Liquid metal flexible electronic device with porous pomelo peel as skeleton and preparation method thereof

Abstract

The application discloses a kind of liquid metal flexible electronic devices with porous shaddock skin as framework and a preparation method thereof, with the porous sponge layer of natural shaddock skin as framework, by mixing liquid metal with solid particles to prepare conductive filler with plasticity, and with the aid of mask and magnetic field, the precise patterning of liquid metal circuit on the surface of shaddock skin is realized.Subsequently, the adhesive pre-gel containing adhesive enhancement component and glycerol / water mixed solvent is injected into the porous structure of shaddock skin, and the adhesive pre-gel is cured by photopolymerization, and finally the liquid metal / shaddock hydrogel composite electronic device is obtained.The electronic device prepared by the application has high conductivity of liquid metal, flexibility of shaddock framework and adhesion of hydrogel, and has excellent anti-freezing and anti-drying performance due to the introduction of glycerol, and can be stably applied in the fields of efficient thermal management and motion detection.The preparation process of the application is simple, low in cost and environmentally friendly, and provides a new idea for the development of flexible electronic devices.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, and more specifically, to a liquid metal flexible electronic device with a porous grapefruit peel as a framework and its preparation method. Background Technology

[0002] Electronic skin, as a novel flexible electronic device capable of mimicking the sensory functions of human skin, shows great promise in wearable health monitoring, human-computer interaction, and flexible robotics. Ideal electronic skin needs to possess flexibility and stretchability similar to human skin, and be able to form stable and reliable adhesion to biological tissues. Liquid metals, especially gallium-based alloys, are considered ideal conductive materials for constructing flexible electronics due to their excellent conductivity, superior fluidity, and good biocompatibility.

[0003] However, the high fluidity of liquid metals also presents challenges such as easy leakage and difficulty in patterning. Existing technologies typically employ complex microfluidic encapsulation techniques to immobilize liquid metals, but these methods are cumbersome, costly, and struggle to achieve good adhesion and long-term stable bonding with complex surfaces. On the other hand, hydrogel materials, due to their excellent biocompatibility and tunable mechanical properties, are widely used as substrates for electronic skins; however, traditional synthetic hydrogels often suffer from insufficient adhesion and are prone to failure in dry or low-temperature environments.

[0004] Therefore, developing a liquid metal flexible electronic device that is simple to fabricate, low in cost, and possesses excellent flexibility, strong adhesion, and environmental adaptability remains a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned shortcomings of the prior art and provide a liquid metal flexible electronic device with a porous grapefruit peel as its framework and its fabrication method. This invention utilizes the porous structure of natural grapefruit peel as an ideal framework, combined with a liquid metal conductive circuit and functionalized hydrogel, to achieve efficient thermal management and motion detection functions of the device, and endows it with excellent anti-freezing and anti-drying properties.

[0006] To achieve the above-mentioned objective, the first aspect of the present invention provides a method for fabricating a liquid metal flexible electronic device with a porous grapefruit peel as a framework, comprising the following steps:

[0007] (1) Pretreatment of grapefruit peel: Remove the yellow outer skin of fresh grapefruit peel, retain the spongy layer, and cut it into the required shape; immerse the cut grapefruit peel pieces in water, and use negative pressure treatment to fully wet the pores with water, and then remove excess water; then soak the grapefruit peel pieces in an alkaline solution for treatment, and then bleach them with an oxidizing solution; finally wash them clean with water and freeze dry them to obtain the pretreated dry grapefruit peel skeleton;

[0008] (2) Preparation of liquid metal conductive filler: Liquid metal is mixed with solid particles, and the solid particles are uniformly dispersed in the liquid metal by mechanical grinding or stirring to obtain a liquid metal conductive filler with plasticity.

[0009] (3) Liquid metal patterning: Based on the designed circuit pattern, a liquid metal conductive filler pattern is formed on the dried grapefruit peel skeleton obtained in step (1); Optionally, the liquid metal conductive filler containing magnetic particles is precisely patterned on the grapefruit peel surface by means of magnetic field assistance.

[0010] (4) Preparation of adhesive pregel: Dissolve the adhesion-enhancing component, polymerizable monomer, crosslinking agent and photoinitiator in a mixed solvent and mix evenly to obtain an adhesive pregel solution;

[0011] (5) Device molding: The adhesive pregel solution prepared in step (4) is injected into the dry grapefruit peel skeleton that has been patterned with liquid metal, so that the pregel solution fully fills the porous structure of grapefruit peel; then the in-situ crosslinking reaction is initiated by photopolymerization to solidify the pregel and form a hydrogel composite electronic device with grapefruit peel as the skeleton and liquid metal circuit embedded inside.

[0012] Furthermore, the solid particles mentioned in step (2) contain magnetic components, and the magnetic field-assisted method mentioned in step (3) is as follows: place the magnet under the grapefruit peel skeleton, cover and fix the mask with the desired hollow pattern on the upper surface of the grapefruit peel skeleton; uniformly coat the liquid metal conductive filler containing magnetic particles on the mask; under the attraction of the magnetic field below, the liquid metal conductive filler is adsorbed and transferred to the area of ​​the grapefruit peel surface not covered by the mask; after removing the mask, the desired pattern is obtained.

[0013] Furthermore, after step (3) and before step (5), a thin layer of photocurable hydrogel is applied to the surface of the grapefruit peel skeleton with the liquid metal pattern to encapsulate the liquid metal pattern and prevent leakage. The composition of the photocurable hydrogel is preferably the same as that of the adhesive pregel.

[0014] Specifically, the adhesion-enhancing component in step (4) is bovine serum albumin (BSA); the polymerizable monomer is selected from any one or a combination of two or more of acrylamide (AAm), gelatin methacrylate (GelMA), and hyaluronic acid methacrylate (HAMA).

[0015] Preferably, in the adhesive pregel solution, the mass concentration of bovine serum albumin is 1-20 wt%, and the mass concentration of the polymerizable monomer is 5-50 wt%.

[0016] Preferably, the crosslinking agent is N,N'-methylenebisacrylamide (bis, MBAA); the photoinitiator is lithium phenyl-2,4,6-trimethylbenzoylphosphonate (Irgacure 2959, LAP) or 2-hydroxy-2-methylphenylacetone (HMPP); and the solvent is a mixture of glycerol and water.

[0017] Preferably, the liquid metal in step (2) is a gallium-indium alloy melt; the solid particles are selected from one or more of nickel powder, silicon dioxide, copper powder, and glass microspheres, and contain iron or iron oxide magnetic components; the size of the solid particles is 1-500 micrometers.

[0018] Preferably, the injection method in step (5) is one of vacuum-assisted permeation, centrifugal permeation, or natural permeation.

[0019] A second aspect of the present invention provides a liquid metal flexible electronic device with a porous grapefruit peel as a framework, prepared according to the above method.

[0020] Furthermore, the present invention also claims protection for the application of the above-mentioned liquid metal flexible electronic device with porous grapefruit peel as a framework in the fabrication of wearable devices.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Natural template, simplified process: The present invention cleverly utilizes the natural, interconnected porous sponge layer structure of grapefruit peel as the reinforcing skeleton of hydrogel and the carrier matrix of liquid metal, avoiding the complex artificial microstructure manufacturing process, significantly simplifying the preparation process and reducing costs.

[0023] (2) The patterning method is simple and efficient: By mixing liquid metal with magnetic / functional particles and combining it with a mask and magnetic field, the liquid metal can be quickly and accurately patterned on the surface of rough and porous natural biomaterials, solving the problem that liquid metal is difficult to localize on non-planar substrates.

[0024] (3) Excellent adhesion and environmental adaptability: By introducing functional components such as bovine serum albumin into the pregel, the adhesion of the hydrogel matrix to various substrates such as biological tissues is enhanced. At the same time, the introduction of glycerol as a co-solvent endows the hydrogel with excellent antifreeze and anti-drying properties, enabling it to work stably for a long time in harsh environments such as cold or dryness.

[0025] (4) Multifunctional integration: The flexible electronic device obtained by the present invention can not only use the internal liquid metal circuit as a heating element to achieve efficient Joule thermal management, but also serve as a strain sensor for real-time motion detection, thus realizing the integration of structure and function. Attached Figure Description

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0027] Figure 1 This is a schematic diagram of the process of using a magnetic field to pattern liquid metal on the surface of a grapefruit peel skeleton in Embodiment 1 of the present invention.

[0028] Figure 2 This invention relates to the patterning of liquid metal on grapefruit peel.

[0029] Figure 3 This is a schematic diagram of the structure of the liquid metal flexible electronic device with a porous grapefruit peel as a framework prepared in Example 1 of the present invention.

[0030] Figure 4 The figure shows the electrothermal effect characterization results of the liquid metal flexible electronic device prepared in Example 1 of the present invention under different applied voltages. Detailed Implementation

[0031] The present invention can be better understood from the following embodiments.

[0032] Example 1

[0033] This embodiment provides a flexible electronic device using porous grapefruit peel as a framework, consisting of nickel powder / liquid metal and its fabrication method.

[0034] (1) Pretreatment of grapefruit peel:

[0035] Select fresh grapefruits, remove the yellow outer peel, retaining the inner white spongy layer, and cut them into rectangular pieces of 3cm × 2cm × 0.5cm. Immerse the grapefruit peel pieces in deionized water and place them in a vacuum desiccator at -0.1MPa for 30 minutes to allow water to fully penetrate the pores. Then, soak the grapefruit peel pieces in a 5wt% NaOH solution for 12 hours, followed by bleaching with a 3wt% hydrogen peroxide solution for 12 hours. Afterward, wash repeatedly with plenty of deionized water until neutral. Finally, freeze-dry the washed grapefruit peel pieces in a freeze dryer for 24 hours to obtain a dry, white, porous grapefruit peel skeleton for later use.

[0036] (2) Preparation of nickel powder / liquid metal conductive filler:

[0037] Weigh 5g of gallium-indium alloy (wt% Ga:In = 75.5:24.5) and place it in an agate mortar. Then weigh 2g of nickel powder with an average particle size of 10 micrometers and add it to the mortar. Grind and stir continuously in the same direction with a grinding rod for about 15 minutes until a uniform, paste-like nickel powder / liquid metal composite conductive filler is formed.

[0038] (3) Patterning of liquid metal on grapefruit peel:

[0039] Place a neodymium magnet under the dried grapefruit peel skeleton prepared in step (1). Cover the grapefruit peel with a polyimide mask featuring an "S"-shaped circuit cutout pattern and secure it around the edges with high-temperature resistant tape. Take an appropriate amount of the conductive filler prepared in step (2) and evenly spread it on the mask with a plastic scraper. Under the attraction of the magnetic field below, the conductive filler is adsorbed and fills the grapefruit peel surface in the cutout area. Carefully peel off the mask to reveal a clear "S"-shaped liquid metal pattern on the grapefruit peel surface, as shown below. Figure 1 and Figure 2 As shown.

[0040] (4) Preparation of adhesive pregels:

[0041] Under light-protected conditions, 2.5 g bovine serum albumin (BSA), 3 g acrylamide (AAm), 0.1 ml 2-hydroxy-2-methylphenylacetone (HMPP), and 0.15 ml N,N'-methylenebisacrylamide (MBAA) solution (20 mg / ml) were sequentially added to 10 ml of a 1:1 glycerol / water mixture. The mixture was magnetically stirred for 30 minutes until all components were completely dissolved, yielding a pale yellow, transparent, adhesive pregel solution.

[0042] (5) Fabrication of liquid metal / pepper flexible electronic devices:

[0043] To prevent liquid metal displacement during subsequent operations, a thin layer of hydrogel of the same composition is gently attached to the pattern surface as a protective layer. The pregel solution prepared in step (4) is carefully dropped onto the side of the grapefruit peel skeleton treated in step (3). After the solution has completely penetrated under the action of capillary force, the sample is taken out and irradiated with a UV lamp (365nm, 10W) ​​for 1-3 minutes to crosslink and solidify the pregel, finally obtaining a liquid metal flexible electronic device with a porous grapefruit peel skeleton, the structure of which is as follows. Figure 3 As shown.

[0044] Example 2

[0045] This embodiment is basically the same as Embodiment 1, except for the composition of the liquid metal conductive filler and the pregel.

[0046] (1) Pretreatment of grapefruit peel: Same as in Example 1.

[0047] (2) Preparation of silica microparticles / liquid metal conductive fillers:

[0048] Liquid gallium-indium alloy was mixed with silica particles with an average particle size of 50 micrometers at mass ratios of 10:1, 8:1, and 5:1, respectively, and then ground evenly in a mortar to obtain conductive fillers.

[0049] (3) Liquid metal patterning:

[0050] Without the aid of a magnetic field, the conductive filler prepared in step (2) is directly printed on the grapefruit peel skeleton by screen printing to form a pre-set interdigitated electrode pattern, and then encapsulated in a thin hydrogel sheet of the same composition as the hydrogel.

[0051] (4) Preparation of adhesive pregels:

[0052] Under light-protected conditions, add 5g BSA, 2g AAm, 0.1ml HMPP, and 0.15ml MBAA stock solution (20mg / ml) to 10ml of glycerol / water mixed solvent with a volume ratio of 3:1, and stir to dissolve.

[0053] (5) Device molding: Same as in Example 1.

[0054] Example 3

[0055] This embodiment provides another flexible electronic device using a porous grapefruit peel as a framework, which is a liquid metal.

[0056] (1) Pretreatment of grapefruit peel: Same as in Example 1.

[0057] (2) Preparation of copper powder / liquid metal conductive filler:

[0058] Liquid gallium-indium alloy was mixed and ground evenly with copper powder with an average particle size of 5 micrometers at mass ratios of 10:1, 8:1, and 5:1, respectively.

[0059] (3) Liquid metal patterning: Same as in Example 1.

[0060] (4) Preparation of adhesive pregels:

[0061] Add 1g BSA, 5g methacrylated gelatin (GelMA), 4g AAm, 0.2ml HMPP and 0.2ml MBAA stock solution (20mg / ml) to 10ml of pure water and dissolve by stirring in a 37℃ water bath in the dark.

[0062] (5) Device molding: Same as in Example 1.

[0063] Example 4: Device Performance Testing

[0064] Taking the liquid metal flexible electronic device prepared in Example 1 as an example, its electrothermal performance and motion detection performance were tested.

[0065] (1) Electrothermal performance test:

[0066] The device was placed at the bottom of a shallow container filled with 10 mm of deionized water and connected to an external DC power supply via a waterproof wire. Different constant currents (0.5A, 0.7A, 0.9A, 1A, 1.2A) were applied, and an infrared thermal imager was used to record the surface temperature changes of the device in real time. The results are as follows: Figure 4 As shown, after power is applied, the device temperature rises rapidly and reaches equilibrium. Furthermore, the higher the constant current, the higher the equilibrium temperature. This demonstrates its potential as a flexible heater in the field of thermal management.

[0067] (2) Motion detection test:

[0068] The device from Example 1 was attached to the index finger joint of a volunteer. When the finger was bent at different angles, the liquid metal circuit of the device deformed, causing a corresponding change in resistance. By monitoring the resistance signal in real time with a digital multimeter, a good linear relationship was found between the rate of resistance change and the finger bending angle, indicating that the device can be used for real-time monitoring of human movement.

[0069] This invention provides a concept and method for fabricating a liquid metal flexible electronic device with a porous grapefruit peel as its framework. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for fabricating a flexible electronic device using porous grapefruit peel as a framework, characterized in that, Includes the following steps: (1) Pretreatment of grapefruit peel: Remove the yellow outer skin of fresh grapefruit peel, retain the spongy layer, and cut it into shape; After washing, degreasing, and bleaching, the peel is freeze-dried to obtain a porous dried grapefruit peel skeleton. (2) Preparation of liquid metal conductive filler: Liquid metal is mixed with solid particles, and the solid particles are dispersed in the liquid metal to obtain a liquid metal conductive filler with plasticity; (3) Liquid metal patterning: On the dried grapefruit peel skeleton obtained in step (1), the liquid metal conductive filler prepared in step (2) is localized and transferred according to the preset circuit pattern to form a liquid metal circuit; (4) Preparation of adhesive pregel: Dissolve the adhesive enhancement component, polymerizable monomer, crosslinking agent and photoinitiator in a solvent and mix them evenly to obtain an adhesive pregel solution; (5) Device molding: The adhesive pregel solution from step (4) is injected into the dry grapefruit peel skeleton that has been patterned with liquid metal, so that it fully fills the porous structure of the grapefruit peel. Then, the pregel is solidified by photopolymerization reaction to obtain the device.

2. The preparation method according to claim 1, characterized in that, The solid particles in step (2) contain magnetic components, and the patterning in step (3) is carried out using a magnetic field-assisted method: a magnet is placed under the grapefruit peel skeleton, and a mask with a hollow pattern is covered and fixed on the upper surface of the grapefruit peel skeleton. Liquid metal conductive filler is coated onto a mask. Under the attraction of a magnetic field, the liquid metal conductive filler is adsorbed and transferred to the area of ​​the grapefruit peel surface not covered by the mask. After removing the mask, the liquid metal circuit pattern is obtained.

3. The preparation method according to claim 1, characterized in that, After step (3) and before step (5), a thin layer of photocurable hydrogel is applied to the surface of the grapefruit peel skeleton with the liquid metal pattern to encapsulate the liquid metal pattern.

4. The preparation method according to claim 1, characterized in that, The adhesion-enhancing component in step (4) is bovine serum albumin; the polymerizable monomer is selected from any one or a combination of two or more of acrylamide, methacrylated gelatin, and methacrylated hyaluronic acid.

5. The preparation method according to claim 4, characterized in that, In the adhesive pregel solution, the mass concentration of bovine serum albumin is 1-20 wt%, and the mass concentration of the polymerizable monomer is 5-50 wt%.

6. The preparation method according to claim 1, characterized in that, The crosslinking agent is N,N'-methylenebisacrylamide; the photoinitiator is selected from lithium phenyl-2,4,6-trimethylbenzoylphosphonate or 2-hydroxy-2-methylphenylacetone; the solvent is a mixture of glycerol and water.

7. The preparation method according to claim 1, characterized in that, The liquid metal mentioned in step (2) is a gallium-indium alloy melt; the solid particles are selected from one or more of nickel powder, silicon dioxide, copper powder, and glass microspheres, and contain iron or iron oxide magnetic components; the size of the solid particles is 1-500 micrometers.

8. The preparation method according to claim 1, characterized in that, The injection method described in step (5) is one of vacuum-assisted permeation, centrifugal permeation, or natural permeation.

9. A flexible electronic device using porous grapefruit peel as a framework, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of the liquid metal flexible electronic device with porous grapefruit peel as a framework as described in claim 9 in the fabrication of wearable devices.

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