid metal antenna includes a flexible substrate with a front and back side, respectively. The substrate includes a first microstrip transmission line, an antisymmetric elliptical ring radiating structure, a second microstrip transmission line, and a rectangular ground layer. The antisymmetric elliptical ring radiating structure comprises a first semi-elliptical ring and a second semi-elliptical ring. The front side of the substrate has the first microstrip transmission line and the first semi-elliptical ring, which are connected to the first microstrip transmission line. The back side of the substrate has a rectangular ground layer, the second microstrip transmission line, and the second semi-elliptical ring. The rectangular ground layer is connected to the second semi-elliptical ring via the second microstrip transmission line. The first microstrip transmission line, the antisymmetric elliptical ring radiating structure, the second microstrip transmission line, and the rectangular ground layer constitute a liquid metal conductive layer. The liquid metal conductive layer is fabricated using micron-level liquid metal ink through direct ink printing technology combined with thermal drive.

[0007] Furthermore, the micron-sized liquid metal ink is prepared as follows: acetic acid, sodium polystyrene sulfonate, and millimeter-sized liquid metal are added sequentially to deionized water to obtain a homogeneous solution. The millimeter-sized liquid metal in the homogeneous solution is then broken into micron-sized liquid metal particles using a probe ultrasonic method to obtain the micron-sized liquid metal ink.

[0008] Furthermore, the millimeter-scale liquid metal uses gallium-based liquid metal with a feature size of 0.5-50 mm, while the micrometer-scale liquid metal particles have a feature size of 0.5-50 μm.

[0009] Furthermore, the probe ultrasound power of the probe ultrasound method is 200-800W, and the time is 10-200min.

[0010] Furthermore, thermal driving involves heating the micron-sized liquid metallic ink to 40-60 degrees Celsius. o C induces acetic acid to remove the oxide scale formed on the surface of micron-sized liquid metal particles.

[0011] Furthermore, the major axis of the first semi-elliptical ring and the major axis of the second semi-elliptical ring are equal and corresponding vertically, the semi-minor axis of the first semi-elliptical ring and the semi-minor axis of the second semi-elliptical ring are equal and oppositely arranged, and the center of the first semi-elliptical ring and the center of the second semi-elliptical ring are corresponding vertically.

[0012] Furthermore, the flexible substrate, a microwave board F4B220M, is obtained by removing the copper layer on its surface with an etchant and depositing polydopamine on the surface.

[0013] Furthermore, the flexible substrate has a thickness of 0.254 mm, a dielectric constant of 2.2, and a loss tangent of 0.009.

[0014] A method for fabricating a flexible ultra-low profile lightweight liquid metal antenna as described in any one of the above claims includes the following steps:

[0015] Step 1: Add 5.4 mL of deionized water to a glass bottle, then add 0.6 mL of acetic acid solution to obtain a 10% diluted acetic acid solution. Add 0.27 g of sodium polystyrene sulfonate to the diluted acetic acid solution and let it stand for 60 min to obtain a homogeneous solution. Transfer 5 g of liquid metal to a glass bottle and sonicate it with a probe at 600 W power in an ice-water bath for 90 min to obtain micron-sized liquid metal ink.

[0016] Step 2, Deposition of polydopamine: Dissolve 100 mL of hydrochloric acid buffer and 2 g of dopamine hydrochloride in 900 mL of deionized water, adjust the pH to 8 and the temperature to 55 °C to obtain a mixed solution. Immerse the copper-free microwave plate F4B220M in the mixed solution for 48 h to achieve polydopamine deposition on the surface of the flexible substrate.

[0017] Step 3: Place 8 mL of micron-sized liquid metallic ink into a 10 mL dispensing syringe. First, fix the flexible substrate with deposited polydopamine on the robotic arm platform. By adjusting the printing parameters, uniformly deposit the micron-sized liquid metallic ink onto the flexible substrate, and then heat it to 40-60°C. o C ensures the shape integrity of the micron-scale liquid metal ink, uses thermally driven acetic acid to remove the oxide scale, promotes the recombination and fusion of liquid metal particles into a liquid metal conductive layer, and completes the fabrication of a flexible ultra-low profile lightweight liquid metal antenna.

[0018] Furthermore, in step 3, the printing parameters are adjusted, specifically: printing height is 0.025-0.200mm, printing speed is 1-70mm / s, printing air pressure is 30-200kPa, and stage temperature is 30-100℃.

[0019] The beneficial effects of this invention are as follows: This flexible ultra-low profile lightweight liquid metal antenna and its fabrication method, by employing an antisymmetric elliptical ring radiation structure and micron-level liquid metal ink, combined with high-precision ink direct writing printing technology and thermal drive, have advantages such as low profile, light weight, high gain and wide bandwidth characteristics. It can overcome the limitation of traditional liquid metal antennas, which are difficult to achieve ultra-low profile lightweight flexible antennas due to the use of ultra-thick polymer encapsulation layers to suppress the fluidity of liquid metal. It can achieve a dense liquid metal conductive layer with high conductivity, effectively reduce dielectric loss and conductor loss, and have high-speed and stable wireless communication capabilities in bending and extreme humidity scenarios. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the flexible ultra-low profile lightweight liquid metal antenna according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the back structure of the flexible ultra-low profile lightweight liquid metal antenna in the embodiment;

[0022] Figure 3 These are schematic diagrams of the flexible ultra-low profile lightweight liquid metal antenna of the embodiment, wherein (a) is a schematic diagram of the front of the flexible ultra-low profile lightweight liquid metal antenna, and (b) is a schematic diagram of the back of the flexible ultra-low profile lightweight liquid metal antenna.

[0023] Figure 4 These are comparative schematic diagrams of the flexible ultra-low profile lightweight liquid metal antenna of the embodiment with an elliptical monopole antenna and an elliptical ring monopole antenna; wherein, (a) is a schematic diagram of an elliptical monopole antenna, (b) is a schematic diagram of an elliptical ring monopole antenna, and (c) is a schematic diagram of the flexible ultra-low profile lightweight liquid metal antenna of the embodiment.

[0024] Figure 5 This is a comparative schematic diagram of the current distribution of the flexible ultra-low profile lightweight liquid metal antenna, the elliptical monopole antenna, and the elliptical ring monopole antenna in the embodiment; wherein, (a) is a schematic diagram of the current distribution of the elliptical monopole antenna, (b) is a schematic diagram of the current distribution of the elliptical ring monopole antenna, and (c) is a schematic diagram of the current distribution of the flexible ultra-low profile lightweight liquid metal antenna in the embodiment.

[0025] Figure 6 This is a schematic diagram of the simulated and measured return loss of the flexible ultra-low profile lightweight liquid metal antenna of the embodiment.

[0026] Figure 7 This is a schematic diagram of the simulation and measured gain of the flexible ultra-low profile lightweight liquid metal antenna of the embodiment;

[0027] Figure 8 This is a schematic diagram demonstrating the mechanical flexibility of the flexible ultra-low profile lightweight liquid metal antenna of the embodiment.

[0028] Figure 9 This is a schematic diagram of the return loss of the flexible ultra-low profile lightweight liquid metal antenna under different bending angles in the embodiment.

[0029] Figure 10 This is a schematic diagram illustrating the gain variation of the flexible ultra-low profile lightweight liquid metal antenna under different bending cycles in this embodiment.

[0030] Wherein: 1-substrate front side, 2-substrate back side, 3-first microstrip transmission line, 4-second microstrip transmission line, 5-rectangular ground layer, 6-first semi-elliptical ring, 7-second semi-elliptical ring. Detailed Implementation

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

[0032] An embodiment provides a flexible, ultra-low profile, lightweight liquid metal antenna, such as... Figure 1 and Figure 2 The system includes a flexible substrate, with a front side 1 and a back side 2, respectively. It includes a first microstrip transmission line 3, an antisymmetric elliptical ring radiation structure, a second microstrip transmission line 4, and a rectangular ground layer 5. The antisymmetric elliptical ring radiation structure includes a first semi-elliptical ring 6 and a second semi-elliptical ring 7. The front side 1 has the first microstrip transmission line 3 and the first semi-elliptical ring 6, which are connected to the first microstrip transmission line 3. The back side 2 has the rectangular ground layer 5, the second microstrip transmission line 4, and the second semi-elliptical ring 7. The rectangular ground layer 5 is connected to the second semi-elliptical ring 7 via the second microstrip transmission line 4. The first microstrip transmission line 3, the antisymmetric elliptical ring radiation structure, the second microstrip transmission line 4, and the rectangular ground layer 5 constitute a liquid metal conductive layer. This liquid metal conductive layer is made using micron-level liquid metal ink through direct ink printing technology combined with thermal drive.

[0033] This flexible, ultra-low profile, lightweight liquid metal antenna, by employing an antisymmetric elliptical ring radiation structure and micron-level liquid metal ink, combined with high-precision ink direct-write printing technology and thermal drive, possesses advantages such as low profile, light weight, high gain, and wide bandwidth. It overcomes the limitations of traditional liquid metal antennas, which rely on ultra-thick polymer encapsulation layers to suppress the fluidity of liquid metal, making it difficult to achieve ultra-low profile, lightweight, and flexible antennas. It can achieve a dense liquid metal conductive layer with high conductivity, effectively reducing dielectric and conductor losses, and providing high-speed and stable wireless communication capabilities in bending and extreme humidity scenarios.

[0034] Micron-sized liquid metal ink is prepared as follows: Acetic acid, sodium polystyrene sulfonate, and millimeter-sized liquid metal are sequentially added to deionized water to obtain a homogeneous solution. The millimeter-sized liquid metal in the homogeneous solution is then broken into micron-sized liquid metal particles using a probe ultrasonic method, resulting in micron-sized liquid metal ink. The millimeter-sized liquid metal is gallium-based liquid metal with a characteristic size of 0.5-50 mm, and the micron-sized liquid metal particles have a characteristic size of 0.5-50 μm. The probe ultrasonic power is 200-800 W, and the time is 10-200 min. The use of micron-sized liquid metal particles effectively suppresses the fluidity of the micron-sized liquid metal ink. The coordination and electrostatic interactions between the liquid metal and sodium polystyrene sulfonate give the resulting composite system excellent printability. The prepared micron-sized liquid metal ink is a low-surface-tension ink with attached sulfonate liquid metal particles. Direct printing with acetic acid assistance can produce a dense conductive layer with high electrical conductivity.

[0035] This flexible, ultra-low profile, lightweight liquid metal antenna features a first semi-elliptical ring 6 with its major axis equal to and vertically aligned with the major axis of the second semi-elliptical ring 7. The semi-minor axis of the first semi-elliptical ring 6 and the semi-minor axis of the second semi-elliptical ring 7 are equal to and opposite to each other. The centers of the first and second semi-elliptical rings are vertically aligned. Using an omnidirectional flexible elliptical monopole antenna as the research object, its elliptical radiation structure is designed as an elliptical ring structure without compromising its bandwidth. Furthermore, the first and second semi-elliptical rings 6 and 7 are placed on the upper and lower surfaces of the flexible substrate to avoid stress concentration on the elliptical rings. By connecting the second semi-elliptical ring 7, located on the back side 2 of the substrate, to the rectangular ground layer 5, a flexible, ultra-low profile, lightweight liquid metal antenna with ultra-wideband and high-gain characteristics can be achieved while effectively reducing the area of ​​the liquid metal conductive layer and significantly reducing the overall weight of the liquid metal antenna.

[0036] Thermal drive involves heating micron-sized liquid metallic ink to 40-60 degrees Celsius. oC-induced acetic acid removes the oxide layer formed on the surface of micron-sized liquid metal particles. The flexible substrate is a microwave board F4B220M, obtained by removing the copper layer on the surface with an etchant and depositing polydopamine on the surface. The flexible substrate has a thickness of 0.254 mm, a dielectric constant of 2.2, and a loss tangent of 0.009. This embodiment of a flexible ultra-low profile lightweight liquid metal antenna has overall dimensions of 30 mm × 50 mm × 0.260-0.354 mm. The fabricated liquid metal antenna has an ultra-low profile, less than 0.354 mm, and an ultra-light weight, with the combined weight of the conductive layer and the flexible substrate less than 1 g. A specific example of the embodiment is as follows: the antenna resonant frequency is 5.8 GHz, the semi-major axis a1 of the first semi-elliptical ring 6 and the semi-major axis a2 of the second semi-elliptical ring 7 are both 19 mm, the semi-minor axis b1 of the first semi-elliptical ring 6 and the semi-minor axis b2 of the second semi-elliptical ring 7 are both 13.2 mm, the width c1 of the first semi-elliptical ring 6 and the width c2 of the second semi-elliptical ring 7 are both 6.2 mm, the width d1 of the first microstrip transmission line 3 and the width d2 of the second microstrip transmission line 4 are both 0.8 mm, the width e of the rectangular ground layer 5 is 5 mm, and the length f of the rectangular ground layer 5 is 6 mm.

[0037] This flexible, ultra-low profile, lightweight liquid metal antenna is characterized by its ultra-low profile, lightweight nature, high gain, and ultra-wideband performance. The ultra-low profile is achieved through a low-profile flexible substrate and an ultra-thin liquid metal layer. By controlling the rheological properties of the ink and the surface characteristics of the substrate to achieve energy matching at the printing interface, micron-level liquid metal ink can be directly fabricated on the surface of a microwave board, avoiding polymer encapsulation. This provides a feasible solution for the high-precision manufacturing of low-loss, flexible liquid metal RF electronics. The antenna's mass is reduced by minimizing the area of ​​the liquid metal layer. Mechanical flexibility is achieved by placing elliptical rings on the front and back sides of the flexible substrate to avoid stress concentration on the elliptical rings. This meets the stringent requirements of flexible wearable devices, aircraft, and deep-sea submersibles in terms of low space occupation, weight control, and mechanical conformality.

[0038] The embodiment also provides a method for fabricating the flexible ultra-low profile lightweight liquid metal antenna as described in any of the above claims, comprising the following steps:

[0039] Step 1: Preparation of micron-sized liquid metal ink: Add 5.4 mL of deionized water to a glass bottle, then add 0.6 mL of acetic acid solution to obtain a 10% diluted acetic acid solution. Add 0.27 g of sodium polystyrene sulfonate to the diluted acetic acid solution and let it stand for 60 min to obtain a homogeneous solution. Transfer 5 g of liquid metal to a glass bottle and sonicate it with a probe at 600 W power in an ice-water bath for 90 min to obtain micron-sized liquid metal ink.

[0040] Step 2, Deposition of polydopamine: Dissolve 100 mL of hydrochloric acid buffer and 2 g of dopamine hydrochloride in 900 mL of deionized water, adjust the pH to 8 and the temperature to 55 °C to obtain a mixed solution. Immerse the copper-free microwave plate F4B220M in the mixed solution for 48 h to achieve polydopamine deposition on the surface of the flexible substrate.

[0041] In step 2, by adding hydrochloric acid buffer and dopamine hydrochloride to deionized water and placing the copper-free microwave plate F4B220M in it, polydopamine is deposited in situ on the surface of the flexible substrate, which can promote the formation of hydrogen bonds between the subsequent micron-scale liquid metal ink and the flexible substrate.

[0042] Step 3: Place 8 mL of micron-sized liquid metallic ink into a 10 mL dispensing syringe. First, fix the flexible substrate with deposited polydopamine on the robotic arm platform. By adjusting the printing parameters, uniformly deposit the micron-sized liquid metallic ink onto the flexible substrate, and then heat it to 40-60°C. o C ensures the shape integrity of the micron-scale liquid metal ink, uses thermally driven acetic acid to remove the oxide scale, promotes the recombination and fusion of liquid metal particles into a liquid metal conductive layer, and completes the fabrication of a flexible ultra-low profile lightweight liquid metal antenna.

[0043] In step 3, the printing parameters are adjusted, specifically: printing height of 0.025-0.200 mm, printing speed of 1-70 mm / s, printing air pressure of 30-200 kPa, and stage temperature of 30-100℃. Rectangular liquid metal films of different thicknesses are prepared by adjusting the printing parameters.

[0044] This flexible, ultra-low profile lightweight liquid metal antenna and its fabrication method achieve high radiation performance while being ultra-lightweight through the use of an anti-symmetric elliptical ring radiation structure. The micron-sized liquid metal ink disperses micron-sized liquid metal particles within a polymer matrix, suppressing flowability and enabling the fabrication of high-precision conductive patterns. Addressing the issue that a stable oxide layer easily forms spontaneously on the surface of the micron-sized liquid metal particles, making it difficult to re-fuse into a dense, continuous, and highly conductive layer, this embodiment employs a thermally driven strategy to remove the oxide layer with acetic acid during the printing process, thereby obtaining a dense and continuous liquid metal conductive layer with high conductivity. Furthermore, by constructing this liquid metal conductive layer on an ultra-thin flexible substrate, the need for a thick encapsulation layer is fundamentally eliminated, laying the foundation for the fabrication of low-profile flexible liquid metal antennas. Utilizing a low-dielectric-loss flexible substrate and effectively reducing the conductor loss of the liquid metal conductive layer, a high gain of 4.7 dBi and ultra-wideband performance of 4-6.3 GHz are achieved, and stable wireless communication is possible under bending and humid conditions.

[0045] This invention addresses the issue that while ultrasonic cavitation can suppress the flow of liquid metal, the resulting oxide layer hinders the fabrication of highly conductive flexible liquid metal films. By developing low-surface-tension micron-scale liquid metal ink and combining it with high-precision ink direct-write printing technology, and utilizing thermally driven acetic acid to remove the oxide layer, the invention promotes the recombination and fusion of liquid metal particles into a dense conductive layer. Based on a low-dielectric-loss substrate, an ultra-low profile and lightweight liquid metal antenna are designed and constructed, providing a feasible path to achieving high-performance flexible ultra-low profile lightweight liquid metal antennas.

[0046] The simulation verification of this flexible ultra-low profile lightweight liquid metal antenna in the embodiment is as follows:

[0047] Figure 3 This is a schematic diagram of the embodiment of the flexible ultra-low profile lightweight liquid metal antenna, and its front pattern is as follows. Figure 3 (a), whose back-side power supply network is as follows Figure 3 (b)

[0048] Figure 4 This is a comparative schematic diagram of the flexible ultra-low profile lightweight liquid metal antenna, elliptical monopole antenna, and elliptical ring monopole antenna in the embodiments. Figure 4 As shown, from the elliptical monopole antenna as... Figure 4 (a) to the elliptical ring monopole antenna, as shown Figure 4 From (b) to the flexible ultra-low profile lightweight liquid metal antenna in the embodiment, such as Figure 4 (c) The area of ​​its conductive layer decreases sequentially, thereby achieving the purpose of lightweight.

[0049] Figure 5 This is a schematic diagram comparing the current distribution of the flexible ultra-low profile lightweight liquid metal antenna with that of an elliptical monopole antenna and an elliptical ring monopole antenna. (See attached diagram.) Figure 5 As shown, the elliptical monopole antenna is as follows Figure 5 (a) and the elliptical ring monopole antenna, as Figure 5 (b) are all monopole antennas, and their current distribution is mainly concentrated along the x-axis; while the flexible ultra-low profile lightweight liquid metal antenna in the embodiment is a loop antenna, such as Figure 5 (c) Its current distribution is converted to be mainly concentrated on the y-axis. This current distribution can be effectively coupled through a flexible substrate to form a sinusoidal current distribution that is approximately symmetrical along the ring path. This current characteristic makes the current of the antenna weaker in the x-axis direction. Bending in this direction has a weaker effect on the current distribution, thus giving it excellent mechanical bending capability along the x-axis direction.

[0050] like Figure 6 As shown, the measured return loss S of this flexible ultra-low profile lightweight liquid metal antenna in the embodiment is...11 The curve achieves good impedance matching in the 4.0-6.3GHz range.

[0051] like Figure 7 As shown, the measured gain diagram of this flexible ultra-low profile lightweight liquid metal antenna in the embodiment shows a measured peak gain of up to 4.7 dBi.

[0052] like Figure 8 and Figure 9 As shown in the physical diagram of the embodiment of the flexible ultra-low profile lightweight liquid metal antenna, it demonstrates good mechanical flexibility. At the same time, its performance remains stable when it is not bent, bent at an angle of 15°, and bent at an angle of 30°.

[0053] like Figure 10 As shown, the gain variation of this flexible ultra-low profile lightweight liquid metal antenna under different bending cycles in the embodiment shows no significant fluctuation in gain after it recovers its flatness after being bent a thousand times.

[0054] Image transmission tests were conducted using the onboard wireless communication platform. The far end of the platform was the transmitter, which used a camera to capture image data in real-time, based on a stopwatch time, and transmitted it to the receiver via a transmitting antenna. The near end was the receiver, which used two receiving antennas to receive the image data and displayed it on a monitor. Comparison between the display and the stopwatch time verified that this flexible ultra-low profile lightweight liquid metal antenna maintained high-speed, low-latency communication performance even under bending conditions. The communication performance of the flexible ultra-low profile lightweight liquid metal antenna was not significantly affected when immersed in water; from the initial immersion to 28 seconds after immersion, it still maintained high-speed, low-latency signal transmission, verifying its communication capabilities in extremely humid environments.

[0055] This flexible, ultra-low profile lightweight liquid metal antenna and its fabrication method, through the design of an antisymmetric elliptical ring radiating structure and micron-sized liquid metal ink, combined with high-precision ink direct-write printing technology and thermal drive, exhibits characteristics such as low profile, light weight, high gain, and wide bandwidth. Low surface tension micron-sized liquid metal ink was developed through the coordination of Ga3+ ions and sulfonate groups in liquid metal particles. The interface energy matching between the micron-sized liquid metal ink and the flexible substrate is achieved by utilizing the hydrogen bonding between the sulfonate groups attached to the surface of the liquid metal particles and the hydroxyl and amino functional groups on the surface of polydopamine. Thermally driven acetic acid is used to eliminate the oxide layer of the liquid metal particles and promote particle recombination and fusion, resulting in a densely printed liquid metal conductive layer with high conductivity, ensuring low dielectric and conductor losses for the antenna. Simulation experiments verified the ultra-low latency high-speed wireless communication performance of the flexible antenna, enabling low-latency high-speed wireless communication under bending conditions and extreme humid environments, providing a feasible solution for the design and fabrication of flexible liquid metal antennas.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. However, the above description is merely a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other embodiments derived by those skilled in the art without departing from the technical solution of the present invention should be covered within the patent scope of the present invention.

Claims

1. A flexible ultra-low profile lightweight liquid metal antenna, comprising a flexible substrate, wherein the upper and lower surfaces of the flexible substrate are respectively the front and back surfaces of the substrate, characterized in that: The substrate comprises a first microstrip transmission line, an antisymmetric elliptical ring radiating structure, a second microstrip transmission line, and a rectangular ground layer. The antisymmetric elliptical ring radiating structure includes a first semi-elliptical ring and a second semi-elliptical ring. The first microstrip transmission line and the first semi-elliptical ring are located on the front side of the substrate, and the first semi-elliptical ring is connected to the first microstrip transmission line. The rectangular ground layer, the second microstrip transmission line, and the second semi-elliptical ring are located on the back side of the substrate, and the rectangular ground layer is connected to the second semi-elliptical ring through the second microstrip transmission line. The first microstrip transmission line, the antisymmetric elliptical ring radiating structure, the second microstrip transmission line, and the rectangular ground layer constitute a liquid metal conductive layer. The liquid metal conductive layer is fabricated using micron-sized liquid metal ink through direct ink printing technology combined with thermal drive. The micron-sized liquid metal ink is prepared as follows: 10% acetic acid, sodium polystyrene sulfonate, and millimeter-sized liquid metal are sequentially added to deionized water to obtain a homogeneous solution. The millimeter-sized liquid metal in the homogeneous solution is broken into micron-sized liquid metal particles using a probe ultrasonic method to obtain the micron-sized liquid metal ink. Thermal drive involves heating the micron-sized liquid metal ink to 40-60°C. o C induces acetic acid to remove the oxide scale formed on the surface of micron-sized liquid metal particles; the major axis of the first semi-elliptical ring and the major axis of the second semi-elliptical ring are equal and correspondingly set vertically, the semi-minor axis of the first semi-elliptical ring and the semi-minor axis of the second semi-elliptical ring are equal and oppositely set, and the center of the first semi-elliptical ring and the center of the second semi-elliptical ring are correspondingly set vertically.

2. The flexible ultra-low profile lightweight liquid metal antenna as described in claim 1, characterized in that: Millimeter-scale liquid metal uses gallium-based liquid metal with a feature size of 0.5-50 mm, while micrometer-scale liquid metal particles have a feature size of 0.5-50 μm.

3. The flexible ultra-low profile lightweight liquid metal antenna as described in claim 1, characterized in that: The probe ultrasound method uses a probe ultrasound power of 200-800W and a duration of 10-200min.

4. The flexible ultra-low profile lightweight liquid metal antenna as described in any one of claims 1-3, characterized in that: The flexible substrate, a microwave board F4B220M, is obtained by removing the copper layer on the surface with an etchant and depositing polydopamine on the surface.

5. The flexible ultra-low profile lightweight liquid metal antenna as described in any one of claims 1-3, characterized in that: The flexible substrate has a thickness of 0.254 mm, a dielectric constant of 2.2, and a loss tangent of 0.

009.

6. A method for fabricating a flexible ultra-low profile lightweight liquid metal antenna according to any one of claims 1-5, characterized in that: Includes the following steps, Step 1: Add 5.4 mL of deionized water to a glass bottle, then add 0.6 mL of acetic acid solution to obtain a 10% diluted acetic acid solution. Add 0.27 g of sodium polystyrene sulfonate to the diluted acetic acid solution and let it stand for 60 min to obtain a homogeneous solution. Transfer 5 g of liquid metal to a glass bottle and sonicate it with a probe at 600 W power in an ice-water bath for 90 min to obtain micron-sized liquid metal ink. Step 2, Deposition of polydopamine: Dissolve 100 mL of hydrochloric acid buffer and 2 g of dopamine hydrochloride in 900 mL of deionized water, adjust the pH to 8 and the temperature to 55 °C to obtain a mixed solution. Immerse the copper-free microwave plate F4B220M in the mixed solution for 48 h to achieve polydopamine deposition on the surface of the flexible substrate. Step 3: Place 8 mL of micron-sized liquid metallic ink into a 10 mL dispensing syringe. First, fix the flexible substrate with deposited polydopamine on the robotic arm platform. By adjusting the printing parameters, uniformly deposit the micron-sized liquid metallic ink onto the flexible substrate, and then heat it to 40-60°C. o C ensures the shape integrity of the micron-scale liquid metal ink, uses thermally driven acetic acid to remove the oxide scale, promotes the recombination and fusion of liquid metal particles into a liquid metal conductive layer, and completes the fabrication of a flexible ultra-low profile lightweight liquid metal antenna.

7. The method for fabricating a flexible ultra-low profile lightweight liquid metal antenna as described in claim 6, characterized in that: In step 3, the printing parameters are adjusted as follows: printing height is 0.025-0.200mm, printing speed is 1-70mm / s, printing air pressure is 30-200kPa, and stage temperature is 30-100℃.

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