CN110430664B - A stretchable and degradable flexible circuit board and its preparation method and application - Google Patents

Abstract

A stretchable and degradable flexible circuit board and its preparation method and application relate to the field of flexible electronics. The stretchable and degradable flexible circuit board is sequentially provided with a substrate layer, a middle protective layer and an upper conductive electrode layer from bottom to top. Preparation method: 1) fixing the substrate layer on the substrate; 2) forming an intermediate protective layer on the substrate layer; 3) forming an upper conductive electrode layer on the intermediate protective layer by inkjet printing and electroplating; 4) putting the substrate layer on top The conductive electrode layer is peeled off from the substrate to obtain a stretchable and degradable flexible circuit board. Stretchable and degradable flexible circuit boards are used in the preparation of wearable sensors, electronic skins, and flexible displays. The conductive particles in the conductive electrode layer are in close contact with each other, and the conductive nano-electrode layer has a nano-stacking structure. The protein substrate has good flexibility, stretchability and degradability.

Description

A stretchable and degradable flexible circuit board and its preparation method and application

technical field

The invention relates to the field of flexible electronics, in particular to a stretchable and degradable flexible circuit board and a preparation method and application thereof.

Background technique

With the rapid development of flexible electronic technology, flexible sensors, flexible displays, and flexible batteries have gradually appeared in our lives, bringing many conveniences to our lives. Flexible circuit boards are key materials for wearable devices, portable medical care, and electronic skin, and are widely used in the medical and health field. However, traditional rigid circuit boards cannot be bent at will, and cannot meet the needs of flexible circuit boards. People are gradually looking for flexible circuit board substrates such as polyimide (PI), polyethylene terephthalate (PET), etc., but this substrate has the defects of poor biocompatibility, non-stretchability, and non-degradability. , will cause environmental pollution. Therefore, it is of great value to find a stretchable and degradable flexible circuit board.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a stretchable and degradable flexible circuit board with a simple process and a preparation method thereof.

Another object of the present invention is to provide an application of a stretchable and degradable flexible circuit board in the preparation of wearable sensors, electronic skins, and flexible display screens.

The stretchable and degradable flexible circuit board is sequentially provided with a substrate layer, an intermediate protective layer and an upper conductive electrode layer from bottom to top;

The substrate layer can be a silk fibroin substrate layer, a wool keratin substrate layer or other natural polymer protein substrate layers. The thickness of the substrate layer may be 50˜300 μm.

The intermediate protective layer can be a PMMA intermediate protective layer; the thickness of the intermediate protective layer can be 100-200 nm.

The upper conductive electrode layer may be a conductive nano-electrode layer; the conductive nano-electrode layer is in a nano-stacking structure.

The preparation method of the stretchable and degradable flexible circuit board includes the following steps:

1) Fix the substrate layer on the substrate;

2) forming an intermediate protective layer on the substrate layer;

3) forming an upper conductive electrode layer on the intermediate protective layer by inkjet printing and electroplating;

4) The substrate layer to the upper conductive electrode layer is peeled off from the substrate to obtain a stretchable and degradable flexible circuit board.

In step 1), the specific method for fixing the substrate layer on the substrate may be: using high-temperature PI tape to stick the four sides of the substrate to the substrate to ensure no air and no bulging, and the substrate can be made of thin aluminum sheet or other thermal conductivity. Better sheet metal.

In step 2), the formation of the intermediate protective layer on the substrate layer may be performed by thermal evaporation, spin coating, spray coating, or blade coating to form the intermediate protective layer.

In step 3), the specific steps of forming the upper conductive electrode layer by the method of inkjet printing and electroplating on the intermediate protective layer may be:

(1) The polymer protein substrate layer and the PMMA intermediate protective layer on the substrate are treated by vacuum plasma or oxygen plasma, so that the upper conductive electrode layer and the intermediate protective layer can be closely attached;

(2) placing the whole processed in step (1) on a substrate at 50-70° C. to avoid the coffee ring effect of the conductive electrode layer during inkjet printing;

(3) the ink of inkjet printing is printed on the whole processed in step (2) by the method of inkjet printing, and the pre-conductive electrode layer is obtained by annealing treatment;

(4) The pre-conductive electrode layer obtained in the step (3) is treated by an electroplating method to further improve the conductivity to obtain a conductive electrode layer.

In step (3), the ink for inkjet printing can use nano-conductive ink, and the nano-conductive ink contains nano-conductive particles; the nano-conductive particles can be selected from silver, gold, carbon, carbon nanotubes, graphene, PEDOT : at least one of PSS, etc.

In step (4), the electroplating material can be selected from at least one of silver, gold, copper, platinum, PEDOT:PSS, PPY, PANI and the like.

The application of the stretchable and degradable flexible circuit board in the preparation of wearable sensors, electronic skins, and flexible display screens.

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

1. The conductive electrode layer of the present invention is realized by the method of inkjet printing and electroplating. Traditional circuit boards require multiple processes to complete, and the whole process is time-consuming and consumables, and is accompanied by environmental pollution. The inkjet printing method is a kind of on-demand printing, which has the advantages of direct writing of patterns and saving raw materials. The inkjet-printed electrode layer presents a nanoparticle stacking structure. In order to make the stacking between the particles more dense, electroplating is further performed on the electrode to increase the conductivity of the electrode layer. The conductive particles in the conductive electrode layer are in close contact with each other, so that they have excellent electrical conductivity; the conductive nano-electrode layer has a nano-stacking structure, and the conductive nanoparticles are in good contact with each other, and are laid flat on the substrate. Has good electrical conductivity.

2. The protein substrate has good flexibility, stretchability and degradability, so that the flexible circuit board prepared by the present invention has good stretchability and degradability, and can be used in wearable devices, electronic skin, biological Electronic fields, etc., have broad application prospects.

Silk fibroin and natural macromolecular protein have good in vivo biocompatibility and are medical materials approved by the US Food and Drug Administration. For example, in the field of biological tissue engineering applications, biological scaffolds made of silk fibroin can avoid Risk of infection with Creutzfeldt-Jakob disease. At the same time, silk fibroin has good mechanical properties, stretchability, flexibility, and degradation characteristics, and can be processed into a flexible film structure, which is easy to fit well with curved surfaces and even human tissues. Its controllable biodegradability allows it to degrade naturally after device failure, preventing the generation of electronic waste and reducing environmental pollution.

3. A thin protective layer of PMMA is formed on the silk fibroin substrate (or other polymer protein substrates). The PMMA layer can not only increase the tolerance of the silk fibroin substrate, but at the same time, it has high adhesion and can form a good contact with the electrode. With PMMA as the support, the electrode is protected from the risk of disintegration caused by the swelling of the silk, and the circuit stability is increased.

Description of drawings

1 is a schematic structural diagram of a stretchable and degradable flexible circuit board according to an embodiment of the present invention;

FIG. 2 is a flowchart of a method for preparing a stretchable and degradable flexible circuit board according to an embodiment of the present invention;

Fig. 3 is the microstructure diagram of the upper conductive electrode layer on the stretchable and degradable flexible circuit board according to the embodiment of the present invention;

Fig. 4 is the electrical conductivity change before and after electroplating of the stretchable and degradable flexible circuit board according to the embodiment of the present invention;

FIG. 5 is a degradation diagram of the stretchable and degradable flexible circuit board according to the embodiment of the present invention.

Detailed ways

In order to facilitate understanding of the present invention, the following embodiments will further illustrate the present invention with reference to the accompanying drawings.

As shown in FIG. 1, the embodiment of the flexible circuit board of the present invention includes: a substrate layer 1, an intermediate protective layer 2 and an upper electrode layer 3; the substrate layer 1 is a silk fibroin substrate layer, the intermediate protective layer 2 is a PMMA layer, and the upper layer The electrode layer 3 is a conductive nano-electrode layer, and the conductive nano-electrode layer has a nano-particle stacking structure.

As shown in FIG. 2 , an embodiment of a method for preparing a stretchable and degradable flexible circuit board includes the following steps:

S10, fixing a silk fibroin substrate on a substrate, wherein the silk fibroin substrate is a substrate layer.

The substrate can be a thin aluminum sheet, or other metal sheet with better thermal conductivity, and the like. High-temperature PI tape is used to attach the four sides of the silk fibroin substrate to the substrate to ensure no air and no bulging.

S20, forming a PMMA intermediate protective layer on the substrate layer.

The intermediate protective layer can be formed on the substrate layer by thermal evaporation, spin coating, spray coating and blade coating.

S30, a conductive electrode layer is formed on the PMMA intermediate protective layer by a method of inkjet printing and electroplating.

Specifically, S1: the entirety of the silk fibroin substrate layer and the PMMA intermediate protective layer on the substrate is treated by vacuum plasma or oxygen plasma, so that the upper conductive electrode layer and the PMMA intermediate protective layer can be closely attached;

S2: placing the whole treated by the S1 method on a substrate at 50-70° C., so that the conductive electrode layer has no coffee ring effect during inkjet printing;

S3: The nano conductive ink is printed on the whole treated by the S2 method by the method of inkjet printing, and the upper pre-conductive electrode layer is obtained by annealing at 90-130 °C;

S4: The pre-conductive electrode layer obtained in S3 is treated by electroplating method to further improve the conductivity.

S40, peel off the silk fibroin substrate layer to the upper conductive electrode layer from the substrate.

Specific examples are given below:

The method for preparing a stretchable and degradable flexible circuit board provided by this embodiment includes the following steps:

S10, the silk fibroin substrate is fixed on the substrate, and the four sides of the silk fibroin substrate are closely attached to the substrate by using high-temperature PI tape to ensure that there is no air and no bulge, so that there will be no expansion when heated, the substrate used For thin metal aluminum flakes.

S20. A PMMA intermediate protective layer is formed on the substrate layer, and the PMMA intermediate protective layer is prepared on the substrate layer by spin coating. The PMMA solvent is dissolved in an organic solvent to obtain a PMMA dispersion liquid, and the power, rotation speed and time of the spin coating are adjusted to control the thickness of the PMMA. Further, a PMMA layer with a concentration of 10 wt % can be obtained by spin coating at a power of 100 W, a rotational speed of 3000 r/min, and a time of 50 s.

S30, forming the conductive electrode layer by the method of inkjet printing and electroplating on the PMMA protective layer includes the following steps:

S301 , the entire silk protein substrate layer and the PMMA layer on the substrate are treated by vacuum plasma or oxygen plasma, so that the upper conductive electrode layer and the intermediate protective layer can be closely attached. The parameters such as vacuum degree, power and time of vacuum plasma treatment or oxygen plasma treatment are adjusted, so that the intermediate protective layer can be lipophilic and hydrophilic. Has better adhesion. In one embodiment, the hydrophilic and lipophilic silk fibroin substrate is obtained after ^10-3 Pa vacuum, 60 W power, and 10 min of treatment.

S302, placing the whole body treated in S301 on a substrate at 50-70°C, so that the conductive electrode layer has no coffee ring effect during inkjet printing; in one embodiment, place it on a substrate at a temperature of 60°C .

S303, the nano-ink is printed on the protective layer by amplifying the ink-jet printing, firstly, the nano-conductive ink is filtered to remove large-sized particles; select the waveform, voltage, and cycle of the parameters of ink-jet printing, and adjust the printing Ink droplets, pre-printed waveforms selected, and annealed to obtain a pre-conductive electrode layer. In one embodiment, the nano-silver conductive ink is filtered to remove large-sized particles; the positive selection wave, voltage 30V, period 20S of the parameters of inkjet printing are selected to obtain a stable droplet state, and pre-printed waveform printing is selected , and annealed at 100°C for 10 minutes to obtain a predetermined conductive electrode layer. FIG. 3 is a microstructure diagram of the upper conductive electrode layer on a stretchable and degradable flexible circuit board. Observing it under a scanning electron microscope, as shown in Figure 3, it can be seen that the nanoparticles are tightly stacked, so they have good electrical conductivity.

S303, using the electroplating method to process the overall solution obtained by the method S302 and containing the material to be plated, selecting the current, controlling the electroplating time, and performing electroplating to further improve the conductivity. The electroplated conductive material can be one or more of silver, gold, copper, nickel, platinum, PEDOT:PSS, PPY, PANI. In one embodiment, in the electroplating solution containing nickel metal ions, a current of 0.5 mA/cm ⁻² is selected, and electroplating is performed for 5 minutes. Figure 4 shows the change of the electrical conductivity of the stretchable and degradable flexible circuit board before and after electroplating. As shown in Figure 4, as the electroplating progresses, the stacking between the particles becomes more compact. The resistance value measurement before and after electroplating can be seen. Enhanced electrical conductivity.

S304, peel off the silk fibroin substrate layer to the upper conductive electrode layer from the substrate. FIG. 5 is a degradation diagram of the stretchable and degradable flexible circuit board. It can be seen from FIG. 5 that the flexible circuit board is degradable.

The present embodiment also provides a preparation method of silk fibroin membrane, the steps are as follows:

First, the silkworm cocoons were removed and cut into pieces, degummed three times in a 0.8% sodium bicarbonate solution, rinsed with water, then dried in an oven at 60 °C to obtain silk fibroin fibers; the silk fibroin fibers were dissolved in 9.3 mol/L LiBr The silk fibroin solution is then placed in a dialysis bag for dialysis to obtain a silk fibroin solution; the obtained silk fibroin solution, a modifier and a plasticizer are evenly blended to obtain a mixed solution; the mixed solution is poured on the surface of a designated substrate and cured to obtain a Prefabricated composite membrane; the prefabricated composite membrane is treated with ethanol steam to obtain a silk fibroin composite membrane, and the prepared silk fibroin composite membrane can be used as a silk fibroin substrate.

The physical and chemical properties of the silk fibroin substrate enable the flexible circuit board of the present invention to have good stretchability and degradability; the PMMA layer increases circuit stability. Due to the stacking structure of conductive electrode layers, the circuit board has excellent conductivity. The invention solves the problem that the flexible circuit board in the prior art cannot meet the technical problems of being stretchable and degradable at the same time, and it is easy to cause environmental pollution.

Claims (7)

1. a stretchable and degradable flexible circuit board is characterized in that it is provided with a substrate layer, an intermediate protective layer and an upper conductive electrode layer in turn from bottom to top; the substrate layer is a silk fibroin substrate layer, wool keratin A substrate layer or other natural macromolecular protein substrate layer; the intermediate protective layer is a PMMA intermediate protective layer; the thickness of the substrate layer is 50-300 μm; the thickness of the intermediate protective layer is 100-200 nm. 2 . The stretchable and degradable flexible circuit board according to claim 1 , wherein the upper conductive electrode layer is a conductive nano-electrode layer; and the conductive nano-electrode layer is in a nano-stacking structure. 3 . 3. The preparation method of a stretchable and degradable flexible circuit board as claimed in claim 1, characterized in that it comprises the following steps: 1) Fix the substrate layer on the substrate; 2) Form an intermediate protective layer on the substrate layer; 3) An upper conductive electrode layer is formed on the intermediate protective layer by inkjet printing and electroplating. The specific steps are: (1) The polymer protein substrate layer and the PMMA intermediate protective layer on the substrate are treated by vacuum plasma or oxygen plasma, so that the upper conductive electrode layer and the intermediate protective layer can be closely attached; (2) Place the whole processed in step (1) on a substrate at 50-70° C. to avoid the coffee ring effect of the conductive electrode layer during inkjet printing; (3) printing the ink jet-printed on the whole processed in step (2) by the method of ink jet printing, and annealing to obtain a pre-conductive electrode layer; (4) The pre-conductive electrode layer obtained in step (3) is treated by an electroplating method to further improve the conductivity and obtain a conductive electrode layer; the electroplating material is selected from silver, gold, copper, platinum, PEDOT:PSS, At least one of PPY and PANI; 4) The substrate layer to the upper conductive electrode layer is peeled off from the substrate to obtain a stretchable and degradable flexible circuit board. 4. the preparation method of a kind of stretchable and degradable flexible circuit board as claimed in claim 3, it is characterized in that in step 1), the concrete method for fixing the substrate layer on the substrate is: using high temperature PI tape to The four sides of the substrate are closely attached to the base plate to ensure no air and no bulging, and the base plate is made of a thin aluminum sheet or other metal sheet with good thermal conductivity. 5. The preparation method of a stretchable and degradable flexible circuit board according to claim 3, wherein in step 2), the intermediate protective layer is formed on the substrate layer by thermal evaporation, spin coating, The intermediate protective layer is formed by spraying and scraping. 6 . The method for preparing a stretchable and degradable flexible circuit board according to claim 3 , wherein in step (3), the ink for inkjet printing adopts nano-conductive ink, and the nano-conductive ink comprises nano-conductive ink. 7 . Conductive particles; the nano conductive particles are selected from at least one of silver, gold, carbon, carbon nanotubes, graphene, and PEDOT:PSS. 7. The stretchable and degradable flexible circuit board according to claim 1 is used in the preparation of wearable sensors, electronic skins, and flexible display screens.

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