A two-bit microfluidic programmable metasurface

Abstract

The present invention aims to provide a two-bit microfluidic programmable metasurface. The reflective artificial electromagnetic surface is composed of a series of coded metasurface units, each of which includes a dielectric substrate, a metal ground is provided on the lower side of the substrate, two metal patches are provided on the upper side, and a microfluidic channel is integrated above the metal patch. By injecting liquid metal into different microfluidic channels, the phase state of each coded metasurface unit can be controlled. The digital numbers "00", "01", "10" and "11" are used to represent the four different phase states of the coded metasurface unit, thereby constructing a two-bit programmable metasurface. This two-bit microfluidic programmable metasurface is not only easy to manufacture and eliminates complex feeding circuits, but also has significant energy-saving advantages, and can effectively overcome the fatigue and life problems of traditional metals and lumped components. Therefore, it shows potential application prospects in tunable antenna design, radar backscatter reduction, etc.

Description

Technical Field

[0001] The present invention belongs to the field of novel artificial electromagnetic materials and relates to a two-bit microfluidic programmable super surface. Background Art

[0002] In recent years, metasurfaces, as an ultra-thin metamaterial, have stood out with their unique advantages, aiming to overcome the limitations of three-dimensional metamaterials and bring new breakthroughs in the field of electromagnetic wave control. Compared with three-dimensional metamaterials, metasurfaces have many significant advantages such as small size, low profile, easy integration, and low loss, which has brought revolutionary progress to electromagnetic wave control. After careful design and optimization, metasurfaces have successfully realized multiple functions such as phase control, holographic imaging, radar cross-section reduction, polarization conversion, and wave absorption of electromagnetic waves. In addition, by loading adjustable devices such as diodes, electromagnets, and micro-electromechanical systems on specific coded metasurface units, the reconfigurability of digital metasurfaces can be achieved. When the external bias voltage changes, the radiation amplitude and phase response of the corresponding coded metasurface unit will change accordingly, thereby realizing real-time control of electromagnetic wave characteristics. However, traditional electrical control methods often involve switching devices, which may not only cause metal fatigue damage and increase system complexity, but also introduce unpredictable crosstalk problems.

[0003] In order to solve these problems, liquid metals have been explored as a new way to regulate electromagnetic waves. Liquid metals are easy to reshape and have good conductivity. EGaIn is an ideal candidate material due to its low melting point and good conductivity. Thanks to its inherent fluid properties, EGaIn maintains stable performance even under significant tensile strain. In addition, EGaIn has other significant advantages, including low toxicity and self-healing ability. By reconstructing EGaIn with a microfluidic device, liquid metal can be precisely reconstructed into a specific shape, thereby achieving precise regulation of electromagnetic waves. Compared with traditional electrical control methods, microfluidic methods are not only more convenient to operate, but also provide the system with higher stability, more energy saving, and effectively reduce crosstalk problems, bringing new possibilities to the field of electromagnetic wave regulation. Summary of the invention

[0004] Purpose of the invention: The present invention aims to provide a two-bit microfluidic programmable metasurface with simple design, low processing cost, energy saving and overcoming the fatigue of traditional metals.

[0005] A two-bit microfluidic programmable metasurface, which includes a programmable reflective artificial electromagnetic surface and a microfluidic chip integrated with the programmable reflective artificial electromagnetic surface. The two-bit microfluidic programmable metasurface includes a plurality of array-arranged coding metasurface units, each of which includes a dielectric substrate, a metal ground located on the lower side of the dielectric substrate, two metal patches arranged on the upper side of the dielectric substrate, a microfluidic channel arranged above the two metal patches, and a microchamber for storing liquid metal. The liquid metal in the microfluidic channel of the coding metasurface unit is driven by a micromotor.

[0006] Preferably, the two metal patches in the coding metasurface unit have the same length and width, which are 1.95-2.05 mm and 2.7-2.8 mm respectively; the two metal patches are hollowed out in the middle; and the length and width of the hollowed-out part of the left metal patch are 1.2-1.3 mm and 1.9-2 mm respectively, and the length and width of the hollowed-out part of the right metal patch are 1.2-1.3 mm and 2.2-2.3 mm respectively.

[0007] Preferably, the two ends of the microfluidic channel are respectively connected by a square microchamber for storing liquid metal and a micromotor. The liquid metal is injected into a hose from the microchamber by the drive of the micromotor. The hose and the microfluidic channel are connected to form a passage. Each hose is provided with an electromagnetic valve to control the opening and closing of the microfluidic channel.

[0008] Preferably, the material of the microfluidic channel is polycarbonate (PC), the width of the microfluidic channel is 0.75-0.85 mm, the depth is 0.25-0.35 mm, and the gap between the microfluidic channels is 0.6-0.7 mm.

[0009] Preferably, the micromotor and the microchamber are arranged on the side of the microfluidic channel, and the hose and the solenoid valve are placed in the middle of the microchamber and the microfluidic channel.

[0010] Preferably, the driving voltage of the micro motor is 0-3V, and the driving voltage of the solenoid valve is 3-3.7V.

[0011] Preferably, the liquid metal is a non-toxic, odorless, low-melting-point eutectic gallium-indium alloy (EGaIn).

[0012] Preferably, within the working frequency band, the liquid metal is controlled to enter different microfluidic channels, and the coded metasurface unit can present four different states with phase differences of 0°, 90°, 180° and 270°, which are represented by the digital numbers "00", "01", "10" and "11" respectively; the two-bit microfluidic programmable metasurface controls the coded metasurface units in an array, and different microfluidic channels can achieve different functions when filled with liquid metal. When the two-bit microfluidic programmable metasurface coding sequence is repeated as "00, 00, 00, 00", the reflected wave is a main beam emitted at 90°; when the two-bit microfluidic programmable metasurface coding sequence is repeated as "00, 00, 10, 10", the reflected wave is two main beams emitted in oblique directions; when the two-bit microfluidic programmable metasurface coding sequence is repeated as "00, 01, 10, 11", the reflected wave is a main beam emitted in an oblique direction.

[0013] 1) Existing electrically controlled digital metasurfaces require connecting diodes or varactors between metal patches. However, switching devices are particularly susceptible to material fatigue and damage, which makes it challenging to maintain their peak performance and reliability. Secondly, integrating circuits into metasurface systems may introduce complexity, leading to nonlinear and complex structural designs. The present invention constructs a microfluidic digital metasurface. Compared with existing electrically controlled digital metasurfaces, microfluidic programmable metasurfaces can be controlled by driving liquid metal into microfluidic channels. There is no need to introduce switching devices inside the metasurface, which greatly reduces the design and implementation complexity of the system and avoids the nonlinearity and complex structural design caused by related devices. Secondly, multiple reconstructions of liquid metal will not affect its performance. The two-bit microfluidic programmable metasurface unit of the present invention integrates a microfluidic channel, and the capacitance value of the unit can be dynamically adjusted with the injection of liquid metal, which can achieve approximately 0 within a wider frequency band. o , 90 o , 180 o and 270 o The phase difference.

[0014] 2) The two-bit microfluidic programmable metasurface of the present invention is simple in design and has low processing cost. The size of the coding metasurface unit is small and has good versatility. By changing the size of the coding metasurface unit structure, it can be designed at different operating frequencies, which is easy to promote and apply.

[0015] 3) The present invention solves the shortcomings of the existing single digital metasurface control method. Compared with the existing electrical control method, the microfluidic method reduces the complexity and crosstalk of the system, is simple in design, has low processing cost, overcomes the metal fatigue and easy damage defects of traditional devices, and has important application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a partial structural diagram of the two-bit microfluidic reflective programmable metasurface and microfluidic chip of the present invention;

[0017] Figure 2 It is a schematic diagram of the coding metasurface unit structure of the two-bit microfluidic reflective programmable metasurface of the present invention. The back of the coding metasurface unit substrate is a metal ground, and the front is two asymmetric metal patch structures. Microfluidic channels and liquid metal are integrated directly above the metal patch structures.

[0018] Figure 3 and Figure 4 They are respectively simulation curves of reflection amplitude and phase changing with frequency when the coding metasurface unit of the present invention realizes the states of "00", "01", "10" and "11";

[0019] Figure 5 It is a schematic diagram of the simulation result of the reflected beam obtained when the coding sequence of the two-bit microfluidic programmable metasurface of the present invention is repeated as "00, 00, 00, 00" at 20.3GHz;

[0020] Figure 6 It is a schematic diagram of the simulation result of the reflected beam obtained when the coding sequence of the two-bit microfluidic programmable metasurface of the present invention is repeated as "00, 00, 10, 10" at 20.3 GHz;

[0021] Figure 7 It is a schematic diagram of the simulation results of the reflected beam obtained when the coding sequence of the two-bit microfluidic programmable metasurface of the present invention is repeated as "00, 01, 10, 11" at 20.3GHz. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the embodiments and drawings of the specification. The present invention designs and manufactures a two-bit microfluidic programmable metasurface, which can realize four coding sequences by controlling the filling of the microfluidic channel with liquid metal. Figure 1 As shown, the two-bit microfluidic programmable metasurface of the present invention includes a digital reflective artificial electromagnetic surface and a liquid metal control module, which is composed of two microfluidic channels and a driving module. The microfluidic channels are integrated above the rectangular patch. The capacitance between the metal patches is controlled by controlling the injection of liquid metal into different channels. Figure 2 It is a schematic diagram of the structure of a coding metasurface unit used in the present invention. The back of the coding metasurface unit is a metal ground, and the front is two asymmetric metal patches, and a microfluidic channel is integrated above the metal patch. Figure 3 and Figure 4 In the present invention, when liquid metal is injected into different microfluidic channels, different capacitance values ​​cause the coding metasurface unit to produce different amplitude and phase responses. Figure 4As shown, the state of the coded metasurface unit can be controlled by microfluidics and liquid metal. The phase difference is selected to be about 0 o , 90 o , 180 o , 270 o In order to reduce costs and simplify the experimental process, three coding sequences "00, 00, 00, 00", "00, 00, 10, 10", and "00, 01, 10, 11" are used to demonstrate the feasibility of the microfluidic digital metasurface. Under three different coding sequences, three different reflected beams can be obtained.

[0023] In order to verify the designed two-bit microfluidic programmable metasurface, simulation was performed using CST software. Figure 3 and Figure 4 The simulated amplitude and phase of the reflection coefficient of the designed coding metasurface unit in the "00" state, "01" state, "10" state and "11" state are given, corresponding to the two side channels being empty, only the left channel being filled with liquid metal, only the right channel being filled with liquid metal and both side channels being filled with liquid metal. It can be seen that when the two side channels are empty and the left channel is filled with liquid metal, the phase difference of the designed coding metasurface unit in the bandwidth range of 20.2-20.45GHz is 77 o -101 o At 20.3 GHz, it is 90 o When the two side channels are empty and the right channel is filled with liquid metal, the phase difference of the designed coding metasurface unit in the bandwidth range of 20.2-20.45GHz is within 160 o -197 o At 20.33 GHz, it is 180 o When both channels are empty and filled with liquid metal, the phase difference of the designed coding metasurface unit is within 260° in the 20-21 GHz bandwidth. o -273 o Between 20.3 GHz and 20.46 GHz, 270 o . Here, the thickness of the substrate is h=0.5mm, the dielectric constant is 2.65, the loss tangent is 0.001, the symmetrical metal patch and metal ground are copper, the thickness is t=0.035mm, and the period of the coding metasurface unit is a=6mm. The following examples list three different reconfigurable microfluidic programmable metasurfaces to illustrate the present invention. The two-bit microfluidic programmable metasurface used in the simulation is composed of 24×24=576 coding units, 24 pairs of microfluidic channels and liquid metal filled inside, with a total area of ​​144×144mm 2 (9.7×9.7λ when the operating frequency is 20.3GHz 2), each coded metasurface unit has a size of 6×6mm 2 (0.41×0.41λ 2 ).

[0024] The two-bit microfluidic programmable metasurface of the present invention includes a digital reflective artificial electromagnetic surface, a microfluidic chip integrated with the reflective artificial electromagnetic surface, and liquid metal for filling microfluidic channels. The digital reflective artificial electromagnetic surface is composed of array-arranged coding metasurface units, and each coding metasurface unit includes a dielectric substrate, a metal ground located on the lower side of the dielectric substrate, two metal patches arranged on the upper side of the dielectric substrate, and a microfluidic channel integrated above the two metal patches. The upper and lower ends of the microfluidic channel are connected to the microchamber storing liquid metal through an electromagnetic valve, and the microchamber storing liquid metal is connected to the drive motor through a hose, and the drive motor is connected to the control module. Further, in the present invention, the microchamber, electromagnetic valve, motor control module and micromotor are all arranged on the dielectric substrate, and the dielectric substrate is integrated with the dielectric substrate of the coding metasurface unit in the digital reflective artificial electromagnetic surface.

[0025] Furthermore, in the present invention, the liquid metal is EGaIn.

[0026] Furthermore, in the present invention, the microfluidic channels are symmetrically distributed, and the microfluidic channels are separated from the metal patch by a PC film substrate.

[0027] Furthermore, in the present invention, the metal patch is rectangular and is asymmetrically arranged, and the hollowed-out areas between the two metal patches are different.

[0028] In one embodiment of the present invention, a two-bit microfluidic programmable metasurface is integrated by a digital reflective artificial electromagnetic metasurface and a microfluidic chip. Among them, the digital reflective metasurface is composed of periodically arranged coding metasurface units, the back of the coding metasurface unit substrate is a metal ground, and the front is two asymmetric metal patch structures. A pair of microfluidic channels are integrated directly above the metal patch structure, and the upper and lower ends of the microfluidic channel are connected to motors respectively through microchambers for storing liquid metal, and the micromotor drives the liquid metal from the microchamber to the microfluidic channel.

[0029] Furthermore, within the working frequency band, by controlling the liquid metal to enter different channels, the coded metasurface unit can present four different states with phase differences of approximately 0°, 90°, 180° and 270°, represented by the digital numbers "00", "01", "10" and "11".

[0030] Furthermore, the two-bit microfluidic programmable metasurface controls the coding metasurface units in an array, and different channels can achieve different functions when filled with liquid metal. When the metasurface coding sequence is repeated as "00, 00, 00, 00", the reflected wave is a main beam emitted at 90°; when the metasurface coding sequence is repeated as "00, 00, 10, 10", the reflected wave is two main beams emitted in oblique directions; when the metasurface coding sequence is repeated as "00, 01, 10, 11", the reflected wave is a main beam emitted in an oblique direction.

[0031] Example 1: This example demonstrates the reflection beam of a microfluidic programmable metasurface under a repeated coding sequence of “00, 00, 00, 00”. Figure 5 As shown, when the frequency is 20.3 GHz, all microfluidic channels are not filled with liquid metal, that is, under the repeated coding sequence of "00, 00, 00, 00", the main reflected beam of the digital metasurface points to the z-axis.

[0032] Example 2: This example demonstrates the reflection beam of a microfluidic programmable metasurface under a repeated coding sequence of “00, 00, 10, 10”. Figure 6 As shown in the figure, when the frequency is 20.3 GHz, the microfluidic channel of the metasurface with a coding sequence of 00 is not perfused with liquid metal, while the microfluidic channel on the left side of the metasurface with a coding sequence of 10 is not perfused with liquid metal, and the microfluidic channel on the right side is perfused with liquid metal. When the metasurface is under the repeated coding sequence of "00, 00, 10, 10", the main reflected beam will be split into two main beams on the xoz plane.

[0033] Example 3: This example demonstrates the reflection beam of a microfluidic programmable metasurface under a repeated coding sequence of “00, 01, 10, 11”. Figure 7 As shown in the figure, at a frequency of 20.3 GHz, the microfluidic channels of the metasurface with a coding sequence of 00 are not perfused with liquid metal, the microfluidic channels on the left side of the metasurface with a coding sequence of 01 are perfused with liquid metal, the microfluidic channels on the right side of the metasurface with a coding sequence of 10 are perfused with liquid metal, and the microfluidic channels on both sides of the metasurface with a coding sequence of 11 are perfused with liquid metal. When the metasurface is in the repeated coding sequence of "00, 01, 10, 11", the main reflected beam will be emitted in an oblique direction on the xoz plane.

[0034] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

Claims

1. A two-bit microfluidic programmable metasurface, characterized in that: The metasurface includes a programmable reflective artificial electromagnetic surface and a microfluidic chip integrated with the programmable reflective artificial electromagnetic surface. The two-bit microfluidic programmable metasurface includes a plurality of array-arranged coding metasurface units. Each of the coding metasurface units includes a dielectric substrate, a metal ground located on the lower side of the dielectric substrate, two metal patches arranged on the upper side of the dielectric substrate, a microfluidic channel arranged above the two metal patches, and a microchamber for storing liquid metal. The liquid metal in the microfluidic channel of the coding metasurface unit is driven by a micromotor; the two ends of the microfluidic channel are respectively connected to the micromotor through a square microchamber for storing liquid metal, and the liquid metal is injected into a hose from the microchamber by the drive of the micromotor. The hose and the microfluidic channel are connected to form a passage, and each hose is provided with an electromagnetic valve to control the opening and closing of the microfluidic channel. Within the working frequency band, the liquid metal is controlled to enter different microfluidic channels, and the coded metasurface unit can present four different states with phase differences of 0°, 90°, 180° and 270°, which are represented by the digital numbers "00", "01", "10" and "11" respectively; the two-bit microfluidic programmable metasurface controls the coded metasurface units in an entirety, and different microfluidic channels can achieve different functions when filled with liquid metal. When the two-bit microfluidic programmable metasurface coding sequence is repeated as "00, 00, 00, 00", the reflected wave is a main beam emitted at 90°; when the two-bit microfluidic programmable metasurface coding sequence is repeated as "00, 00, 10, 10", the reflected wave is two main beams emitted in oblique directions; when the two-bit microfluidic programmable metasurface coding sequence is repeated as "00, 01, 10, 11", the reflected wave is a main beam emitted in an oblique direction.

2. A two-bit microfluidic programmable metasurface according to claim 1, characterized in that: The two metal patches in the coding metasurface unit have the same length and width, which are 1.95-2.05 mm and 2.7-2.8 mm respectively; the two metal patches are hollowed out in the middle; and the length and width of the hollowed-out part of the left metal patch are 1.2-1.3 mm and 1.9-2 mm respectively, and the length and width of the hollowed-out part of the right metal patch are 1.2-1.3 mm and 2.2-2.3 mm respectively.

3. The two-bit microfluidic programmable metasurface according to claim 1, characterized in that: The material of the microfluidic channel is polycarbonate, the width of the microfluidic channel is 0.75-0.85 mm, the depth is 0.25-0.35 mm, and the gap between the microfluidic channels is 0.6-0.7 mm.

4. The two-bit microfluidic programmable metasurface according to claim 1, characterized in that: The micro motor and the micro chamber are arranged on the side of the micro fluidic channel, and the hose and the electromagnetic valve are placed in the middle of the micro chamber and the micro fluidic channel.

5. A two-bit microfluidic programmable metasurface according to any one of claims 1 to 4, characterized in that: The driving voltage of the micro motor is 0-3V, and the driving voltage of the solenoid valve is 3-3.7V.

6. A two-bit microfluidic programmable metasurface according to any one of claims 1 to 4, characterized in that: The liquid metal is a eutectic gallium-indium alloy that is non-toxic, has no special smell and has a low melting point.

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