Multi-layer flexible stretchable liquid metal interconnection circuit based on flexible substrate

Abstract

The utility model relates to a multilayer flexible stretchable liquid metal interconnection circuit based on a flexible substrate, and belongs to the field of flexible electronics. The flexible packaging structure comprises a flexible substrate layer with gradient modulus, a first liquid metal circuit, a flexible insulating layer, a second liquid metal circuit and a flexible packaging layer from bottom to top, electrical connection between the first liquid metal circuit and the second liquid metal circuit is realized through a through hole in the flexible insulating layer; and realizing device packaging by using a flexible packaging layer. According to the flexible substrate with the gradient modulus, smooth transition from hard to soft of the flexible substrate is realized, and the problems of tensile stress concentration, even assembly failure and the like caused by mismatching of the modulus of a rigid electronic component and the modulus of the flexible substrate in a flexible circuit are solved; and by designing a multi-layer liquid metal interconnection circuit, reliable electrical connection of the flexible circuit is realized, and meanwhile, the integration density of the flexible circuit is improved. According to the utility model, the working reliability and the integration level of the rigid electronic component on the flexible stretchable circuit are improved.

Description

Technical Field

[0001] The utility model relates to a multi-layer flexible stretchable liquid metal interconnection circuit based on a flexible substrate, belonging to the technical field of flexible electronics. Background Art

[0002] Flexible circuits combine rigid electronic components with flexible materials to make the circuits stretchable and bendable. Compared with traditional rigid circuits, flexible circuits have better fit in non-planar environments, and are therefore widely used in healthcare, soft robotics, wearable devices, and other fields. However, the modulus mismatch between rigid electronic components and flexible substrates limits the stretchability and stability of flexible circuits. Due to the large modulus difference, when stretching occurs, stress concentration occurs in the area where the rigid electronic components are located, resulting in the separation of the rigid electronic components and the flexible substrate, which greatly limits the application of flexible circuits.

[0003] At present, in order to solve the problem of modulus mismatch between rigid electronic components and flexible substrates, strain isolation strategies are often used. The existing technology usually uses a method of embedding a rigid island with a large modulus in a flexible substrate to achieve strain isolation of rigid electronic components. However, the direct connection between the rigid island and the flexible area will cause a sudden stress change at the connection point due to the large difference in modulus between the two, and interface fracture often occurs at the connection point.

[0004] In addition, as flexible devices develop towards intelligence, miniaturization and integration, flexible devices usually require a large number of rigid electronic components, and single-layer flexible circuits can no longer meet the demand. Utility Model Content

[0005] In order to solve the problems existing in the above-mentioned prior art, the utility model provides a multi-layer flexible stretchable liquid metal interconnection circuit based on a flexible substrate. Through a flexible substrate with a gradient modulus, a smooth transition of strain is achieved, and the instability problem caused by the mismatch between the rigid electronic components and the flexible substrate modulus in the flexible circuit is solved; and through the design of a multi-layer liquid metal interconnection circuit, a reliable electrical connection of the flexible circuit is achieved, while the integration density of the flexible circuit is improved.

[0006] The technical solution of the utility model is: a multi-layer flexible stretchable liquid metal interconnection circuit based on a flexible substrate, comprising a substrate layer 1, a first liquid metal circuit layer 2, a flexible insulating layer 3, a second liquid metal circuit layer 4, and a flexible packaging layer 5, which are, from bottom to top, the substrate layer 1 with a gradient modulus, the first liquid metal circuit layer 2, the flexible insulating layer 3, the second liquid metal circuit layer 4, and the flexible packaging layer 5.

[0007] The substrate layer 1 with gradient modulus includes a high modulus region 1.1, a transition region 1.2 and a low modulus region 1.3; the high modulus region 1.1 and the low modulus region 1.3 are connected through the transition region 1.2; a rigid electronic component 2.1 is placed on the upper surface of the high modulus region 1.1 of the substrate layer 1 with gradient modulus, and a first liquid metal circuit 2 is arranged on the upper surfaces of the transition region 1.2 and the low modulus region 1.3; a second liquid metal circuit 4 is arranged on the upper surface of the flexible insulating layer 3, and the electrical connection between the first liquid metal circuit 2 and the second liquid metal circuit 4 is achieved through the through hole 3.1 on the flexible insulating layer 3; and a flexible packaging layer 5 is used to achieve device packaging.

[0008] Furthermore, the Young's modulus of the high modulus region 1.1 is 750-900 MPa, and the Young's modulus of the low modulus region 1.3 is 2-5 MPa.

[0009] Furthermore, the high modulus region 1.1 and the low modulus region 1.3 are connected via a transition region 1.2 formed by diffusion of the polymer solution due to different concentrations.

[0010] Furthermore, the connection between the high modulus region 1.1 and the low modulus region 1.3 is achieved by spontaneous diffusion of the polymer solution A into the polymer solution B and formation of the transition region 1.2 after solidification.

[0011] Furthermore, the first liquid metal circuit 2 is arranged on the transition region 1.2 and the low modulus region 1.3 of the substrate layer 1 with gradient modulus by inkjet printing, the liquid metal is one of gallium-indium alloy or gallium-indium-tin alloy, and the thickness of the first liquid metal circuit 2 is 100-150nm.

[0012] Further, the material of the flexible insulating layer 3 is one of styrene-butadiene-styrene block copolymer or polyurethane;

[0013] The flexible packaging layer 5 is one of silica gel, ethylene-butadiene-styrene block copolymer or polyurethane.

[0014] Furthermore, the second liquid metal circuit 4 is provided on the upper surface of the flexible insulating layer 3 by inkjet printing, the thickness of the second liquid metal circuit 4 is 100-150 nm, and the through hole 3.1 is provided by laser cutting.

[0015] The utility model discloses a method for preparing a multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate, which specifically comprises the following steps:

[0016] Step 1, preparing polymer solution A and polymer solution B;

[0017] Step 2, pouring polymer solution A and polymer solution B on a glass substrate in sequence and curing them, wherein polymer solution A forms a high modulus region 1.1 after curing, polymer solution B forms a low modulus region 1.3 after curing, and the contact region between polymer solution A and polymer solution B forms a transition region 1.2, thereby obtaining a substrate layer 1 with a gradient modulus;

[0018] Step 3, a first liquid metal circuit 2 is arranged on the upper surface of the low modulus region 1.3 and the transition region 1.2 of the substrate layer 1 with gradient modulus, and a rigid electronic component 2.1 is placed on the upper surface of the high modulus region 1.1;

[0019] Step 4: pouring a layer of flexible film on the first liquid metal circuit 2 and the rigid electronic component 2.1 to form a flexible insulating layer 3;

[0020] Step 5, disposing a second liquid metal circuit 4 and a through hole 3.1 on the flexible insulating layer 3; achieving electrical connection between the first liquid metal circuit 2 and the second liquid metal circuit 4 through the through hole 3.1 on the flexible insulating layer 3;

[0021] Step 6: Use a flexible packaging layer 5 to package the above-obtained circuit.

[0022] Preferably, in step 1, the polymer solution A comprises the following components: an ionic monomer solution, 55% to 65% by mass of 2-hydroxyethyl methacrylate, 0.5% to 1% by mass of polyethylene glycol diacrylate, and 0.5% to 1% by mass of photoinitiator 2959, the sum of the components being 100%;

[0023] The polymer solution B includes the following components: an ionic monomer solution, 55% to 65% by mass of 2-hydroxyethyl methacrylate, 0.5% to 1% by mass of polyethylene glycol diacrylate, 1% to 2% by mass of photoinitiator 2959, and 15% to 16.7% by mass of deionized water, and the sum of the components is 100%.

[0024] Preferably, in step 1, the ionic monomer solution is synthesized from acrylic acid and choline chloride under heating conditions, and the mass ratio of acrylic acid to choline chloride is 13-15:14-16.

[0025] Preferably, in step 2, the curing method is one of light curing or thermal curing.

[0026] Preferably, in step 2, the Young's modulus of the high modulus region 1.1 is 750-900 MPa, and the Young's modulus of the low modulus region 1.3 is 2-5 MPa.

[0027] Preferably, in step 2, the connection between the high modulus region 1.1 and the low modulus region 1.3 is achieved by spontaneous diffusion of solution A into solution B to form a transition region 1.2 after solidification.

[0028] Preferably, in step 3, the first liquid metal circuit 2 is provided on the substrate layer 1 having a gradient modulus by inkjet printing, the liquid metal is one of gallium-indium alloy or gallium-indium-tin alloy, and the thickness of the first liquid metal circuit 2 is 100 to 150 nm.

[0029] Preferably, in step 4, the material of the flexible insulating layer 3 is one of styrene-butadiene-styrene block copolymer or polyurethane;

[0030] The flexible packaging layer 5 is one of silica gel, ethylene-butadiene-styrene block copolymer or polyurethane.

[0031] Preferably, in step 5, the method of providing the second liquid metal circuit 4 on the flexible insulating layer 3 is inkjet printing, the thickness of the second liquid metal circuit 4 is 100-150 nm, and the way of providing the through hole 3.1 is laser cutting.

[0032] The working principle of this utility model:

[0033] The modulus of the film formed after the polymer solution is cured is positively correlated with the concentration of the crosslinker and polymer in the solution. When solutions of different concentrations are mixed together, the chemical elements will spontaneously diffuse from high concentration to low concentration, forming a gradient modulus distribution after curing.

[0034] In the utility model, the transition area formed by spontaneous diffusion of concentration closely combines the high modulus area and the low modulus area, and realizes a gradual change of modulus from low to high. When the flexible circuit is stretched, the high modulus area will basically not be strained, and strain isolation is realized. Therefore, the rigid electronic components placed on the upper surface of the high modulus area will not be displaced or fall off due to stretching, thereby solving the circuit instability problem caused by the separation of the rigid electronic components and the flexible substrate.

[0035] The fluidity of liquid metal enables it to maintain high conductivity when stretched. In the utility model, by using liquid metal as a conductive medium between rigid electronic components, stable electrical connection is ensured when the flexible circuit is stretched, and a two-layer liquid metal circuit is designed to realize a three-dimensional structure circuit. Multiple rigid electronic components can be integrated into the flexible circuit, thereby improving the integration density of the flexible circuit.

[0036] The beneficial effects of the utility model are:

[0037] 1. The utility model prepares a flexible substrate with a gradient modulus, which can achieve a smooth transition of strain, thereby avoiding the separation of rigid electronic components and the flexible substrate; at the same time, it combines a multilayer liquid metal circuit to improve the integration density of the flexible circuit.

[0038] 2. The flexible circuit proposed by the utility model maintains the flexibility and stretchability of the flexible device, while improving the stability and reliability of the flexible device;

[0039] 3. The process is simple and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The schematic diagram is a structural diagram of a multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate;

[0041] Figure 2 Schematic cross-sectional view of a multilayer flexible stretchable liquid metal interconnect circuit based on a flexible substrate.

[0042] Figure numerals: 1-substrate layer with gradient modulus, 1.1-high modulus region, 1.2-transition region, 1.3-low modulus region, 2-first liquid metal circuit, 2.1-electronic component, 3-flexible insulating layer, 3.1-through hole, 4-second liquid metal circuit, 5-flexible packaging layer. DETAILED DESCRIPTION

[0043] The utility model is further described below in conjunction with the accompanying drawings and specific embodiments.

[0044] Example 1: Figure 1-Figure 2 As shown, this embodiment is a multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate, including a substrate layer 1, a first liquid metal circuit layer 2, a flexible insulating layer 3, a second liquid metal circuit layer 4, and a flexible packaging layer 5, which are, from bottom to top, the substrate layer 1 with a gradient modulus, the first liquid metal circuit layer 2, the flexible insulating layer 3, the second liquid metal circuit layer 4, and the flexible packaging layer 5.

[0045] It includes a substrate layer 1, a first liquid metal circuit layer 2, a flexible insulating layer 3, a second liquid metal circuit layer 4, and a flexible packaging layer 5, which are, from bottom to top, a substrate layer 1 with a gradient modulus, a first liquid metal circuit layer 2, a flexible insulating layer 3, a second liquid metal circuit layer 4, and a flexible packaging layer 5.

[0046] The substrate layer 1 with gradient modulus includes a high modulus region 1.1, a transition region 1.2 and a low modulus region 1.3; the high modulus region 1.1 and the low modulus region 1.3 are connected through the transition region 1.2; a rigid electronic component 2.1 is placed on the upper surface of the high modulus region 1.1 of the substrate layer 1 with gradient modulus, and a first liquid metal circuit 2 is arranged on the upper surfaces of the transition region 1.2 and the low modulus region 1.3; a second liquid metal circuit 4 is arranged on the upper surface of the flexible insulating layer 3, and the electrical connection between the first liquid metal circuit 2 and the second liquid metal circuit 4 is achieved through the through hole 3.1 on the flexible insulating layer 3; and a flexible packaging layer 5 is used to achieve device packaging.

[0047] Furthermore, the Young's modulus of the high modulus region 1.1 is 750-900 MPa, and the Young's modulus of the low modulus region 1.3 is 2-5 MPa.

[0048] Furthermore, the high modulus region 1.1 and the low modulus region 1.3 are connected via a transition region 1.2 formed by diffusion of the polymer solution due to different concentrations.

[0049] Furthermore, the connection between the high modulus region 1.1 and the low modulus region 1.3 is achieved by spontaneous diffusion of the polymer solution A into the polymer solution B and formation of the transition region 1.2 after solidification.

[0050] Furthermore, the first liquid metal circuit 2 is arranged on the transition region 1.2 and the low modulus region 1.3 of the substrate layer 1 with gradient modulus by inkjet printing, the liquid metal is one of gallium-indium alloy or gallium-indium-tin alloy, and the thickness of the first liquid metal circuit 2 is 100-150nm.

[0051] Further, the material of the flexible insulating layer 3 is one of styrene-butadiene-styrene block copolymer or polyurethane;

[0052] The flexible packaging layer 5 is one of silica gel, ethylene-butadiene-styrene block copolymer or polyurethane.

[0053] Furthermore, the second liquid metal circuit 4 is provided on the upper surface of the flexible insulating layer 3 by inkjet printing, the thickness of the second liquid metal circuit 4 is 100-150 nm, and the through hole 3.1 is provided by laser cutting.

[0054] The utility model discloses a method for preparing a multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate, which specifically comprises the following steps:

[0055] Step 1, preparing polymer solution A and polymer solution B;

[0056] Step 2, pouring polymer solution A and polymer solution B on a glass substrate in sequence and curing them, wherein polymer solution A forms a high modulus region 1.1 after curing, polymer solution B forms a low modulus region 1.3 after curing, and the contact region between polymer solution A and polymer solution B forms a transition region 1.2, thereby obtaining a substrate layer 1 with a gradient modulus;

[0057] Step 3, a first liquid metal circuit 2 is arranged on the upper surface of the low modulus region 1.3 and the transition region 1.2 of the substrate layer 1 with gradient modulus, and a rigid electronic component 2.1 is placed on the upper surface of the high modulus region 1.1;

[0058] Step 4: pouring a layer of flexible film on the first liquid metal circuit 2 and the rigid electronic component 2.1 to form a flexible insulating layer 3;

[0059] Step 5, disposing a second liquid metal circuit 4 and a through hole 3.1 on the flexible insulating layer 3; achieving electrical connection between the first liquid metal circuit 2 and the second liquid metal circuit 4 through the through hole 3.1 on the flexible insulating layer 3;

[0060] Step 6: Use a flexible packaging layer 5 to package the above-obtained circuit.

[0061] Preferably, in step 1, the polymer solution A comprises the following components: an ionic monomer solution, 55% by mass of 2-hydroxyethyl methacrylate, 0.5% by mass of polyethylene glycol diacrylate, and 0.5% by mass of photoinitiator 2959, and the sum of the components is 100%;

[0062] The polymer solution B includes the following components: an ionic monomer solution, 55% by mass of 2-hydroxyethyl methacrylate, 0.5% by mass of polyethylene glycol diacrylate, 1% by mass of photoinitiator 2959, and 15% by mass of deionized water, and the sum of the components is 100%.

[0063] Preferably, in step 1, the ionic monomer solution is synthesized from acrylic acid and choline chloride under heating conditions, and the mass ratio of acrylic acid to choline chloride is 13:14.

[0064] Preferably, in step 2, the curing method is one of light curing or thermal curing.

[0065] Preferably, in step 2, the Young's modulus of the high modulus region 1.1 is 750 MPa, and the Young's modulus of the low modulus region 1.3 is 2 MPa.

[0066] Preferably, in step 2, the connection between the high modulus region 1.1 and the low modulus region 1.3 is achieved by spontaneous diffusion of solution A into solution B to form a transition region 1.2 after solidification.

[0067] Preferably, in step 3, the first liquid metal circuit 2 is provided on the substrate layer 1 having a gradient modulus by inkjet printing, the liquid metal is one of gallium-indium alloy or gallium-indium-tin alloy, and the thickness of the first liquid metal circuit 2 is 100 nm.

[0068] Preferably, in step 4, the material of the flexible insulating layer 3 is one of styrene-butadiene-styrene block copolymer or polyurethane;

[0069] The flexible packaging layer 5 is one of silica gel, ethylene-butadiene-styrene block copolymer or polyurethane.

[0070] Preferably, in step 5, the method of providing the second liquid metal circuit 4 on the flexible insulating layer 3 is inkjet printing, the thickness of the second liquid metal circuit 4 is 100 nm, and the way of providing the through hole 3.1 is laser cutting.

[0071] Embodiment 2: A method for preparing a multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate. This embodiment is the same as Embodiment 1, except that:

[0072] Preferably, in step 1, the polymer solution A comprises the following components: an ionic monomer solution, 65% by mass of 2-hydroxyethyl methacrylate, 1% by mass of polyethylene glycol diacrylate, and 1% by mass of photoinitiator 2959, and the sum of the components is 100%;

[0073] The polymer solution B includes the following components: an ionic monomer solution, 65% by mass of 2-hydroxyethyl methacrylate, 1% by mass of polyethylene glycol diacrylate, 2% by mass of photoinitiator 2959, and 16.7% by mass of deionized water, and the sum of the components is 100%.

[0074] Preferably, in step 1, the ionic monomer solution is synthesized from acrylic acid and choline chloride under heating conditions, and the mass ratio of acrylic acid to choline chloride is 15:16.

[0075] Preferably, in step 2, the Young's modulus of the high modulus region 1.1 is 900 MPa, and the Young's modulus of the low modulus region 1.3 is 5 MPa.

[0076] Preferably, in step 3, the first liquid metal circuit 2 is provided on the substrate layer 1 having a gradient modulus by inkjet printing, the liquid metal is one of gallium-indium alloy or gallium-indium-tin alloy, and the thickness of the first liquid metal circuit 2 is 150 nm.

[0077] Preferably, in step 5, the method of setting the second liquid metal circuit 4 on the flexible insulating layer 3 is inkjet printing, the thickness of the second liquid metal circuit 4 is 150 nm, and the way of setting the through hole 3.1 is laser cutting.

[0078] Embodiment 3: A method for preparing a multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate. This embodiment is the same as Embodiment 1, except that:

[0079] Preferably, in step 1, the polymer solution A comprises the following components: an ionic monomer solution, 60% by mass of 2-hydroxyethyl methacrylate, 0.7% by mass of polyethylene glycol diacrylate, and 0.8% by mass of photoinitiator 2959, and the sum of the components is 100%;

[0080] The polymer solution B includes the following components: an ionic monomer solution, 60% by mass of 2-hydroxyethyl methacrylate, 0.7% by mass of polyethylene glycol diacrylate, 1.5% by mass of photoinitiator 2959, and 16% by mass of deionized water, and the sum of the components is 100%.

[0081] Preferably, in step 1, the ionic monomer solution is synthesized from acrylic acid and choline chloride under heating conditions, and the mass ratio of acrylic acid to choline chloride is 14:15.

[0082] Preferably, in step 2, the Young's modulus of the high modulus region 1.1 is 800 MPa, and the Young's modulus of the low modulus region 1.3 is 4 MPa.

[0083] Preferably, in step 3, the first liquid metal circuit 2 is provided on the substrate layer 1 having a gradient modulus by inkjet printing, the liquid metal is one of gallium-indium alloy or gallium-indium-tin alloy, and the thickness of the first liquid metal circuit 2 is 120 nm.

[0084] Preferably, in step 5, the method of setting the second liquid metal circuit 4 on the flexible insulating layer 3 is inkjet printing, the thickness of the second liquid metal circuit 4 is 120 nm, and the way of setting the through hole 3.1 is laser cutting.

[0085] Embodiment 4: Embodiment 4 of the present utility model provides a method for preparing a multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate, which specifically includes the following steps:

[0086] Step 1, 14.5 g of acrylic acid and 14 g of choline chloride were mixed and heated at 80° C. for 2 hours to obtain a uniform ionic monomer solution;

[0087] The ionic monomer solution was mixed with 65% by mass of 2-hydroxyethyl methacrylate, 1% by mass of polyethylene glycol diacrylate and 1% by mass of photoinitiator 2959, the sum of the components being 100%; the mixture was mixed by ultrasonic treatment at room temperature to obtain a polymer solution A with a higher concentration;

[0088] The ionic monomer solution was mixed with 65% by mass of 2-hydroxyethyl methacrylate, 1% by mass of polyethylene glycol diacrylate, 2% by mass of photoinitiator 2959 and 16.7% by mass of deionized water, the sum of the components being 100%; the mixture was mixed by ultrasonic treatment at room temperature to obtain a polymer solution B with a lower concentration;

[0089] Step 2, pouring polymer solution A and polymer solution B onto a glass substrate, and using light curing, irradiating under ultraviolet light for 40 minutes; the area where polymer solution A is located forms a high modulus area 1.1, the area where solution B is located forms a low modulus area 1.3, polymer solution A and polymer solution B form a transition area 1.2 due to diffusion, and the high modulus area 1.1 and the low modulus area 1.2 are connected through the transition area 1.2, so as to obtain a substrate layer 1 with a gradient modulus;

[0090] Step 3: Gallium-indium alloy is used to set a liquid metal circuit with a thickness of 100 nm on the upper surface of the low modulus region 1.3 and the transition region 1.2 by inkjet printing to form a first liquid metal circuit 2, and a rigid electronic component 2.1 is placed on the upper surface of the high modulus region 1.1;

[0091] Step 4: prepare a 100 mg / mL styrene-butadiene-styrene block copolymer solution, the solvent is toluene, cast the styrene-butadiene-styrene block copolymer solution on the first liquid metal circuit 2 and the rigid electronic component 2.1, and place them in a fume hood for 12 hours to volatilize the solvent, thereby forming a flexible insulating layer 3;

[0092] Step 5: using inkjet printing to form a second liquid metal 4 on the upper surface of the flexible insulating layer 3, and using laser cutting to form a through hole 3.1 on the flexible insulating layer 3, and injecting the gallium-indium alloy into the through hole 3.1 to achieve connection between the first liquid metal circuit 2 and the second liquid metal circuit 4;

[0093] Step 6: prepare a 100 mg / mL styrene-butadiene-styrene block copolymer solution, with toluene as the solvent, and cast the styrene-butadiene-styrene block copolymer solution on the second liquid metal circuit 4 to realize a flexible packaging layer.

[0094] The specific embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate, characterized in that: The invention comprises a substrate layer (1), a first liquid metal circuit (2), a flexible insulating layer (3), a second liquid metal circuit (4), and a flexible packaging layer (5), wherein from bottom to top, the substrate layer (1) having a gradient modulus, the first liquid metal circuit (2), the flexible insulating layer (3), the second liquid metal circuit (4), and the flexible packaging layer (5); The substrate layer (1) with gradient modulus comprises a high modulus region (1.1), a transition region (1.2) and a low modulus region (1.3); the high modulus region (1.1) and the low modulus region (1.3) are connected via the transition region (1.2); a rigid electronic component (2.1) is placed on the upper surface of the high modulus region (1.1) of the substrate layer (1) with gradient modulus, and a first liquid metal circuit (2) is arranged on the upper surfaces of the transition region (1.2) and the low modulus region (1.3); a second liquid metal circuit (4) is arranged on the upper surface of the flexible insulating layer (3), and electrical connection between the first liquid metal circuit (2) and the second liquid metal circuit (4) is achieved via a through hole (3.1) on the flexible insulating layer (3); and device packaging is achieved using a flexible packaging layer (5).

2. The multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate according to claim 1, characterized in that: The Young's modulus of the high modulus region (1.1) is 750 to 900 MPa, and the Young's modulus of the low modulus region (1.3) is 2 to 5 MPa.

3. The multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate according to claim 1, characterized in that: The high modulus region (1.1) and the low modulus region (1.3) are connected via a transition region (1.2) formed by diffusion of a polymer solution due to different concentrations.

4. The multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate according to claim 1, characterized in that: The connection between the high modulus region (1.1) and the low modulus region (1.3) is achieved by spontaneous diffusion of the polymer solution A into the polymer solution B, and the formation of a transition region (1.2) after solidification.

5. The multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate according to claim 1, characterized in that: The first liquid metal circuit (2) is arranged on the transition region (1.2) and the low modulus region (1.3) of the substrate layer (1) having a gradient modulus by inkjet printing, the liquid metal is one of a gallium-indium alloy or a gallium-indium-tin alloy, and the thickness of the first liquid metal circuit (2) is 100 to 150 nm.

6. The multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate according to claim 1, characterized in that: The material of the flexible insulating layer (3) is one of styrene-butadiene-styrene block copolymer or polyurethane; The flexible packaging layer (5) is one of silica gel, ethylene-butadiene-styrene block copolymer or polyurethane.

7. The multi-layer flexible stretchable liquid metal interconnect circuit based on a flexible substrate according to claim 1, characterized in that: The method of setting the second liquid metal circuit (4) on the upper surface of the flexible insulating layer (3) is inkjet printing, the thickness of the second liquid metal circuit (4) is 100-150nm, and the way of setting the through hole (3.1) is laser cutting.

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