A flexible stretchable integrated circuit and a method of manufacturing the same

Abstract

The present application belongs to the technical field of flexible electronics and liquid metal circuit, and particularly relates to a flexible stretchable integrated circuit and a preparation method thereof. The flexible stretchable integrated circuit is obtained by forming a groove on an acrylate stretchable flexible substrate, and filling the groove with an oxidized liquid metal, so as to obtain a flexible stretchable integrated circuit with higher structural stability, higher integration and stronger anti-leakage capability. Meanwhile, the preparation method is simple in process and suitable for batch manufacturing. As a more optimal implementation, the flexible stretchable integrated circuit further comprises a via-in-pad structure arranged in a pad and located below a component pin, so as to reduce the surface wiring area and improve the stretchable circuit integration and conductive stability.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronics and liquid metal circuit technology, specifically relating to a flexible stretchable integrated circuit and its fabrication method. Background Technology

[0002] In recent years, flexible and stretchable integrated circuits, with their superior deformability, lightweight characteristics, and excellent conformal capabilities, have been able to meet the stringent requirements of cutting-edge fields such as wearable health monitoring devices, flexible artificial skin, and soft robots. Among these, the selection of conductive materials is crucial for realizing the functionality of flexible circuits. Gallium-based liquid metals (such as gallium indium tin alloy) not only remain liquid at room temperature but also possess high conductivity of up to 10... 6 S m -1 Liquid metal exhibits excellent electrical conductivity. Compared to the irreversible fracture of traditional metallic materials (such as copper and silver) under tensile deformation, and the relatively low electrical conductivity of novel flexible materials (such as graphene, carbon nanotubes, and conductive polymers), liquid metal has become the most promising candidate conductive medium for stretchable integrated circuits.

[0003] However, existing flexible and stretchable integrated circuits based on liquid metal still face multiple severe challenges in practical fabrication and long-term application. First, the inherently high surface tension of liquid metal makes it difficult to achieve high-precision patterning on polymer substrates using conventional inkjet or transfer printing methods. Simultaneously, its high fluidity makes it prone to lateral leakage on planar substrates or under tensile stress. Second, with the increasing functional requirements of flexible circuits and the continuous increase in integration density, traditional through-hole lead technology not only requires a large amount of substrate area, resulting in excessively high wire density, but also significantly increases the risk of short-circuit failures between adjacent interleaved circuits. Furthermore, existing multi-layer microfluidic packaging technologies are not only cumbersome and costly in terms of process flow, but also have limited interfacial adhesion, leading to extreme instability of currently existing flexible and stretchable electronic systems under high tensile strain. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies, such as difficulty in patterning liquid metal, easy lateral leakage, large substrate area occupied by traditional via leads, and insufficient interface bonding stability. It provides a flexible stretchable integrated circuit and its fabrication method. This flexible stretchable integrated circuit is fabricated by forming grooves on an acrylate stretchable flexible substrate. In a preferred embodiment, the flexible stretchable integrated circuit also includes a disk-in-hole structure, with the grooves filled with oxidized liquid metal, to obtain a flexible stretchable integrated circuit with high structural stability, high integration density, and strong leakage resistance. Furthermore, this fabrication method is simple and suitable for mass production.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a flexible stretchable integrated circuit, the flexible stretchable integrated circuit comprising a flexible substrate layer, an upper circuit layer, an lower circuit layer, and electronic components;

[0007] The flexible substrate layer is made of an acrylic film, with patterned upper and lower grooves formed on its upper and lower surfaces according to a circuit layout design using a CO2 laser. The acrylic film itself has stretchability and adhesion. The upper and lower grooves are collectively referred to as grooves, channels, or microchannels. The flexible substrate layer also has through holes penetrating the lower layer of the flexible substrate. It should be noted that the upper and lower grooves do not penetrate the flexible substrate layer in non-through hole areas. The through holes, upper grooves, and lower grooves are all filled with oxidized liquid metal.

[0008] After the upper and lower grooves are filled with liquid metal, they form the upper circuit and the lower circuit, respectively. The through holes are filled with oxidized liquid metal to enable the connection between the upper circuit and the lower circuit, or to enable the connection between the pins of electronic components, the upper circuit and the lower circuit.

[0009] The liquid metal of the upper circuit connection components serves as a pad to support the pins of electronic components, such as chips, resistors, and capacitors.

[0010] Technical Principle: The inner surfaces of the upper and lower grooves have carboxyl and ester functional groups formed by CO2 laser-induced carbonization. Therefore, the flexible substrate layer is an acrylate substrate with surface adhesion. After oxidation treatment, the liquid metal raw material yields liquid metal with reduced surface tension, which is easily and precisely filled into the grooves as needed. An interfacial bond is formed between the functional groups of the carbonized new material and the oxide layer on the surface of the oxidized liquid metal. This interfacial bond includes chemical hydrogen bonding, physical adsorption, and adhesion. Using this method, while achieving high-precision patterning of liquid metal, the intrinsic adhesion and interfacial bonding of the flexible substrate layer can alleviate the patterning difficulties caused by the high surface tension of the liquid metal and reduce the risk of lateral leakage.

[0011] Preferably, the oxidized liquid metal is an oxidized gallium indium tin alloy.

[0012] Preferably, the thickness of the stretchable flexible substrate ranges from 0.5 mm to 2.0 mm; the width of the upper groove and the bottom groove ranges from 150 μm to 500 μm, and the ablation depth is 150 μm to 400 μm.

[0013] Preferably, the electronic components may be surface-mount integrated circuit components, including but not limited to surface-mount resistors, surface-mount capacitors, Schottky diodes, surface-mount LEDs, and operational amplifiers.

[0014] Preferably, the oxidized liquid metal is an oxidized gallium indium tin alloy, which is prepared by placing the gallium indium tin alloy in an oxidizing environment and mechanically shearing and stirring it to form an oxide layer on the surface of the gallium indium tin alloy. The mechanical shearing and stirring speed is 500~1000 r / min, and the stirring and oxidation time is 0.5~1.5 hours.

[0015] Secondly, as a preferred method for fabricating the flexible and stretchable integrated circuit of the present invention, the method includes the following steps: selecting a stretchable and adhesive acrylic film, removing the plastic film from the surface of the acrylic film, and flattening release paper on the upper and lower surfaces of the flexible substrate layer respectively; applying pressure using a steel ruler or other flat tool to expel air between the release paper and the interface of the flexible substrate; according to design requirements, using a CO2 laser to sequentially perform direct writing on the upper and lower surfaces of the substrate, forming a customized pattern slit for an integrated integrated circuit on the surface of the release paper; simultaneously, forming patterned upper and lower grooves on the surface of the acrylic film; sequentially drilling through holes on the upper and lower sides of the substrate using a double-sided alignment process, while maintaining the uniformity of the diameter of the through holes; coating an oxidized liquid metal onto the patterned release paper surface; the liquid metal passes through the slits, achieving simultaneous filling of the grooves and through holes, forming a conductive integrated circuit path. At the connection between electronic components and circuits, liquid metal serves as a pad, conductive circuit, and solder, avoiding the process of adding solder and reducing interface contact loss caused by heterogeneous metals. Electronic components are mounted in the corresponding positions, and the intrinsic adhesion of the acrylic film and the liquid metal pads are used to connect and fix them together.

[0016] Preferably, when the CO2 laser performs direct writing sequentially on the upper and lower surfaces of the substrate, the width and ablation depth of the groove are controlled by adjusting the output power and scanning speed of the CO2 laser. The output power of the CO2 laser is 60% to 80% of the rated maximum output power (20W) of the laser emitter, and the laser direct writing scanning speed is 50 mm / s to 150 mm / s. When forming the via, the output power of the CO2 laser is increased to 80% to 95% of the rated maximum output power of the laser emitter, and two alignment repeat ablations are performed on the upper and lower layers at the same preset drilling position. The radius of the via is 250 μm to 500 μm, and the diameter of the via is determined according to the pad size and preset CAD pattern.

[0017] In a preferred embodiment of the present invention, in the flexible and stretchable integrated circuit, the through-hole for realizing the conductive connection between the electronic component, the upper circuit, and the lower circuit is disposed in the pad directly below the pin of the electronic component, denoted as a pad-in-hole, and preferably, the radius of the pad-in-hole is in the range of 150~500 μm. Specifically, as shown... Figure 1 As shown, some or all of the pads on the stretchable flexible substrate have in-pad via structures that penetrate the stretchable flexible substrate and connect the upper and lower layer circuits. The metal leads of the electronic components are in direct contact with the pads and are electrically connected to the lower layer circuit through anodized gallium indium tin alloy filled within the in-pad via structure. Using a double-sided alignment process, holes are drilled on both sides of the flexible substrate at corresponding positions on the pads where the electronic component leads are placed, according to design requirements, to form uniformly sized in-pad via structures. This operation reduces the number of surface leads and wiring area, lowers surface wiring density, and reduces the risk of short-circuit failures between adjacent interleaved circuits.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention utilizes a CO2 laser with a specific energy range to perform direct-write ablation on an acrylate substrate. While forming micron-sized grooves, the inner surface of these grooves undergoes laser-induced carbonization, resulting in the formation of oxygen-containing functional groups such as carboxyl and ester groups. These oxygen-containing functional groups enhance the interfacial bonding between the acrylate substrate and the oxidized gallium indium tin alloy (GaInTL), allowing the oxidized GaInTL alloy to remain more stably within the grooves and vias. This reduces the risk of lateral leakage of liquid metal during stretching and improves the structural and conductive stability of the flexible stretchable integrated circuit. In some embodiments, the flexible stretchable integrated circuit maintains electrical continuity under 500% tensile strain, with a resistance change rate of less than 0.3% during stretching. Within 500% tensile strain, the strain stability coefficient GF is less than 0.001.

[0020] The preparation method provided by this invention combines CO2 laser direct writing technology, template printing technology and material surface carbonization treatment. It does not require complex photolithography process and vacuum mask equipment, the process flow is relatively simple, the preparation cost can be reduced, and it is suitable for mass production.

[0021] In a preferred embodiment of the present invention, the flexible stretchable integrated circuit employs a via-hole structure located within the pads and below the electronic component pins. This via-hole structure enables conductive connections between the upper and lower layer circuits and the electronic component pins along the thickness direction of the flexible substrate. This structure reduces the area occupied by surface-parallel wiring, lowers the risk of short circuits caused by dense wire crossings and lateral overflow of liquid metal, and improves the wiring density and integration level of the flexible stretchable integrated circuit. Attached Figure Description

[0022] Figure 1 This is a partial cross-sectional schematic diagram showing the spatial connection relationship between the hole structure in the disk and the electronic components in an embodiment of the present invention, wherein the electronic components are shown as resistors as an example;

[0023] Figure 2 This is a schematic diagram of the fabrication process of the flexible and stretchable integrated circuit in an embodiment of the present invention;

[0024] Figure 3 This is the infrared spectrum analysis of the acrylate substrate after CO2 laser etching and carbonization in Example 1 of the present invention;

[0025] Figure 4a This is a magnified electron microscope image of the upper groove formed by CO2 laser etching and carbonization of the flexible substrate layer in Embodiment 1 of the present invention.

[0026] Figure 4b This is a magnified electron microscope image of the pads and hole structures formed by CO2 laser etching and carbonization of the flexible substrate layer in Embodiment 1 of the present invention.

[0027] Figure 5a The circuit conduction state diagram of the flexible stretchable integrated circuit with a hole-in-the-disk structure prepared in Example 1 under 500% macroscopic ultimate tensile strain.

[0028] Figure 5b The circuit conduction state diagram of the flexible stretchable integrated circuit with a hole-in-the-disk structure prepared in Example 2 under 300% macroscopic ultimate tensile strain.

[0029] Figure 5c The circuit conduction state diagram of the flexible stretchable integrated circuit with a hole-in-the-disk structure prepared in Example 3 under 400% macroscopic ultimate tensile strain.

[0030] Figure 6 The strain ranges and resistance change rate curves of the flexible stretchable integrated circuits with a hole-in-the-disk structure prepared in Examples 1 to 3 are 300%, 500%, and 400%, respectively.

[0031] Figure 7aThe channel width formed when the CO2 laser output power is 60% of the rated maximum output power in Example 2;

[0032] Figure 7b The ablation depth is defined in Example 2 when the CO2 laser output power is 60% of the rated maximum output power.

[0033] Figure 7c The channel width formed when the CO2 laser output power is 70% of the rated maximum output power in Example 1;

[0034] Figure 7d The ablation depth is the depth formed when the CO2 laser output power is 70% of the rated maximum output power in Example 1.

[0035] Figure 7e The channel width formed when the CO2 laser output power is 80% of the rated maximum output power in Example 3;

[0036] Figure 7f The ablation depth is the depth formed when the CO2 laser output power is 80% of the rated maximum output power in Example 3.

[0037] Figure 8 The left figure shows the CAD design of the upper circuit of a flexible stretchable integrated circuit using a through-hole structure; the right figure shows the CAD design of the upper circuit of a flexible stretchable integrated circuit without a through-hole structure; the red solid dots and red circles represent through-hole or through-hole structures, respectively.

[0038] Figure 9 The left image shows a sample of the upper layer circuit of a flexible and stretchable integrated circuit fabricated using a CO2 laser and a hole-in-the-disk structure; the right image shows a sample of the upper layer circuit of a flexible and stretchable integrated circuit fabricated without the hole-in-the-disk structure.

[0039] Figure 10 This is a partial comparison image of flexible stretchable integrated circuits with and without a via-in-the-disk structure.

[0040] Figure 11 This is another partial comparison image of flexible stretchable integrated circuits with and without a via-in-the-disk structure.

[0041] Figure 12 This is a top view of a stretchable circuit assembled based on the process of Example 1;

[0042] Figure 13 for Figure 12 Stretchable circuit stretching state diagram. Detailed Implementation

[0043] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed explanation of a flexible and stretchable integrated circuit and its fabrication method provided by the present invention. Through the following description and embodiments, the technical solution, advantages, and features of the present invention will become clearer. It should be noted that the accompanying drawings are simplified and not drawn to precise scale, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention, and do not constitute a limitation on the scope of protection of the present invention.

[0044] The main sources of raw materials involved in the following examples are as follows:

[0045] The liquid gallium indium tin alloy (Ga: 68.5%, In: 22%, Sn: 9.5%) was purchased from Dongguan Dingguan Metal Technology Co., Ltd.

[0046] The acrylate flexible film VHB was purchased from an officially authorized distributor of 3M.

[0047] Example 1

[0048] like Figure 2 As shown, this embodiment provides a highly stable flexible stretchable integrated circuit with a hole-in-the-disk structure and its fabrication process.

[0049] Step S1.1: Measure 2 mL of liquid gallium indium tin alloy at room temperature and place it in a 20 mL transparent glass bottle, adding a 2 mm long magnetic stirrer. Start the magnetic stirrer and set the mechanical shear stirring speed to 850 r / min, continuously stirring and oxidizing in an atmospheric oxidation environment for 0.5 hours. This process forms an irregular oxide layer on the surface of the liquid metal, obtaining an oxidized gallium indium tin alloy.

[0050] Step S1.2: Provide a 1 mm thick commercial acrylic pressure-sensitive adhesive substrate VHB as a flexible base layer. Peel off the plastic film on its surface, and apply release paper to the upper and lower surfaces of the flexible base layer, respectively. Apply pressure using a steel ruler to expel air between the release paper and the interface of the flexible base layer, completing the assembly of the flexible base layer.

[0051] Step S1.3: Use CAD software to draw a wiring pattern including the locations of the upper layer circuit, lower layer circuit, vias, and in-disk holes, and import it into the control software of the CO2 laser direct writing device. Place the assembled flexible substrate on the platform, and set the laser emitter parameters as follows: spot size 0.005 mm, frequency 20 kHz, and scanning rate 100 mm / s. When ablation forms the upper and lower layer grooves, set the CO2 laser output power to 70% of the rated maximum output power and perform a single ablation. The resulting upper and lower layer grooves have a channel width of approximately 325 μm and an ablation depth of approximately 250 μm. This laser processing can perform surface carbonization on the acrylate substrate, forming oxygen-containing functional groups such as carboxyl and ester groups on the inner surface of the groove. When forming the interlayer connection structure, the CO2 laser output power is increased to 85% of the rated maximum output power. Through a double-sided alignment process, the corresponding preset drilling positions on the upper and lower surfaces of the flexible substrate are repeatedly ablated to form through-holes and in-disk holes that penetrate the flexible substrate. The diameter of the through-holes and in-disk holes is approximately 500 μm, and their size is determined according to the pad size and the preset hole diameter in the CAD pattern. Figure 7c This is a test diagram of the channel width formed at 70% power. Figure 7d This is a test image of the ablation depth formed at 70% power.

[0052] Figure 4a This is a magnified electron microscope image of the upper circuit channel formed by CO2 laser etching and carbonization of the flexible substrate layer in Embodiment 1 of the present invention. Figure 4b This is a magnified electron microscope image of the pad area and the hole structure formed by CO2 laser etching and carbonization of the flexible substrate layer in Embodiment 1 of the present invention.

[0053] like Figure 3 The image shown is the infrared spectrum of the acrylate substrate after CO2 laser etching and carbonization in Example 1 of this invention. The 1700 cm⁻¹... -1 ~ 1710 cm -1 The nearby absorption peak corresponds to a characteristic peak related to carboxyl groups, at 1740 cm⁻¹. -1 ~ 1745cm -1 The nearby absorption peaks correspond to characteristic peaks related to ester groups. Infrared spectroscopy results indicate that CO2 laser treatment generates oxygen-containing functional groups such as carboxyl and ester groups on the surface of the acrylate substrate, which is beneficial to enhancing the hydrogen-bonded interfacial bonding between the substrate and the oxidized gallium indium tin alloy.

[0054] Step S1.4: Using the release paper patterned by CO2 laser as a template, place the oxidized gallium indium tin alloy (GaInTW) obtained in step S1.1 onto the surface of the release paper. Use a stainless steel scraper to press it into the upper groove, lower groove, in-disk hole structure, and connecting via using a template printing method. After filling, remove the release paper, leaving the oxidized GaInTW within the upper groove, lower groove, in-disk hole structure, and connecting via. Then, mount the integrated circuit components to the corresponding pads, ensuring direct contact between the component leads and the oxidized GaInTW within the pads. Because the inner surface of the grooves has oxygen-containing functional groups such as carboxyl and ester groups, it enhances the interfacial bonding between the oxidized GaInTW and the oxide layer on the surface of the oxidized GaInTW, through hydrogen bonds, thereby improving the retention stability of the oxidized GaInTW within the grooves / channels and vias. Liquid metal readily diffuses on unablated substrate surfaces. High-precision circuitry is formed within the ablated trenches, and the circuitry remains connected during the deformation process.

[0055] Testing showed that the flexible stretchable integrated circuit prepared in Example 1 did not exhibit significant leakage after undergoing 300% ultimate tensile deformation, and the resistance change rate was less than 0.3%. The resistance change rate is calculated according to... Calculate, where R0 is the initial resistance before stretching, and R is the real-time resistance during the stretching process.

[0056] like Figure 12 This is a top view of a stretchable circuit assembled based on the process of Example 1. Figure 13 This is a diagram showing the stretched state of a stretchable circuit.

[0057] Example 2

[0058] The difference from Example 1 is that in step S1.3 of this example, when ablation forms the upper and lower layer grooves, the CO2 laser output power is set to 60% of the rated maximum output power, and a single ablation is performed. The channel width of the formed upper and lower layer grooves is about 275 μm, and the ablation depth is about 150 μm. When forming the interlayer connection structure, the CO2 laser output power is increased to 85% of the rated maximum output power, and two aligned repeated ablations are performed on the upper and lower layers at the same preset drilling position to form through-holes and in-hole structures that penetrate the flexible substrate. The diameter of the through-holes and in-hole structures does not exceed 500 μm, and their size is determined according to the pad size and the preset hole diameter in the CAD pattern. Figure 7a The diagram shows the channel width test results at 60% power. Figure 7b This is a test image of the ablation depth formed at 60% power.

[0059] Example 3

[0060] The difference from Example 1 is that in step S1.3 of this example, when ablation forms the upper and lower grooves, the CO2 laser output power is set to 80% of the rated maximum output power and a single ablation is performed. The channel width of the upper and lower grooves is about 330 μm and the ablation depth is about 290 μm.

[0061] When forming the interlayer connection structure, the CO2 laser output power is increased to 85% of the rated maximum output power, and the upper and lower layers at the same preset drilling position are each subjected to two alignment repeat ablations to form through-hole and pad-in-hole structures that penetrate the flexible substrate. The diameter of the through-hole and pad-in-hole structures does not exceed 500 μm, and its size is determined according to the pad size and the preset hole diameter in the CAD pattern. Figure 7e This is a test diagram of the channel width formed at 80% power. Figure 7f This is a test image of the ablation depth formed at 80% power.

[0062] Comparative Example 1

[0063] The only difference between this comparative example and Example 1 is that Comparative Example 1 does not perform repeated ablation on the pad position directly below the electronic component pin, so it does not form a hole-in-the-pad structure located in the pad. Instead, it uses the conventional method of setting through holes outside the pad to connect the electronic component pin.

[0064] Figure 8 The image in the middle left shows the CAD design of the upper-layer circuit of a flexible, stretchable integrated circuit using a through-hole structure. Figure 8 The right-middle figure shows the CAD design of the upper-layer circuit of a flexible stretchable integrated circuit without a through-hole structure; the solid red dots and red rings represent vias used for interlayer electrical connections, and the difference in their display is caused by the different hole diameters. The vias include through-hole structures.

[0065] Figure 9 The left image shows a sample of the upper circuit layer of a flexible and stretchable integrated circuit fabricated using a CO2 laser and a disk-in-hole structure. Figure 9 The right figure shows a sample of the upper circuit of a flexible stretchable integrated circuit that was not fabricated using a hole-in-the-pan structure. Both samples are covered with white release paper. Figure 9 After the left and right circuits in the diagram are printed and components are mounted, the same local area is magnified for observation, and the results are obtained. Figure 10 and Figure 11 .

[0066] Figure 10 The images show a partial comparison of flexible stretchable integrated circuits with and without a via-in-the-pad structure. The left image shows a partial circuit with the via-in-the-pad structure, and the right image shows a partial circuit without the via-in-the-pad structure. Figure 11 This is another partial comparison of flexible stretchable integrated circuits with and without a through-disk structure. The upper part of the image shows a circuit section with the through-disk structure, and the lower part shows a circuit section without the through-disk structure.

[0067] Depend on Figure 10 The right image and Figure 11 As shown in the figure below, without using a through-hole structure, the vias need to be placed outside the pads and connected to the pad area via additional leads, thereby increasing the surface wiring area and reducing the wiring density and integration of the circuit.

[0068] Test Example 1

[0069] This test example was used to test the electrical stability of different samples under macroscopic tensile strain. Three samples for tensile testing were prepared using the same fabrication and printing processes as in Examples 1-3. The samples were rectangular flexible stretchable circuits, 12 cm long and 3 cm wide. Figure 12 This is a top view of a stretchable circuit assembled based on the process of Example 1. Figure 13 This is a diagram showing the stretched state of a stretchable circuit.

[0070] The sample, from top to bottom, comprises: a 0 Ω resistor in a 0603 package, a 3 cm long upper-layer circuit, a stretchable flexible substrate, a 3 cm long lower-layer circuit, and a via structure located within the 0 Ω resistor pad and penetrating the stretchable flexible substrate. The upper-layer and lower-layer circuits of the three samples were fabricated using 60%, 70%, and 80% laser output power, respectively, as described in Examples 2, 1, and 3. When forming the via structure, the laser output power was increased to 85% of the rated maximum output power, and two aligned repeated ablation operations were performed on both the upper and lower layers at the same preset drilling position to form the via structure penetrating the stretchable flexible substrate.

[0071] A 20 cm long copper wire was connected to the end of the upper circuit, and another 20 cm long copper wire was connected to the end of the lower circuit. Rigid insulating cardboard was used to clamp the two ends of the sample, the copper wires at both ends, and the connections between the copper wires and the upper and lower circuits. The sample resistance was measured using a Tonghui TH287B bridge and TH2817B+ software, and a tensile test was performed on the sample using an INSTRON tensile testing machine. During the test, the bridge was first turned on, and after the sample resistance stabilized, the tensile testing machine was started, stretching upwards uniaxially at a rate of 1 mm / s. Simultaneously, the resistance change data during the stretching process was recorded using the bridge.

[0072] Figure 5a , Figure 5b and Figure 5cThe circuit conduction status and resistance values ​​of samples prepared with 70%, 60%, and 80% laser output power are shown respectively under macroscopic ultimate tensile strain of 500%, 300%, and 400%. Figure 6 The resistance change rate curves of the flexible stretchable circuits with a hole-in-the-disk structure prepared in Examples 1-3 under different macroscopic tensile strains are shown. The test results show that the resistance change rate of the samples is less than 0.3% during the stretching process, indicating that the hole-in-the-disk structure can maintain a relatively stable electrical connection under macroscopic tensile conditions.

[0073] Test Example 2

[0074] Using the same preparation and printing processes as in Examples 1-3, three types of stretchable test samples, identical to those in Test Example 1, were prepared. The samples were subjected to bending and stretching cycle tests using an INSTRON stretching machine. After one thousand or more stretching cycles at 200% stretching rate, no open circuits were observed in the three types of stretchable samples.

Claims

1. A flexible and stretchable integrated circuit, characterized in that, The flexible stretchable integrated circuit includes a flexible substrate layer, an upper circuit, a lower circuit, and electronic components. The flexible substrate layer is a substrate made by forming patterned upper and lower grooves on the upper and lower surfaces of an acrylic film using a CO2 laser according to a circuit layout design. The flexible substrate layer also has through holes penetrating the lower layer of the flexible substrate. The through holes, upper grooves, and lower grooves are all filled with oxidized liquid metal. The upper and lower grooves, after being filled with oxidized liquid metal, form the upper circuit and the lower circuit, respectively. The through holes, after being filled with oxidized liquid metal, are used to connect the upper and lower circuits, or to connect the pins of electronic components, the upper circuit, and the lower circuit. The liquid metal connecting the components in the upper circuit serves as a pad to support the pins of the electronic components.

2. The flexible and stretchable integrated circuit as described in claim 1, characterized in that, The oxidized liquid metal is an oxidized gallium indium tin alloy.

3. The flexible and stretchable integrated circuit as described in claim 2, characterized in that, The oxidized liquid metal is prepared by mechanically shearing and stirring a gallium indium tin alloy in an oxidizing environment to form an oxide layer on the surface of the gallium indium tin alloy. The mechanical shearing and stirring speed is 500~1000 r / min, and the stirring and oxidation time is 0.5~1.5 hours.

4. A flexible and stretchable integrated circuit as described in claim 1, characterized in that, The thickness of the stretchable flexible substrate ranges from 0.5 mm to 2.0 mm; the width of the upper groove and the lower groove ranges from 150 μm to 500 μm, and the ablation depth is 150 μm to 400 μm.

5. A flexible and stretchable integrated circuit as described in claim 1, characterized in that, The electronic components are surface-mount integrated circuit components, including surface-mount resistors, surface-mount capacitors, Schottky diodes, surface-mount LEDs, and operational amplifiers.

6. The method for fabricating the flexible and stretchable integrated circuit according to claim 1, characterized in that, The preparation method includes the following steps: selecting a stretchable and adhesive acrylic film, peeling off the plastic film on the surface of the acrylic film, and flattening release paper on the upper and lower surfaces of the flexible substrate layer respectively, and applying pressure with a flattening tool to expel the air between the release paper and the flexible substrate interface; Using a CO2 laser, direct writing is performed sequentially on the upper and lower surfaces of the substrate to form a customized pattern slit for an integrated circuit on the release paper surface. At the same time, patterned upper and lower grooves are formed on the acrylic film surface. Through holes are formed sequentially on the upper and lower sides of the substrate through a double-sided alignment process.

7. The method for fabricating a flexible and stretchable integrated circuit as described in claim 6, characterized in that, When the CO2 laser performs direct writing on the upper and lower surfaces of the substrate sequentially, the width and ablation depth of the groove are controlled by adjusting the output power and scanning speed of the CO2 laser. The output power of the CO2 laser is 60% to 80% of the rated maximum output power of the laser emitter (20W), and the laser direct writing scanning speed is 50 mm / s to 150 mm / s. When forming the through hole, the output power of the CO2 laser is increased to 80% to 95% of the rated maximum output power of the laser emitter, and two alignment repeat ablations are performed on the upper and lower layers at the same preset drilling position. The radius of the through hole is 250 μm to 500 μm.

8. A flexible and stretchable integrated circuit as described in claim 1, characterized in that, In the flexible and stretchable integrated circuit, a hole is provided in the pad directly below the pin of the electronic component. The hole is a through hole used to realize the conductive connection between the electronic component, the upper circuit and the lower circuit.

9. A flexible and stretchable integrated circuit as described in claim 8, characterized in that, The radius of the hole in the disk ranges from 150 to 500 μm.

10. A flexible and stretchable integrated circuit as described in claim 8, characterized in that, The stretchable flexible substrate has a hole-in-the-pad structure in some or all of the pads, which penetrates the stretchable flexible substrate and connects the upper layer circuit and the lower layer circuit. The metal pins of the electronic components are in direct contact with the pads and are electrically connected to the lower layer circuit through an oxidized gallium indium tin alloy filled in the hole-in-the-pad structure.

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