CN102589759B - Biomimetic flexible tactile sensing array based on combination of piezoresistive and capacitive - Google Patents

Abstract

The invention discloses a bionic flexible touch sense sensing array based on piezoresistive type and capacitance type combination. The bionic flexible touch sense sensing array is successively composed of a flexible substrate layer, a capacitance layer, a piezoresistive layer and a surface packaging layer from bottom to top. The sensing array is simultaneously integrated with two types of touch sense force sensitive components based on the piezoresistive type and the capacitance type; a piezoresistive type force sensitive layer is overlaid on a capacitance-type force sensitive layer; the resolution of a piezoresistive layer space is 1mm; the resolution of a capacitance layer space is 2mm; a piezoresistive type force sensitive layer circuit is a matrix circuit; each node of the matrix circuit is provided with a semilunar electrode and a bar-shaped electrode; the two electrodes are connected by PDMS (Polydimethylsiloxane) conducting rubber; a capacitance-type force sensitive layer circuit is a matrix circuit; the lower layer of the matrix circuit forms a capacitance lower polar plate; the upper layer of the matrix circuit forms a capacitance upper polar plate; a PDMS dielectric layer with surface patterns is arranged between the two polar plates; the piezoresistive layer and the capacitance layer respectively measure static force and transient force; and the comprehensive performance of the bionic flexible touch sense sensing array can be improved.

Description

Biomimetic flexible tactile sensing array based on combination of piezoresistive and capacitive

technical field

The invention relates to a bionic flexible tactile sensing array, in particular to a bionic flexible tactile sensing array based on the combination of piezoresistive and capacitive types.

technical background

The skin is the largest organ in the human body, with an area of about 1.2-2 m ² , accounting for about 16% of the body weight, and is composed of subcutaneous tissue, dermis and epidermis. The subcutaneous tissue is located below the dermis and is connected to tissues such as the sarcolemma, and is composed of a large number of fat cells and thick connective tissue fiber bundles; the dermis is located below the epidermis, and is composed of collagen fibers, elastic fibers, reticular fibers, matrix, cells, etc.; Located on the outside of the skin, it is keratinized stratified squamous epithelium, most of which are keratinocytes. It can be seen that the skin is a complex system composed of multi-layer tissue structure and multiple components, and its biomechanical properties are mainly determined by the tissue structure of collagen fibers and elastic fibers in the dermis, as well as the content of water and protein.

There are four types of mechanical stimulation receptors in human skin, namely Merkel Disk, Meissner's Corpusde, Ruffini Ending and Pacinian Corpusde. . These four mechanical stimulus sensing cells are sensitive to different types of force. Merkel's contact disc and Meyer's body are located in the superficial layer of the dermis, which are sensitive to static force and transient force respectively; Raffini's body is located in the lower layer of the dermis. In the deep place, it is only sensitive to the tangential force parallel to the skin; the annular body is located in the deep layer of the dermis, and is very sensitive to transient force and vibration, and its sensitivity to transient force and vibration is higher than that of Merlin's body . And the distribution density of these four kinds of mechanical stimulation sensing cells is not the same, and their distribution density relationship from large to small is: Meyer's body, Meckel's contact disk, Raffini's body, and ring body.

Mechatronic artificial prosthetics can enable amputees to take care of themselves in daily life. In order to make artificial prostheses have a good ability to interact with the outside world, it is necessary to reshape the sensory function. Sensory functions include touch, temperature perception, pain, and more. Among them, touch is an important sense when the human body is in contact with the external environment. It is a synthesis of multiple senses, including rich sensory information such as light touch, pressure, and vibration. If the tactile information can be restored accurately, so that the artificial limb has "feeling", this will be a great progress in the reconstruction of human motor function. the

In addition, with the development of robot technology, tactile perception is the basis for realizing its intelligence. The tactile perception of the robot is to recognize various physical information of the target object or object through tactile sensitive components, such as the size of the contact force, softness, hardness, elasticity, roughness, material, etc. In recent years, "robot flexible tactile sensitive skin" has become a new research hotspot in the field of intelligent robot tactile sensing technology.

The flexible and tactile sensitive skin of the robot can enhance its ability to complete fine and complex operations in various environments, improve the operation level and intelligence level of the robot system, and micro-drive advanced service robots, space robots and precision operations in dangerous environments. Robots and more will have an important impact.

In biomedicine, surgical robots have been able to perform surgeries on vital organs such as the human heart and brain. However, in addition to microscopic magnification and visual monitoring, the surgical robot system has an increasing demand for detection and perception of multi-dimensional contact force information.

Contents of the invention

The purpose of the present invention is to provide a bionic flexible tactile sensing array based on the combination of piezoresistive and capacitive, which has the characteristics of excellent static and dynamic properties.

The technical scheme adopted in the present invention is:

The bionic flexible tactile sensing array of the present invention is sequentially composed of a flexible base layer, a capacitor layer, a piezoresistive layer and a surface packaging layer from bottom to top, and a four-layer structure is stacked together; the structure of each layer is as follows:

(a) Flexible base layer: from bottom to top, it is composed of silicon wafer, PDMS (polydimethylsiloxane) flexible base and PDMS conductive rubber shielding layer together;

(b) Capacitor layer: from bottom to top, the first PI electrode substrate with a Ti/Au capacitor lower electrode attached to its upper surface, the quadrangular pyramid dielectric layer patterned into a small area of quadrangular pyramid on its upper surface, and the upper surface The second PI electrode substrate with the Ti/Au capacitor upper electrode plate on the surface is stacked together. The Ti/Au capacitor upper electrode plate electrodes and the Ti/Au capacitor lower electrode plate electrodes are arranged in an orthogonal direction. Each pair of Ti A capacitor is formed between the upper and lower plates of the /Au capacitor, and there is a small rectangular pyramid area as a capacitor dielectric layer between each capacitor. Each capacitor is a sensing unit, and all the capacitive sensing units form a capacitor array;

(c) piezoresistive layer: from bottom to top, it consists of a PDMS conductive rubber shielding layer, a third PI electrode substrate with a strip-shaped distribution of Ti/Au piezoresistive layer electrodes on its upper surface, a hemispherical conductive rubber layer, and its upper surface. A fourth PI electrode substrate with through holes and a PDMS protective layer with a half-moon-shaped electrode array and a strip-shaped electrode array formed alternately on the upper surface are stacked together; The lower electrode of the Ti/Au piezoresistive layer is electrically connected; the hemispherical conductive rubber on the hemispherical conductive rubber layer covers the respective half-moon electrodes and strip electrodes, so that each column of strip electrodes is electrically connected to the respective half-moon electrodes. Connected; each conductive rubber in the hemispherical conductive rubber layer is a sensing unit, and all the hemispherical conductive rubbers form a piezoresistive conductive rubber array;

(d) Surface encapsulation layer: It is a layer of patterned film made of PDMS micro-protrusions on the upper surface and made of PDMS.

The ratio of the spatial resolution of the capacitive layer to the piezoresistive layer is 2:1, that is, the ratio of the number of sensing units of the capacitive layer to the number of sensing units of the piezoresistive layer is 1:4 under the same area.

A combination of a half-moon electrode and a strip electrode is attached to the fourth PI electrode substrate in the piezoresistive layer.

The beneficial effects that the present invention has are:

(1) Based on the concept of simplified design, the present invention selects the sensory cell ring body and the Merkel contact disk as the bionic objects. The capacitive layer mainly imitates the ring corpuscle in the human skin, and this sensory cell is the most sensitive cell in the human skin to transient force and vibration; while the conductive rubber piezoresistive layer mainly imitates the Merkel contact plate, It is characterized by being sensitive to static force but insensitive to transient force. This tactile sensing array integrates piezoresistive conductive rubber suitable for measuring static force and capacitance suitable for measuring transient force and micro vibration into a tactile sensing array, which can meet the measurement requirements of static force and transient force , has good comprehensive performance.

(2) Micro-contact printing technology is used in the manufacturing process of the bionic tactile sensing array. Micro-contact printing technology has its unique advantages in printing tiny metal circuits and manufacturing micro-nano three-dimensional structures, and can realize large-area and high-efficiency production , and can be used to print circuits on curved surfaces.

(3) By simulating the distribution density and distribution depth of sensory cell ring corpuscles and Merkle contact disks, the capacitive layer is placed under the piezoresistive layer, and the spatial resolution of the capacitive layer is different from that of the piezoresistive layer. The ratio is 1:2, such a design can take advantage of bionics and provide guidance for the optimization of the tactile sensing array.

(4) The method of micro-contact printing is used to manufacture surface patterns on the surface of the PDMS dielectric layer of the capacitor layer, which greatly enhances the deformation capacity of the capacitor and enhances its sensitivity.

(5) The piezoresistive layer and the capacitive layer of the flexible tactile sensing array are controlled by a separate circuit, which can reduce interference, and the capacitive layer is surrounded by a PDMS conductive rubber shielding layer, which can minimize the impact of the piezoresistive layer and the external environment on the sensor. interference.

Description of drawings

Fig. 1 is a split perspective view of the layered structure of the present invention;

Fig. 2 is a cross-sectional view of a flexible base layer with a silicon base in the present invention;

Fig. 3 is a disassembled perspective view of the capacitive layer layered structure of the present invention;

Fig. 4 is a disassembled perspective view of the piezoresistive layer layered structure of the present invention;

Fig. 5 is a plan view of the PI substrate of the upper layer electrode of the piezoresistive layer of the present invention;

6 is a plan view of the upper electrode layer of the piezoresistive layer of the present invention;

Fig. 7 is a schematic diagram of the PDMS hemispherical conductive rubber installation structure of the present invention;

Fig. 8 is a plan view of the surface package of the present invention;

Fig. 9 is a perspective view of the flexible tactile sensing array of the present invention.

In the figure: 1. Flexible substrate layer, 2. Capacitive layer, 3. Piezoresistive layer, 4. Surface encapsulation layer, 5. Silicon wafer, 6. PDMS flexible substrate, 7. PDMS conductive rubber shielding layer, 8. The first PI Electrode substrate, 9, Ti/Au capacitor lower plate, 10, quadrangular pyramid dielectric layer, 11, second PI electrode substrate, 12, Ti/Au capacitor upper plate, 13, PDMS conductive rubber shielding layer, 14 , the third PI electrode substrate, 15, Ti/Au piezoresistive layer lower electrode, 16, the fourth PI electrode substrate, 17, strip electrode, 18, half-moon electrode, 19, hemispherical conductive rubber layer, 20, PDMS protection layer, 21, PI through hole, 22, small area of quadrangular pyramid, 23, surface layer PDMS micro-projection.

Detailed ways

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

As shown in Figure 1, it is a split perspective view of the layered structure of the present invention. The bionic flexible tactile sensing array consists of a flexible base layer 1, a capacitive layer 2, a piezoresistive layer 3 and a surface packaging layer 4 from bottom to top, four-layer structure Layered together; the structure of each layer is as follows:

(a) Flexible base layer 1 as shown in Figure 2: from bottom to top, it is composed of silicon wafer 5, PDMS flexible base 6 and PDMS conductive rubber shielding layer 7 stacked together.

(b) Capacitor layer 2 as shown in Figure 3: from bottom to top, the first PI electrode substrate 8 with Ti/Au capacitor lower electrode 9 attached to its upper surface, and its upper surface is patterned into a small quadrangular pyramid area 22 The quadrangular pyramid dielectric layer 10 and the second PI electrode substrate 12 with the Ti/Au capacitor upper electrode plate 12 attached to its upper surface are stacked together to form; the Ti/Au capacitor upper electrode plate 12 electrode and the Ti/Au capacitor lower electrode Plate 9 electrodes are arranged in an orthogonal direction, and a capacitor is formed between the upper and lower plates of each pair of relative Ti/Au capacitors. There is a small quadrangular pyramid area 22 as a capacitor dielectric layer between each capacitor, and each capacitor is One sensing unit, all capacitive sensing units form a capacitive array.

(c) piezoresistive layer 3 as shown in Figure 4: from bottom to top, there is a PDMS conductive rubber shielding layer 13, and a third PI electrode substrate with strip-shaped distribution of Ti/Au piezoresistive layer electrodes 15 attached to its upper surface 14. The hemispherical conductive rubber layer 19, the fourth PI electrode substrate 16 (as shown in FIG. shown) and the PDMS protective layer 20 are stacked together; the half-moon-shaped electrode 18 is electrically connected to the lower electrode 15 of the Ti/Au piezoresistive layer through the PI through hole 21 on the fourth PI electrode substrate 16; as shown in Figure 7, The hemispherical conductive rubber on the hemispherical conductive rubber layer 19 is respectively covered on the respective half-moon electrodes 18 and the strip electrodes 17, so that each row of strip electrodes 17 is electrically connected with the respective half-moon electrodes 18; the hemispherical conductive rubber Each conductive rubber in layer 19 is a sensing unit, and all the hemispherical conductive rubbers form a piezoresistive conductive rubber array.

(d) Surface encapsulation layer 4 as shown in Figure 8: It is a layer of patterned film made of PDMS micro-projections 23 on the upper surface and made of PDMS.

The ratio of the spatial resolution of the capacitive layer 2 to the piezoresistive layer 3 is 2:1, that is, under the same area, the ratio of the number of sensing units in the capacitive layer to the number of sensing units in the piezoresistive layer is 1:4.

A combination of a half-moon electrode 18 and a strip electrode 17 is attached to the fourth PI electrode substrate 16 in the piezoresistive layer 3 .

The sensing array of the present invention is a rectangle with a total thickness of about 0.5mm and a side length of 10mm, wherein the capacitive layer includes 5×5 sensitive units, and the piezoresistive layer includes 10×10 sensitive units, that is, the spatial resolution of the capacitive layer is 2mm, and the spatial resolution of the piezoresistive layer is 1mm, which can fully meet the bionic skin requirements of artificial prostheses. The fabrication steps to complete the combined piezoresistive and capacitive bionic flexible tactile sensing array are as follows:

(1) Prepare ordinary single-polished silicon wafer 5 as the rigid carrier of flexible devices; mix Sylgard 184 PDMS prepolymer and curing agent at a ratio of 10:1 (mass ratio), stir evenly, and vacuumize to remove air bubbles, and use spin coating method A 50 μm PDMS flexible substrate 6 is coated on the rigid silicon wafer 5, and is cured with a hot plate or a heating furnace.

(2) Mix Sylgard 184 PDMS prepolymer and curing agent in a certain proportion, add nano-conductive particles, mix, stir well, vacuumize to remove air bubbles, and coat 10 μm of the above-mentioned on the PDMS flexible substrate 6 by spin coating. The PDMS with conductive particles is insulated and cured with a hot plate or a heating furnace to form a conductive rubber shielding layer 7 .

(3) Spin-coat the first PI electrode substrate 8 with a thickness of 10 μm on the conductive rubber shielding layer 7, and heat and cure it with a hot plate or a heating furnace; deposit 10 nm of Ti and 200 nm of Ti on the first PI electrode substrate 8. Au, use the micro-contact printing method based on PDMS soft stamp to manufacture the Ti/Au capacitor lower plate 9; then spin-coat a layer of PI with a thickness of 4 μm on the electrode as a protective layer, and use a hot plate or a heating furnace to keep warm and cure.

(4) Pour PDMS solution on the silicon mold complementary to the quadrangular pyramid dielectric layer 10, turn the silicon wafer 5 and the entire sensing array upside down on the silicon mold, apply a certain pressure and heat it with a heating furnace to cure, and then peeling off to form the structure of the quadrangular pyramid dielectric layer 10 .

(5) Spin-coat a layer of second PI electrode substrate 11 with a thickness of 10 μm on another new silicon wafer, heat and cure it with a hot plate or a heating furnace, and then peel off the silicon wafer. The surface of the second PI electrode substrate 11 Oxygen plasma activation treatment is performed, and then covered on the quadrangular pyramid dielectric layer 10 as a support for the upper plate 12 of the Ti/Au capacitor.

(6) Deposit 10nm of Ti and 200nm of Au on the second PI electrode substrate 11, and use the microcontact printing method based on PDMS soft stamp to manufacture the Ti/Au capacitor upper plate 12; then spin-coat a layer of thickness on the electrode 4 μm PI as a protective layer.

(7) Mix Sylgard 184 PDMS prepolymer and curing agent in a certain proportion, add nano conductive particles, mix, stir well, vacuumize to remove air bubbles, and coat 10μm on the PI protective layer in step 6 by spin coating The above-mentioned PDMS with conductive particles is heat-preserved and cured with a hot plate or a heating furnace to form a conductive rubber shielding layer 13 .

(8) Spin-coat a third PI electrode substrate 14 with a thickness of 10 μm on the conductive rubber shielding layer 13, heat and cure it with a hot plate or a heating furnace; deposit 10 nm of Ti and 200 nm of Ti on the third PI electrode substrate 14. Au, the Ti/Au piezoresistive layer lower electrode 15 is manufactured by using the micro-contact printing method based on the PDMS soft stamp.

(9) Spin-coat a layer of 4 μm fourth PI electrode substrate 16 on the lower electrode 15 of the Ti/Au piezoresistive layer, heat and cure it with a hot plate or a heating furnace, and then use a carbon dioxide laser on the fourth PI electrode substrate 16 A PI through hole 21 is made to expose a part (through hole portion) of the lower layer electrode 15 of the Ti/Au piezoresistive layer.

(10) Deposit 10nm of Ti and 200nm of Au on the fourth PI electrode substrate 16, and use the microcontact printing method based on PDMS soft stamp to manufacture strip electrodes 17 and half-moon electrodes 18, wherein the half-moon electrodes 18 and Ti The lower electrode 15 of the /Au piezoresistive layer is electrically connected.

(11) Mix Sylgard 184 PDMS prepolymer and curing agent in a certain proportion, add nano-conductive particles, and prepare a pressure-sensitive PDMS conductive rubber solution; use a dispenser to manufacture hemispheres on the strip electrodes 17 and half-moon electrodes 18 Shaped PDMS conductive rubber layer 19; carry out insulation curing with a hot plate or a heating furnace.

(12) Cast PDMS solution on the hemispherical conductive rubber layer 19 to cover the conductive rubber, and the thickness cannot be higher than 4 μm from the top of the conductive rubber. In order to achieve the goal of 4μm, it is possible to not completely cover the conductive rubber when casting the PDMS solution. After the casting part is insulated and cured with a hot plate or a heating furnace, continue to cover the PDMS with the method of spin coating. The rotation speed precisely controls the height of the PDMS, and finally forms the PDMS protective layer 20 .

(13) Make a structure with a cavity on the silicon mold, cast PDMS solution on it, heat it with a hot plate or a heating furnace and then peel it off to make a PDMS surface package 4 with surface PDMS micro-protrusions 23. The lower surface of the PDMS surface package 4 is adhered to the PDMS protective layer 20 after being activated by oxygen plasma.

As long as the sensor array is peeled off from the silicon plate 5, the entire sensor array is manufactured, as shown in FIG. 9 . In this way, the manufactured sensing array has good static and dynamic performance, and the sensing array can acquire tactile information well no matter for an instant touch or a continuous squeeze.

Claims (3)

1. Bionic flexible tactile sensing array based on the combination of pressure resistance type and condenser type, it is characterized in that: the Bionic flexible tactile sensing array is from bottom to up successively by flexible base layer (1), capacitor layers (2), piezoresistance layer (3) and surface encapsulation layer (4), four-layer structure formation stacked together; Its structure of every layer is as follows:

(a) flexible base layer (1): stack formation by silicon chip (5), PDMS flexible substrates (6) and PDMS conductive rubber screen layer (7) successively from bottom to up;

(b) capacitor layers (2): stack formation by its upper surface with patterned the 2nd PI electrode substrate (12) of having a Ti/Au electric capacity upper electrode plate (12) for the rectangular pyramid dielectric layer (10) of rectangular pyramid zonule (22) and its upper surface of a PI electrode substrate (8), its upper surface of Ti/Au capacitor lower electrode (9) successively from bottom to up; Ti/Au electric capacity upper electrode plate (12) electrode and Ti/Au capacitor lower electrode plate (9) the electrode direction that is orthogonal is arranged, form an electric capacity between every pair of relative upper and lower pole plate of Ti/Au electric capacity, rectangular pyramid zonule (22) as capacitance dielectric layer is all arranged between each electric capacity, each electric capacity is a sensing unit, and all capacitance sensing unit form capacitor array;

(c) piezoresistance layer (3): from bottom to up successively by PDMS conductive rubber screen layer (13), its upper surface is with the 3rd PI electrode substrate (14) that is bar shaped distribution Ti/Au piezoresistance layer lower electrode (15), its upper surface is with semilune electrode (18) array of alternate composition and band through hole the 4th PI electrode substrate (16) of strip electrode (17) array, semisphere conductive rubber layer (19) and PDMS protective seam (20) stack formation; Semilune electrode (18) is followed Ti/Au piezoresistance layer lower electrode (15) electrical communication by the PI through hole (21) on the 4th PI electrode substrate (16); Semisphere conductive rubber on the semisphere conductive rubber layer (19) covers respectively on separately the semilune electrode (18) and strip electrode (17), make every row strip electrode (17) all with separately semilune electrode (18) electrical communication; Each conductive rubber in the semisphere conductive rubber layer (19) is a sensing unit, and all semisphere conductive rubbers form pressure resistance type conductive rubber array;

(d) surface encapsulation layer (4): be that upper surface is the miniature boss of PDMS (23) and one deck patterned film of being made into PDMS.

2. a kind of Bionic flexible tactile sensing array based on the combination of pressure resistance type and condenser type according to claim 1, it is characterized in that: described capacitor layers (2) is 2:1 with the ratio of piezoresistance layer (3) spatial resolution, namely under equal area, the sensing unit quantity of capacitor layers is 1:4 with the ratio of piezoresistance layer sensing unit quantity.

3. a kind of Bionic flexible tactile sensing array based on pressure resistance type and condenser type combination according to claim 1 is characterized in that: adhered to the combination of semilune electrode (18) with strip electrode (17) on the 4th PI electrode substrate (16) in the described piezoresistance layer (3).

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