CN108007617A - Pressure resistance type flexible touch sensation sensor and its manufacture method with micro- frustum of a cone substrate - Google Patents

Abstract

The invention discloses a piezoresistive flexible touch sensor with a micro-cone truncated base and a manufacturing method thereof. It is composed of a flexible film substrate, an electrode array, a graphene film array, and a micro-cone substrate stacked from top to bottom. The graphene film array is formed by an array of graphene film sheets, and the electrode array is composed of strip electrodes; The electrode array is closely attached to the graphene film array, and strip electrodes are arranged on both sides of the surface of each graphene film sheet, and two strip electrodes are connected to form a closed loop; the manufacturing method includes the manufacture of a flexible film substrate and the electrode array, Preparation and etching of graphene film arrays, fabrication of silicon molds and micro-cone substrates, and bonding and assembly of flexible tactile sensors, etc. The invention uses the micro-conical truncated substrate as the support of the graphene film, which produces greater deformation and resistance change when stressed, improves the sensitivity of the sensor, and solves the problem of connection reliability between the graphene film and electrodes.

Description

Piezoresistive flexible tactile sensor with micro-conical truncated substrate and manufacturing method thereof

technical field

The invention relates to a flexible tactile sensor and a manufacturing method thereof, in particular to a piezoresistive flexible tactile sensor with a micro-cone base and a manufacturing method thereof.

technical background

With the continuous development of robot technology, the research of robot intelligence becomes more and more important. At present, one of the development goals of robot intelligence lies in the perception ability of robots and the two-way interaction ability between robots and humans. Tactile sensors are an important way to achieve this goal. At the same time, as one of the wearable electronic devices, tactile sensors have important application prospects in many aspects such as electronic skin, detection of human body signs, and collection of human activity data.

Tactile sensors can be divided into the following types according to their sensing mechanisms: piezoresistive, capacitive, piezoelectric, optical, etc. Among them, piezoresistive tactile sensors are widely used for their high stability and wide dynamic range. focus on. Traditional piezoresistive sensors are mainly made of metal strain gauges and micro-nano silicon wafers, which have poor flexibility and low strength, making it difficult to fit robots or human body surfaces. The piezoresistive sensor based on organic soft materials has excellent flexibility and ductility, can be applied in multiple occasions, and can reduce the impact damage of external stimuli to the sensor, so it is more suitable for the needs of wearable electronic devices.

The main manufacturing process of the piezoresistive flexible tactile sensor is the blending preparation of conductive particles and organic soft materials, the molding of piezoresistive materials, and the bonding and assembly of piezoresistive materials and peripheral electrodes. Among them, the lamination of the piezoresistive material and the peripheral electrodes is usually realized by a colloid with high conductivity and certain adhesion, such as conductive silver glue. However, the currently commonly used conductive colloid has poor flexibility and ductility, so the sensor prepared by this method is often damaged due to the fracture of the conductive colloid or separation from the piezoresistive material when the sensor undergoes a large deformation. Therefore, adopting a more stable method to bond the piezoresistive material and peripheral electrodes is crucial to the stability of the sensor.

Contents of the invention

In order to make up for the deficiencies in the prior art, the object of the present invention is to provide a piezoresistive flexible tactile sensor with a truncated micro-cone substrate and a manufacturing method thereof, which can improve the flexibility of the sensor and enhance the connection strength between the graphene film and the electrode. Improve sensor stability.

The technical scheme adopted in the present invention is:

1. A piezoresistive flexible tactile sensor with a micro-conical truncated base:

The flexible tactile sensor is mainly composed of a flexible film substrate, an electrode array, a graphene film array and a micro-cone substrate sequentially stacked from top to bottom. The flexible film substrate is used as an electrode support, and the micro-cone substrate is used as a bottom support and is used to receive external stimulus.

The graphene film array is mainly composed of graphene film sheets arranged in the same plane array to form an array structure of M rows×N columns, and the electrode array is mainly arranged on the graphene film array and located on the graphene film array. It consists of strip electrodes on both sides of the sheet, and all the strip electrodes are arranged in an array on the same plane.

The electrode array is closely attached to the graphene film array, and strip electrodes are arranged on both sides of the surface of each graphene film, and each graphene film is connected by two strip electrodes to form a closed loop, and the graphene film The electrodes on one side of each row in the array are connected in series through a peripheral circuit, and the electrodes on the other side of each column are connected in series through a peripheral circuit.

The micro-conical frustum base is mainly composed of a polydimethylsiloxane (PDMS) film and an array of frustum-shaped bosses on the surface of the film. It is a flexible film with a micron-scale frusto-conical boss array structure, and the height of a single boss is It is about 15-25 μm, the diameter of the bottom of the boss is 20-30 μm, the cone angle is 50-60°, and the thickness of the whole base is about 100-120 μm.

The micro-cone truncated substrate of the present invention can increase the deformation degree of the graphene film when subjected to external force, thereby increasing the resistance change of the graphene film and improving the sensitivity of the sensor.

When the sensor is subjected to an external force, the internal conductivity of the graphene film changes when the external force is applied, which is sensed by the graphene film as a change in resistance, and then converted to obtain the magnitude of the applied force.

The flexible film substrate, the graphene film array and the truncated micro-cone substrate all use materials with good flexibility and ductility.

Two, a kind of manufacturing method of the piezoresistive flexible tactile sensor with microconical truncated base, comprises the following steps:

1) Mix the main agent of polydimethylsiloxane (PDMS) and the curing agent evenly, spin-coat on the glass substrate, and obtain a flexible film substrate after heating and curing;

2) Make an electrode mask with a pattern, pre-coat a layer of photoresist on the surface of the flexible film substrate, and use photolithography to transfer the pattern of the electrode mask to the photoresist on the surface of the flexible film substrate. The metal electrode is manufactured on the flexible film substrate in the pattern of the electrode mask by the magnetron sputtering method, that is, the metal electrode is made in the hollow pattern of the photoresist to obtain an electrode array;

3) uniformly mixing the graphene nanosheets and polydimethylsiloxane (PDMS), preparing a micron-scale graphene film on the surface of the electrode array on the flexible film substrate by a spin coating method, and heating and curing;

4) Make a film mask with a pattern, pre-coat a layer of photoresist on the surface of the electrode array on the flexible film substrate, and use photolithography to transfer the pattern of the film mask to the photolithography of the graphene film surface On the glue, the graphene film other than the film mask pattern is removed by plasma etching to obtain a graphene film array;

5) Make a silicon mold mask with a pattern, the surface of the silicon wafer is pre-coated with a layer of photoresist, and the pattern of the silicon mold mask is transferred to the photoresist on the surface of the silicon wafer by photolithography. Fabricate a silicon mold with a groove structure corresponding to the micro-cone truncated by etching;

6) Passivate the silicon mold with a fluorine-based surface modifier to reduce the surface activity of the silicon mold and make it easy to demould. After demoulding the silicon mold, mix the main agent of polydimethylsiloxane (PDMS) and curing agent evenly, pour polydimethylsiloxane (PDMS) on the silicon mold, compact and heat cure Finally, peel off from the silicon mold to obtain the micro-conical truncated substrate;

7) Plasma active treatment is performed on the connection surface between the micro-cone substrate and the graphene film array to improve the surface activity, and then the micro-cone substrate and the graphene film array are aligned and bonded, and heated and bonded after compaction. Get the flexible tactile sensor.

In the specific implementation, the remaining photoresist of each layer of the sensor is removed by soaking in acetone.

The material of the flexible film base and the micro-cone base is polydimethylsiloxane (PDMS). Graphene nanosheets and polydimethylsiloxane were uniformly dispersed in an organic solvent by ultrasonic dispersion, and the organic solvent was removed by evaporation, and then the mixture of graphene and polydimethylsiloxane was prepared by spin coating into thin films with a thickness of several microns.

The existing traditional way of preparing graphene film arrays is to make graphene films on glass substrates, and cut them to form graphene film sheets. The graphene film sheets are adhered to the electrode surface with conductive adhesive. Moreover, the flexibility is poor, which reduces the connection strength with the electrodes, reduces the stability of the sensor, and also reduces the flexibility of the sensor.

In the present invention, the graphene film is directly fabricated on the surface of the electrode array, without the need for conductive adhesive adhesion, so that the connection strength between the graphene film and the electrodes can be enhanced, the stability of the sensor is improved, and the flexibility of the sensor is improved.

The beneficial effects that the present invention has are:

(1) Graphene film is prepared by using graphene nanosheets and PDMS. The film has good electrical conductivity and piezoresistivity, as well as excellent flexibility and ductility, so it is more suitable for application requirements such as electronic skin.

(2) Using the micro-conical truncated convex platform microstructure array, the deformation of the graphene film is amplified when the force is applied, thereby increasing the resistance change caused by the force, and improving the sensitivity of the sensor.

(3) Spin-coating is used to directly fabricate a graphene film with a thickness of micron scale on the electrode, and use plasma etching to remove the excess film, so that the connection between the graphene film and the electrode has high connection strength and reliability .

Description of drawings

Fig. 1 is an exploded perspective view of the layered structure of the present invention.

Fig. 2 is a front view of the sensor unit of the present invention.

Fig. 3 is a schematic diagram of the manufacturing process flow of the sensor of the present invention.

Fig. 4 is a schematic diagram of an electrode mask plate of the present invention.

Fig. 5 is a schematic diagram of an electrode array of the present invention.

Fig. 6 is a schematic diagram of a graphene film mask of the present invention.

Fig. 7 is a schematic diagram of a graphene film array of the present invention.

Fig. 8 is a schematic diagram of a silicon mold mask plate of the present invention.

Fig. 9 is a schematic diagram of a silicon mold with micro-conical frustum grooves according to the present invention.

Fig. 10 is a schematic diagram of a truncated micro-cone substrate of the present invention.

Fig. 11 is a front view of the final flexible tactile sensor of the present invention.

In the figure: 1. Flexible film substrate, 2. Electrode array, 3. Graphene film array, 4. Micro-cone substrate, 5. Flexible film, 6. Strip electrode, 7. Graphene film sheet, 8. Micro-cone Taiwan, 9, an electrode mask, 10, a graphene film mask, 11, a silicon mold mask, 12, a silicon mold with micro-conical truncated grooves.

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments.

As shown in Fig. 1, Fig. 2 and Fig. 10, the piezoresistive flexible tactile sensor of the present invention is mainly composed of a flexible film substrate 1, an electrode array 2, a graphene film array 3 and a micro-cone substrate 4 sequentially stacked from top to bottom. In this way, the flexible film substrate 1 is used as an electrode support, and the micro-cone substrate 4 is used as a bottom support and used to receive external force stimulation.

As shown in Figure 1, Figure 2, and Figure 5, the graphene film array 3 is mainly formed by the graphene film sheets arranged in the same plane array, forming an array structure of M rows×N columns, and the electrode array 2 is mainly composed of Arranged on the graphene film array 3, it is composed of strip electrodes located on both sides of the graphene film sheet, and all the strip electrodes are arranged in the same plane array. The electrode array 2 is closely attached to the graphene film array 3, and strip electrodes are arranged on both sides of the surface of each graphene film, and each graphene film is connected by two strip electrodes to form a closed loop, and the graphene film The electrodes on one side of each row in the array 3 are connected in series through a peripheral circuit, and the electrodes on the other side of each column are connected in series through a peripheral circuit.

As shown in Fig. 1, Fig. 2 and Fig. 9, the micro-conical frustum substrate 4 is mainly composed of a polydimethylsiloxane (PDMS) film and an array of conical bosses on the surface of the film, and is a micron-scale truncated conical boss. For the flexible film with an array structure, the height of a single boss is about 15-25 μm, the diameter of the bottom of the boss is 20-30 μm, the cone angle is 50-60°, and the thickness of the entire base is about 100-120 μm. As shown in FIG. 2 , taking a single sensor unit as an example, the micro-cone truncated cone 8 can increase the degree of deformation of the graphene film 7 when subjected to an external force, thereby increasing the resistance change of the graphene film 7 and improving the sensitivity of the sensor.

The manufacturing method provided by the invention, specifically, the invention mainly includes the manufacture of flexible film substrates and electrode arrays, the preparation and etching of graphene film arrays, the manufacture of silicon molds and micro-cone substrates, and the lamination of flexible tactile sensors Assembly steps.

As shown in Figure 3, an embodiment of the present invention and its implementation process are as follows:

1. Manufacture of flexible film substrate and electrode array:

The material used for the flexible film substrate 1 in the present invention is polydimethylsiloxane (PDMS). First, mix the main agent of PDMS and curing agent at a ratio of 10:1, and defoam; secondly, drop PDMS onto the surface of a glass substrate, and prepare a film with a thickness of about 100 μm by spin coating, and dry it in a vacuum oven at 80 ℃ for 2 hours to heat and cure to obtain a flexible film substrate 1 .

As shown in Figure 4, the electrode mask plate 9 with pattern is made, a layer of photoresist is coated on the flexible film substrate 1, and the pattern of the electrode mask plate 9 is transferred to the surface of the flexible film substrate 1 by photolithography On the photoresist, 50nm of chromium and 200nm of copper were respectively covered by magnetron sputtering, and then soaked in acetone to remove the photoresist to obtain an electrode array 2 with a striped pattern, as shown in FIG. 5 .

2. Preparation and etching of graphene film array:

The materials used to prepare the graphene film array 3 in the present invention are graphene nanosheets and polydimethylsiloxane (PDMS). First, mix the graphene nanosheets with an organic solvent, and disperse them for 1 hour at a power of 50W through an ultrasonic breaker; then, add PDMS, and continue to ultrasonically disperse for 2 hours after mechanical stirring for 30 minutes; finally, heat the mixed solution Stir and evaporate the organic solvent at 80°C.

Drop the graphene PDMS mixture onto the electrode array 2 of the flexible film substrate 1, prepare a graphene film with a thickness of about 1-2 μm by spin coating, move it to a vacuum drying oven and heat and cure at 60 degrees Celsius for 1 hour; then, As shown in Figure 6, manufacture the graphene film mask plate with pattern, coat one deck photoresist on the graphene film, adopt photolithography to transfer the pattern of graphene film mask plate 10 to the graphene film On the photoresist on the surface, the redundant graphene film is removed by plasma etching method to obtain a patterned graphene film array 3 as shown in FIG. 7 .

The graphene film prepared by the spin coating method has a smaller thickness and higher flatness than ordinary coating processes such as the scraper coating method, which is conducive to the smaller overall thickness of the sensor and the improvement of flexibility. Using photolithography and plasma etching to manufacture the graphene film array 3, compared with the traditional cutting process after the coating film is cured, has higher manufacturing accuracy, and saves the traditional process of bonding the graphene film and electrodes. Conductive adhesive required. Although the currently commonly used conductive adhesive has good adhesion, it has poor flexibility. Therefore, sensors made of conductive adhesive usually cause the graphene film to separate from the electrode or the conductive adhesive to break due to excessive deformation of the sensor. The graphene thin film array 3 manufactured by the manufacturing method in the present invention, due to directly solidifying on the surface of the electrode array 2, utilizes the viscosity of PDMS to form a higher bonding strength with the surface of the electrode array 2, while ensuring that the graphene thin film array 3 and the surface of the electrode array 2 The reliable electrical connection of the electrode array 2 improves the flexibility and stability of the sensor.

3. Manufacture of silicon mold and micro-conical frustum substrate:

The material used for the truncated micro-cone substrate 4 in the present invention is polydimethylsiloxane (PDMS). As shown in Figure 8, make the silicon mold mask plate with pattern, coat one deck photoresist on silicon wafer, adopt the photolithography that the pattern of silicon mold mask plate 11 is transferred to silicon wafer surface On the glue, utilize potassium hydroxide (KOH) to carry out wet etching to manufacture the silicon mold 12 with micro-conical truncated grooves, as shown in Figure 9; Place the silicon mold 12 with micro-conical truncated grooves in a vacuum oven , drop a small amount of fluorine-based surface modifier, and leave it in vacuum for 12 hours to passivate the silicon mold, reduce the surface activity of the silicon mold, and make it easy to demould.

As shown in Figure 10, the main agent of PDMS and the curing agent are uniformly mixed at 10:1, and defoamed; the PDMS is dropped onto the surface of the silicon mold 12 with micro-conical truncated grooves, and after the entire mold is filled, put it into vacuum drying Stand in the box for defoaming; heat and cure the PDMS at 80 degrees Celsius for 2 hours, and then peel it off to obtain the micro-conical frustoconical substrate 4 . The overall thickness of the manufactured micro-cone base is about 100 μm, the height of a single micro-cone is about 20 μm, the diameter of the bottom of the micro-cone is about 25 μm, and the cone angle is 54.7°.

4. Fitting and assembly of flexible tactile sensors:

As shown in Figure 11, carry out plasma active treatment to the connecting surface between micro-cone base 4 and graphene film array 3, processing time is 5s, improves surface active energy; Then micro-cone base 4 and graphene film array 3 Alignment and bonding, heating and bonding after compaction, to obtain a flexible tactile sensor.

In the specific implementation, polydimethylsiloxane (PDMS) uses Dow Corning's SYLGARD 184 silicone rubber; graphene nanosheets use few-layer graphene from Suzhou Carbonfeng Graphene Technology Co., Ltd.; AR-P 5350 Positive Photoresist from Technology Ltd.

The piezoresistive flexible tactile sensor and the manufacturing method thereof of the present invention enable the sensor to have better flexibility and stability; the convex microstructure in the shape of a micro-cone is used to amplify the deformation of the graphene film under force, thereby improving the sensor Sensitivity; Spin-coating and plasma etching are used to directly fabricate a micron-scale graphene film array on the electrode, so that the graphene film and the electrode have high connection strength and reliability, and the stability of the sensor is improved. It is more suitable for application requirements such as electronic skin.

Claims (8)

1. A piezoresistive flexible tactile sensor with a micro-conical truncated base is characterized in that: the flexible tactile sensor is mainly composed of flexible film substrate (1), electrode array (2), graphene film array (3) and micro The truncated cone substrates (4) are stacked sequentially from top to bottom, the flexible film substrate (1) is used as an electrode support, and the micro-conical truncated substrate (4) is used as a bottom support and used to receive external force stimulation. 2. A kind of piezoresistive flexible tactile sensor with micro-conical truncated base according to claim 1, is characterized in that: described graphene film array (3) is mainly arranged in same plane array by graphene film sheet formed, forming an array structure of M rows×N columns, and the electrode array (2) is mainly composed of strip electrodes arranged on the graphene film array (3) and located on both sides of the graphene film sheet. 3. A kind of piezoresistive flexible tactile sensor with micro-conical truncated base according to claim 2, is characterized in that: described electrode array (2) and graphene thin film array (3) fit closely, each graphite Strip electrodes are arranged on both sides of the graphene film surface, and each graphene film is connected by two strip electrodes to form a closed loop, and one side electrode of each row in the graphene film array (3) is connected in series through a peripheral circuit, The electrodes on the other side of each column are connected in series through peripheral circuits. 4. A kind of piezoresistive flexible tactile sensor with micro-cone base according to claim 1, is characterized in that: described micro-cone base (4) is mainly made of polydimethylsiloxane film and The surface of the film is composed of an array of truncated conical bosses. The height of a single boss is about 15-25 μm, the diameter of the bottom of the boss is 20-30 μm, the cone angle is 50-60°, and the thickness of the entire substrate is about 100-120 μm. 5. A kind of piezoresistive flexible tactile sensor with micro-conical truncated base according to claim 1, is characterized in that: described graphene film internal conductivity changes when being subjected to external force, by graphene film sense Measured as a change in resistance, and then converted to obtain the magnitude of the force. 6. be used for the manufacturing method of the piezoresistive flexible tactile sensor that has micro-cone base any one of claim 1-5, comprises the following steps: 1) Mix the main agent of polydimethylsiloxane and the curing agent evenly, spin-coat on the glass substrate, heat and cure to obtain a flexible film substrate (1); 2) Make an electrode mask with a pattern, transfer the pattern of the electrode mask to the photoresist on the surface of the flexible film substrate (1) by photolithography, and manufacture the metal electrode on the flexible film substrate (1) by magnetron sputtering. On the film substrate (1), an electrode array (2) is obtained; 3) uniformly mixing graphene and polydimethylsiloxane, preparing a micron-scale graphene film on the surface of the electrode array (2) on the flexible film substrate (1) by a spin coating method, and heating and curing; 4) Make a patterned film mask, use photolithography to transfer the pattern of the film mask to the photoresist on the surface of the graphene film, and use plasma etching to remove the graphene beyond the film mask pattern The film is removed to obtain a graphene film array (3); 5) Make a silicon mold mask with a pattern, transfer the pattern of the silicon mold mask to the photoresist on the surface of the silicon wafer by photolithography, and use wet etching to manufacture grooves corresponding to the micro-cone truncated Silicon mold of the structure; 6) After demoulding the silicon mold, mix the main agent of polydimethylsiloxane (PDMS) and curing agent evenly, pour polydimethylsiloxane (PDMS) on the silicon mold, and compact it peeling off from the silicon mold after heating and curing to obtain a micro-conical truncated substrate (4); 7) performing plasma active treatment on the connecting surface between the truncated micro-cone substrate (4) and the graphene film array (3), and then aligning and bonding the truncated-cone substrate (4) and the graphene film array (3), After compaction, heating and bonding, a flexible tactile sensor is obtained. 7. a kind of manufacturing method of the piezoresistive flexible tactile sensor with micro-cone base according to claim 6, is characterized in that: described flexible film substrate (1) and micro-cone base (4) material are Polydimethylsiloxane (PDMS). 8. A kind of manufacture method of the piezoresistive flexible tactile sensor with truncated micro-cone substrate according to claim 6, is characterized in that: the materials used for the graphene film are graphene nanosheets and polydimethylsiloxane alkane, graphene nanosheets and polydimethylsiloxane were uniformly dispersed in an organic solvent by ultrasonic dispersion, the organic solvent was removed by evaporation, and then the mixture of graphene and polydimethylsiloxane was spin-coated films with a thickness of a few micrometers were prepared.