Method for realizing liquid metal patterning on paper substrate and functional paper-based electronic device

Abstract

The invention discloses a method for achieving liquid metal patterning on a paper substrate and a functional paper-based electronic device. The method comprises the following steps that liquid metal is made into a solid metal film; spreading the solid metal film on the fiber-containing sheet substrate, and spreading the protective film on the solid metal film to form a three-layer structure; drawing a target pattern on the three-layer structure by applying shear force to the formed three-layer structure; in the process of applying the shearing force, the solid metal film is adhered to the fiber-containing sheet-shaped substrate and is embedded into the fiber porous structure of the fiber-containing sheet-shaped substrate; and heating the three-layer structure to melt the solid metal film, removing the protective film and the liquid metal which does not participate in the formation of the target pattern, and finally forming the liquid metal pattern on the fiber-containing sheet-shaped substrate.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronic technology, and specifically relates to a method for realizing liquid metal patterning on a paper substrate and a functional paper-based electronic device. Background Art

[0002] Room temperature liquid metal is an emerging functional material with high electrical conductivity, high thermal conductivity, fluidity and good biocompatibility. It is widely used in flexible electronics, soft robotics and energy management. Patterning of liquid metal is a key step in realizing the functionalization of liquid metal. Patterning liquid metal on various flexible substrates can construct functional flexible electronic devices. Among various flexible substrates, paper substrates with plant fibers or synthetic fibers as the main raw materials have the advantages of environmental protection, biodegradability, porosity, good biocompatibility, light weight and low preparation cost. However, due to the high surface tension of liquid metal and its low wettability with paper substrates, it is very difficult to pattern liquid metal directly on paper substrates.

[0003] At present, patterning of liquid metal on paper substrates is mainly achieved by modifying the liquid metal or the paper substrate to increase the wettability between the two. These methods can usually only pattern liquid metal on the surface of the paper substrate. However, due to the fluidity of liquid metal, this surface liquid metal circuit is extremely susceptible to mechanical damage and failure. Although the encapsulation operation can protect the liquid metal from damage, it also limits the interaction between the liquid metal and the outside world, as well as the potential application of liquid metal paper-based electronics in electrophysiological signal acquisition or bioelectric stimulation.

[0004] Therefore, it remains challenging to construct liquid metal patterns on paper substrates that are resistant to mechanical damage. Summary of the invention

[0005] Purpose of the invention: In order to solve the technical difficulties in constructing a liquid metal pattern that is resistant to mechanical damage on a paper substrate, the present invention proposes a method for realizing liquid metal patterning on a paper substrate and a functional paper-based electronic device.

[0006] Technical solution: A method for realizing liquid metal patterning on a paper substrate, comprising the following steps:

[0007] Making liquid metal into solid metal film;

[0008] Spreading a solid metal film on a sheet-like substrate containing fibers, and spreading a protective film on the solid metal film to form a three-layer structure;

[0009] By applying shear force to the formed three-layer structure, a target pattern is drawn on the three-layer structure; during the shear force application process, the solid metal film adheres to the fiber-containing sheet substrate and is embedded in the fiber porous structure of the fiber-containing sheet substrate;

[0010] The three-layer structure is heated to melt the solid metal film and remove the protective film and liquid metal that does not participate in the formation of the target pattern, ultimately forming a liquid metal pattern on the fiber-containing sheet substrate.

[0011] Furthermore, the fibers include plant fibers and synthetic fibers.

[0012] Furthermore, the liquid metal is a liquid metal with a melting point below 200°C.

[0013] Furthermore, the fiber-containing sheet substrate is a sheet substrate with a thickness of less than 200 μm.

[0014] Furthermore, the protective film is a flexible high molecular polymer protective film.

[0015] Furthermore, the protective film is a flexible high molecular polymer protective film with a thickness of less than 200 μm.

[0016] Furthermore, during the process of applying the shear force, the shear force is not less than 10 MPa, and the shear speed is not less than 10 mm / min.

[0017] The present invention also discloses a functional paper-based electronic device, which is obtained by patterning the liquid metal on a fiber-containing sheet substrate using the above-disclosed method for realizing liquid metal patterning on a paper substrate.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0019] (1) The method of the present invention utilizes metal phase change and metal wear to achieve effective liquid metal patterning on a paper substrate, which has the characteristics of simple process, universality, environmental protection, and low cost. It can prepare functional liquid metal paper-based electronics and has broad application prospects.

[0020] (2) The method of the present invention does not require modification of the paper substrate and the liquid metal, and utilizes the solid-liquid phase transition of the liquid metal and metal wear to achieve a simple and efficient liquid metal pattern on the paper substrate;

[0021] (3) The liquid metal pattern prepared by the method of the present invention has a unique structure, is embedded in the porous structure of the paper substrate fiber, and has the ability to resist mechanical damage;

[0022] (4) The method of the present invention has wide applicability to paper substrates and can realize liquid metal patterning on various common paper substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of a method for realizing liquid metal patterning on a paper substrate proposed by the present invention;

[0024] Figure 2 Optical images of different liquid metal patterns on cardboard;

[0025] Figure 3 This is an electron microscope image of the jammed liquid metal circuit;

[0026] Figure 4 The micro-computed tomography results of the jammed liquid metal;

[0027] Figure 5 Optical images of liquid metal patterns on different substrates;

[0028] Figure 6 The resistance of the liquid metal circuit changes with the number of frictions;

[0029] Figure 7 This is an electron microscope image of the liquid metal circuit before and after fifty frictions. DETAILED DESCRIPTION

[0030] The present invention discloses a method for patterning liquid metal on a paper substrate. The method firstly forms the liquid metal into a solid metal film and spreads the solid metal film on the paper substrate; then, spreads a protective film on the solid metal film, and uses a rigid tip to apply shear force to the three-layer structure to draw a pattern; finally, heats and melts the solid metal film, and removes the protective film and excess liquid metal that does not participate in the pattern formation, thereby obtaining a target liquid metal pattern on the paper substrate. The target liquid metal pattern obtained by this method is partially embedded in the fiber porous structure of the paper substrate and has the ability to resist mechanical damage.

[0031] The technical solution of the present invention is now further described in conjunction with the accompanying drawings and embodiments.

[0032] Embodiment 1:

[0033] like Figure 1 As shown, this embodiment discloses a method for realizing liquid metal patterning on a paper substrate, and the detailed preparation process is as follows:

[0034] Step 1: Preparation of solid gallium film:

[0035] The mold was made by using two polyethylene terephthalate films (5 cm × 5 cm) as the upper and lower bases of the mold and sandwiching a 30 μm thick tape gasket;

[0036] Inject 0.2 ml of liquid gallium into the mold;

[0037] After pressure molding, the film is frozen in a -20°C environment, and after the liquid gallium is completely solidified, it is demolded to obtain a solid liquid gallium film with a thickness of 30 μm.

[0038] Step 2: Printing Liquid Metal on Paper Substrate:

[0039] From bottom to top, commercial black cardboard with a thickness of 100 μm, the solid liquid gallium film with a thickness of 30 μm obtained in step 1, and a PET protective film with a thickness of 25 μm are laid in sequence to obtain a three-layer stacking structure.

[0040] The three-layer stacked structure was placed on a commercial writing machine, a 0.5 mm ballpoint pen tip was fixed, and the height of the ballpoint pen tip was adjusted so that it exerted a shear force of about 6 N during writing, and the speed of the writing machine was set to 1000 mm / min. The pen tip position was adjusted so that the writing area was within the three-layer stacked structure.

[0041] After the paths of the Peano curve, microelectrode array, and butterfly pattern are input into the control software, the writer cuts and prints according to the preset path. During the shear force application process, the solid metal film and the paper substrate will undergo adhesion and wear, and the solid metal will adhere to the paper surface and embed into the fibrous porous structure.

[0042] After the writer stops working, remove the ballpoint pen, use a hot air gun to heat and melt the solid liquid gallium film, and then peel off the PET protective film.

[0043] Finally, use another cardboard piece of size 3cm×3cm to scrape off the liquid metal that is not involved in the pattern formation on the cardboard. The resulting pattern is as follows: Figure 2 shown.

[0044] The liquid metal circuits were observed using a scanning electron microscope, and local patterns were cut out for micro-computed tomography. The results showed that the liquid metal was embedded in the porous structure of the paper fibers, so it has the characteristics of resisting mechanical damage, such as Figure 3 shown.

[0045] The liquid gallium used in this embodiment can be replaced by other metals with a melting point below 200°C, including but not limited to mercury, gallium, gallium-indium alloy, gallium-indium-tin alloy, indium-tin-bismuth alloy, and indium-bismuth alloy; the thickness of the solid liquid gallium film obtained in step 1 should be less than 200μm.

[0046] In this embodiment, commercial black cardboard with a thickness of 100 μm is used as the paper substrate, which can also be replaced by other fiber-containing sheets, including but not limited to printing paper, carbon paper, toilet paper, rice paper, kraft paper, and filter paper; preferably, the thickness of the selected paper substrate should be less than 200 μm.

[0047] The PET protective film used in this embodiment can be replaced by other high molecular polymer protective films with certain flexibility, including but not limited to: polyethylene terephthalate (PET), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), polyimide (PI), polyethylene naphthalate (PEN); preferably, the thickness of the selected protective film should be less than 200 μm. By selecting a soft and thin protective film, the solid metal film can be prevented from being damaged during the application of shear force, and the dissipation of shear force can be reduced.

[0048] The ballpoint pen tip used in this embodiment can be replaced by other types of rigid tips, which come from an object or tool with a hard, sharp front end, including but not limited to a metal stick, a ballpoint pen, a nail, etc.; the diameter of the selected rigid tip should be less than 1 mm.

[0049] The shear force applied in this embodiment can be applied manually or with the aid of a displacement device, including but not limited to a writer and a high-precision XYZ three-axis motion platform; the applied shear force should be no less than 10 MPa, and the shear speed should be no less than 10 mm / min.

[0050] The hot air gun used in this embodiment can be replaced by other heating tools, including but not limited to ovens, hot plates, and induction cookers. The heating temperature should be higher than the melting point of the solid metal film.

[0051] In this embodiment, other thin sheets can also be used to scrape off the liquid metal on the cardboard that is not involved in the pattern formation. The liquid metal that is not involved in the pattern formation comes from the solid metal film area that is not subjected to shear force. Since the liquid metal has poor wettability on the paper substrate, it is easy to be removed.

[0052] Embodiment 2:

[0053] The only difference between this embodiment and embodiment 1 is that filter paper, newspaper, kraft paper and napkin paper are used as paper substrates, and the letters "LM" are used as target patterns; the other process steps are the same.

[0054] Figure 5 Optical images of liquid metal patterns on different paper substrates are shown, from which it can be seen that the method of the present invention achieves effective liquid metal patterning on paper substrates, and has wide applicability to paper substrates, and can achieve liquid metal patterning on various common paper substrates.

[0055] Embodiment 3:

[0056] The difference between this embodiment and embodiment 1 is that the target pattern is a single liquid metal circuit. The other process steps are the same. This embodiment is used to characterize the mechanical damage resistance of the liquid metal circuit.

[0057] Use an eraser to repeatedly rub a single liquid metal circuit on a paper substrate, and use a multimeter to measure the change in resistance, such as Figure 6 The circuit changes before and after 50 times of friction were observed using a scanning electron microscope, as shown in Figure 7 shown.

[0058] It can be seen that the liquid metal pattern prepared by the method of the present invention has a unique structure, is embedded in the porous structure of the paper substrate fiber, and has the ability to resist mechanical damage.

[0059] Embodiment 4:

[0060] This embodiment proposes a liquid metal paper-based electronic device, which is manufactured by the method disclosed in Example 1.

Claims

1. A method for patterning liquid metal on a paper substrate, characterized in that: The following steps are involved: Making liquid metal into solid metal film; Spreading a solid metal film on a sheet-like substrate containing fibers, and spreading a protective film on the solid metal film to form a three-layer structure; By applying shear force to the formed three-layer structure, a target pattern is drawn on the three-layer structure; during the shear force application process, the solid metal film adheres to the fiber-containing sheet substrate and is embedded in the fiber porous structure of the fiber-containing sheet substrate; The three-layer structure is heated to melt the solid metal film and remove the protective film and liquid metal that does not participate in the formation of the target pattern, ultimately forming a liquid metal pattern on the fiber-containing sheet substrate.

2. A method for realizing liquid metal patterning on a paper substrate according to claim 1, characterized in that: The fibers include plant fibers and synthetic fibers.

3. The method for realizing liquid metal patterning on a paper substrate according to claim 1, characterized in that: The liquid metal is a liquid metal with a melting point lower than 200°C.

4. The method for realizing liquid metal patterning on a paper substrate according to claim 1, characterized in that: The fiber-containing sheet-like substrate is a sheet-like substrate having a thickness of less than 200 μm.

5. The method for patterning liquid metal on a paper substrate according to claim 1, characterized in that: The protective film is a flexible high molecular polymer protective film.

6. The method for patterning liquid metal on a paper substrate according to claim 1, characterized in that: The protective film is a flexible high molecular polymer protective film with a thickness of less than 200 μm.

7. The method for patterning liquid metal on a paper substrate according to claim 1, characterized in that: During the process of applying the shear force, the shear force is not less than 10 MPa and the shear speed is not less than 10 mm / min.

8. A functional paper-based electronic device, characterized in that: The method for realizing liquid metal patterning on a paper substrate as claimed in any one of claims 1 to 7 is adopted to construct the liquid metal patterning on a fiber-containing sheet substrate.

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