CN106382998B - A kind of Flexible graphene composite pressure sensor and preparation method thereof - Google Patents

Abstract

The invention discloses a screen printing pressure sensor of a flexible graphene composite material and a preparation method thereof. The screen-printed pressure sensor of the flexible graphene composite material includes: a flexible substrate, electrodes and metal interconnection lines, a force sensitive resistance layer and a reference resistance layer. The electrodes and metal interconnection lines, the force sensitive resistor layer and the reference resistor layer are sequentially printed on the flexible substrate by means of screen printing. The invention also discloses a preparation method of the screen printing pressure sensor of the flexible graphene composite material, which is characterized in that the required sensor and its circuit can be patterned for large-scale industrial production. The sensor of the present invention is light, thin and soft, and has the advantages of being wearable, attachable, good tensile deformation performance and the like.

Description

A kind of flexible graphene composite material pressure sensor and preparation method thereof

technical field

The invention belongs to the field of sensors and preparation methods thereof, in particular to a flexible graphene composite material pressure sensor and a preparation method thereof.

Background technique

In recent years, with the development of flexible electronics, electronic skin has great development prospects in the fields of medical treatment, military affairs, and artificial intelligence. Flexible sensors are an important support for electronic skin. Therefore, how to prepare flexible sensors with excellent performance, unique structure, high sensitivity, and mass production has attracted widespread attention at home and abroad.

Traditional pressure sensors are mostly silicon-based pressure sensors. Since its substrate is a non-flexible material, it is not suitable for electronic skin. The silicon-based pressure sensor uses a Wheatstone bridge structure to measure its resistance change. The Wheatstone bridge structure has the advantages of simple calculation and high detection accuracy when measuring the resistance change. This is also a structure that can be considered in the preparation of flexible sensors.

At present, a research group uses graphene oxide-coated polyurethane sponge material to prepare resistive pressure sensors, but the thickness of the graphene oxide-coated polyurethane sponge material of the pressure sensor is too thick and not wear-resistant, so it is not suitable for electronic skin field.

In addition, some people have used a mixture of polydimethylsiloxane and carbon materials to prepare a film with a three-dimensional porous structure for the preparation of a resistive pressure sensor. However, due to the Shore hardness of polydimethylsiloxane and the limitation of elastic strain range, polydimethylsiloxane is not suitable for preparing flexible sensors used in large strain ranges. And it is found through experiments that the composite material of polydimethylsiloxane and graphene, wherein polydimethylsiloxane as a flexible part, has poor material adhesion. So PDMS is not a good choice for flexible sensors.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the above-mentioned background technology, provide a flexible graphene composite pressure sensor and its preparation method, and solve the problem that the pressure sensor is difficult to make a flexible, bendable, portable form and circuit diagram is difficult to pattern , and this method is suitable for industrial production.

A flexible graphene composite material pressure sensor involved in the present invention includes: a flexible substrate, an electrode and a metal connection, a force-sensitive resistor layer, and a reference resistor layer; On the substrate, the force sensitive resistor layer and the reference resistor layer are on the electrodes and the metal wiring;

There are 8 electrodes in total, electrode a and electrode b are adjacent to two electrodes of the same resistance, electrodes c and electrode d are adjacent to two electrodes of the same resistance, electrodes e and electrode f are adjacent to two electrodes of the same resistance, electrodes g and Electrode h is adjacent to two electrodes of the same resistance; electrode a and electrode d are connected with a metal wire and lead out the metal wire to the positive pole of the power supply; electrode b and electrode f are connected with a metal wire and lead out a section of metal wire; electrode c Connect with electrode g with a metal connection and lead out a section of metal connection; electrode e and electrode h are connected with metal connection and lead out a metal connection to the negative pole of the power supply;

Electrode c, electrode d and the force sensitive resistor layer on it form a force sensitive resistor, electrode a, electrode b and the reference resistor layer on it form the first reference resistor, electrode e, electrode f and the reference resistor layer on it form the first reference resistor The specific resistance layer forms the second reference resistance, and the electrode g, the electrode h and the reference resistance layer thereon form the third reference resistance;

The size of the force-sensitive resistor layer just covers electrodes c and d, the size of the reference resistance layer of the first reference resistor just covers electrodes a and b, and the size of the reference resistor layer of the second reference resistor just covers electrode e and electrode f, the size of the reference resistance layer of the third reference resistor just covers electrode g and electrode h;

The force-sensitive resistor is connected in series with the third reference resistor, the first reference resistor is connected in series with the second reference resistor, the series circuit of the force-sensitive resistor and the third reference resistor is connected in series with the first reference resistor and the second reference resistor circuits in parallel.

The flexible substrate is polyethylene terephthalate PET or polydimethylsiloxane, a material with good biocompatibility, with a thickness of 10-500 μm;

Electrodes and metal wires are conductive silver paste or conductive ink, and the thickness of electrodes and metal wires is 5-100 μm;

The material used for the force-sensitive resistor layer is a composite material of graphene powder and polyurethane elastomer, the percentage of graphene in the total mass is 5% to 30%, and the thickness is 10 to 200 μm;

The reference resistance layer is silver, copper, platinum or palladium, with a thickness of 5-200 μm;

Va is the potential between the first reference resistor and the second reference resistor, Vb is the potential between the force sensitive resistor and the third reference resistor, Vc is the positive potential of the power supply, and Vd is the negative potential of the power supply; ΔV _ab =| Va-Vb|, ΔV _cd = |Vc-Vd|; ΔV _ab can be measured, ΔV _cd is the potential difference between the positive and negative poles of the power circuit, which can be adjusted; R ₃ is the resistance value of the third reference resistor, R _X is the resistance value of the force-sensitive resistor, and ΔR _X is the change amount of the resistance value of the force-sensitive resistor. ΔR _X can be based on the formula Get it.

The preparation method step of a kind of flexible graphene composite material pressure sensor involved in the present invention is as follows:

S1, the preparation of silk screen plate:

1. Tighten the screen on the screen frame, and the number of screens should be 100-400 mesh. Screen area selection S = 34mm * 61mm ~ 60mm * 100mm. Clean the screen and let it dry naturally. After a day, the screen tension is stable before it can be used.

2. Then apply photosensitive adhesive evenly on both sides of the screen, and then put it in an oven at 80-140°C for 60s-180s. The thickness of the photosensitive adhesive is about 5-300μm.

3. Then expose the screen with photosensitive adhesive under the mask plate with circuit pattern and calibration mark pattern. After exposure, bake at 80-140°C for 15-45min. The photoresist of different manufacturers will indicate the rotation Coating rotation number and baking time to reduce standing wave effect.

4. Then spray developer and flushing solution continuously at 15-25°C. After the photosensitive adhesive on the exposed part is washed away, the hard film is baked at 100-180°C, and the prepared screen plate is obtained.

S2. Screen printing of electrodes and metal wiring:

1. Prepare the screen plate according to the preparation of the screen plate in step S1;

2. Clean the screen plate and scraper with net washing water, and wait for it to dry naturally in a dark place for later use;

3. Clean the flexible substrate for printing with double distilled water, dry it and bake it in an oven at 120-160°C for 2 hours to prevent the flexible substrate from being deformed in the subsequent high-temperature heating process, resulting in a decrease in the precision of the printed electrode. Backup. The flexible substrate is polyethylene terephthalate PET or polydimethylsiloxane, which has good biocompatibility, and has a thickness of 10-500 μm.

4. To print electrodes, adjust the inclination angle between the scraper and the screen plate to a suitable angle of 45-80 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 3-6 mm, and fix the screen plate.

5. Place the slurry for preparing electrodes and metal wires on the screen plate, brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right, after trial printing, adjust the air pressure to make the surface of the electrode printed flat, and The difference between batches of electrode resistance is less than 5%. The paste for preparing electrodes and metal connections is conductive silver paste or conductive ink, and the thickness of electrodes and metal connections is 5-100 μm;

6. Print electrodes and metal wiring on the flexible substrate, and then dry at 80-120°C for 10-30 minutes, that is, the electrodes, metal wiring and calibration marks are printed on the flexible substrate;

There are 8 electrodes in total, electrode a and electrode b are adjacent to the same two electrodes, electrode c and electrode d are adjacent to two electrodes of the same resistance, electrode e and electrode f are adjacent to two electrodes of the same resistance, electrode g and electrode h is adjacent to two electrodes of the same resistance; electrode a and electrode d are connected with a metal connection and lead out the metal connection to the positive pole of the power supply; electrode b and electrode f are connected with a metal connection and lead out a section of metal connection; electrode c Connect with electrode g with a metal connection and lead out a section of metal connection; electrode e and electrode h are connected with metal connection and lead out a metal connection to connect to the negative pole of the power supply;

7. Recover the slurry to clean the screen plate and scraper.

S3, screen printing of force sensitive resistor layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Prepare the slurry of the force sensitive resistor, select a suitable organic solvent, such as tetrahydrofuran, dimethyl sulfoxide, dimethylformamide or acetone, and prepare a polyurethane elastomer solution with a mass percentage of 10% to 30%;

4. Evenly mix the conductive graphene powder material with the same organic solvent used to prepare the polyurethane elastomer solution at a mass ratio of 1:10 to 1:100, and then use an ultrasonic device to ultrasonicate for 10 to 30 minutes with a power of 400 to 1200W to form Graphene homogeneous dispersion;

5. Add the graphene dispersion liquid to the polyurethane elastomer solution, and disperse it by ultrasonic and dispersion equipment to form a uniform graphene/polyurethane elastomer composite solution, so that the final graphene accounts for 30% of the total mass of graphene and polyurethane elastomer. The percentage is 5% to 30%;

6. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to a suitable angle of 45-80 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 3-6mm, and align the calibration mark on the screen plate with the substrate Align the calibration marks printed on the screen to secure the screen plate.

7. Place the graphene/polyurethane elastomer composite solution on the screen plate, and brush the graphene/polyurethane elastomer composite solution on the screen plate with the pattern reciprocating left and right with a scraper. After trial printing, adjust the air pressure to make the electrode The surface is printed flat; the force-sensitive resistor layer is printed on the flexible substrate printed with electrodes, and its size just covers the electrodes c and d; the thickness is 10-200 μm;

8. Then dry at 80-140°C for 10-30 minutes, recover the slurry and clean the screen plate and scraper.

S4. Screen printing of reference resistance layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to a suitable angle of 45-80 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 3-6mm, and align the calibration marks on the screen plate with the substrate Align the calibration marks printed on the screen to secure the screen plate.

4. Place the slurry on the screen plate, and brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right. After the trial printing, adjust the air pressure to make the electrode surface printed flat, and the reference resistance layer is printed on the printing plate. on a flexible substrate with electrodes. The reference resistance layer has three small pieces, and the size of the three small pieces of the reference resistance layer is just to cover electrode a and electrode b, electrode e and electrode f, electrode g and electrode h respectively. The printing paste of the selected reference resistor is silver, copper, platinum or palladium; the thickness of the reference resistor layer is 5-200 μm;

5. Then dry at 80-140°C for 10-30 minutes, recover the slurry and clean the screen plate and scraper.

A flexible graphene composite pressure sensor of the present invention can be attached to the skin for pulse detection, blood pressure detection, physical sign detection, motion detection and the like. The preparation method of a flexible graphene composite pressure sensor of the present invention has the advantages of cheap raw materials, simple process and convenient operation, and can be industrially produced in a large scale and patterned. Both the flexible substrate and the force sensitive resistance layer adopted in the present invention have good biocompatibility, and when the material is in contact with the skin, it has no toxicity, no allergic or inflammatory reaction, and the like. The force-sensitive resistance material that the present invention adopts is the composite material of polyurethane elastomer and graphene, compares with other macromolecular flexible materials such as PDMS, PUA, PI etc., polyurethane elastomer and graphene can form uniform dispersion liquid system, at the same time After the film is formed, the composite material has better elasticity, tensile deformation, bending deformation and adhesion. Devices fabricated using this patternable graphene/polyurethane elastomer flexible conductive film have the characteristics of strong adhesion, foldability, stretchability, light weight, non-fragility, good flexibility, and strong conductivity.

Description of drawings

Fig. 1 is the top view of a kind of flexible graphene composite material pressure sensor;

Fig. 2 is a sectional view of a flexible graphene composite pressure sensor;

Fig. 3 is a schematic diagram of an electrode and a metal wiring circuit;

Fig. 4 is the layout of electrode and metal connection printing silk screen;

Fig. 5 is the screen pattern layout of force sensitive resistor layer screen printing;

Fig. 6 is the silk screen layout of reference resistance layer screen printing;

Fig. 7 is a schematic circuit diagram of a flexible graphene composite pressure sensor;

In the figure above, 1 is electrode a, 2 is electrode b, 3 is electrode c, 4 is electrode d, 5 is electrode e, 6 is electrode f, 7 is electrode g, 8 is electrode h, 9 is calibration mark, 10 is the flexible substrate, Rx is the force sensitive resistor, R1 is the _first reference resistor, R2 is the _second reference resistor, _R3 is the third reference resistor, Va is the first reference resistor and the second reference resistor The potential between the resistors, Vb is the potential between the force sensitive resistor and the third reference resistor, Vc is the positive potential of the power supply, and Vd is the negative potential of the power supply.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, and the technical solutions in the embodiments of the present invention will be clearly and completely described. Apparently, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Embodiment one:

A kind of flexible graphene composite material pressure sensor, its top view is as shown in Figure 1, and cross-sectional view is as shown in Figure 2, comprises: flexible substrate 10, electrode and metal wiring, force sensitive resistance layer, reference resistance layer; Flexible The substrate 10 is at the bottom layer, the electrodes and metal wiring are on the flexible substrate 10, and the force sensitive resistor layer and the reference resistor layer are on the electrodes and the metal wiring; the schematic diagram of the electrode and metal wiring circuit is shown in Figure 3 .

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to two electrodes of the same resistance, electrodes c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrodes e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrodes g7 and The electrode h8 is adjacent to two electrodes of the same resistance; the electrode a1 and the electrode d4 are connected with a metal wire and lead out the metal wire to the positive pole of the power supply; the electrode b2 and the electrode f6 are connected with a metal wire and lead out a metal wire; the electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to the negative pole of the power supply;

Electrode c3, electrode d4 and the force sensitive resistor layer on it form the force sensitive resistor Rx, electrode a1, electrode b2 and the reference resistor layer on it form the first reference resistor R1, electrode e5, electrode f6 and the above The reference resistance layer forms the second reference resistance R2, and the electrode g7, the electrode h8 and the reference resistance layer thereon form the third reference resistance R3;

The size of the force-sensitive resistor layer just covers the electrodes c3 and d4, the size of the reference resistor layer of the first reference resistor R1 just covers the electrodes a1 and electrode b2, and the size of the reference resistor layer of the second reference resistor R2 The electrode e5 and the electrode f6 are just covered, and the size of the reference resistance layer of the third reference resistor R3 just covers the electrode g7 and the electrode h8;

The force-sensitive resistor Rx is connected in series with the third reference resistor R3, the first reference resistor R1 is connected in series with the second reference resistor R2, and the series circuit of the force-sensitive resistor Rx and the third reference resistor R3 is connected with the first reference resistor R1, The series circuit of the second reference resistor R2 is connected in parallel. The schematic diagram of the pressure sensor circuit is shown in Figure 7.

The flexible substrate 10 is polyethylene terephthalate PET, a material with good biocompatibility, with a thickness of 10 μm;

Electrodes and metal connections are conductive silver paste, and the thickness of electrodes and metal connections is 5 μm;

The material used in the force-sensitive resistor layer is a composite material of graphene powder and polyurethane elastomer, the percentage of graphene in the total mass is 5%, and the thickness is 10 μm;

The reference resistance layer is silver with a thickness of 5 μm;

Va is the potential between the first reference resistor R1 and the second reference resistor R2, Vb is the potential between the force sensitive resistor Rx and the third reference resistor R3, Vc is the positive potential of the power supply, and Vd is the negative potential of the power supply; ΔV _ab ＝|Va-Vb|, ΔV _cd ＝|Vc-Vd|; ΔV _ab can be measured, ΔV _cd is the potential difference between the positive and negative poles of the power circuit, which can be adjusted; R ₃ is the third reference resistor R3 Resistance value, R _X is the resistance value of the force-sensitive resistor Rx, and ΔR _X is the change in resistance of the force-sensitive resistor Rx. The resistance change ΔR _X of the force sensitive resistor Rx can be based on the formula Get it.

A preparation method for a flexible graphene composite pressure sensor, the steps are as follows:

S1, the preparation of silk screen plate:

1. Tighten the screen on the screen frame, and select 100 mesh for the number of screens. Screen area selection S = 34mm * 61mm. Clean the screen and let it dry naturally. After a day, the screen tension is stable before it can be used.

2. Then apply photosensitive adhesive evenly on both sides of the screen, and then put it in an oven for 60 seconds at 80°C. The thickness of the photosensitive adhesive is about 5 μm.

3. Then expose the screen with photosensitive adhesive under the mask plate with circuit pattern and calibration mark 9 pattern, bake at 80°C for 15min after exposure, and the photoresist of different manufacturers will indicate the number of rotations of spin coating and baking time to reduce the standing wave effect.

4. Then spray developer and flushing solution continuously at 15°C. After the photosensitive adhesive on the exposed part is washed away, the hard film is baked at 100°C, and the prepared screen plate is obtained.

S2. Screen printing of electrodes and metal wiring:

1. Prepare the screen plate according to the preparation of the screen plate in step S1, and the pattern is shown in Figure 4;

2. Clean the screen plate and scraper with net washing water, and wait for it to dry naturally in a dark place for later use;

3. Wash the flexible substrate 10 for printing with double distilled water, dry it and bake it in an oven at 120°C for 2 hours to prevent the flexible substrate 10 from being deformed in the subsequent high-temperature heating process, resulting in a decrease in the precision of the printed electrode. Backup. The flexible substrate 10 is polyethylene terephthalate PET, a material with good biocompatibility, with a thickness of 10 μm.

4. To print the electrode, adjust the inclination angle between the scraper and the screen plate to a suitable angle of 45 degrees, and adjust the distance between the screen plate and the substrate to be 3 mm, and fix the screen plate.

5. Place the slurry for preparing electrodes and metal wires on the screen plate, brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right, after trial printing, adjust the air pressure to make the surface of the electrode printed flat, and The difference between batches of electrode resistance is less than 5%. The paste for preparing electrodes and metal connections is conductive silver paste, and the thickness of electrodes and metal connections is 5 μm;

6. Print electrodes and metal wiring on the flexible substrate 10, and then dry at 80°C for 10 minutes, that is, print electrodes, metal wiring and calibration marks 9 on the flexible substrate 10, as shown in Figure 4;

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to the same two electrodes, electrode c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrode e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrode g7 and electrode Adjacent to h8 are two electrodes of the same resistance; electrode a1 and electrode d4 are connected with a metal connection and lead out the metal connection to the positive pole of the power supply; electrode b2 and electrode f6 are connected with a metal connection and lead out a section of metal connection; electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to connect to the negative pole of the power supply;

7. Recover the slurry to clean the screen plate and scraper.

S3, screen printing of force sensitive resistor layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 5;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Prepare the slurry of the force sensitive resistor Rx, select a suitable organic solvent tetrahydrofuran, and prepare a polyurethane elastomer solution with a mass percentage of 10%;

4. Evenly mix the conductive graphene powder material with the same organic solvent used to prepare the polyurethane elastomer solution at a mass ratio of 1:10, and then use an ultrasonic device to ultrasonicate for 10 minutes with a power of 400W to form a uniform dispersion of graphene;

5. Add the graphene dispersion liquid to the polyurethane elastomer solution, and disperse it by ultrasonic and dispersion equipment to form a uniform graphene/polyurethane elastomer composite solution, so that the final graphene accounts for 30% of the total mass of graphene and polyurethane elastomer. The percentage is 5%;

6. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 45 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 3 mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The alignment marks 9 are aligned and the silk screen plate is fixed.

7. Place the graphene/polyurethane elastomer composite solution on the screen plate, and brush the graphene/polyurethane elastomer composite solution on the screen plate with the pattern reciprocating left and right with a scraper. After trial printing, adjust the air pressure to make the electrode The surface is printed flat; the force sensitive resistor layer is printed on the flexible substrate 10 printed with electrodes, and its size just covers the electrodes c3 and electrodes d4, as shown in Figure 5; the thickness is 10 μm;

8. Then dry at 80°C for 10 minutes, recover the slurry and clean the screen plate and scraper.

S4. Screen printing of reference resistance layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 6;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 45 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 3 mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The calibration marks 9 are aligned and the silk screen plate is fixed.

4. Place the slurry on the screen plate, and brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right. After the trial printing, adjust the air pressure to make the electrode surface printed flat, and the reference resistance layer is printed on the printing plate. on a flexible substrate 10 with electrodes. As shown in Figure 6, the reference resistance layer has three small pieces, and the size of the three small pieces of the reference resistance layer just covers the electrode a1 and the electrode b2, the electrode e5 and the electrode f6, the electrode g7 and the electrode h8, and the pressure sensor. The schematic diagram of the circuit is shown in Figure 7. The printing paste of the selected reference resistor is silver; the thickness of the reference resistor layer is 5 μm;

5. Then dry at 80°C for 10 minutes, recover the slurry and clean the screen plate and scraper.

In the above embodiments, conductive ink can be used to replace conductive silver paste as the material for preparing electrodes and metal wiring, and copper, platinum or palladium can be used to replace silver as the material for preparing reference resistors.

Embodiment two:

A kind of flexible graphene composite material pressure sensor, its top view is as shown in Figure 1, and cross-sectional view is as shown in Figure 2, comprises: flexible substrate 10, electrode and metal wiring, force sensitive resistance layer, reference resistance layer; Flexible The substrate 10 is at the bottom layer, the electrodes and metal wiring are on the flexible substrate 10, and the force sensitive resistor layer and the reference resistor layer are on the electrodes and the metal wiring; the schematic diagram of the electrode and metal wiring circuit is shown in Figure 3 .

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to two electrodes of the same resistance, electrodes c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrodes e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrodes g7 and The electrode h8 is adjacent to two electrodes of the same resistance; the electrode a1 and the electrode d4 are connected with a metal wire and lead out the metal wire to the positive pole of the power supply; the electrode b2 and the electrode f6 are connected with a metal wire and lead out a metal wire; the electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to the negative pole of the power supply;

Electrode c3, electrode d4 and the force sensitive resistor layer on it form the force sensitive resistor Rx, electrode a1, electrode b2 and the reference resistor layer on it form the first reference resistor R1, electrode e5, electrode f6 and the above The reference resistance layer forms the second reference resistance R2, and the electrode g7, the electrode h8 and the reference resistance layer thereon form the third reference resistance R3;

The size of the force-sensitive resistor layer just covers the electrodes c3 and d4, the size of the reference resistor layer of the first reference resistor R1 just covers the electrodes a1 and electrode b2, and the size of the reference resistor layer of the second reference resistor R2 The electrode e5 and the electrode f6 are just covered, and the size of the reference resistance layer of the third reference resistor R3 just covers the electrode g7 and the electrode h8;

The force-sensitive resistor Rx is connected in series with the third reference resistor R3, the first reference resistor R1 is connected in series with the second reference resistor R2, and the series circuit of the force-sensitive resistor Rx and the third reference resistor R3 is connected with the first reference resistor R1, The series circuit of the second reference resistor R2 is connected in parallel. The schematic diagram of the pressure sensor circuit is shown in Figure 7.

The flexible substrate 10 is polyethylene terephthalate PET, a material with good biocompatibility, with a thickness of 100 μm;

Electrodes and metal connections are conductive silver paste, and the thickness of electrodes and metal connections is 40 μm;

The material used for the force-sensitive resistor layer is a composite material of graphene powder and polyurethane elastomer, the percentage of graphene in the total mass is 15%, and the thickness is 70 μm;

The reference resistance layer is silver with a thickness of 70 μm;

Va is the potential between the first reference resistor R1 and the second reference resistor R2, Vb is the potential between the force sensitive resistor Rx and the third reference resistor R3, Vc is the positive potential of the power supply, and Vd is the negative potential of the power supply; ΔV _ab ＝|Va-Vb|, ΔV _cd ＝|Vc-Vd|; ΔV _ab can be measured, ΔV _cd is the potential difference between the positive and negative poles of the power circuit, which can be adjusted; R ₃ is the third reference resistor R3 Resistance value, R _X is the resistance value of the force-sensitive resistor Rx, and ΔR _X is the change in resistance of the force-sensitive resistor Rx. The resistance change ΔR _X of the force sensitive resistor Rx can be based on the formula Get it.

A preparation method for a flexible graphene composite pressure sensor, the steps are as follows:

S1, the preparation of silk screen plate:

1. Tighten the screen on the screen frame, and select 200 mesh for the number of screens. Screen area selection S = 40mm * 70mm. Clean the screen and let it dry naturally. After a day, the screen tension is stable before use.

2. Then apply photosensitive adhesive evenly on both sides of the screen, and then put it in an oven to dry at 100°C for 100s. The thickness of the photosensitive adhesive is about 100μm.

3. Then expose the screen with photosensitive adhesive under the mask plate with circuit pattern and calibration mark 9 pattern, bake at 100°C for 25min after exposure, and the photoresist of different manufacturers will indicate the spin coating rotation number and baking time to reduce the standing wave effect.

4. Then spray developer and flushing solution continuously at 18°C. After the photosensitive adhesive on the exposed part is washed away, the hard film is baked at 120°C, and the prepared screen plate is obtained.

S2. Screen printing of electrodes and metal wiring:

1. Prepare the screen plate according to the preparation of the screen plate in step S1, and the pattern is shown in Figure 4;

2. Clean the screen plate and scraper with net washing water, and wait for it to dry naturally in a dark place for later use;

3. Clean the flexible substrate 10 for printing with double distilled water, dry it and bake it in an oven at 130°C for 2 hours to prevent the flexible substrate 10 from being deformed in the subsequent high-temperature heating process, resulting in a decrease in the precision of the printed electrode. Backup. The flexible substrate 10 is polyethylene terephthalate PET, a material with good biocompatibility, with a thickness of 100 μm.

4. To print the electrode, adjust the inclination angle between the scraper and the screen plate to a suitable angle of 60 degrees, and adjust the distance between the screen plate and the substrate to be 4 mm, and fix the screen plate.

5. Place the slurry for preparing electrodes and metal wires on the screen plate, brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right, after trial printing, adjust the air pressure to make the surface of the electrode printed flat, and The difference between batches of electrode resistance is less than 5%. The paste for preparing electrodes and metal connections is conductive silver paste, and the thickness of electrodes and metal connections is 40 μm;

6. Print electrodes and metal wires on the flexible substrate 10, and then dry at 90°C for 20 minutes, that is, print electrodes, metal wires and calibration marks 9 on the flexible substrate 10, as shown in Figure 4;

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to the same two electrodes, electrode c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrode e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrode g7 and electrode Adjacent to h8 are two electrodes of the same resistance; electrode a1 and electrode d4 are connected with a metal connection and lead out the metal connection to the positive pole of the power supply; electrode b2 and electrode f6 are connected with a metal connection and lead out a section of metal connection; electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to connect to the negative pole of the power supply;

7. Recover the slurry to clean the screen plate and scraper.

S3, screen printing of force sensitive resistor layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 5;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Prepare the slurry of the force sensitive resistor Rx, select a suitable organic solvent dimethyl sulfoxide, and prepare a polyurethane elastomer solution with a mass percentage of 20%;

4. Evenly mix the conductive graphene powder material with the same organic solvent used to prepare the polyurethane elastomer solution at a mass ratio of 1:30, and then use an ultrasonic device to ultrasonicate for 20 minutes with a power of 700W to form a uniform dispersion of graphene;

5. Add the graphene dispersion liquid to the polyurethane elastomer solution, and disperse it by ultrasonic and dispersion equipment to form a uniform graphene/polyurethane elastomer composite solution, so that the final graphene accounts for 30% of the total mass of graphene and polyurethane elastomer. The percentage is 15%.

6. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 60 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 4mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The calibration marks 9 are aligned and the silk screen plate is fixed.

7. Place the graphene/polyurethane elastomer composite solution on the screen plate, and brush the graphene/polyurethane elastomer composite solution on the screen plate with the pattern reciprocating left and right with a scraper. After trial printing, adjust the air pressure to make the electrode The surface is printed flat; the force sensitive resistor layer is printed on the flexible substrate 10 printed with electrodes, and its size just covers the electrodes c3 and electrodes d4, as shown in Figure 5; the thickness is 70 μm;

8. Then dry at 100°C for 20 minutes, recover the slurry and clean the screen plate and scraper.

S4. Screen printing of reference resistance layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 6;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 60 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 4mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The calibration marks 9 are aligned and the silk screen plate is fixed.

4. Place the slurry on the screen plate, and brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right. After the trial printing, adjust the air pressure to make the electrode surface printed flat, and the reference resistance layer is printed on the printing plate. on a flexible substrate 10 with electrodes. As shown in Figure 6, the reference resistance layer has three small pieces, and the size of the three small pieces of the reference resistance layer just covers the electrode a1 and the electrode b2, the electrode e5 and the electrode f6, the electrode g7 and the electrode h8, and the pressure sensor. The schematic diagram of the circuit is shown in Figure 7. The printing paste of the selected reference resistor is silver; the thickness of the reference resistor layer is 70 μm;

5. Then dry at 100°C for 20 minutes, recover the slurry and clean the screen plate and scraper.

In the above embodiments, conductive ink can be used to replace conductive silver paste as the material for preparing electrodes and metal wiring, and copper, platinum or palladium can be used to replace silver as the material for preparing reference resistors.

Embodiment three:

A kind of flexible graphene composite material pressure sensor, its top view is as shown in Figure 1, and cross-sectional view is as shown in Figure 2, comprises: flexible substrate 10, electrode and metal wiring, force sensitive resistance layer, reference resistance layer; Flexible The substrate 10 is at the bottom layer, the electrodes and metal wiring are on the flexible substrate 10, and the force sensitive resistor layer and the reference resistor layer are on the electrodes and the metal wiring; the schematic diagram of the electrode and metal wiring circuit is shown in Figure 3 .

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to two electrodes of the same resistance, electrodes c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrodes e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrodes g7 and The electrode h8 is adjacent to two electrodes of the same resistance; the electrode a1 and the electrode d4 are connected with a metal wire and lead out the metal wire to the positive pole of the power supply; the electrode b2 and the electrode f6 are connected with a metal wire and lead out a metal wire; the electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to the negative pole of the power supply;

Electrode c3, electrode d4 and the force sensitive resistor layer on it form the force sensitive resistor Rx, electrode a1, electrode b2 and the reference resistor layer on it form the first reference resistor R1, electrode e5, electrode f6 and the above The reference resistance layer forms the second reference resistance R2, and the electrode g7, the electrode h8 and the reference resistance layer thereon form the third reference resistance R3;

The size of the force-sensitive resistor layer just covers the electrodes c3 and d4, the size of the reference resistor layer of the first reference resistor R1 just covers the electrodes a1 and electrode b2, and the size of the reference resistor layer of the second reference resistor R2 The electrode e5 and the electrode f6 are just covered, and the size of the reference resistance layer of the third reference resistor R3 just covers the electrode g7 and the electrode h8;

The force-sensitive resistor Rx is connected in series with the third reference resistor R3, the first reference resistor R1 is connected in series with the second reference resistor R2, and the series circuit of the force-sensitive resistor Rx and the third reference resistor R3 is connected with the first reference resistor R1, The series circuit of the second reference resistor R2 is connected in parallel. The schematic diagram of the pressure sensor circuit is shown in Figure 7.

The flexible substrate 10 is polydimethylsiloxane, a material with good biocompatibility, with a thickness of 300 μm;

Electrodes and metal connections are conductive silver paste, and the thickness of electrodes and metal connections is 70 μm;

The material used for the force-sensitive resistor layer is a composite material of graphene powder and polyurethane elastomer, the percentage of graphene in the total mass is 20%, and the thickness is 150 μm;

The reference resistance layer is silver with a thickness of 150 μm;

Va is the potential between the first reference resistor R1 and the second reference resistor R2, Vb is the potential between the force sensitive resistor Rx and the third reference resistor R3, Vc is the positive potential of the power supply, and Vd is the negative potential of the power supply; ΔV _ab ＝|Va-Vb|, ΔV _cd ＝|Vc-Vd|; ΔV _ab can be measured, ΔV _cd is the potential difference between the positive and negative poles of the power circuit, which can be adjusted; R ₃ is the third reference resistor R3 Resistance value, R _X is the resistance value of the force-sensitive resistor Rx, and ΔR _X is the change in resistance of the force-sensitive resistor Rx. The resistance change ΔR _X of the force sensitive resistor Rx can be based on the formula Get it.

A preparation method for a flexible graphene composite pressure sensor, the steps are as follows:

S1, the preparation of silk screen plate:

1. Tighten the screen on the screen frame, and choose 300 mesh for the number of screens. Screen area selection S = 50mm * 80mm. Clean the screen and let it dry naturally. After a day, the screen tension is stable before it can be used.

2. Then apply photosensitive adhesive evenly on both sides of the screen, and then put it in an oven to dry at 120°C for 140s. The thickness of the photosensitive adhesive is about 200μm.

3. Then expose the screen with photosensitive adhesive under the mask plate with circuit pattern and calibration mark 9 pattern, bake at 120°C for 30min after exposure, and the photoresist of different manufacturers will indicate the spin coating rotation number and baking time to reduce the standing wave effect.

4. Then spray developer and flushing solution continuously at 20°C. After the photosensitive adhesive on the exposed part is washed away, the hard film is baked at 150°C, and the prepared screen plate is obtained.

S2. Screen printing of electrodes and metal wiring:

1. Prepare the screen plate according to the preparation of the screen plate in step S1, and the pattern is shown in Figure 4;

2. Clean the screen plate and scraper with net washing water, and wait for it to dry naturally in a dark place for later use;

3. Wash the flexible substrate 10 for printing with double distilled water, dry it and bake it in an oven at 150°C for 2 hours to prevent the flexible substrate 10 from being deformed in the subsequent high-temperature heating process, resulting in a decrease in the precision of the printed electrode. Backup. The flexible substrate 10 is polydimethylsiloxane, a material with good biocompatibility, with a thickness of 300 μm.

4. To print the electrode, adjust the inclination angle between the scraper and the screen plate to a suitable angle of 70 degrees, and adjust the distance between the screen plate and the substrate to be 5 mm, and fix the screen plate.

5. Place the slurry for preparing electrodes and metal wires on the screen plate, brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right, after trial printing, adjust the air pressure to make the surface of the electrode printed flat, and The difference between batches of electrode resistance is less than 5%. The paste for preparing electrodes and metal connections is conductive silver paste, and the thickness of electrodes and metal connections is 70 μm;

6. Print electrodes and metal wiring on the flexible substrate 10, and then dry at 100°C for 25 minutes, that is, print electrodes, metal wiring and calibration marks 9 on the flexible substrate 10, as shown in Figure 4;

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to the same two electrodes, electrode c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrode e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrode g7 and electrode Adjacent to h8 are two electrodes of the same resistance; electrode a1 and electrode d4 are connected with a metal connection and lead out the metal connection to the positive pole of the power supply; electrode b2 and electrode f6 are connected with a metal connection and lead out a section of metal connection; electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to connect to the negative pole of the power supply;

7. Recover the slurry to clean the screen plate and scraper.

S3, screen printing of force sensitive resistor layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 5;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Prepare the slurry of the force sensitive resistor Rx, select a suitable organic solvent dimethylformamide, and prepare a polyurethane elastomer solution with a mass percentage of 25%;

4. Evenly mix the conductive graphene powder material with the same organic solvent used to prepare the polyurethane elastomer solution at a mass ratio of 1:60, and then use an ultrasonic device to ultrasonicate for 25 minutes with a power of 1000W to form a uniform dispersion of graphene;

5. Add the graphene dispersion liquid to the polyurethane elastomer solution, and disperse it by ultrasonic and dispersion equipment to form a uniform graphene/polyurethane elastomer composite solution, so that the final graphene accounts for 30% of the total mass of graphene and polyurethane elastomer. The percentage is 20%.

6. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 70 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 5mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The calibration marks 9 are aligned and the silk screen plate is fixed.

7. Place the graphene/polyurethane elastomer composite solution on the screen plate, and brush the graphene/polyurethane elastomer composite solution on the screen plate with the pattern reciprocating left and right with a scraper. After trial printing, adjust the air pressure to make the electrode The surface is printed flat; the force-sensitive resistor layer is printed on the flexible substrate 10 printed with electrodes, and its size just covers the electrodes c3 and electrodes d4, as shown in Figure 5; the thickness is 150 μm;

8. Then dry at 100°C for 25 minutes, recover the slurry and clean the screen plate and scraper.

S4. Screen printing of reference resistance layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 6;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 70 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 5mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The calibration marks 9 are aligned and the silk screen plate is fixed.

4. Place the slurry on the screen plate, and brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right. After the trial printing, adjust the air pressure to make the electrode surface printed flat, and the reference resistance layer is printed on the printing plate. on a flexible substrate 10 with electrodes. As shown in Figure 6, the reference resistance layer has three small pieces, and the size of the three small pieces of the reference resistance layer just covers the electrode a1 and the electrode b2, the electrode e5 and the electrode f6, the electrode g7 and the electrode h8, and the pressure sensor. The schematic diagram of the circuit is shown in Figure 7. The printing paste of the selected reference resistor is silver; the thickness of the reference resistor layer is 150 μm;

5. Then dry at 100°C for 25 minutes, recover the slurry and clean the screen plate and scraper.

In the above embodiments, conductive ink can be used to replace conductive silver paste as the material for preparing electrodes and metal wiring, and copper, platinum or palladium can be used to replace silver as the material for preparing reference resistors.

Embodiment four:

A kind of flexible graphene composite material pressure sensor, its top view is as shown in Figure 1, and cross-sectional view is as shown in Figure 2, comprises: flexible substrate 10, electrode and metal wiring, force sensitive resistance layer, reference resistance layer; Flexible The substrate 10 is at the bottom layer, the electrodes and metal wiring are on the flexible substrate 10, and the force sensitive resistor layer and the reference resistor layer are on the electrodes and the metal wiring; the schematic diagram of the electrode and metal wiring circuit is shown in Figure 3 .

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to two electrodes of the same resistance, electrodes c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrodes e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrodes g7 and The electrode h8 is adjacent to two electrodes of the same resistance; the electrode a1 and the electrode d4 are connected with a metal wire and lead out the metal wire to the positive pole of the power supply; the electrode b2 and the electrode f6 are connected with a metal wire and lead out a metal wire; the electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to the negative pole of the power supply;

Electrode c3, electrode d4 and the force sensitive resistor layer on it form the force sensitive resistor Rx, electrode a1, electrode b2 and the reference resistor layer on it form the first reference resistor R1, electrode e5, electrode f6 and the above The reference resistance layer forms the second reference resistance R2, and the electrode g7, the electrode h8 and the reference resistance layer thereon form the third reference resistance R3;

The size of the force-sensitive resistor layer just covers the electrodes c3 and d4, the size of the reference resistor layer of the first reference resistor R1 just covers the electrodes a1 and electrode b2, and the size of the reference resistor layer of the second reference resistor R2 The electrode e5 and the electrode f6 are just covered, and the size of the reference resistance layer of the third reference resistor R3 just covers the electrode g7 and the electrode h8;

The force-sensitive resistor Rx is connected in series with the third reference resistor R3, the first reference resistor R1 is connected in series with the second reference resistor R2, and the series circuit of the force-sensitive resistor Rx and the third reference resistor R3 is connected with the first reference resistor R1, The series circuit of the second reference resistor R2 is connected in parallel. The schematic diagram of the pressure sensor circuit is shown in Figure 7.

The flexible substrate 10 is polydimethylsiloxane, a material with good biocompatibility, with a thickness of 500 μm;

Electrodes and metal connections are conductive silver paste, and the thickness of electrodes and metal connections is 100 μm;

The material used for the force-sensitive resistor layer is a composite material of graphene powder and polyurethane elastomer, the percentage of graphene in the total mass is 30%, and the thickness is 200 μm;

The reference resistance layer is silver with a thickness of 200 μm;

Va is the potential between the first reference resistor R1 and the second reference resistor R2, Vb is the potential between the force sensitive resistor Rx and the third reference resistor R3, Vc is the positive potential of the power supply, and Vd is the negative potential of the power supply; ΔV _ab ＝|Va-Vb|, ΔV _cd ＝|Vc-Vd|; ΔV _ab can be measured, ΔV _cd is the potential difference between the positive and negative poles of the power circuit, which can be adjusted; R ₃ is the third reference resistor R3 Resistance value, R _X is the resistance value of the force-sensitive resistor Rx, and ΔR _X is the change in resistance of the force-sensitive resistor Rx. The resistance change ΔR _X of the force sensitive resistor Rx can be based on the formula Get it.

A preparation method for a flexible graphene composite pressure sensor, the steps are as follows:

S1, the preparation of silk screen plate:

1. Tighten the screen on the screen frame, and select 400 mesh for the number of screens. Screen area selection S = 60mm * 100mm. Clean the screen and let it dry naturally. After a day, the screen tension is stable before it can be used.

2. Then apply photosensitive adhesive evenly on both sides of the screen, and then put it in an oven to dry at 140°C for 180s. The thickness of the photosensitive adhesive is about 300μm.

3. Then expose the screen with photosensitive adhesive under the mask plate with circuit pattern and calibration mark 9 pattern, bake at 140°C for 45min after exposure, and the photoresist of different manufacturers will indicate the spin coating rotation number and baking time to reduce the standing wave effect.

4. Then spray developer and flushing solution continuously at 25°C. After the photosensitive adhesive on the exposed part is washed away, the hard film is baked at 180°C, and the prepared screen plate is obtained.

S2. Screen printing of electrodes and metal wiring:

1. Prepare the screen plate according to the preparation of the screen plate in step S1, and the pattern is shown in Figure 4;

2. Clean the screen plate and scraper with net washing water, and wait for it to dry naturally in a dark place for later use;

3. Wash the flexible substrate 10 for printing with double distilled water, dry it and bake it in an oven at 160°C for 2 hours to prevent the flexible substrate 10 from being deformed in the subsequent high-temperature heating process, resulting in a decrease in the precision of the printed electrode. Backup. The flexible substrate 10 is polydimethylsiloxane, a material with good biocompatibility, with a thickness of 500 μm.

4. To print the electrode, adjust the inclination angle between the scraper and the screen plate to a suitable angle of 80 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 6 mm, and fix the screen plate.

5. Place the slurry for preparing electrodes and metal wires on the screen plate, brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right, after trial printing, adjust the air pressure to make the surface of the electrode printed flat, and The difference between batches of electrode resistance is less than 5%. The paste for preparing electrodes and metal connections is conductive silver paste, and the thickness of electrodes and metal connections is 100 μm;

6. Print electrodes and metal wiring on the flexible substrate 10, and then dry at 120°C for 30 minutes, that is, print electrodes, metal wiring and calibration marks 9 on the flexible substrate 10, as shown in Figure 4;

There are 8 electrodes in total, electrode a1 and electrode b2 are adjacent to the same two electrodes, electrode c3 and electrode d4 are adjacent to two electrodes of the same resistance, electrode e5 and electrode f6 are adjacent to two electrodes of the same resistance, electrode g7 and electrode Adjacent to h8 are two electrodes of the same resistance; electrode a1 and electrode d4 are connected with a metal connection and lead out the metal connection to the positive pole of the power supply; electrode b2 and electrode f6 are connected with a metal connection and lead out a section of metal connection; electrode c3 Connect with electrode g7 with a metal connection and lead out a section of metal connection; electrode e5 and electrode h8 are connected with a metal connection and lead out a metal connection to connect to the negative pole of the power supply;

7. Recover the slurry to clean the screen plate and scraper.

S3, screen printing of force sensitive resistor layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 5;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Prepare the slurry of the force sensitive resistor Rx, select a suitable organic solvent acetone, and prepare a polyurethane elastomer solution with a mass percentage of 30%;

4. Evenly mix the conductive graphene powder material with the same organic solvent used to prepare the polyurethane elastomer solution at a mass ratio of 1:100, and then use an ultrasonic device to ultrasonicate for 30 minutes with a power of 1200W to form a uniform dispersion of graphene;

5. Add the graphene dispersion liquid to the polyurethane elastomer solution, and disperse it by ultrasonic and dispersion equipment to form a uniform graphene/polyurethane elastomer composite solution, so that the final graphene accounts for 30% of the total mass of graphene and polyurethane elastomer. The percentage is 30%.

6. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 80 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 6 mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The calibration marks 9 are aligned and the silk screen plate is fixed.

7. Place the graphene/polyurethane elastomer composite solution on the screen plate, and brush the graphene/polyurethane elastomer composite solution on the screen plate with the pattern reciprocating left and right with a scraper. After trial printing, adjust the air pressure to make the electrode The surface is printed flat; the force-sensitive resistor layer is printed on the flexible substrate 10 printed with electrodes, and its size just covers the electrodes c3 and electrodes d4, as shown in Figure 5; the thickness is 200 μm;

8. Then dry at 140°C for 30 minutes, recover the slurry and clean the screen plate and scraper.

S4. Screen printing of reference resistance layer

1. Prepare the screen plate according to the preparation of the screen plate in step S1, as shown in Figure 6;

2. Then clean the screen plate and scraper with net washing water, and wait for them to dry naturally in a dark place for later use.

3. Print the intermediate film material, adjust the inclination angle of the scraper and the screen plate to an appropriate angle of 80 degrees, and adjust the distance between the screen plate and the substrate to a suitable distance of 6 mm, and align the calibration mark 9 on the screen plate with the one printed on the substrate. The calibration marks 9 are aligned and the silk screen plate is fixed.

4. Place the slurry on the screen plate, and brush the slurry on the screen plate with the pattern with a scraper reciprocating left and right. After the trial printing, adjust the air pressure to make the electrode surface printed flat, and the reference resistance layer is printed on the printing plate. on a flexible substrate 10 with electrodes. As shown in Figure 6, the reference resistance layer has three small pieces, and the size of the three small pieces of the reference resistance layer just covers the electrode a1 and the electrode b2, the electrode e5 and the electrode f6, the electrode g7 and the electrode h8, and the pressure sensor. The schematic diagram of the circuit is shown in Figure 7. The printing paste of the selected reference resistor is silver; the thickness of the reference resistor layer is 200 μm;

5. Then dry at 140°C for 30 minutes, recover the slurry and clean the screen plate and scraper.

In the above embodiments, conductive ink can be used to replace conductive silver paste as the material for preparing electrodes and metal wiring, and copper, platinum or palladium can be used to replace silver as the material for preparing reference resistors.

Claims (2)

1. a kind of Flexible graphene composite pressure sensor, it is characterised in that connect including flexible substrate, electrode and metal Line, force sensing resistance layer, reference resistor layer；Flexible substrate in orlop, electrode and metal connecting line on flexible substrate, the quick electricity of power Resistance layer and reference resistor layer are on electrode and metal connecting line；

Electrode has 8, and electrode a and electrode b closes on two electrodes for same resistance, and it is same electricity that electrode c and electrode d closes on Two electrodes of resistance, electrode e and electrode f closes on two electrodes for same resistance, and it is same resistance that electrode g and electrode h closes on Two electrodes；Electrode a is connected and draws metal connecting line and is connected to positive source with electrode d metal connecting lines；Electrode b and electrode f It is connected and draws one section of metal connecting line with metal connecting line；Electrode c is connected with electrode g metal connecting lines and draws one section of metal and connects Line；Electrode e is connected and draws metal connecting line and is connected to power cathode with electrode h metal connecting lines；

Electrode c, electrode d and the layer of force sensing resistance thereon constitute force sensing resistance, electrode a, electrode b and the layer of reference resistor thereon The first reference resistor is constituted, electrode e, electrode f and the layer of reference resistor thereon constitute the second reference resistor, electrode g, electrode H and the layer of reference resistor thereon constitute the 3rd reference resistor；

The size of force sensing resistance layer just covers electrode c and electrode d, and the size of the reference resistor layer of the first reference resistor is just Cover electrode a and electrode b, the size of the reference resistor layer of the second reference resistor just covers electrode e and electrode f, the 3rd The size of the reference resistor layer of reference resistor just covers electrode g and electrode h；

Force sensing resistance is connected with the 3rd reference resistor, and the first reference resistor is connected with the second reference resistor, force sensing resistance, the 3rd ginseng The series circuit of ratio resistance is in parallel with the series circuit of the first reference resistor, the second reference resistor；

Flexible substrate is material polyethylene terephtalate or polydimethylsiloxanes with good biocompatibility Alkane, thickness is 10~500 μm；

Electrode and metal connecting line are conductive silver paste or electrically conductive ink, and electrode and metal connecting line thickness are 5~100 μm；

Force sensing resistance layer material therefor is the composite of graphene powder and polyurethane elastomer, gross mass shared by Graphene Percentage is 5%~30%, and thickness is 10~200 μm；

Reference resistor layer is silver, copper, platinum or palladium, and thickness is 5~200 μm.

2. a kind of preparation method of Flexible graphene composite pressure sensor, it is characterised in that step is as follows：

The preparation of S1, silk screen plate：

1. silk screen is tightened on screen frame, silk screen number selects 100~400 mesh；Silk screen area selection S=34mm*61mm~ 60mm*100mm；Screen bath is clean, dry naturally；Cross after one day, silk screen tension stability could be used；

2. and then light-sensitive emulsion is uniformly coated with silk screen two sides, is then placed in baking oven 80~140 DEG C of drying 60s~180s, it is photosensitive Glue thickness is about 5~300 μm；

3. and then by the silk screen with light-sensitive emulsion exposed under the mask plate with circuit pattern and calibration mark pattern, after exposure 15~45min is bakeed at 80~140 DEG C, the photoresist of different manufacturers can indicate spin coating revolution and baking time, stayed with reducing Wave effect；

4. continuous spray developer solution and flushing liquor and then at 15~25 DEG C；It is to be cleaned fall exposed portion light-sensitive emulsion after, 100 Post bake baking is carried out at~180 DEG C, that is, the silk screen plate made；

The silk-screen printing of S2, electrode and metal connecting line：

1. silk screen plate is prepared according to the preparation of S1 step silk screen plates；

2. silk screen plate, scraper are cleaned up with net washing water, it is standby after it is volatilized naturally in shady place；

3. by printing with flexible substrate cleaned with redistilled water, dry 120~160 DEG C of baking 2h in rearmounted baking oven, in case Only flexible substrate deforms in subsequent high temperature heating process, causes the precision that prints electrode to decline, standby after cooling；Flexible substrate It is material polyethylene terephtalate or dimethyl silicone polymer with good biocompatibility, thickness is 10 ~500 μm；

4. print electrode, the angle of inclination of scraper and silk screen plate is modulated to 45~80 degree of suitable angle, and adjust silk screen Plate is suitable 3~6mm of distance with substrate, and silk screen plate is fixed；

5. the slurry that electrode and metal connecting line will be prepared is placed on silk screen plate, is back and forth being carried slurry brush with scraper or so On the silk screen plate of pattern, after examination print, regulation air pressure makes electrode surface print smooth and electrode resistance difference between batch less than 5%；System The slurry of standby electrode and metal connecting line is conductive silver paste or electrically conductive ink, and electrode and metal connecting line thickness are 5~100 μm；

6. print electrode on flexible substrates and metal connecting line, afterwards 80~120 DEG C of 10~30min of drying, i.e., in flexible substrate Electrode and metal connecting line and calibration mark in upper printing；

Electrode has 8, and it is two same electrodes that electrode a and electrode b closes on, and it is same resistance that electrode c and electrode d closes on Two electrodes, electrode e and electrode f close on two electrodes for same resistance, and it is the two of same resistance that electrode g and electrode h closes on Individual electrode；Electrode a is connected with electrode d metal connecting lines and draws metal connecting line can be connected to positive source；Electrode b and electrode f is used Metal connecting line is connected and draws one section of metal connecting line；Electrode c is connected with electrode g metal connecting lines and draws one section of metal connecting line； Electrode e is connected with electrode h metal connecting lines and draws metal connecting line can be connected to power cathode；

7. slurry cleaning web plate, scraper are reclaimed；

The silk-screen printing of S3, force sensing resistance layer

1. silk screen plate is prepared according to the preparation of S1 step silk screen plates；

2. and then silk screen plate, scraper are cleaned up with net washing water, it is standby after it is volatilized naturally in shady place；

3. the slurry of force sensing resistance is prepared, suitable organic solvent is selected, organic solvent is tetrahydrofuran, dimethyl sulfoxide, diformazan Base formamide or acetone, prepare the polyurethane elastomer solution that mass percent is 10%~30%；

4. by conductive graphene powder body material as prepare polyurethane elastomer solution used by as organic solvent in mass ratio 1:10~1:100 uniform mixing, then using ultrasonic device 10~30min of ultrasound, power is 400~1200W, forms Graphene Uniform dispersion；

5. graphene dispersing solution is added in polyurethane elastomer solution, is disperseed by ultrasound and dispersing apparatus, form uniform Graphene/polyurethane elastomer composite solution so that Graphene and the total quality of polyurethane elastomer shared by final Graphene Percentage be 5%~30%；

6. intermediate film material is printed, scraper and silk screen plate angle of inclination suitable 45~80 degree of angle is modulated into, and adjust Silk screen plate is suitable 3~6mm of distance, the calibration mark that will be printed in the calibration mark on silk screen plate and substrate with substrate Alignment, silk screen plate is fixed；

7. Graphene/polyurethane elastomer composite solution is placed on silk screen plate, it is reciprocal by Graphene/poly- with scraper or so On the figuratum silk screen plate of band, after examination print, it is smooth that regulation air pressure prints electrode surface to urethane elastomer composite solution brush； Force sensing resistance layer is just printed in the flexible substrate for being printed with electrode, and its size just covers electrode c and electrode d；Thickness is 10~200 μm；

8. and then 80~140 DEG C of 10~30min of drying, slurry cleaning web plate, scraper are reclaimed；

S4. the silk-screen printing of reference resistor layer

1. silk screen plate is prepared according to the preparation of S1 step silk screen plates；

2. and then silk screen plate, scraper are cleaned up with net washing water, it is standby after it is volatilized naturally in shady place；

3. intermediate film material is printed, scraper and silk screen plate angle of inclination suitable 45~80 degree of angle is modulated into, and adjust Silk screen plate is suitable 3~6mm of distance, the calibration mark that will be printed in the calibration mark on silk screen plate and substrate with substrate Alignment, silk screen plate is fixed；

4. slurry is placed on silk screen plate, with scraper or so back and forth by slurry brush on the figuratum silk screen plate of band, examination After print, it is smooth that regulation air pressure prints electrode surface, and reference resistor layer is just printed in the flexible substrate for being printed with electrode；Reference Resistive layer has three fritters, and the size of the reference resistor layer of this three fritter has just been covered each by electrode a and electrode b, electrode e and electricity Pole f, electrode g and electrode h；The printing slurry of selected reference resistor is silver, copper, platinum or palladium；Reference resistor thickness degree be 5~ 200μm；

5. and then 80~140 DEG C of 10~30min of drying, slurry cleaning web plate, scraper are reclaimed.