Method for preparing liquid metal flexible conductive circuit based on airflow-assisted laser ablation
By using airflow-assisted laser ablation technology, the problems of complex processes and high costs in the fabrication of liquid metal flexible conductive circuits have been solved, enabling the fabrication of high-precision and high-efficiency liquid metal conductive circuits suitable for flexible electronic devices.
Patent Information
- Application Number
- CN202511113947.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-11
- Publication Date
- 2025-11-04
AI Technical Summary
Existing methods for fabricating flexible conductive circuits in liquid metal suffer from problems such as complex processes, high costs, or low precision, making it difficult to achieve high-precision, high-efficiency, and low-cost fabrication.
By employing airflow-assisted laser ablation technology, an oxidized liquid metal slurry is obtained through mechanical stirring. Combined with an ultraviolet laser marking machine and an industrial blower, the liquid metal is stably adhered to a flexible substrate, and the oxidized liquid metal slurry in non-wire areas is selectively removed to form a high-precision conductive circuit.
Stable adhesion between liquid metal and flexible substrates was achieved, forming a continuous and well-adhesive conductive film, resulting in high-precision liquid metal conductive circuits. The process is simple, low-cost, and highly efficient, making it suitable for the manufacture of flexible electronic devices.
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Figure CN120897341A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of electronic circuit processing, in particular to a liquid metal flexible conductive circuit preparation method based on airflow assisted laser ablation. BACKGROUND
[0002] Liquid metal (LM) is an ideal conductive material for building flexible electronic devices due to its excellent electrical conductivity, intrinsic stretchability, and good biocompatibility. It has shown great potential in the fields of stretchable wires, flexible sensors, wearable electronics, soft robots, and health monitoring devices. Liquid metal flexible conductive circuits can effectively overcome the inherent defects of traditional rigid metal wires, such as easy breakage and dramatic increase in resistance on flexible substrates, achieving stable conduction under large deformation. Therefore, it is crucial to develop efficient, reliable, and simple liquid metal flexible conductive circuit preparation technology.
[0003] However, there is significant non-wetting between liquid metal and flexible substrates, which prevents liquid metal from spontaneously spreading and stably adhering to the surface of flexible substrates. This seriously hinders the construction of high-resolution, patterned liquid metal conductive circuits, becoming a key bottleneck restricting their application.
[0004] There are three main ways to achieve liquid metal conductive circuit preparation in existing technology. The first is the micro-channel physical constraint method, which uses negative pressure to inject liquid metal into the micro-channel inside the elastomer to form a conductive circuit. This method has good precision and stability, but the micro-channel manufacturing requires soft lithography or MEMS, which is complex and costly. Moreover, the liquid metal injection process is prone to air bubbles or overflow, making it difficult to ensure product quality and meet the needs of large-scale, batch production. The second is the template-assisted interfacial adhesion method, which first deposits a metal interface layer (such as Cr, Cu) on the surface of the flexible substrate through evaporation or sputtering process. The liquid metal and the interface layer form an alloy (such as CuGa2) to achieve selective adhesion, thereby obtaining a conductive circuit. This method has high precision and good stability. However, its core defect is that it requires pre-deposition of a metal interface layer on the flexible substrate, involving a complex vacuum coating process, which also leads to complicated preparation steps and high cost. The third is the liquid metal modification direct patterning method, which blends liquid metal with nano-metal particles (such as Ni, Cu) to reduce its surface energy and improve its wettability on flexible substrates. The modified liquid metal can be obtained by template printing, brushing, or femtosecond laser selective removal of the coating layer to obtain a conductive circuit. This method solves the problem of non-wetting and improves the stability of liquid metal on the surface of flexible substrates. However, the resolution of the template printing process is low, making it difficult to meet the requirements of high-precision circuits. While femtosecond laser processing has high precision, the equipment is extremely expensive, and the running and maintenance costs are high, which severely limits industrial applications and large-scale production.
[0005] In summary, the existing liquid metal flexible conductive circuit preparation method generally has the problems of complex process, high cost or insufficient precision. In particular, there is a lack of a practical preparation technology that can balance high precision, high efficiency, simple process and low cost advantages. This technical bottleneck seriously restricts the application and industrial development of high-performance liquid metal flexible conductive circuit in the field of flexible electronics. Therefore, it is urgent to develop a liquid metal flexible conductive circuit preparation method with high precision, high efficiency, simple process and low cost advantages. SUMMARY
[0006] The present application is to solve the problems of complex process, high cost or low precision in the existing implementation of liquid metal conductive circuit preparation method, and provides a liquid metal flexible conductive circuit preparation method based on airflow assisted laser ablation.
[0007] The present application is implemented by adopting the following technical solutions:
[0008] S1: centrifuging the liquid metal by a centrifugal electric mixer to obtain an oxidized liquid metal slurry;
[0009] S2: preparing a flexible substrate, tightly attaching a mask plate to the surface of the flexible substrate, and removing the mask in the circuit area along the outer contour of the pre-designed circuit pattern by using an ultraviolet laser marking machine to expose the underlying flexible substrate;
[0010] S3: uniformly coating the oxidized liquid metal slurry prepared in S1 on the exposed flexible substrate in the circuit area;
[0011] S4: using an ultraviolet laser marking machine to accurately ablate the oxidized liquid metal slurry in the non-conductive area of the circuit area according to the pre-designed circuit pattern, thereby directly forming a liquid metal conductive circuit in the area defined by the mask plate; wherein, during the laser ablation process, an industrial hair dryer is used to continuously provide a tangential auxiliary airflow;
[0012] S5: coating a packaging material on the upper surface of the liquid metal conductive circuit, and completing the packaging after solidification to obtain a liquid metal flexible conductive circuit.
[0013] Further, the speed of the centrifugal electric mixer is 1000-4000r / min, and the stirring time is 20-60min.
[0014] Further, the liquid metal is a gallium-based liquid metal.
[0015] Further, the flexible substrate is made of one of polydimethylsiloxane, Ecoflex silicone of Smooth-On company, Dragon Skin silicone of Smooth-On company, thermoplastic polyurethane, polyethylene terephthalate, and polyimide.
[0016] Further, the laser scanning speed of the ultraviolet laser marking machine is 300-600 mm / s, and the laser power is 20-75 W.
[0017] Further, the rotation speed of the industrial hair dryer is 8000-17000 r / min.
[0018] Further, the preparation method of the flexible substrate is a blade coating method, a spin coating method or a template method.
[0019] Further, the packaging method is a blade coating method or a spin coating method.
[0020] Further, the packaging material is one of polydimethylsiloxane, Ecoflex silicone of Smooth-On company, Dragon Skin silicone of Smooth-On company and thermoplastic polyurethane.
[0021] The application provides a liquid metal flexible conductive circuit preparation method based on airflow-assisted laser ablation, obtains oxidized liquid metal through a mechanical stirring process, significantly reduces the surface tension of the liquid metal, can realize stable adhesion of the liquid metal and the flexible substrate, forms a continuous and well-adhered liquid metal conductive film, and simultaneously, based on the airflow-assisted laser ablation technology, can selectively remove the oxidized liquid metal slurry in the non-wire area in the circuit area on the liquid metal conductive film, and obtain a high-precision liquid metal conductive circuit; in addition, the method provided by the application is simple in process, low in cost and high in efficiency, and can realize high-precision, high-efficiency and low-cost manufacturing of the liquid metal flexible conductive circuit. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 is a preparation flowchart of the application.
[0023] Figure 2 is a schematic diagram of the surface contact of the unoxidized and oxidized liquid metal and the flexible substrate.
[0024] Figure 3 is a schematic diagram of the flexible substrate surface before and after laser ablation.
[0025] Figure 4 is a comparison diagram of the adhesion energy of the oxidized liquid metal to the flexible substrate surface before and after laser ablation in Example 1 of the application.
[0026] Figure 5 is a schematic diagram of a liquid metal flexible conductive interdigital electrode structure capacitive flexible strain sensor prepared based on the application.
[0027] Figure 6is an ablation sample comparison chart of conductive interdigital electrodes with different design widths in Example 3 of the present application.
[0028] Figure 7 is a quantitative ablation accuracy chart of ablation samples of conductive interdigital electrodes with different design widths in Example 3 of the present application.
[0029] Figure 8 is a response chart of a liquid metal flexible conductive interdigital electrode structure capacitive flexible strain sensor with a design length, width, pitch, and interdigital index of 32 mm, 0.2 mm, 0.2 mm, and 100, respectively, prepared in Example 4 of the present application.
[0030] Figure 9 is a response chart of liquid metal flexible conductive interdigital electrode structure capacitive flexible strain sensors with different geometric parameters prepared in Example 4 of the present application.
[0031] Figure 10 is a structural schematic diagram of a liquid metal flexible conductive interdigital electrode circuit after laser ablation with and without tangential gas flow assistance in Comparative Example 1 of the present application.
[0032] In the figure: 1, liquid metal; 2, oxidized liquid metal-liquid metal; 21, oxidation shell layer; 22, liquid metal core; 3, oxidized liquid metal; 4, flexible substrate; 5, silicon wafer; 6, ultraviolet laser marking machine; 7, oxidized liquid metal ablation; 8, tangential auxiliary gas flow; 9, packaging layer; 10, conductive interdigital electrode. DETAILED DESCRIPTION
[0033] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.
[0034] Example 1
[0035] A liquid metal flexible conductive circuit preparation method based on gas flow assisted laser ablation, as shown in the accompanying drawings, comprises the following steps: Figure 1
[0036] S1: Centrifuging eutectic gallium-indium alloy liquid metal by a centrifugal electric stirrer, the rotation speed of the centrifugal electric stirrer is 3000 r / min, and the stirring time is 30 min, to obtain an oxidized liquid metal slurry; as shown in the accompanying drawings, Figure 1 (1) as shown, in the mechanical centrifugal process, the eutectic gallium-indium alloy liquid metal changes from liquid metal 1 state to oxidized liquid metal-liquid metal 2 state, at this time, the oxide shell 21 covers the liquid metal core 22, and finally changes to the state of oxidized liquid metal 3.
[0037] S2: Prepare flexible substrate 4, mix A and B of Ecoflex 00-30 silicone glue of Smooth-On company with a mass ratio of 1:1 using a centrifugal electric mixer for 3 minutes to obtain a mixed liquid, then drop 10 ml of the mixed liquid on the center of the silicon wafer 5, spin it on the spin coater at a speed of 400 r / min for 2 min to form a uniform liquid film, and heat it on the heating table at 60℃ for 2h to obtain the flexible substrate 4; by controlling the volume of the mixed liquid, the spin coating speed and time, the flexible substrate 4 with the required thickness is prepared. The mask plate is tightly attached to the surface of the flexible substrate 4, and the mask in the circuit area is removed along the outer contour of the pre-designed circuit pattern using the ultraviolet laser marking machine 6, exposing the underlying flexible substrate 4; the laser scanning speed of the ultraviolet laser marking machine 6 is 400 mm / s, and the laser power is 75 W.
[0038] S3: as shown in the accompanying Figure 1 (2) as shown, the oxidized liquid metal slurry prepared in S1 is uniformly coated on the exposed flexible substrate 4 in the circuit area.
[0039] as shown in the accompanying Figure 2 Compared with the unoxidized liquid metal, the oxidized liquid metal 3 can significantly reduce the surface tension of the liquid metal, and realize stable adhesion with the flexible substrate.
[0040] S4: as shown in the accompanying Figure 1 (3) as shown, the ultraviolet laser marking machine 6 is used to accurately ablate the oxidized liquid metal slurry in the non-conductive area of the circuit area according to the pre-designed circuit pattern, so as to directly form the liquid metal conductive circuit in the area defined by the mask plate; wherein, during the laser ablation process, an industrial hair dryer is used to continuously provide a tangential auxiliary air flow 8 at a speed of 10000 r / min to remove the oxidized liquid metal ablation 7.
[0041] as shown in the accompanying Figure 3 , accompanying Figure 4 As shown in the accompanying
[0042] S5: Spin-coat Ecoflex prepolymer as encapsulation layer 9 onto the upper surface of the liquid metal conductive circuit, and cure at 60°C for 2 hours to complete the encapsulation, as shown in the attached diagram. Figure 1 (4) shows that a liquid metal flexible conductive circuit is obtained; the Ecoflex prepolymer is obtained by uniformly mixing the A agent and the B agent of Ecoflex 00-30 silicone from Smooth-On at a mass ratio of 1:1.
[0043] Example 2
[0044] A method for fabricating flexible conductive circuits in liquid metal based on airflow-assisted laser ablation, as shown in the attached figure. Figure 1 As shown, it includes the following steps:
[0045] S1: The eutectic gallium-indium alloy liquid metal is mechanically centrifuged using a centrifugal electric stirrer at a speed of 3000 r / min for 30 min to obtain an oxide liquid metal slurry; as shown in the attached figure. Figure 1 As shown in (1), during the mechanical centrifugation process, the eutectic gallium indium alloy liquid metal changes from liquid metal 1 state to oxidized liquid metal-liquid metal 2 state. At this time, the oxide shell 21 covers the liquid metal core 22, and finally changes to the oxidized liquid metal 3 state.
[0046] S2: Prepare the flexible substrate 4. Use a centrifugal electric mixer to mix the main agent and curing agent of polydimethylsiloxane at a mass ratio of 10:1 for 3 minutes to obtain a mixture. Then, take 10 ml of the mixture and drop it onto the center of the silicon wafer 5. Place it in a spin coater and spin coat it at a speed of 400 r / min for 2 minutes to form a uniform liquid film. Then, heat it on a heating stage at 60°C for 2 hours to obtain the flexible substrate 4. By controlling the volume of the mixture, the spin coat speed and time, the flexible substrate 4 of the required thickness is prepared. The mask is tightly attached to the surface of the flexible substrate 4, and the mask of the circuit area is removed along the outer contour of the pre-designed circuit pattern using an ultraviolet laser marking machine 6 to expose the flexible substrate 4 underneath. The laser scanning speed of the ultraviolet laser marking machine 6 is 400 mm / s and the laser power is 70 W.
[0047] S3: As attached Figure 1 As shown in (2), the oxidized liquid metal paste obtained in S1 is uniformly coated onto the exposed flexible substrate 4 in the circuit area.
[0048] As attached Figure 2 As shown, compared with unoxidized liquid metal, oxidized liquid metal 3 can significantly reduce the surface tension of liquid metal and achieve stable adhesion to flexible substrate 4.
[0049] S4: As attached Figure 1(3) as shown, using a UV laser marking machine 6, according to the pre-designed circuit pattern, the oxidized liquid metal paste in the circuit area is ablated to form a liquid metal conductive circuit in the area defined by the mask; wherein, during the laser ablation process, an industrial hair dryer is used to continuously provide a tangential auxiliary air flow 8 at a speed of 10000r / min to remove the oxidized liquid metal ablation 7.
[0050] S5: spin-coat polydimethylsiloxane as an encapsulation layer 9 on the upper surface of the liquid metal conductive circuit, and after heating and curing at 60℃ for 2 hours, the encapsulation is completed, as shown in FIG. Figure 1 (4) as shown, to obtain a liquid metal flexible conductive circuit; the polydimethylsiloxane is obtained by uniformly mixing the main agent with the curing agent at a mass ratio of 10:1.
[0051] Example 3
[0052] The difference between this embodiment and Example 1 is that the pre-designed circuit pattern is a conductive interdigital electrode structure, as shown in FIG. Figure 5 Finally, a liquid metal flexible conductive interdigital electrode circuit is prepared, and the remaining preparation steps are the same as those of Example 1.
[0053] Through the preparation method of this embodiment, liquid metal flexible conductive interdigital electrode structure capacitive flexible strain sensors with design widths of conductive interdigital electrodes 10 of 1mm, 0.8mm, 0.6mm, 0.4mm, 0.3mm, 0.2mm, and 0.15mm are prepared in sequence, but the design length is uniform at 32mm, the pitch is uniform at 0.2mm, and the interdigital number is uniform at 100.
[0054] Figure 6 is an ablation sample comparison diagram of conductive interdigital electrodes 10 with design widths of 1mm, 0.8mm, 0.6mm, 0.4mm, 0.3mm, 0.2mm, and 0.15mm, as shown in the figure, through the preparation method of the present application, a continuous, smooth and good conductive liquid metal flexible conductive interdigital electrode structure can be obtained; and when the design width of the conductive interdigital electrode 10 is 0.15mm, the oxidized liquid metal 3 structure appears obvious discontinuity, and cannot form a continuous conductive interdigital electrode 10, which determines that the reliable minimum design width that can be realized by the laser ablation process in the present application is 0.2mm.
[0055] Figure 7To obtain quantitative ablation accuracy curves for ablation samples of conductive interdigitated electrodes 10 with designed widths of 1 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.3 mm, 0.2 mm, and 0.15 mm, respectively, optical microscopes were used to precisely measure the ablation samples. The graphs show that the actual width of the conductive interdigitated electrodes 10 is generally smaller than the designed width, with a difference between 0.07 mm and 0.1 mm. This systematic deviation stems from the specific process of laser ablation. The laser ablation process preferentially and precisely ablates the contour boundary of the conductive interdigitated electrodes 10 along the designed path. Subsequently, the laser performs a filling scan within the ablated boundary frame to remove the internal liquid oxide metal 3. The boundary ablation step not only removes the liquid oxide metal 3 outside the boundary line but also ablates the liquid oxide metal 3 at the boundary line itself, resulting in the final electrode's actual width inevitably being smaller than the original designed width. Therefore, when designing the width of the conductive interdigitated electrodes 10, the designed width must be 0.07 mm to 0.1 mm wider than the actual width.
[0056] Example 4
[0057] The difference between this embodiment and Embodiment 3 is that the designed widths of the conductive interdigitated electrodes 10 are 0.5mm, 0.45mm, 0.4mm, 0.35mm, 0.3mm, 0.25mm, and 0.2mm, respectively, and the design length range corresponding to each design width is 28-36mm. The spacing is uniformly 0.2mm, and the interdigitation index is uniformly 100. These are liquid metal flexible conductive interdigitated electrode structure capacitive flexible strain sensors. Strain response tests were performed on these sensors, and the tests show that these sensors all have good response characteristics, as shown in the attached figure. Figure 8 Appendix Figure 9 As shown, the liquid metal flexible conductive interdigitated electrode structure has good stability and reliability.
[0058] Comparative Example 1
[0059] The difference between this comparative example and Example 3 is that in step S4, no tangential auxiliary airflow 8 is provided during the laser ablation process, while the rest of the preparation steps are the same as in Example 3.
[0060] As attached Figure 10 As shown, under the same preparation process and parameters, the liquid metal flexible conductive interdigitated electrode circuit after laser ablation without tangential airflow assistance has edge burrs and debris of oxidized liquid metal ablation material 7, as indicated by the arrow; the liquid metal flexible conductive interdigitated electrode circuit after laser ablation with tangential airflow assistance has neat edges and no debris. Therefore, it can be seen that the airflow-assisted laser ablation technology can selectively remove the oxidized liquid metal slurry in the non-wire area of the circuit region on the liquid metal conductive film, and obtain a high-precision liquid metal flexible conductive interdigitated electrode circuit.
[0061] In the implementation process, the material selection of the liquid metal includes but is not limited to gallium, gallium-indium alloy and gallium-indium-tin alloy; the centrifugal electric mixer is selected from the SC-S300 centrifugal electric mixer of Shenzhen Zhanchuang Technology Co., Ltd.; and the ultraviolet laser marking machine 6 is selected from the 3W ultraviolet laser marking machine of Wainlux Company.
[0062] In the description of the present application, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.
[0063] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.
Claims
1. A method for fabricating flexible conductive circuits in liquid metal based on airflow-assisted laser ablation, characterized in that: Includes the following steps: S1: The liquid metal is mechanically centrifuged using a centrifugal electric mixer to obtain an oxidized liquid metal slurry; S2: Prepare a flexible substrate, attach the mask tightly to the surface of the flexible substrate, and use a UV laser marking machine to remove the mask of the circuit area along the outer contour of the pre-designed circuit pattern to expose the flexible substrate underneath; S3: The oxidized liquid metal paste obtained in S1 is uniformly coated onto the exposed flexible substrate within the circuit area; S4: An ultraviolet laser marking machine is used to precisely ablate the non-wire areas of the circuit region with liquid metal slurry according to the pre-designed circuit pattern, thereby directly forming a liquid metal conductive circuit within the area defined by the mask; during the laser ablation process, an industrial blower is used to continuously provide tangential auxiliary airflow. S5: Coat the upper surface of the liquid metal conductive circuit with encapsulation material, and complete the encapsulation after curing to obtain a liquid metal flexible conductive circuit.
2. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The centrifugal electric mixer has a rotation speed of 1000-4000 r / min and a mixing time of 20-60 min.
3. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The liquid metal is a gallium-based liquid metal.
4. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The flexible substrate is made of one of the following: polydimethylsiloxane, Smooth-On's Ecoflex silicone, Smooth-On's Dragon Skin silicone, thermoplastic polyurethane, polyethylene terephthalate, or polyimide.
5. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The ultraviolet laser marking machine has a laser scanning speed of 300-600 mm / s and a laser power of 20-75W.
6. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The industrial blower has a rotation speed of 8000~17000 r / min.
7. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The flexible substrate is prepared by a scraping method, a spin coating method, or a template method.
8. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The encapsulation method is either blade coating or spin coating.
9. The method for fabricating a flexible conductive circuit of liquid metal based on airflow-assisted laser ablation according to claim 1, characterized in that: The encapsulation material is one of polydimethylsiloxane, Smooth-On's Ecoflex silicone, Smooth-On's Dragon Skin silicone, or thermoplastic polyurethane.