Stretchable circuit structure and preparation method

Abstract

The invention discloses a stretchable circuit structure and a preparation method, and belongs to the technical field of electronic circuits. The stretchable circuit structure comprises a patterned circuit, the patterned circuit comprises at least two conductive points and at least one wire, the circle center distance between the adjacent conductive points is within a target distance range, the wire is connected between the adjacent conductive points, and the wire has a micro-nano-scale wire width. According to the invention, the wire width of the wire can be reduced to a micro-nano level, and the fineness of the stretchable circuit is improved.

Description

Technical Field

[0001] The present application belongs to the field of electronic circuit technology, and in particular, relates to a stretchable circuit structure and a preparation method thereof. Background Art

[0002] As the basis for building stretchable electronic devices, stretchable circuits are of great significance for promoting their applications in physiological monitoring, electronic skin, intelligent robots and other fields. Stretchable circuits not only need to have high electrical conductivity, but also need to maintain good electrical properties under various mechanical deformations such as stretching to meet the above application requirements. Compared with rigid metals and conductive polymers, gallium-based liquid metals not only have high electrical conductivity comparable to rigid metals, but are also liquid at room temperature and have high deformability.

[0003] However, due to the high surface tension of liquid metal, it reacts with oxygen under atmospheric conditions to form an oxide layer, making it difficult to form a patterned conductive circuit on the substrate. In order to achieve patterned processing of liquid metal, conductive ink based on liquid metal is usually prepared and patterned by printing or other methods. However, the line width of the stretchable wire produced by this method is still relatively wide. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a stretchable circuit structure and a preparation method, which can reduce the line width of the conductor to the micro-nano level and improve the fineness of the stretchable circuit.

[0005] In a first aspect, the present application provides a stretchable circuit structure, comprising:

[0006] A patterned circuit comprises at least two conductive dots and at least one conductive wire, wherein the center distance between adjacent conductive dots is within a target spacing range, the conductive wires are connected between adjacent conductive dots, and the conductive wires have a micro-nanoscale line width.

[0007] According to the stretchable circuit structure of the present application, by setting at least two conductive points, the center distance of adjacent conductive points is within the target spacing range, and a wire connecting the adjacent conductive points is set between the conductive points, so that the line width of the wire is as low as micro-nano level, thereby ensuring that the stretchable circuit has high conductivity and improving the fineness of the stretchable circuit.

[0008] According to one embodiment of the present application, the conductive wire is in a straight line.

[0009] According to an embodiment of the present application, the conductive dots have a micrometer-scale diameter.

[0010] According to one embodiment of the present application, the stretchable circuit structure further includes:

[0011] A hydrophobic substrate, wherein the patterned circuit is located on the hydrophobic substrate.

[0012] According to one embodiment of the present application, the contact angle of the hydrophobic substrate is negatively correlated with the line width of the conductive wire, and negatively correlated with the maximum center distance between adjacent conductive points; and / or,

[0013] The relationship between the contact angle of the hydrophobic substrate and the line width of the conductive line is: a=-1.13exp(-x / 12.6)+1.59, wherein a is the line width of the conductive line, and x is the contact angle of the hydrophobic substrate.

[0014] According to one embodiment of the present application, the contact angle of the hydrophobic substrate is 80°-110°; and / or,

[0015] The hydrophobic substrate includes any one of PDMS, TPU and PC.

[0016] According to one embodiment of the present application, the target spacing range includes 30 μm-250 μm; and / or,

[0017] The line width of the conductive line is 600nm-10μm.

[0018] In a second aspect, the present application provides a method for preparing a stretchable circuit structure, comprising:

[0019] Forming at least two conductive dots on a hydrophobic substrate, wherein the center distance between adjacent conductive dots is within a target spacing range;

[0020] Liquid metal water-based slurry is used to self-assemble on the hydrophobic substrate to form wires connecting adjacent conductive points.

[0021] According to one embodiment of the present application, the viscosity of the liquid metal water-based slurry is positively correlated with the line width of the conductive wire; and / or,

[0022] The relationship between the viscosity of the liquid metal water-based slurry and the line width of the conductive line is: a=-0.056+0.0034b, wherein a is the line width of the conductive line, and b is the viscosity of the liquid metal water-based slurry.

[0023] According to one embodiment of the present application, the liquid metal aqueous slurry comprises liquid metal, a water-soluble polymer, water and an acid; and / or,

[0024] The viscosity of the liquid metal water-based slurry is 200 Pa·s-350 Pa·s; and / or,

[0025] The target spacing range includes 30 μm-250 μm; and / or,

[0026] The line width of the conductive line is 600nm-10μm.

[0027] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0028] At least two conductive points are set so that the center distance between adjacent conductive points is within the target spacing range. The de-wetting property of the liquid metal aqueous slurry on the hydrophobic substrate and the wettability on the conductive points are utilized to form a wire connecting adjacent conductive points between the conductive points. The line width of the wire is reduced to the micro-nano level, thereby improving the fineness of the stretchable circuit while ensuring that the stretchable circuit has a high conductivity.

[0029] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0031] Figure 1 It is one of the structural schematic diagrams of the stretchable circuit structure provided in the embodiment of the present application;

[0032] Figure 2 This is the second structural schematic diagram of the stretchable circuit structure provided in the embodiment of the present application;

[0033] Figure 3 This is the third structural schematic diagram of the stretchable circuit structure provided in the embodiment of the present application;

[0034] Figure 4 is a curve diagram showing the relationship between the viscosity of the liquid metal aqueous slurry and the line width of the conductor in the stretchable circuit structure provided in the embodiment of the present application;

[0035] Figure 5 is a curve diagram showing the relationship between the contact angle of the hydrophobic substrate and the line width of the conductor in the stretchable circuit structure provided in the embodiment of the present application;

[0036] Figure 6 is a curve diagram showing the relationship between the tensile strain and the resistance retention rate of the stretchable circuit structure provided in an embodiment of the present application;

[0037] Figure 7 is a schematic flow chart of a method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0038] Figure 8 It is one of the structural schematic diagrams of the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0039] Fig. 9This is the second structural schematic diagram of the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0040] Fig.10 This is the third structural schematic diagram of the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0041] Fig.11 This is the fourth structural schematic diagram of the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0042] Fig.12 This is the fifth structural schematic diagram of the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0043] Fig.13 This is the fourth structural schematic diagram of the stretchable circuit structure provided in the embodiment of the present application;

[0044] Fig.14 This is one of the contact angle schematic diagrams of the hydrophobic substrate in the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0045] Fig.15 This is the second schematic diagram of the contact angle of the hydrophobic substrate in the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0046] Fig.16 This is the third schematic diagram of the contact angle of the hydrophobic substrate in the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0047] Fig.17 This is the fourth schematic diagram of the contact angle of the hydrophobic substrate in the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0048] Fig.18 This is the fifth schematic diagram of the contact angle of the hydrophobic substrate in the method for preparing a stretchable circuit structure provided in an embodiment of the present application;

[0049] Fig.19 This is a comparison chart of the viscosities of liquid metal aqueous slurries with different component proportions in the method for preparing a stretchable circuit structure provided in an embodiment of the present application. DETAILED DESCRIPTION

[0050] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0051] The stretchable circuit structure and preparation method provided in the embodiments of the present application are described below with reference to the accompanying drawings.

[0052] Figures 1 to 3 A schematic diagram of the structure of a stretchable circuit structure provided in an embodiment of the present application.

[0053] like Figures 1 to 3 As shown, the stretchable circuit structure provided in the embodiment of the present application includes a patterned circuit 1, and the patterned circuit 1 is a stretchable circuit.

[0054] The patterned circuit 1 includes at least two conductive dots 11 and at least one conductive wire 12. At least two conductive dots 11 are arranged at intervals, and the center distance between adjacent conductive dots 11 (i.e., the distance between the centers of two adjacent conductive dots 11) is within the target spacing range. The conductive wires 12 are connected between adjacent conductive dots 11, and the conductive wires 12 are stretchable conductive wires. Each conductive wire 12 is connected to a conductive dot 11 at both ends, and each conductive dot 11 is connected to at least one conductive wire 12, such as a conductive dot 11 at the head or end of the patterned circuit 1 connected to a conductive dot 12, and the remaining conductive dots 11 (other conductive dots except the head or end) are connected to at least two conductive wires 12. The conductive wire 12 has a micro-nano line width, that is, the line width of the conductive wire 12 is micrometer or nanometer.

[0055] The number of conductive dots 11 can be set according to actual needs. Since the wires 12 are connected between adjacent conductive dots 11, the number of conductive dots 11 can be adjusted to adjust the overall line length of the patterned circuit 1 to meet the stretchable circuit requirements of different line lengths.

[0056] The distribution of the conductive dots 11 can be set according to actual needs. By adjusting the distribution of the conductive dots 11, the pattern of the patterned circuit 1 can be adjusted to meet the stretchable circuit requirements of different patterns.

[0057] The center distance of adjacent conductive points 11 can be set according to actual needs. Two adjacent conductive points 11 are different, and the center distance of adjacent conductive points 11 can be the same or different, but the center distance of any adjacent conductive points 11 is within the target spacing range. The center distance of adjacent conductive points 11 in this embodiment is within the target spacing range to avoid the center distance of adjacent conductive points 11 being too large, resulting in the wire 12 being unable to connect the adjacent conductive points 11, and to avoid the center distance of adjacent conductive points 11 being too small, resulting in the inability to effectively form a wire 12 between adjacent conductive points 11.

[0058] In some embodiments, the target pitch range includes 30 μm-250 μm, so that the conductive wires 12 can be formed between adjacent conductive dots 11 , and the conductive wires 12 connect the adjacent conductive dots 11 .

[0059] It should be noted that the conductor 12 can be self-assembled between adjacent conductive points 11 using liquid metal aqueous slurry. The liquid metal aqueous slurry may include liquid metal, water-soluble polymer, water and acid. The water-soluble polymer is used to stabilize the dispersion of liquid metal particles, and the acid is used to react with the oxide layer of the liquid metal to activate the liquid metal particles. The liquid metal may include gallium and indium, the water-soluble polymer may include sodium hydroxymethyl cellulose, and the acid may include acetic acid. The mass ratio of liquid metal, water-soluble polymer, water and acid may be 1:0.02-0.06:2:0.2. For example, the liquid metal aqueous slurry may include 2.00g of liquid metal (gallium mass fraction is 75%, indium mass fraction is 25%), 0.04-0.12g of sodium hydroxymethyl cellulose, 4.00g of water and 0.40g of acetic acid.

[0060] In this embodiment, liquid metal water-based slurry is used to self-assemble between adjacent conductive dots 11 to form a conductor 12, so that the line width of the conductor 12 is reduced to micrometer level or even nanometer level, effectively improving the fineness of the stretchable circuit. Moreover, the conductor 12 has high conductivity and still has good electrical properties under various mechanical deformations such as stretching.

[0061] In some embodiments, the viscosity of the liquid metal water-based slurry is within a target viscosity range. The viscosity of the liquid metal water-based slurry cannot be too large to prevent the liquid metal from being difficult to completely break and unable to obtain micro-nano liquid metal particles, thereby failing to form a wire 12 with a micro-nano line width. The viscosity of the liquid metal water-based slurry cannot be too small to prevent the liquid metal particles from being quickly deposited and unable to form a wire 12 connecting adjacent conductive points 11. Within the target viscosity range, the viscosity of the liquid metal water-based slurry can be set according to actual needs.

[0062] In some embodiments, the target viscosity range includes 200Pa·s-350Pa·s, that is, the viscosity of the liquid metal aqueous slurry is 200Pa·s-350Pa·s, so that the line width of the wire 12 self-assembled between adjacent conductive dots 11 using the liquid metal aqueous slurry can be as low as micrometer level or even nanometer level.

[0063] In some embodiments, the viscosity of the liquid metal aqueous slurry is positively correlated with the line width of the conductive line 12 .

[0064] By adjusting the amount of the water-soluble polymer, the viscosity of the liquid metal water-based slurry can be adjusted, and then the line width of the wire 12 can be adjusted. When the viscosity of the liquid metal water-based slurry is within the target viscosity range, the greater the viscosity of the liquid metal water-based slurry, the greater the line width of the wire 12; the smaller the viscosity of the liquid metal water-based slurry, the smaller the line width of the wire 12. According to actual needs, the viscosity of the liquid metal water-based slurry is adjusted to adjust the line width of the wire 12 to meet the line width requirements of the wire 12.

[0065] In some embodiments, the relationship between the viscosity of the liquid metal water-based slurry and the line width of the wire 12 is: a=-0.056+0.0034b, where a is the line width of the wire 12 and b is the viscosity of the liquid metal water-based slurry.

[0066] like Figure 4 As shown, when the viscosity of the liquid metal water-based slurry is 200 Pa·s-350 Pa·s, as the viscosity of the liquid metal water-based slurry increases, the line width of the conductive line 12 increases linearly.

[0067] In some embodiments, the conductive wire 12 is in a straight line. Liquid metal aqueous slurry is used to self-assemble between adjacent conductive dots 11 to form the conductive wire 12, so that the conductive wire 12 between adjacent conductive dots 11 is in a straight line.

[0068] By adjusting the distribution of the conductive dots 11, the pattern of the patterned circuit 1 can be adjusted. Figure 1 As shown, different conductive dots 11 are distributed on the same straight line, and the pattern of the patterned circuit 1 can be a straight line. For example, the diameter of the conductive dots 11 is 10 microns, the center distance between adjacent conductive dots 11 is 30 microns, and the line width is 0.89 microns. Different conductive dots 11 are distributed on multiple straight lines, and the pattern of the patterned circuit 1 can be a broken line. Figure 2 As shown, the pattern of the patterned circuit 1 is a sawtooth zigzag line. For example, the diameter of the conductive dot 11 is 10 microns, the center distance between adjacent conductive dots 11 is 100 microns, the center distance between adjacent conductive dots 11 is 150 microns, the line width is 0.89 microns, and the total length of the patterned circuit 1 is 500 microns. The resistance is 10.9 ohms when tested by a multimeter, and the conductivity is calculated to be 2.0×104S cm -1 .like Figure 3 As shown, the pattern of the patterned circuit 1 is in the form of multiple broken lines. For example, the diameter of the conductive dot 11 is 10 microns, and the distance between the centers of adjacent conductive dots 11 is 75 microns.

[0069] In some embodiments, the conductive dot 11 has a micrometer-level diameter. The conductive dot 11 may be circular. The diameter of the conductive dot 11 may not be too large or too small. The diameter of the conductive dot 11 may be greater than or equal to the line width of the conductive wire 12. For example, the diameter of the conductive dot 11 may be 10 μm. The diameters of different conductive dots 11 may be the same or different.

[0070] It should be noted that the conductive dots 11 can be formed by printing liquid metal aqueous slurry. The liquid metal aqueous slurry for forming the conductive dots 11 and the liquid metal aqueous slurry for forming the conductive wires 12 may have the same composition, that is, both may include liquid metal, water-soluble polymer, water and acid. The mass ratio of the components of the liquid metal aqueous slurry for forming the conductive dots 11 and the liquid metal aqueous slurry for forming the conductive wires 12 may be the same or different. The proportion of the water-soluble polymer in the liquid metal aqueous slurry for forming the conductive dots 11 may be greater than or equal to the proportion of the water-soluble polymer in the liquid metal aqueous slurry for forming the conductive wires 12, so that the viscosity of the liquid metal aqueous slurry for forming the conductive dots 11 may be greater than or equal to the viscosity of the liquid metal aqueous slurry for forming the conductive wires 12, so that the diameter of the conductive dots 11 is greater than or equal to the line width of the conductive wires 12.

[0071] In some embodiments, the stretchable circuit structure further includes a hydrophobic substrate 2 , and the patterned circuit 1 is located on the hydrophobic substrate 2 .

[0072] The hydrophobic substrate 2 has a physical property of mutually repelling the droplets, that is, the droplets are not easy to spread on the surface of the hydrophobic substrate 2, but form a smaller contact area. The droplets contact the surface of the hydrophobic substrate 2 to form a contact angle. According to the size of the contact angle, the hydrophobicity of the surface of the hydrophobic substrate 2 can be detected. The greater the hydrophobicity of the hydrophobic substrate 2, that is, the smaller the wettability of the hydrophobic substrate 2, the greater the contact angle of the hydrophobic substrate 2; the smaller the hydrophobicity of the hydrophobic substrate 2, that is, the greater the wettability of the hydrophobic substrate 2, the smaller the contact angle of the hydrophobic substrate 2.

[0073] It should be noted that the liquid metal water-based slurry utilizes its dewetting property on the hydrophobic substrate 2 and its wettability on the conductive dots 11 to form a liquid bridge between adjacent conductive dots 11, rather than being distributed on the entire hydrophobic substrate 2. The liquid bridge is then dried, and the solvent evaporates to form a wire 12 connecting adjacent conductive dots 11.

[0074] The hydrophobic substrate 2 may have a plurality of patterned circuits 1. The center distance between adjacent conductive dots 11 in the same patterned circuit 1 is within the target spacing range, and the center distance between any two conductive dots 11 in different patterned circuits 1 is greater than the upper limit of the target spacing range. The patterns of different patterned circuits 1 may be the same or different. The number and distribution of the conductive dots 11 and the number of conductive wires 12 in different patterned circuits 1 may be the same or different.

[0075] In some embodiments, the contact angle of the hydrophobic substrate 2 is within the target contact angle range. The contact angle of the hydrophobic substrate 2 cannot be too large (i.e., the hydrophobicity of the hydrophobic substrate 2 cannot be too large), so as to prevent the liquid metal aqueous slurry from forming a liquid bridge between adjacent conductive dots 11 and thus preventing the formation of a wire 12 connecting adjacent conductive dots 11. The contact angle of the hydrophobic substrate 2 cannot be too small (i.e., the hydrophobicity of the hydrophobic substrate 2 cannot be too small), so as to prevent the liquid metal aqueous slurry from spreading on the hydrophobic substrate 2 and thus preventing the formation of a wire 12 with a micro-nano line width between adjacent conductive dots 11. Within the target contact angle range, the contact angle of the hydrophobic substrate 2 can be set according to actual needs.

[0076] In some embodiments, the target contact angle range includes 80°-110°, that is, the contact angle of the hydrophobic substrate 2 is 80°-110°, so that the line width of the wire 12 self-assembled between adjacent conductive dots 11 using the liquid metal aqueous slurry is as low as micrometer level or even nanometer level.

[0077] In some embodiments, the hydrophobic substrate 2 includes any one of PDMS (polydimethylsiloxane), TPU (thermoplastic polyurethane elastomer), and PC (polycarbonate).

[0078] When the hydrophobic substrate 2 includes PDMS, the contact angle of the hydrophobic substrate 2 is 110°; when the hydrophobic substrate 2 includes TPU, the contact angle of the hydrophobic substrate 2 is 103°; when the hydrophobic substrate 2 includes PC, the contact angle of the hydrophobic substrate 2 is 84°.

[0079] In some embodiments, the contact angle of the hydrophobic substrate 2 is negatively correlated with the line width of the conductive line 12 , and the contact angle of the hydrophobic substrate 2 is negatively correlated with the maximum center distance between adjacent conductive dots 11 .

[0080] By adjusting the contact angle of the hydrophobic substrate 2, the hydrophobicity of the hydrophobic substrate 2 can be adjusted, and then the line width of the conductor 12 can be adjusted. When the contact angle of the hydrophobic substrate 2 is within the target contact angle range, the larger the contact angle of the hydrophobic substrate 2, the smaller the line width of the conductor 12, and the smaller the maximum center distance between adjacent conductive points 11 (i.e., the upper limit of the target spacing range); the smaller the contact angle of the hydrophobic substrate 2, the larger the line width of the conductor 12, and the larger the maximum center distance between adjacent conductive points 11. According to actual needs, the contact angle of the hydrophobic substrate 2 is adjusted, thereby adjusting the line width of the conductor 12 to meet the line width requirements of the conductor 12.

[0081] In some embodiments, the relationship between the contact angle of the hydrophobic substrate 2 and the line width of the conductive line 12 is: a=-1.13exp(-x / 12.6)+1.59, where a is the line width of the conductive line, and x is the contact angle of the hydrophobic substrate.

[0082] By fitting the contact angle of the hydrophobic substrate 2 and the line width of the conductor 12, it can be found that the two present a nonlinear inverse proportional function relationship. Figure 5 As shown, when the contact angle of the hydrophobic substrate 2 is 80°-110°, as the contact angle of the hydrophobic substrate 2 decreases, the hydrophobicity of the hydrophobic substrate 2 decreases, and the line width of the conductive line 12 increases slowly and then rapidly. By setting a patterned circuit on a hydrophobic substrate of different materials and testing its contact angle, the possible line width of the conductive line 12 can be obtained through this formula.

[0083] In some embodiments, the line width of the conductive line 12 is 600 nm-10 μm.

[0084] By adjusting the viscosity of the liquid metal water-based slurry and / or the contact angle of the hydrophobic substrate 2, the line width of the wire 12 can be adjusted to be as low as micrometer level or even nanometer level. The line width of the wire 12 can be below 10 μm, and the minimum line width of the wire 12 can be as low as about 600 nm.

[0085] like Figure 6 As shown, the stretchable circuit structure is subjected to a stretch test. In the case where the diameter of the conductive dots 11 in the patterned circuit 1 is 10 microns, the center distance between adjacent conductive dots 11 is 30 microns, and the line width is 0.89 microns, the resistance retention rate under 0% (initial state), 100%, 200% and 300% tensile strain is detected, and the value is higher than 90%, indicating that the circuit can still maintain stable electrical properties under tensile deformation and has good electromechanical properties.

[0086] According to the stretchable circuit structure provided in the embodiment of the present application, by setting at least two conductive points 11, the center distance between adjacent conductive points 11 is within the target spacing range, and a wire 12 connecting the adjacent conductive points 11 is set between the conductive points 11, so that the line width of the wire 12 is as low as the micro-nano level, thereby ensuring that the stretchable circuit has high conductivity and improving the fineness of the stretchable circuit.

[0087] Correspondingly, an embodiment of the present application also provides a method for preparing a stretchable circuit structure, which can produce the stretchable circuit structure in the above embodiment.

[0088] like Figure 7 As shown, the method for preparing a stretchable circuit structure provided in an embodiment of the present application includes step 110 and step 120.

[0089] Step 110: forming at least two conductive dots on the hydrophobic substrate, wherein the center distance between adjacent conductive dots is within a target spacing range.

[0090] In this embodiment, conductive dots are first formed on the hydrophobic substrate as hydrophilic sites so that wires can be formed between the conductive dots later. At least two conductive dots are arranged at intervals, and the center distance of adjacent conductive dots (i.e., the distance between the centers of two adjacent conductive dots) is within the target spacing range.

[0091] In some embodiments, the conductive dots have a micrometer-level diameter. The conductive dots may be circular. The diameter of the conductive dots cannot be too large or too small. The diameter of the conductive dots may be greater than or equal to the line width of the conductive wire.

[0092] In some embodiments, forming at least two conductive dots on the hydrophobic substrate in step 110 includes:

[0093] placing a template having holes on a hydrophobic substrate;

[0094] Dropping a liquid metal aqueous slurry onto the hydrophobic substrate through the hole;

[0095] Remove the template;

[0096] The liquid metal aqueous slurry on the hydrophobic substrate is dried to form at least two conductive dots on the hydrophobic substrate.

[0097] Combination Figure 8 As shown, a template 31 is placed on the hydrophobic substrate 2, and the template 31 has at least two holes 32. At least two holes 32 are arranged at intervals, and the distance between adjacent holes 32 is within the target distance range. The hydrophobic substrate 2 and the template 31 are placed on a 65°C hot plate as a whole, 500 microliters of liquid metal water-based slurry 33 is added, and a scraper 34 is used to quickly scrape and apply, as shown in FIG. Fig. 9 As shown, the liquid metal water-based slurry 33 is formed on the hydrophobic substrate 2 through the holes 32. Then, the template 31 is removed, and the liquid metal water-based slurry 33 on the hydrophobic substrate 2 is dried to form at least two conductive dots 11 on the hydrophobic substrate 2, as shown in FIG. Fig.10 shown.

[0098] Step 120: Using liquid metal water-based slurry, self-assemble on the hydrophobic substrate to form wires connecting adjacent conductive points.

[0099] The conductive wire 12 is in a straight line shape. Liquid metal water-based slurry is used to self-assemble between adjacent conductive dots 11 to form the conductive wire 12, so that the conductive wire 12 between adjacent conductive dots 11 is in a straight line shape.

[0100] In some embodiments, the step 120 of using a liquid metal aqueous slurry to self-assemble on a hydrophobic substrate to form a wire connecting adjacent conductive dots includes:

[0101] Dropping a liquid metal aqueous slurry on the hydrophobic substrate and covering the cover plate, so that the liquid metal aqueous slurry moves between the hydrophobic substrate and the cover plate to form a liquid bridge between adjacent conductive points;

[0102] Remove the cover;

[0103] The liquid bridge is dried to self-assemble on the hydrophobic substrate to form a wire connecting adjacent conductive dots.

[0104] After forming at least two conductive dots 11 on the hydrophobic substrate 2, the hydrophobic substrate 2 with the conductive dots 11 is placed on a water platform. Fig.11 As shown, 500 microliters of liquid metal water-based slurry 35 is dripped onto the hydrophobic substrate 2, and a hydrophobically modified cover plate (such as a glass substrate) 36 is covered on top. Fig.12 As shown. The liquid metal water-based slurry moves between the hydrophobic substrate 2 and the cover plate 36, shrinks between the conductive points 11, and forms a liquid bridge connecting the conductive points 11. The whole is placed in the air for drying, the upper cover plate 36 is removed, and heated on a 65°C hot plate for 5 minutes to form a wire 12 connecting adjacent conductive points 11, and a patterned circuit 1 is obtained, as shown Fig.13 shown.

[0105] This embodiment utilizes the de-wetting property of the liquid metal aqueous slurry on the hydrophobic substrate and the wettability on the conductive points, so that the liquid metal aqueous slurry forms a liquid bridge between adjacent conductive points, rather than being distributed on the entire hydrophobic substrate. After the liquid metal aqueous slurry dries, it forms a wire connecting the conductive points to obtain a one-dimensional patterned circuit. This embodiment can prepare liquid metal stretchable wires with line widths as low as micrometers or even nanometers, solving the problem of difficulty in patterning liquid metal and difficulty in fine processing. Moreover, the preparation method is simple, does not require complex templates or precision instruments, and is low cost.

[0106] It should be noted that by adjusting the distribution of holes in the template, multiple patterned circuits 1 can be formed simultaneously on the hydrophobic substrate 2. The center distance between adjacent conductive dots 11 in the same patterned circuit 1 is within the target spacing range, and the center distance between any two conductive dots 11 in different patterned circuits 1 is greater than the upper limit of the target spacing range.

[0107] After preparing the stretchable circuit structure, the stretchable circuit structure can be tested, including: observing the stretchable circuit through a microscope to measure the line width; testing its hydrophobicity through the contact angle; measuring the slurry viscosity through a rheometer; measuring its resistance through a multimeter; and stretching the stretchable circuit through a universal mechanical testing machine.

[0108] In some embodiments, the target pitch range includes 30 μm-250 μm.

[0109] For example, the hydrophobic substrate is PDMS, the diameter of the conductive dots is 10 μm, and the center distances of adjacent conductive dots are 20, 60, 100, 150, and 200 μm, respectively. Liquid metal water-based slurry is used to form wires between adjacent conductive dots, and the liquid metal, water-soluble polymer, water, and acid in the liquid metal water-based slurry are 2 g, 0.08 g, 4 g, and 0.4 g, respectively.

[0110] For adjacent conductive points with a center distance of 60 and 100 microns, micro-nanoscale wires connecting adjacent conductive points can be formed, and the line width of the wires is 0.89 microns. For adjacent conductive points with a center distance of 20 microns, since the conductive points are too close to each other, it is difficult to form an isolated point distribution after drying, so subsequent wire preparation is impossible. For adjacent conductive points with a center distance of 150 and 200 microns, since the conductive points are far apart, the dewetting of the hydrophobic substrate is the main driving force, resulting in the liquid metal only being distributed around the conductive points instead of forming a connection.

[0111] In some embodiments, the contact angle of the hydrophobic substrate 2 is within a target contact angle range, wherein the target contact angle range includes 80°-110°, that is, the contact angle of the hydrophobic substrate 2 is 80°-110°.

[0112] In some embodiments, the hydrophobic substrate 2 includes any one of PDMS (polydimethylsiloxane), TPU (thermoplastic polyurethane elastomer), and PC (polycarbonate).

[0113] For example, the diameter of the conductive point is 10 μm, and the center distances of adjacent conductive points are 30, 60, 100, 150, 200, 250, and 280 μm, respectively. Liquid metal aqueous slurry is used to form wires on hydrophobic substrates with different hydrophobicities. Among them, the liquid metal, water-soluble polymer, water, and acid in the liquid metal aqueous slurry are 2 g, 0.08 g, 4 g, and 0.4 g, respectively. The hydrophobic substrates with different hydrophobicities are PDMS, PTFE (polytetrafluoroethylene), TPU, PC, and PET (polyethylene terephthalate). The hydrophobicity of PTFE, PDMS, TPU, PC, and PET decreases in sequence.

[0114] For PDMS, TPU and PC substrates, it is possible to form wires with micro-nanoscale line widths between adjacent conductive points. Among them, for TPU substrates, the length of the connection between two conductive points that can be prepared ranges from 30 to 200 microns, and the line width is about 1.2 microns. For PC substrates, the length of the connection between two conductive points that can be prepared ranges from 30 to 250 microns, and the line width is about 1.5 microns. For PTFE substrates, since the wettability of the liquid metal water-based slurry on the substrate is too low, the droplets are only distributed on the conductive points and cannot self-assemble to form lines. For PET substrates, due to their low hydrophobicity, the liquid metal water-based slurry spreads on the substrate and cannot self-assemble between the substrate and the conductive points to form a patterned circuit.

[0115] In order to qualitatively illustrate the hydrophobicity of different hydrophobic substrates, the contact angle of water droplets on different hydrophobic substrates is used to characterize, such as Figures 14 to 18 As shown in the figure, the contact angles of PTFE, PDMS, TPU, PC, and PET are 122°, 110°, 103°, 84°, and 69°, respectively, that is, when the contact angle is within the range of 110°-80°, the hydrophobicity is suitable, and the patterned wires can be effectively self-assembled. Moreover, as the hydrophobicity increases, the length of the connection between the two conductive points decreases, and the line width decreases. When it is higher than 110°, it is difficult to infiltrate, and when it is lower than 80°, it is completely spread and difficult to pattern.

[0116] In some embodiments, the contact angle of the hydrophobic substrate 2 is negatively correlated with the line width of the conductive line 12 , and the contact angle of the hydrophobic substrate 2 is negatively correlated with the maximum center distance between adjacent conductive dots 11 .

[0117] In order to further clarify the relationship between substrate hydrophobicity and line width, the contact angle and line width were fitted, as shown in Figure 5 As shown, the two show a nonlinear inverse proportional function relationship, and the relationship is a = -1.13exp(-x / 12.6) + 1.59, and the feasibility R2 = 0.999, where x is the contact angle and a is the line width at the contact angle. As the contact angle decreases, the hydrophobicity decreases, and the line width increases slowly at first and then rapidly. The patterned wires are prepared on different substrates, and by testing their contact angles, the possible line width can be obtained through the fitting formula.

[0118] In some embodiments, the liquid metal aqueous slurry may include liquid metal, a water-soluble polymer, water, and an acid. The water-soluble polymer is used to stabilize the dispersion of the liquid metal particles, and the acid is used to react with the oxide layer of the liquid metal to activate the liquid metal particles. The liquid metal may include gallium and indium, the water-soluble polymer may include sodium hydroxymethylcellulose, and the acid may include acetic acid.

[0119] The preparation method of liquid metal aqueous slurry can be: liquid metal, water-soluble polymer, water and acid are added into a centrifuge tube according to the mass ratio, an ultrasonic probe is immersed in the bottom of the centrifuge tube, and ultrasonication is performed at 100% power for 1 minute to obtain liquid metal aqueous slurry.

[0120] The liquid metal water-based slurry in this embodiment uses water as a processing solvent, which is green and environmentally friendly and reduces pollution.

[0121] In some embodiments, the mass ratio of liquid metal, water-soluble polymer, water and acid can be 1:0.02-0.06:2:0.2. The viscosity of the liquid metal water-based slurry can be adjusted by adjusting the proportion of the water-soluble polymer in the liquid metal water-based slurry.

[0122] In some embodiments, the viscosity of the liquid metal water-based slurry is within a target viscosity range, wherein the target viscosity range may include 200 Pa·s-350 Pa·s, that is, the viscosity of the liquid metal water-based slurry may be 200 Pa·s-350 Pa·s.

[0123] For example, the hydrophobic substrate is PDMS, the diameter of the conductive point is 10μm, and the center distance between adjacent conductive points is 30μm. Liquid metal aqueous slurries C1, C2, C3, C4 and C5 with different proportions of water-soluble polymers are used to form wires. Among them, the liquid metal, water-soluble polymer, water and acid in C1 correspond to 2g, 0.08g, 4g and 0.4g respectively; the liquid metal, water-soluble polymer, water and acid in C2 correspond to 2g, 0.16g, 4g and 0.4g respectively; the liquid metal, water-soluble polymer, water and acid in C3 correspond to 2g, 0.12g, 4g and 0.4g respectively; the liquid metal, water-soluble polymer, water and acid in C4 correspond to 2g, 0.04g, 4g and 0.4g respectively; the liquid metal, water-soluble polymer, water and acid in C5 correspond to 2g, 0.02g, 4g and 0.4g respectively.

[0124] C1, C3 and C4 can all form wires with micro-nano line widths connecting conductive points. Among them, the line width of the wire formed by C1 is 0.89μm, the line width of the wire formed by C3 is 1.1μm, and the line width of the wire formed by C1 is 0.64μm. In the process of making wires using C2, due to the large amount of water-soluble polymer added and the high viscosity of the slurry, it is still difficult to completely break up the liquid metal after a long period of ultrasound, so that micron-sized liquid metal particles cannot be obtained. In the process of making wires using C5, due to the low viscosity of the slurry, the liquid metal particles are quickly deposited and cannot be evenly dispersed between the two conductive points.

[0125] The viscosity of the slurry was measured by rheometer, such as Fig.19As shown in the figure, taking the viscosity corresponding to an angular velocity of 10 rad / s as an example, the viscosity of C2 is 494 Pa·s, and the viscosity of C5 is 122 Pa·s. Therefore, the viscosity range of the slurry (such as C1, C3 and C4) that can successfully prepare the wire with micro-nano line width connecting the conductive dots is 200 Pa·s-350 Pa·s, that is, when the viscosity range of the slurry is 200 Pa·s-350 Pa·s, a well-dispersed slurry can be successfully prepared for the preparation of patterned circuits.

[0126] In some embodiments, the viscosity of the liquid metal aqueous slurry is positively correlated with the line width of the conductive line.

[0127] In order to further clarify the relationship between the slurry viscosity and the wire width, the viscosity and line width are fitted, such as Figure 4 As shown, it can be seen that the two are in a proportional function relationship, and the relationship is a = -0.056 + 0.0034b, R2 = 0.99, where b is viscosity and a is line width. As the viscosity of the slurry increases, the line width increases linearly. From this formula, it can be inferred that when the viscosity of the prepared slurry increases further, the line width can be further increased. However, when the viscosity is small, the wire cannot be successfully prepared.

[0128] In some embodiments, the line width of the conductive line 12 is 600 nm-10 μm.

[0129] By adjusting the viscosity of the liquid metal water-based slurry and / or the contact angle of the hydrophobic substrate 2, the line width of the wire 12 can be adjusted to be as low as micrometer level or even nanometer level. The line width of the wire 12 can be below 10 μm, and the minimum line width of the wire 12 can be as low as about 600 nm.

[0130] According to the preparation method of the stretchable circuit structure provided by the embodiment of the present application, by setting at least two conductive points 11, the center distance of adjacent conductive points 11 is within the target spacing range, and the dewetting property of the liquid metal aqueous slurry on the hydrophobic substrate and the wettability on the conductive points are utilized to form a wire 12 connecting adjacent conductive points 11 between the conductive points 11, so that the line width of the wire 12 is as low as the micro-nano level, while ensuring that the stretchable circuit has high conductivity, the fineness of the stretchable circuit is improved, and the problem of liquid metal patterning being difficult and difficult to process is solved. Moreover, the preparation method is simple, does not require complex templates or precision instruments, and is low in cost. Moreover, water is used as the processing solvent, which is green and environmentally friendly and reduces pollution.

[0131] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more.

[0132] In the description of the present application, “plurality” means two or more.

[0133] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0134] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A stretchable circuit structure, characterized in that: include: A patterned circuit comprises at least two conductive dots and at least one conductive wire, wherein the center distance between adjacent conductive dots is within a target spacing range, the conductive wires are connected between adjacent conductive dots, and the conductive wires have a micro-nanoscale line width.

2. The stretchable circuit structure according to claim 1, characterized in that: The wire is in a straight line.

3. The stretchable circuit structure according to claim 1, characterized in that: The conductive dots have a micrometer-sized diameter.

4. The stretchable circuit structure according to claim 1, characterized in that: The stretchable circuit structure further comprises: A hydrophobic substrate, wherein the patterned circuit is located on the hydrophobic substrate.

5. The stretchable circuit structure according to claim 4, characterized in that: The contact angle of the hydrophobic substrate is negatively correlated with the line width of the conductive wire and negatively correlated with the maximum center distance between adjacent conductive dots; and / or, The relationship between the contact angle of the hydrophobic substrate and the line width of the conductive line is: a=-1.13exp(-x / 12.6)+1.59, wherein a is the line width of the conductive line, and x is the contact angle of the hydrophobic substrate.

6. The stretchable circuit structure according to claim 4, characterized in that: The contact angle of the hydrophobic substrate is 80°-110°; and / or, The hydrophobic substrate includes any one of PDMS, TPU and PC.

7. The stretchable circuit structure according to any one of claims 1 to 6, characterized in that: The target spacing range includes 30 μm-250 μm; and / or, The line width of the conductive line is 600nm-10μm.

8. A method for preparing a stretchable circuit structure, characterized in that: include: Forming at least two conductive dots on a hydrophobic substrate, wherein the center distance between adjacent conductive dots is within a target spacing range; Liquid metal water-based slurry is used to self-assemble on the hydrophobic substrate to form wires connecting adjacent conductive points.

9. The method for preparing a stretchable circuit structure according to claim 8, characterized in that: The viscosity of the liquid metal water-based slurry is positively correlated with the line width of the wire; and / or, The relationship between the viscosity of the liquid metal water-based slurry and the line width of the conductive line is: a=-0.056+0.0034b, wherein a is the line width of the conductive line, and b is the viscosity of the liquid metal water-based slurry.

10. The method for preparing a stretchable circuit structure according to claim 8, characterized in that: The liquid metal aqueous slurry comprises liquid metal, a water-soluble polymer, water and an acid; and / or, The viscosity of the liquid metal water-based slurry is 200 Pa·s-350 Pa·s; and / or, The target spacing range includes 30 μm-250 μm; and / or, The line width of the conductive line is 600nm-10μm.

Images