CN114234791B - Preparation method of composite film strain sensor based on dropping deposition - Google Patents

Abstract

The invention discloses a preparation method of a composite film strain sensor based on droplet deposition, which comprises the following steps: S1: adding polyvinyl alcohol powder into distilled water to completely dissolve the polyvinyl alcohol to obtain a uniform polyvinyl alcohol aqueous solution; S2: Completely mix the carbon black solution with the polyvinyl alcohol solution to obtain a uniform carbon black/polyvinyl alcohol solution; S3: remove the mixed air in the solution to obtain a pure carbon black/polyvinyl alcohol solution; S4: combine the obtained The carbon black/polyvinyl alcohol solution is put into a micro coater, and the solution is coated on the substrate by the droplet deposition method; S5: The carbon black/polyvinyl alcohol film is heated and cured to obtain a carbon black/polyvinyl alcohol composite Thin film strain sensor. The present invention can improve the controllability of the thickness and size of the film and reduce the loss of materials while ensuring the uniformity of the film by means of droplet deposition.

Description

A preparation method of composite thin film strain sensor based on droplet deposition

technical field

The invention relates to the technical field of strain sensor preparation, in particular to a preparation method of a composite film strain sensor based on droplet deposition.

Background technique

The strain sensor is a sensing device that converts the deformation of the measured object due to external stimulus signals such as force and vibration into other electrical signals. At present, the traditional strain sensors on the market are mainly made of rigid materials such as semiconductors, ceramics, and metals. They have ideal sensitivity, but the traditional strain sensors have high cost and poor flexibility, and the sensitivity will decrease with the increase of applied strain. Flexible strain sensors, on the other hand, have better stretchability and can adapt to larger deformations. This has led to the extensive research and promotion of flexible strain sensors in the fields of human-computer interaction, health monitoring, wearable devices, artificial skin, and prosthetics, which have attracted much attention in recent years.

In this context, the method of preparing a flexible composite film strain sensor by mixing conductive fillers and non-conductive polymers came into being. The strain sensor prepared by this combination of materials has good flexibility, free bending, thin thickness, Advantages of high sensitivity.

However, for composite thin film strain sensors, besides the choice of materials, the way of film formation is also very important. The film formation method determines the uniformity, flatness and thickness of the film, which are closely related to the performance of the sensor.

At present, the method of preparing composite films is mainly the spraying method. The spraying method is to place the conductive dispersion in the spray gun, and then compress the air to atomize the dispersion into small droplets. Under the action of the air flow, these small droplets will be deposited on the pre- On a hot substrate, a conductive film is formed after drying; the rod coating method is to place the conductive dispersed ink on the substrate, and then roll the rod at a certain speed to disperse the ink, thereby forming a uniform conductive film; the drop coating method is a A process in which the liquid to be coated is directly dropped on the target substrate, and then dried to form a film; in the process of preparing a thin film by the spin coating method, the substrate is usually rotated on a high-speed rotating turntable. The dispersion liquid on the substrate diffuses to the entire substrate area to form a thin film; the solution casting method is to pour an appropriate amount of solution on the substrate to spread the solution evenly on the surface of the substrate, and then heat to completely evaporate the solvent into a Film; The vapor deposition method is a technology that vaporizes a material source and deposits it on the surface of a substrate to form a thin film.

The equipment of the spraying method is simple, easy to operate, and can realize large-scale production, but the uniformity of the film prepared by it is poor; the rod coating method is suitable for mass production, but it requires the dispersion to have a high viscosity and a large surface tension; drop coating During the operation of the method, the nanoparticles are prone to agglomeration, and the "coffee ring effect" is prone to appear after drying, which affects the uniformity of the film; the film area that can be prepared by the spin coating method is limited, and the film thickness cannot be controlled; the solution casting method The prepared film has a large intermolecular distance, a loose structure, low film strength, high production cost, high energy consumption, and low production speed; although the film prepared by the deposition method is uniform in texture, there are harsh preparation conditions and equipment. The disadvantages of high price and low efficiency. It can be seen that among the existing thin film preparation methods, there is no film forming method that takes into account low cost, simple operation, and controllable film size and thickness.

Contents of the invention

In order to at least solve or partially solve the above problems, a preparation method of a composite thin film strain sensor based on droplet deposition is provided. Through droplet deposition, the controllability of film thickness and size can be improved while ensuring the uniformity of the film , reduce material loss.

In order to achieve the above object, the present invention provides the following technical solutions:

A kind of preparation method of the composite film strain sensor based on drop liquid deposition of the present invention, comprises the following steps:

S1: Add polyvinyl alcohol powder into distilled water to completely dissolve polyvinyl alcohol to obtain a uniform polyvinyl alcohol aqueous solution;

S2: Completely mix the carbon black solution with the polyvinyl alcohol solution to obtain a uniform carbon black/polyvinyl alcohol solution;

S3: Remove the mixed air in the solution to obtain a pure carbon black/polyvinyl alcohol solution;

S4: Put the obtained carbon black/polyvinyl alcohol solution into a micro coater, and apply the solution onto the substrate by a droplet deposition method;

S5: heating and curing the carbon black/polyvinyl alcohol film to obtain a carbon black/polyvinyl alcohol composite film strain sensor.

As a preferred technical solution of the present invention, in the step S2, the step of completely mixing the carbon black solution with the polyvinyl alcohol solution is: adding the carbon black solution to the prepared aqueous polyvinyl alcohol solution, and putting the mixed solution into Stir and mix in a planetary centrifugal mixer, perform ultrasonic treatment in an ultrasonic cleaner, and stir for 10 minutes after taking it out.

As a preferred technical solution of the present invention, in the step S3, the step of removing the mixed air in the solution is: putting the carbon black/polyvinyl alcohol solution obtained in S2 into a vacuum drying oven for vacuum suction treatment.

As a preferred technical solution of the present invention, in the step S1, the step of completely dissolving the polyvinyl alcohol is: heating to 90° C. and stirring at this temperature for 20 minutes.

As a preferred technical solution of the present invention, in the step S4, the step of the droplet deposition method is: using a non-contact mode, the applicator does not contact the substrate, but only makes the droplet contact the substrate to form a droplet Points, through software control can determine the location of droplet deposition, so as to make the pattern of the composite film.

Compared with the prior art, the beneficial effects of the present invention are as follows:

The preparation method of a composite film strain sensor based on droplet deposition proposed by the present invention can be completed by using only a micro coater and a computer, and the equipment is relatively simple.

The method has the advantage of simple operation due to the non-contact deposition of droplets of the polymer solution on the substrate and the use of a computer to control the location of the droplet deposition.

Since the needle tip of the applicator is very small, the size of the droplets produced by it is also very small, which can be guaranteed to be at the micron level, which can effectively prevent the material from overflowing the designed shape and size, so as to accurately grasp the size and shape of the film, The waste of materials is reduced, and the preparation cost is reduced.

The conductive thin film prepared by the droplet deposition method can reach a very small thickness, so that the prepared strain sensor has a high gauge factor under very small strain.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the schematic diagram of the principle of the film preparation method based on droplet deposition proposed by the present invention;

Fig. 2 is a film-forming mechanism diagram of the droplet deposition method proposed by the present invention;

Fig. 3 is the dimensional drawing of the drop point of the embodiment of the present invention;

Fig. 4 is the optical image of the composite film of the embodiment of the present invention;

Fig. 5 is the composite thin film strain-resistance test figure of the embodiment of the present invention;

In the figure: 1 is the tip of the micro-coater, 2 is the composite solution, and 3 is the substrate.

Detailed ways

The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention. The same reference numerals in the drawings all refer to the same components.

Also, detailed descriptions of known arts will be omitted if they are unnecessary to illustrate the features of the present invention.

Example 1

As shown in Figure 1, the present invention provides a method for preparing a composite film strain sensor based on droplet deposition. Under the action of surface tension and intermolecular attraction, the liquid forms spherical droplets at the tip of the micro-coater. As shown in Figure 1-1, the micro-applicator is moved down so that the droplet is in contact with the substrate, but the applicator is not in contact with the substrate. It can be seen from Figure 1-2 that when the applicator leaves, part of the droplet at the tip of the needle is on the substrate, and part of it remains on the tip of the needle.

As shown in Figure 2-1, Figure 2-2, and Figure 2-3, the moving micro-applicator deposits two droplets in succession. It can be seen from Figures 2-4 that there is an overlapping portion between the two deposited droplet points. Due to the fluidity of the liquid, the gaps between the interface molecules of the overlapping droplets are small, and the liquid molecules inside the droplets will attract each other. At the same time, under the action of surface tension, the overlapping droplet points will merge to form a new droplet point, as shown in Figure 2-5, and finally form a composite film.

Weigh 1g of polyvinyl alcohol and place it in a beaker, add 15ml of distilled water, heat to 90°C and stir at this temperature for 20 minutes to completely dissolve the polyvinyl alcohol to obtain a uniform aqueous solution of polyvinyl alcohol.

Weigh 4g of CB carbon black solution with a concentration of 10% and add it to the prepared polyvinyl alcohol aqueous solution, put the carbon black/polyvinyl alcohol mixed solution into a centrifugal mixer and stir for 10 minutes, put it into an ultrasonic cleaner at 40kHz The frequency of ultrasonic treatment for 60 minutes, take it out and stir for 10 minutes, so that the carbon black solution and polyvinyl alcohol solution are completely mixed to obtain a uniform carbon black/polyvinyl alcohol solution.

Put the carbon black/polyvinyl alcohol solution obtained in the second step into a vacuum drying oven for vacuum suction for 60 minutes to obtain a pure carbon black/polyvinyl alcohol solution.

The obtained carbon black/polyvinyl alcohol solution is put into a micro coater, and the solution is applied to the glass substrate by the droplet deposition method, as shown in Figure 3, the diameter of the droplet is about 100 μm, and the distance between the two droplets The center-to-center distance is about 80 μm.

Place the film on a heating platform, dry and solidify at 80°C for 30 minutes to obtain a carbon black/polyvinyl alcohol composite film strain sensor, the optical image of which is shown in Figure 4, it can be seen that the present invention is beneficial to improve the uniformity of the film controllability and film size.

As shown in FIG. 5 , a resistance-strain test was performed on the composite film strain sensor described in the embodiment. It can be seen that the resistance value of the composite film increases with the increase of the strain. Because the thickness of the prepared film is small, there is also an obvious resistance change under the strain change of one ten thousandth. Therefore, the composite film strain of this embodiment The sensor has a high sensitivity.

The substrate is a glass substrate, the length of the glass substrate is 20 mm, the width is 20 mm, and the thickness is about 300 μm.

Specifically, the non-contact mode is adopted, the applicator does not contact the substrate, but only makes the droplet contact the substrate to form a droplet point, and the position of the droplet deposition can be determined through software control, thereby making the pattern of the composite film.

Utilizing the attraction force and surface tension between droplet molecules, partially overlapping droplets will attract each other and fuse to form a whole droplet, so that the prepared film has better continuity and uniformity.

Since the size of the droplet is very small, the original minimum size of the film prepared by the droplet deposition method is the size of a droplet, so the size of the film is highly controllable, thereby reducing the waste of materials.

The main mechanism of the preparation method of the composite film strain sensor based on droplet deposition of the present invention is related to the mutual attraction between molecules and the surface tension. Due to the mutual attraction between the molecules, the CB/PVA droplet can be hemispherical at the needle tip without falling. The surface tension between the substrate and the air interface is greater than the surface tension between the substrate and the liquid cross-section, so when the drop approaches the upper surface of the substrate, a portion of the drop on the applicator tip is used to wet the substrate surface, i.e. the liquid The drop forms a plano-convex lens shape on the surface of the substrate, and the other part remains on the needle tip without contact between the applicator and the substrate. When the center-to-center distance between two droplets is smaller than the diameter of the droplets, there will be an overlapping portion between the two droplets. The liquid has fluidity, and the small gap between the molecules of the overlapping droplet interface will cause the liquid molecules inside it to attract each other, and at the same time, under the action of surface tension, they will form a new droplet point. The linear movement of the device will cause the droplets to form a droplet strip, and when multiple droplet strips overlap, a carbon black/polyvinyl alcohol droplet film will be formed.

The purpose of stirring for a period of time at a temperature of 90°C is to fully dissolve the polyvinyl alcohol.

The steps of putting the solution into a centrifugal mixer for stirring and ultrasonic treatment are all to fully mix the carbon black and polyvinyl alcohol in the solution.

During the solution preparation process, air will be mixed in, which will affect the uniformity of the film. Vacuum suction in a vacuum drying oven can remove the mixed air in the solution.

Except for vacuum suction, the above steps were all carried out under normal pressure.

Finally, it should be noted that: the above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still The technical solutions recorded in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (1)

1. A preparation method of a composite film strain sensor based on dropping deposition is characterized by comprising the following steps:

s1: adding polyvinyl alcohol powder into distilled water to completely dissolve polyvinyl alcohol to obtain a uniform polyvinyl alcohol aqueous solution;

s2: completely mixing the carbon black solution with the polyvinyl alcohol solution to obtain a uniform carbon black/polyvinyl alcohol solution;

s3: removing air mixed in the solution to obtain pure carbon black/polyvinyl alcohol solution;

s4: putting the obtained carbon black/polyvinyl alcohol solution into a micro-coater, and coating the solution on a substrate by adopting a droplet deposition method;

s5: heating and curing the carbon black/polyvinyl alcohol film to obtain a carbon black/polyvinyl alcohol composite film strain sensor;

wherein, in the step S2, the step of completely mixing the carbon black solution and the polyvinyl alcohol solution comprises: adding the carbon black solution into the prepared polyvinyl alcohol aqueous solution, putting the mixed solution into a planetary centrifugal mixer, stirring and mixing, carrying out ultrasonic treatment in an ultrasonic cleaning machine, taking out and stirring for 10 minutes;

in the step S3, the step of removing air mixed in the solution includes: putting the carbon black/polyvinyl alcohol solution obtained in the step S2 into a vacuum drying oven for vacuum suction treatment;

in the step S1, the step of completely dissolving the polyvinyl alcohol includes: heating to 90 ℃ and stirring at this temperature for 20 minutes;

in step S4, the droplet deposition method includes: the non-contact mode is adopted, the coating device is not in contact with the substrate, only the liquid drop is in contact with the substrate to form a liquid drop point, and the deposition position of the liquid drop can be determined through software control, so that the pattern of the composite film is manufactured;

the substrate is a glass substrate.

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