A flexible composite sensing array with ultrasonic and pressure sensing functions

Abstract

The application discloses a flexible composite sensing array with ultrasonic and pressure sensing functions, which comprises a PDMS upper packaging layer with a pyramid boss, an ultrasonic sensing array, an ultrasonic sensing array substrate layer, a flexible pressure sensing array, a flexible pressure sensing array substrate layer and a PDMS lower packaging layer with a pyramid groove in a top-bottom stacking mode; under alternating current, the ultrasonic sensing array emits ultrasonic waves which are received after being reflected by an object; pressure is transferred to the flexible pressure sensing array; the PDMS upper packaging layer with the pyramid boss and the PDMS lower packaging layer with the pyramid groove form an interlocking positioning structure. The application guarantees the ultrasonic sensing detection precision, solves the interference problem of ultrasonic sensing in the pressing process, reduces the heat flux of the PVDF sensitive layer unit, improves the sensitivity and imaging precision of the ultrasonic sensing function, has a small environmental influence, has high detection precision and has a long detection distance.

Description

TECHNICAL FIELD

[0001] The present application relates to a flexible sensor, in particular to a flexible composite sensing array with ultrasonic and pressure sensing functions. BACKGROUND

[0002] With the rapid development of the field of robots, integrating flexible sensors on intelligent robots enables them to have sensing capabilities, transforming traditional one-way open-loop manual operation into a two-way closed-loop human-machine interaction process, improving the ability of robots to perform complex and delicate tasks, and promoting the coexistence and interaction of human-machine environments, which has great potential in applications.

[0003] The demand for sensing capabilities of robots not only includes contact sensing capabilities, but also includes non-contact sensing capabilities. Contact sensing capabilities enable robots to obtain rich information about the surface of objects, thereby providing data support and feedback for the execution of tasks by robots. Non-contact sensing has two main applications. The first is safety detection, which is particularly important when a collision is about to occur, and the equipment is stopped in time to protect the safety of the operator. The second application is in grasping, where non-contact sensing can first detect the shape of an object to determine the required grasping gesture, and can also ensure that multiple fingers of a robot touch the grasped object simultaneously to improve the accuracy of grasping and avoid unnecessary movement before manipulating the object. Traditionally, non-contact sensing is achieved through visual detection, which has very good advantages for detecting large targets at a distance. However, when the detection range is reduced to less than 50 cm, visual detection begins to have problems, such as being blocked by objects, which can lead to detection failure, especially when the detection distance is further reduced to the proximity zone below 10 cm. In addition, visual detection is greatly affected by the environment and has low precision, which limits its application in close proximity. Therefore, it is necessary to integrate non-contact sensing capabilities based on mature flexible tactile sensors. Among the flexible sensors reported to have contact and non-contact sensing capabilities, the implementation of non-contact sensing capabilities mainly relies on magnetic field, electric field, triboelectricity, and humidity field principles. The magnetic field principle can only detect magnetic objects. The electric field principle mainly uses the capacitance principle, but there are many factors that affect the capacitance, limiting its application. The triboelectricity principle and the humidity field principle have small detection distances and are greatly affected by the environment. SUMMARY

[0004] To solve the problems in the background art, the present application provides a flexible composite sensing array with ultrasonic and pressure sensing functions.

[0005] The application adopts ultrasonic wave for close-range sensing, avoids the problem that the magnetic field principle can only detect magnetic objects, has small environmental influence, high detection precision and long detection distance; adopts piezoresistance principle for pressure sensing, has simple principle, convenient manufacturing and high sensitivity. The two sensing functions can work simultaneously, the pyramid interlocking positioning structure is introduced, so that the ultrasonic sensing is not disturbed, the ultrasonic sensing detection precision is ensured, the interference problem of ultrasonic sensing in the pressing process is solved, the PVDF sensitive layer unit for transmitting and receiving ultrasonic waves adopts concentric circle structure design, so that the ultrasonic wave can work at multiple frequencies, the heat flux of the PVDF sensitive layer unit for transmitting and receiving ultrasonic waves is reduced, and the sensitivity and imaging precision of the ultrasonic sensing function are improved.

[0006] The technical scheme adopted by the application is:

[0007] One, a flexible composite sensing array with ultrasonic and pressure sensing functions:

[0008] The flexible composite sensing array comprises a PDMS upper packaging layer with a pyramid boss, an ultrasonic sensing array, an ultrasonic sensing array substrate layer, a flexible pressure sensing array, a flexible pressure sensing array substrate layer and a PDMS lower packaging layer with a pyramid groove, which are sequentially stacked from top to bottom. Under the action of alternating current, the ultrasonic sensing array transmits ultrasonic waves by using inverse piezoelectric effect, receives and outputs voltage signals after being reflected by external objects; when external pressure is applied to the flexible composite sensing array, the external pressure is transmitted to the flexible pressure sensing array through the PDMS upper packaging layer with the pyramid boss and the ultrasonic sensing array substrate layer, so that the flexible pressure sensing array generates and outputs pressure signals; the PDMS upper packaging layer with the pyramid boss and the PDMS lower packaging layer with the pyramid groove form an interlocking positioning structure.

[0009] The ultrasonic sensing array substrate layer and the flexible pressure sensing array substrate layer both have complete coverage area.

[0010] The ultrasonic sensing array and the upper surface of the ultrasonic sensing array substrate layer are closely attached, the ultrasonic sensing array is composed of an ultrasonic sensing array upper electrode layer, a PVDF sensitive layer for transmitting and receiving ultrasonic waves, a circular insulating spacer of the ultrasonic sensing array, and an ultrasonic sensing array lower electrode layer.

[0011] The upper electrode layer of the ultrasonic sensing array is composed of N rows and N columns of ultrasonic sensing upper electrode units arranged in an array, the PVDF sensitive layer for transmitting and receiving ultrasonic waves is composed of N rows and N columns of PVDF sensitive units arranged in an array, and the lower electrode layer of the ultrasonic sensing array is composed of N rows and N columns of ultrasonic sensing lower electrode units arranged in an array. Each ultrasonic sensing upper electrode unit, one PVDF sensitive unit and one ultrasonic sensing lower electrode unit are stacked together from top to bottom to form an ultrasonic sensing unit. A plurality of ultrasonic sensing units are arranged on the upper surface of the ultrasonic sensing array substrate layer to form a uniform N rows and N columns array structure.

[0012] Each ultrasonic sensing upper electrode unit has one electrode line, and there are N×N electrode lines in total. N×N ultrasonic sensing lower electrode units are connected in series and have one electrode line in total. The electrode line of each ultrasonic sensing upper electrode unit and the electrode line of the ultrasonic sensing lower electrode unit are connected to the peripheral circuit to collect the ultrasonic sensing signals fed back by each ultrasonic sensing unit, respectively. Circular insulating isolation blocks are arranged at the intersections between the electrode lines of the ultrasonic sensing upper electrode units and the electrode lines of the ultrasonic sensing lower electrode units for insulation and isolation. The upper electrode layer of the ultrasonic sensing array, the lower electrode layer of the ultrasonic sensing array and the PVDF sensitive layer for transmitting and receiving ultrasonic waves form a closed loop. An alternating current is passed between the electrode lines of the upper electrode layer of the ultrasonic sensing array and the lower electrode layer of the ultrasonic sensing array. Through the inverse piezoelectric effect, the PVDF sensitive layer for transmitting and receiving ultrasonic waves converts electrical energy into mechanical vibration, thereby exciting ultrasonic waves.

[0013] The working frequencies of different ultrasonic sensing units can be different or the same. Preferably, the frequencies are different.

[0014] The flexible pressure sensitive sensing array is closely attached to the upper surface of the flexible pressure sensitive sensing array substrate layer. The flexible pressure sensitive sensing array is composed of a graphene pattern array, a flexible pressure sensitive sensing array lower electrode layer, a circular insulating isolation block of the flexible pressure sensitive sensing array, and a flexible pressure sensitive sensing array upper electrode layer.

[0015] The graphene pattern array is composed of N rows and N columns of graphene units arranged in an array. Each graphene unit has two output pins. One output pin of each graphene unit in the same row is connected in series through the electrode line of the flexible pressure sensitive sensing lower electrode to form a group of graphene unit groups. Another output pin of each graphene unit in the same column is connected in series through the electrode line of the flexible pressure sensitive sensing lower electrode to form another group of graphene unit groups. There are N+N groups in total. Each group of graphene unit groups has one electrode line. The electrode signals are concentrated and output through the electrode line. There are N+N electrode lines in total. The row and column scanning mode is adopted to collect the pressure sensing signals of the flexible pressure sensitive sensing array. Circular insulating isolation blocks of the flexible pressure sensitive sensing array are arranged at the intersections between the electrode lines of the flexible pressure sensitive sensing upper electrode layer and the electrode lines of the flexible pressure sensitive sensing lower electrode layer for insulation and isolation.

[0016] Each graphene unit and flexible pressure sensitive sensing lower electrode layer electrode line connection after the formation of a pressure sensing unit, a plurality of pressure sensing unit on the surface of the flexible pressure sensitive sensing array substrate layer arranged to form a uniform spacing N rows × N column array structure.

[0017] The PDMS upper packaging layer with pyramid boss and the PDMS lower packaging layer with pyramid groove each include the same N rows × N column uniform array arranged unit cell, which is aligned with the array arrangement of the ultrasonic sensing unit in the ultrasonic sensing array and the pressure sensing unit in the flexible pressure sensitive sensing array; in each unit cell, the bottom surface of the PDMS upper packaging layer with pyramid boss has a plurality of pyramid bosses, the bottom surface of the PDMS lower packaging layer with pyramid groove has a plurality of pyramid grooves, the pyramid bosses and the pyramid grooves are arranged one by one and nested with each other, and the pyramid bosses and the pyramid grooves are located at the position without the ultrasonic sensing unit, but at the position of the pressure sensing unit, and the pyramid boss is pressed to embed only the ultrasonic sensing array substrate layer, the flexible pressure sensitive sensing array, and the flexible pressure sensitive sensing array substrate layer into the pyramid groove.

[0018] The PVDF sensitive layer unit for transmitting and receiving ultrasonic waves adopts a concentric circle structure distribution and is divided into three parts of an inner circle, an inner ring and an outer ring. When an alternating current is applied to the PVDF sensitive layer unit for transmitting and receiving ultrasonic waves, the three parts of the inner circle, the inner ring and the outer ring generate ultrasonic waves of different frequencies.

[0019] In each unit cell, the PVDF sensitive unit is composed of a circular region, a pair of small arc regions and a pair of large arc regions arranged concentrically, the circular region is located at the center, the pair of small arc regions and the pair of large arc regions are each composed of two arc regions located on the same circumference and symmetrically on both sides of the circular region, the circumference on which the pair of small arc regions is located is smaller in diameter than the circumference on which the pair of large arc regions is located, the ultrasonic sensing upper electrode unit and the ultrasonic sensing lower electrode unit are each composed of an electrode pattern in the shape of 8, the electrode pattern passes through the pair of small arc regions and the pair of large arc regions of the PVDF sensitive unit, the electrode pattern is provided with a bridge region in the middle, and the bridge region passes through the circular region; meanwhile, four pyramid bosses or pyramid grooves arranged in the corners of a prism are provided, wherein the two pyramid bosses / pyramid grooves located at the symmetric two corners of the prism are respectively located at the vacancies on the circumference on which the pair of small arc regions of the PVDF sensitive unit is located.

[0020] The coverage of the electrode area in the upper and lower electrode layers of the ultrasonic sensing array reaches 2 / 3 of the area of ​​the sensitive material in the PVDF sensitive layer, which can improve the efficiency of the PVDF sensitive layer in converting electrical energy into mechanical energy and increase the transmission sensitivity of ultrasonic waves.

[0021] The PVDF sensitive layer is made of PVDF material mixed with ZnO.

[0022] The graphene pattern array is made of silicone rubber mixed with graphene nanosheets.

[0023] The ultrasonic sensing array upper electrode layer and ultrasonic sensing array lower electrode layer in the ultrasonic sensing array, and the flexible pressure sensing array lower electrode layer and flexible pressure sensing array upper electrode layer in the flexible pressure sensing array are all made of silver nano-conductive particles and silicone rubber composite.

[0024] This invention employs ultrasonic and piezoresistive principles to achieve contact and non-contact sensing functions, respectively. The ultrasonic principle offers advantages such as long detection distance, high accuracy, the ability to detect any object, and minimal environmental influence, enabling non-contact detection of information surrounding or within an object. The piezoresistive principle, with its simple structure, ease of manufacturing, and high sensitivity, is used for contact detection of information on the object's surface. Spatially, a pyramid interlocking positioning structure is used, which improves the deformation of the flexible pressure-sensitive array while staggering it with the ultrasonic sensing array, reducing interference between the ultrasonic and pressure-sensing signals.

[0025] The PVDF sensitive layer unit of this invention adopts a concentric circle regional structure distribution, which reduces the energy dissipation of the PVDF sensitive layer unit that transmits and receives ultrasonic waves, and can perform ultrasonic multi-frequency operation, thereby improving the sensitivity of ultrasonic sensing function and the accuracy of ultrasonic imaging.

[0026] II. A method for fabricating a flexible composite sensor array with ultrasonic and pressure sensing functions:

[0027] Includes the following steps

[0028] 1) Making molds and screen printing plates

[0029] The mold of the upper PDMS packaging layer with pyramid bosses and the lower PDMS packaging layer with pyramid grooves is manufactured by using a light-cured 3D printer; the screen printing plate of the upper electrode layer of the ultrasonic sensing array with patterned grooves, the screen printing plate of the lower electrode layer of the ultrasonic sensing array, the screen printing plate of the PVDF sensitive layer for transmitting and receiving ultrasonic waves, the screen printing plate of the circular insulating isolation block of the ultrasonic sensing array, the screen printing plate of the lower electrode layer of the flexible pressure-sensitive sensing array, the screen printing plate of the graphene pattern array, the screen printing plate of the circular insulating isolation block of the flexible pressure-sensitive sensing array, and the screen printing plate of the upper electrode layer of the flexible pressure-sensitive sensing array are manufactured by using a laser processing method;

[0030] 2) Making packaging layers and substrate layers

[0031] After the PDMS liquid material is mixed with a curing agent and stirred in a planetary mixer, the PDMS composite material is obtained after defoaming treatment, the PDMS composite material is injected into the mold of the upper PDMS packaging layer with pyramid bosses and the lower PDMS packaging layer with pyramid grooves prepared in advance, and then placed in a vacuum drying box, and left to stand at room temperature for defoaming, taken out and cured on a heating table, and then peeled off from the mold to obtain the upper PDMS packaging layer with pyramid bosses and the lower PDMS packaging layer with pyramid grooves; the PDMS composite material configured and defoamed is spin-coated on a glass substrate, and the flexible film is obtained after curing on a heating table, and the ultrasonic sensing array substrate layer and the flexible pressure-sensitive sensing array substrate layer are obtained by using a laser cutting machine;

[0032] 3) Configuring the sensitive layer and electrode layer materials in the ultrasonic sensing array and the flexible pressure-sensitive sensing array

[0033] After the PVDF powder is dissolved in a dimethylformamide solution, ultrasonic mixing and dispersion are performed with ZnO and tetrahydrofuran, a mixed solution with uniform texture is formed, the mixed solution is stirred on a heating table to promote the volatilization of tetrahydrofuran to obtain a viscous PVDF composite material, and the viscous PVDF composite material is placed in a polarization device for polarization, so that the viscous PVDF composite material exhibits piezoelectricity, and then used to make the PVDF sensitive layer for transmitting and receiving ultrasonic waves; the graphene nanosheet, silicone rubber and tetrahydrofuran are mixed and stirred in a planetary mixer to obtain a viscous graphene composite material, which is used to make a graphene pattern array; the silver nanosheet, silicone rubber, polyvinylpyrrolidone and tetrahydrofuran are mixed and ultrasonically dispersed, and then heated and stirred on a heating table to volatilize the tetrahydrofuran solution to obtain a viscous silver nanosheet composite material;

[0034] 4) Making an ultrasonic sensing array

[0035] The screen printing plate of the electrode layer under the ultrasonic sensing array, the screen printing plate of the PVDF sensitive layer for transmitting and receiving ultrasonic waves, the screen printing plate of the circular insulating spacer of the ultrasonic sensing array and the screen printing plate of the electrode layer on the ultrasonic sensing array are aligned one by one and closely attached to the base layer of the ultrasonic sensing array in sequence, and the silver nanosheet composite, the PVDF composite, the PDMS composite and the silver nanosheet composite are scraped into the patterned grooves of the screen printing plates one by one, after each screen printing plate is peeled off, the next layer is scraped after being cured on the heating table.

[0036] 5) Flexible pressure sensitive sensing array

[0037] The screen printing plate of the graphene pattern array, the screen printing plate of the electrode layer under the flexible pressure sensitive sensing array, the screen printing plate of the circular insulating spacer of the flexible pressure sensitive sensing array and the screen printing plate of the electrode layer on the flexible pressure sensitive sensing array are aligned one by one and closely attached to the base layer of the flexible pressure sensitive sensing array in sequence, and the silver nanosheet composite, the graphene composite, the PDMS composite and the silver nanosheet composite are scraped into the patterned grooves of the screen printing plates one by one, after each screen printing plate is peeled off, the next layer is scraped after being cured on the heating table.

[0038] 6) Flexible composite sensing array

[0039] The connecting surfaces between the PDMS upper packaging layer with pyramid bosses, the ultrasonic sensing array, the base layer of the ultrasonic sensing array, the flexible pressure sensitive sensing array, the base layer of the flexible pressure sensitive sensing array and the PDMS lower packaging layer with pyramid grooves are subjected to plasma activation treatment, and then aligned and attached under an optical microscope, and the packaging is completed after compaction and heating.

[0040] The present application has the following advantages:

[0041] The present application adopts ultrasonic principle and piezoresistance principle to realize contact and non-contact sensing functions respectively, wherein the ultrasonic principle has the advantages of long detection distance, high detection precision and the ability to detect any object; the piezoresistance principle has simple structure, convenient manufacturing and high sensitivity. In terms of spatial distribution, the pyramid interlocking positioning structure is adopted to improve the deformation of the flexible pressure sensitive sensing array, and the ultrasonic sensing array is arranged in a staggered manner to reduce the interference between the ultrasonic sensing and pressure sensing detection signals. The PVDF sensitive layer unit for transmitting and receiving ultrasonic waves adopts a concentric circle structure, which reduces the energy dissipation of the PVDF sensitive layer unit for transmitting and receiving ultrasonic waves, and can work at multiple frequencies, improving the sensitivity of ultrasonic sensing function and the accuracy of ultrasonic imaging. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is an exploded schematic view of the layered structure of the flexible composite sensing array of the present application;

[0043] Figure 2 is the top view of the PDMS upper encapsulation layer with pyramid protrusions;

[0044] Figure 3 is the top view of the PDMS lower encapsulation layer with pyramid recesses;

[0045] Figure 4 is the schematic diagram of the principle of the double-layer pyramid protrusion and recess interlocking positioning structure;

[0046] Figure 5 is the top view of the ultrasonic sensing array electrode layout;

[0047] Figure 6 (a) of is the schematic diagram of the screen printing plate of the upper electrode layer of the ultrasonic sensing array;

[0048] Figure 6 (b) of is the schematic diagram of the screen printing plate of the lower electrode layer of the ultrasonic sensing array;

[0049] Figure 6 (c) of is the schematic diagram of the screen printing plate of the PVDF sensitive layer for transmitting and receiving ultrasonic waves;

[0050] Figure 6 (d) of is the schematic diagram of the screen printing plate of the circular insulating isolation block of the ultrasonic sensing array;

[0051] Figure 6 In, the black area is blank, and the white area is the product to be made.

[0052] Figure 7 is the top view of the flexible pressure sensing array electrode layout;

[0053] Figure 8 (a) of is the schematic diagram of the screen printing plate of the lower electrode layer of the flexible pressure sensing array;

[0054] Figure 8 (b) of is the schematic diagram of the screen printing plate of the graphene pattern array;

[0055] Figure 8 (c) of is the schematic diagram of the screen printing plate of the circular insulating isolation block of the flexible pressure sensing array;

[0056] Figure 8 (d) of is the schematic diagram of the screen printing plate of the upper electrode layer of the flexible pressure sensing array;

[0057] Figure 8 In, the black area is blank, and the white area is the product to be made.

[0058] Figure 9is a structural schematic diagram of a PDMS upper encapsulation layer mold with pyramid protrusions;

[0059] Figure 10 is a structural schematic diagram of a PDMS lower encapsulation layer mold with pyramid recesses;

[0060] In the figure: 1, PDMS upper encapsulation layer with pyramid protrusions, 2, ultrasonic sensing array, 3, ultrasonic sensing array substrate layer, 4, flexible pressure sensitive sensing array, 5, flexible pressure sensitive sensing array substrate layer, 6, PDMS lower encapsulation layer with pyramid recesses, 7, ultrasonic sensing array upper electrode layer, 8, PVDF sensing layer for transmitting and receiving ultrasonic waves, 9, circular insulating isolation block of ultrasonic sensing array, 10, ultrasonic sensing array lower electrode layer, 11, graphene pattern array, 12, flexible pressure sensitive sensing array lower electrode layer, 13, circular insulating isolation block of flexible pressure sensitive sensing array, 14, flexible pressure sensitive sensing array upper electrode layer, 15, ultrasonic sensing unit, 16, ultrasonic sensing array upper electrode layer screen printing plate, 17, ultrasonic sensing array lower electrode layer screen printing plate, 18, PVDF sensing layer screen printing plate for transmitting and receiving ultrasonic waves, 19, circular insulating isolation block screen printing plate of ultrasonic sensing array, 20, pressure sensing unit, 21, flexible pressure sensitive sensing array lower electrode layer screen printing plate, 22, graphene pattern array screen printing plate, 23, circular insulating isolation block screen printing plate of flexible pressure sensitive sensing array, 24, flexible pressure sensitive sensing array upper electrode layer screen printing plate, 25, PDMS upper encapsulation layer mold with pyramid protrusions, 26, PDMS lower encapsulation layer mold with pyramid recesses, 27, PVDF sensing layer unit for transmitting and receiving ultrasonic waves. DETAILED DESCRIPTION

[0061] The application will be further described below in conjunction with the drawings and examples.

[0062] As Figure 1As shown, the flexible composite sensing array includes, from top to bottom, a PDMS upper packaging layer 1 with pyramid bosses, an ultrasonic sensing array 2, an ultrasonic sensing array substrate layer 3, a flexible pressure-sensitive sensing array 4, a flexible pressure-sensitive sensing array substrate layer 5, and a PDMS lower packaging layer 6 with pyramid grooves; under the action of alternating current, the ultrasonic sensing array 2 emits ultrasonic waves using the inverse piezoelectric effect, and after being reflected by external objects, the ultrasonic waves are received by the ultrasonic sensing array 2 and output voltage signals; when external pressure is applied to the flexible composite sensing array, the external pressure is transmitted to the flexible pressure-sensitive sensing array 4 through the PDMS upper packaging layer 1 with pyramid bosses and the ultrasonic sensing array substrate layer 3, causing the flexible pressure-sensitive sensing array 4 to generate and output pressure signals; the PDMS upper packaging layer 1 with pyramid bosses and the PDMS lower packaging layer 6 with pyramid grooves form an interlocking positioning structure, which reduces interference to the ultrasonic sensing array 2 under pressure sensing, thereby achieving accurate detection of the ultrasonic sensing array 2 and the flexible pressure-sensitive sensing array 4 at the same time.

[0063] As shown in FIG. 1, the flexible composite sensing array includes, from top to bottom, a PDMS upper packaging layer 1 with pyramid bosses, an ultrasonic sensing array 2, an ultrasonic sensing array substrate layer 3, a flexible pressure-sensitive sensing array 4, a flexible pressure-sensitive sensing array substrate layer 5, and a PDMS lower packaging layer 6 with pyramid grooves; under the action of alternating current, the ultrasonic sensing array 2 emits ultrasonic waves using the inverse piezoelectric effect, and after being reflected by external objects, the ultrasonic waves are received by the ultrasonic sensing array 2 and output voltage signals; when external pressure is applied to the flexible composite sensing array, the external pressure is transmitted to the flexible pressure-sensitive sensing array 4 through the PDMS upper packaging layer 1 with pyramid bosses and the ultrasonic sensing array substrate layer 3, causing the flexible pressure-sensitive sensing array 4 to generate and output pressure signals; the PDMS upper packaging layer 1 with pyramid bosses and the PDMS lower packaging layer 6 with pyramid grooves form an interlocking positioning structure, which reduces interference to the ultrasonic sensing array 2 under pressure sensing, thereby achieving accurate detection of the ultrasonic sensing array 2 and the flexible pressure-sensitive sensing array 4 at the same time. Figure 1 Figure 5 As shown in FIG. 2, the ultrasonic sensing array 2 is closely attached to the upper surface of the ultrasonic sensing array substrate layer 3, and the ultrasonic sensing array 2 is composed of an ultrasonic sensing array upper electrode layer 7, a PVDF sensing layer 8 for transmitting and receiving ultrasonic waves, a circular insulating spacer 9 of the ultrasonic sensing array, and an ultrasonic sensing array lower electrode layer 10;

[0064] The ultrasonic sensing array upper electrode layer 7 is composed of N rows × N columns of ultrasonic sensing upper electrode units, the PVDF sensing layer 8 for transmitting and receiving ultrasonic waves is composed of N rows × N columns of PVDF sensing units, and the ultrasonic sensing array lower electrode layer 10 is composed of N rows × N columns of ultrasonic sensing lower electrode units. Each ultrasonic sensing upper electrode unit, one PVDF sensing unit, and one ultrasonic sensing lower electrode unit are sequentially laminated together from top to bottom to form an ultrasonic sensing unit 15, and a plurality of ultrasonic sensing units 15 are arranged on the upper surface of the ultrasonic sensing array substrate layer 3 to form a uniform and spaced N rows × N columns array structure.

[0065] ​Each ultrasonic sensing upper electrode unit has an electrode wire led out, totaling N×N electrode wires. N×N ultrasonic sensing lower electrode units are connected in series, each leading out a single electrode wire. The electrode wires of each ultrasonic sensing upper electrode unit and lower electrode unit are connected to an external circuit to collect the ultrasonic sensing signals fed back from each ultrasonic sensing unit 15. Circular insulating isolation blocks 9 of the ultrasonic sensing array 2 are placed at the intersections of the electrode wires led out by the ultrasonic sensing upper and lower electrode units for insulation. The ultrasonic sensing array upper electrode layer 7, the ultrasonic sensing array lower electrode layer 10, and the PVDF sensitive layer 8 that emits and receives ultrasonic waves form a closed loop. Alternating current is applied between the electrode wires of the ultrasonic sensing array upper electrode layer 7 and the ultrasonic sensing array lower electrode layer 10. Through the inverse piezoelectric effect, the PVDF sensitive layer 8 that emits and receives ultrasonic waves converts electrical energy into mechanical vibration, thereby exciting ultrasonic waves.

[0066] Specifically, an alternating current is applied between the upper and lower ultrasonic sensing electrode units within an ultrasonic sensing unit 15. The upper and lower ultrasonic sensing electrode units form a capacitor. The alternating current applied to the capacitor excites the PVDF sensing unit, converting electrical energy into mechanical energy to generate vibration and emit ultrasonic waves. The ultrasonic waves are reflected by external objects with different acoustic impedances and return to the PVDF sensing unit, causing the vibration of the PVDF sensing unit to weaken or increase. The result of weakening or increasing is obtained based on the vibration of the PVDF sensing unit, thereby obtaining the ultrasonic sensing signal of the external object.

[0067] Normally, downward pressure stretches and deforms the ultrasonic sensing structure, resulting in reduced detection accuracy. The pyramid interlocking structure can maintain the ultrasonic intensity and avoid the problem of interference between the two layers when they are stretched.

[0068] Different ultrasonic sensing units 15 may operate at different frequencies, but they can be the same. Preferably, they have different frequencies.

[0069] like Figure 1 and Figure 7 As shown, the flexible pressure-sensitive array 4 is tightly attached to the upper surface of the flexible pressure-sensitive array substrate layer 5. The flexible pressure-sensitive array 4 is composed of a graphene pattern array 11, a flexible pressure-sensitive array lower electrode layer 12, a circular insulating isolation block 13 of the flexible pressure-sensitive array, and a flexible pressure-sensitive array upper electrode layer 14.

[0070] The graphene pattern array 11 is composed of N rows × N columns of graphene units, each graphene unit has two output pins, one output pin of N graphene units in the same row is connected in series through the electrode line of the flexible pressure-sensitive lower electrode to form a group of graphene unit groups, the other output pin of N graphene units in the same column is connected in series through the electrode line of the flexible pressure-sensitive lower electrode to form a group of graphene unit groups, a total of N+N groups, each group of graphene unit groups is connected to a root electrode line, and the electrode signal is output through the root electrode line, a total of N+N root electrode lines, the pressure sensing signals of the flexible pressure-sensitive array 4 are collected in row-column scanning mode, and the pressure signals generated by the flexible pressure-sensitive array 4 are output.

[0071] Each graphene unit and the flexible pressure-sensitive lower electrode layer electrode line are connected to form a pressure sensing unit 20, and a plurality of pressure sensing units 20 are arranged on the surface of the flexible pressure-sensitive array substrate layer 5 to form a uniform and spaced N rows × N columns array structure.

[0072] The flexible pressure-sensitive upper electrode is not connected to the graphene unit, and the flexible pressure-sensitive upper electrode is only the part of the flexible pressure-sensitive lower electrode that is disconnected, and the role is to add an insulating isolation block to prevent signal crosstalk at the intersection of the electrode lines. In the pressure sensing layer, there is only one electrode layer, if there is no intersection in the electrode line pattern design, the electrode layer is only the flexible pressure-sensitive lower electrode layer, which is different from the ultrasonic sensing layer. The upper and lower electrodes of the ultrasonic sensing layer are used to add alternating current to generate ultrasonic waves, and the pressure sensing part only needs to connect the graphene unit and the electrode line to form a closed loop for measurement. As shown in FIG. 6, 3 rows and 3 columns are connected to 6 electrode lines, of which the first, third and fifth are electrode lines connected by the same column of graphene unit groups, and the second, fourth and sixth are electrode lines connected by the same row of graphene unit groups. Figure 7

[0073] The PDMS upper packaging layer 1 with a pyramid boss, the ultrasonic sensing array substrate layer 3, the flexible pressure-sensitive array substrate layer 5, and the PDMS lower packaging layer 6 with a pyramid groove serve as structural support, the ultrasonic sensing array upper electrode layer 7, the ultrasonic sensing array lower electrode layer 10, and the flexible pressure-sensitive array lower electrode layer 12 are connected to the peripheral circuit, the ultrasonic sensing signal fed back by each ultrasonic sensing unit 15 is collected through each electrode line of the ultrasonic sensing array upper electrode layer 7 and the electrode line of the ultrasonic sensing array lower electrode layer 10 respectively, and the pressure sensing signals of the flexible pressure-sensitive array 4 are collected in row-column scanning mode.

[0074] As shown in FIG. 6, 3 rows and 3 columns are connected to 6 electrode lines, of which the first, third and fifth are electrode lines connected by the same column of graphene unit groups, and the second, fourth and sixth are electrode lines connected by the same row of graphene unit groups. Figure 2 and Figure 3 and​Figure 4 As shown, the PDMS upper packaging layer 1 with pyramid bosses and the PDMS lower packaging layer 6 with pyramid grooves each have the same N rows x N columns uniform array arrangement of unit cells, which is aligned with the array arrangement of the ultrasonic sensing units 15 in the ultrasonic sensing array 2 and the pressure sensing units 20 in the flexible pressure sensitive sensing array 4. In each unit cell, the bottom surface of the PDMS upper packaging layer 1 with pyramid bosses has a plurality of pyramid bosses, and the bottom surface of the PDMS lower packaging layer 6 with pyramid bosses has a plurality of pyramid grooves. The pyramid bosses and the pyramid grooves are arranged one-to-one and nested with each other, that is, one pyramid boss is located directly above one corresponding pyramid groove. The pyramid bosses and the pyramid grooves are located at positions where no ultrasonic sensing units 15 are arranged, but at positions where pressure sensing units 20 are arranged. Pressing the pyramid bosses causes only the ultrasonic sensing array base layer 3, the flexible pressure sensitive sensing array 4, and the flexible pressure sensitive sensing array base layer 5 to be pressed and embedded into the pyramid grooves, thereby forming a pyramid interlocking positioning structure.

[0075] After one pyramid boss is pressed into one pyramid groove, the single pressure sensing unit 20 and the ultrasonic sensing array base layer 3 and the flexible pressure sensitive sensing array base layer 5 above and below it between the pyramid boss and the pyramid groove are all deformed by pressing. The pressure sensing unit 20 produces a large deformation, causing the resistance of the graphene pattern array to change more and the detected signal to be stronger, and the sensitivity of the pressure sensing to be higher.

[0076] If the ultrasonic sensing unit 15 deforms, it will produce a positive piezoelectric effect, converting mechanical energy into electrical energy, affecting the output voltage signal of the ultrasonic sensing array 2, and thus greatly reducing the detection accuracy of the ultrasonic sensing unit 15. The pyramid interlocking positioning structure described above reduces the influence of the deformation caused by pressing on the ultrasonic sensing unit 15 and reduces the interference of the ultrasonic sensing unit 15,

[0077] At the same time, the pyramid interlocking positioning structure allows the electrodes inside the flexible pressure sensitive sensing array 4 to not deviate from each other in the plane during the pressing process, as shown in Figure 4

[0078] The transmission and reception of ultrasonic waves in the PVDF sensitive layer unit 27 in the transmission and reception of ultrasonic waves in the PVDF sensitive layer 8 adopts a concentric circle structure, which is divided into three parts: an inner circle, an inner ring, and an outer ring. When an alternating current is applied to the transmission and reception of ultrasonic waves in the PVDF sensitive layer unit 27, the inner circle, the inner ring, and the outer ring generate ultrasonic waves of different frequencies, achieving a multi-frequency state of the ultrasonic waves and improving the ultrasonic imaging accuracy.

[0079] ​The PVDF sensitive layer units 27 for transmitting and receiving ultrasonic waves are arranged in a concentric circle structure to reduce the heat flux of the PVDF sensitive layer units 27 for transmitting and receiving ultrasonic waves and reduce the energy dissipation of the PVDF sensitive layer units 27 for transmitting and receiving ultrasonic waves, so as to improve the sensitivity and accuracy of the ultrasonic sensing function.

[0080] As shown in Figure 6 each unit cell, the PVDF sensitive unit is arranged in a concentric circle, which is composed of a circular region, a pair of small arc regions and a pair of large arc regions. The circular region is located at the center, and the pair of small arc regions and the pair of large arc regions are each composed of two arc regions located on the same circle and symmetrically arranged on both sides of the circular region. The pair of small arc regions is arranged on a smaller circle than the pair of large arc regions. The ultrasonic sensing upper electrode unit and the ultrasonic sensing lower electrode unit are each composed of an electrode pattern in the shape of an 8. The electrode pattern passes through the pair of small arc regions and the pair of large arc regions of the PVDF sensitive unit. The electrode pattern is provided with a bridge region in the middle, and the bridge region passes through the circular region.

[0081] As shown in Figure 9 and Figure 10 The PDMS upper packaging layer with pyramid bosses and the PDMS lower packaging layer with pyramid grooves are provided with four pyramid bosses or pyramid grooves arranged at the four corners of a prism, and two pyramid bosses / pyramid grooves located at the symmetric corners of the prism are arranged at the vacancies on the circle where the pair of small arc regions of the PVDF sensitive unit are located.

[0082] This makes the pyramid boss or groove structure in the upper and lower unit cells interlock and be arranged in a staggered manner with the ultrasonic sensing array 2, and arranged in a symmetrical manner with the flexible pressure sensitive sensing array 4. When external pressure acts on the flexible composite sensing array, the pressure is transmitted to the graphene pattern array 11 through the PDMS upper packaging layer 1 with pyramid bosses and the ultrasonic sensing array base layer 3, causing the graphene pattern array 11 to stretch and deform, changing the electrical conductivity inside the graphene pattern array 11, and thus changing the electrical resistance of the graphene pattern array 11. As a result, the pressure signal is converted into a resistance change signal output by the electrode lines of the flexible pressure sensitive sensing array lower electrode layer 12. At the same time, due to the staggered arrangement of the pyramid structure and the ultrasonic sensing array 2, the positive piezoelectric effect of the pressure on the ultrasonic sensing array 2 is greatly reduced.

[0083] The mechanical vibration of the ultrasonic wave generates heat, and thus through the above-mentioned block shape design of the PVDF sensitive unit, the energy loss can be reduced, the heat flux in each block region can be reduced, and the sensitivity and imaging accuracy of the ultrasonic sensing function can be improved.

[0084] The emitted ultrasonic waves of the PVDF sensitive layer have no directivity, and the same ultrasonic waves are generated on the front and back surfaces. The acoustic impedance of the ultrasonic sensing array substrate layer, the flexible pressure sensitive sensing array, and the flexible pressure sensitive sensing array substrate layer is much higher than that of air. The ultrasonic sensing array substrate layer 3, the flexible pressure sensitive sensing array 4, and the flexible pressure sensitive sensing array substrate layer 5 act as a backing of the ultrasonic sensing array 2, absorb the reverse ultrasonic waves generated by the ultrasonic sensing array 2, and reduce the influence of artifacts in ultrasonic imaging.

[0085] The ultrasonic sensing is specifically to generate ultrasonic waves by using the inverse piezoelectric effect of the PVDF material, and to detect the information around or inside an object in a non-contact manner. The pressure sensing is specifically to change the internal electrical conductivity and then cause the change of the resistance when the pressure sensitive material is pulled, and to detect the surface information of an object in a contact manner.

[0086] The coverage rate of the electrode area in the upper electrode layer 7 and the lower electrode layer 10 of the ultrasonic sensing array reaches 2 / 3 of the sensitive material area in the PVDF sensitive layer 8, which can improve the efficiency of the PVDF sensitive layer 8 in converting electrical energy into mechanical energy, and increase the emission sensitivity of ultrasonic waves.

[0087] In the flexible composite sensing array, the PDMS upper packaging layer 1 with a pyramid boss, the ultrasonic sensing array substrate layer 3, the flexible pressure sensitive sensing array substrate layer 5, and the PDMS lower packaging layer 6 with a pyramid groove are made of a PDMS composite material.

[0088] The PVDF sensitive layer 8 is made of a mixture of PVDF material and ZnO. The addition of ZnO greatly increases the piezoelectric properties of the PVDF material.

[0089] The graphene pattern array 11 is made of a mixture of silicone rubber and graphene nanosheets.

[0090] The upper electrode layer 7 of the ultrasonic sensing array 2, the lower electrode layer 10 of the ultrasonic sensing array 2, the lower electrode layer 12 of the flexible pressure sensitive sensing array 4 in the flexible pressure sensitive sensing array 4, and the upper electrode layer 14 of the flexible pressure sensitive sensing array 4 are all made of a composite of silver nano-conductive particles and silicone rubber, and polyvinylpyrrolidone is added as a dispersant during the manufacturing process.

[0091] The circular insulating isolation block 9 in the ultrasonic sensing array 2 and the circular insulating isolation block 13 in the flexible pressure sensitive sensing array 4 are both made of a PDMS composite material.

[0092] As Figure 1 and Figure 5As shown, the ultrasonic sensing array 2 is composed of an ultrasonic sensing array upper electrode layer 7, a PVDF sensitive layer 8 for transmitting and receiving ultrasonic waves, a circular insulating isolation block 9 of the ultrasonic sensing array, and an ultrasonic sensing array lower electrode layer 10, and is closely attached to the ultrasonic sensing array substrate layer 3, and the thickness of each layer is 100 um; the coverage rate of the electrode area in the ultrasonic sensing array upper electrode layer 7 and the ultrasonic sensing array lower electrode layer 10 reaches 2 / 3 of the sensitive material area in the PVDF sensitive layer 8 for transmitting and receiving ultrasonic waves; the same specific area of the ultrasonic sensing array upper electrode layer 7, the PVDF sensitive layer 8 for transmitting and receiving ultrasonic waves, and the ultrasonic sensing array lower electrode layer 10 when attached together constitutes an ultrasonic sensing unit 15. The ultrasonic sensing is specifically to generate ultrasonic waves by using the inverse piezoelectric effect of the PVDF material, and to detect the information around or inside the object in a non-contact manner.

[0093] In a specific implementation, the thickness of each layer in the ultrasonic sensing array 2 is 100 um. The coverage rate of the electrode area in the ultrasonic sensing array upper electrode layer 7 and the ultrasonic sensing array lower electrode layer 10 reaches 2 / 3 of the sensitive material area in the PVDF sensitive layer 8 for transmitting and receiving ultrasonic waves.

[0094] A plurality of ultrasonic sensing units 15 are arranged on the upper surface of the ultrasonic sensing array substrate layer 3 to form a uniformly spaced 3-row-by-3-column array structure, and the center distance between adjacent units is 16 mm; each unit in the ultrasonic sensing array upper electrode layer 7 is led out with an electrode line, and there are a total of 9 electrode lines, and the units in the ultrasonic sensing array lower electrode layer 10 are connected in series with each other, and are led out with a total of 1 electrode line; the 10 electrode lines of the upper and lower electrode layers 7 and 10 are arranged side by side, the width of the electrode line is 0.5 mm, and the end-to-end arrangement interval is 0.5 mm; the intersection between the electrode lines of the ultrasonic sensing array upper electrode layer 7 and the ultrasonic sensing array lower electrode layer 10 is provided with the circular insulating isolation block 9 of the ultrasonic sensing array for insulation and isolation, and the diameter of the circular insulating isolation block 9 of the ultrasonic sensing array is 2 mm.

[0095] The PVDF sensitive layer 8 for transmitting and receiving ultrasonic waves includes nine PVDF sensitive layer units 2 for transmitting and receiving ultrasonic waves arranged in a 3x3 uniform array.

[0096] In a specific implementation, the thickness between each layer in the flexible pressure-sensitive sensing array 4 is 100 um; the plurality of pressure sensing units 20 are arranged on the surface of the flexible pressure-sensitive sensing array substrate layer 5 to form a uniformly spaced 3-row x 3-column array structure, and the center distance between adjacent units is 16 mm; each unit in the graphene pattern array 11 has two square pins for connecting with the electrode lines of the flexible pressure-sensitive sensing array lower electrode layer 12, so that the three pressure sensing units 20 in the same row are connected in series to form a group, and the three pressure sensing units 20 in the same column are also connected in series to form a group, a total of 9 groups, each group of pressure sensing units 20 has one electrode line, a total of 9 electrode lines are connected with the peripheral circuit, the electrode line width is 0.5 mm, and the end arrangement interval is 0.5 mm. The pressure sensing signal of the flexible pressure-sensitive sensing array 4 is collected in a row-column scanning mode. The diameter of the circular insulating isolation block 13 of the insulating flexible pressure-sensitive sensing array is 2 mm. The upper electrode of the pressure sensing does not have an electrode line, which is used to add an insulating isolation block, cut off a part of the lower electrode, and then complete the electrode after adding the isolation block.

[0097] The pressure sensing is specifically to use the change of internal electrical conductivity when the pressure-sensitive material is pulled to cause the change of resistance, and to detect the surface information of the object by using the contact method.

[0098] The PDMS upper packaging layer 1 with pyramid bosses and the PDMS lower packaging layer 6 with pyramid grooves include nine 3x3 uniformly arranged unit cells, which are matched with the ultrasonic sensing units 15 and the pressure sensing units 20, and the center distance between adjacent unit cells is 16 mm. The thickness of the PDMS upper packaging layer 1 with pyramid bosses and the PDMS lower packaging layer 6 with pyramid grooves is 1.4 mm, the unit cell is a square groove with a side length of 14 mm and a depth of 1 mm, and the distance between adjacent unit cells is 2 mm; each unit cell has four pyramid boss or groove structures arranged in a prismatic shape, the distance between the pyramid boss or groove structure and the center position of the unit cell is 3 mm and 5.5 mm respectively, the size of the pyramid boss is equal to the size of the pyramid groove, the pyramid boss or groove structure in the up-down co-located unit cell forms interlocking, and is arranged in a staggered manner with the ultrasonic sensing array 2, and is arranged in an up-down co-located manner with the flexible pressure-sensitive sensing array 4.

[0099] When external pressure acts on the flexible composite sensing array, the pressure is transmitted to the graphene pattern array 11 through the PDMS upper encapsulation layer 1 with pyramid bosses and the ultrasonic sensing array base layer 3, causing the graphene pattern array 11 to stretch and deform, changing the conductivity inside the graphene pattern array 11, and in turn changing the resistance of the graphene pattern array 11, resulting in the conversion of the pressure signal into a resistance change signal output by the electrode line of the flexible pressure-sensitive sensing array lower electrode layer 12. At the same time, due to the staggered arrangement of the pyramid structure and the ultrasonic sensing array 2, the positive piezoelectric effect of the pressure on the ultrasonic sensing array 2 is greatly reduced.

[0100] The specific implementation steps of the present application are as follows:

[0101] 1) Making molds and screen printing plates

[0102] The PDMS upper encapsulation layer mold 25 with pyramid bosses and the PDMS lower encapsulation layer mold 26 with pyramid grooves are manufactured using a light-cured 3D printer; the ultrasonic sensing array upper electrode layer screen printing plate 16 with patterned grooves, the ultrasonic sensing array lower electrode layer screen printing plate 17, the PVDF sensitive layer screen printing plate 18 for transmitting and receiving ultrasonic waves, the circular insulating isolation block screen printing plate 19 of the ultrasonic sensing array, the flexible pressure-sensitive sensing array lower electrode layer screen printing plate 21, the graphene pattern array screen printing plate 22, the circular insulating isolation block screen printing plate 23 of the flexible pressure-sensitive sensing array, and the flexible pressure-sensitive sensing array upper electrode layer screen printing plate 24 are manufactured using a laser processing method; after ultrasonic cleaning of the above-mentioned molds and screen printing plates in anhydrous ethanol for 10 minutes, a release agent is uniformly sprayed into the grooves of the molds and screen printing plates, and then they are placed in a vacuum drying box and left to stand at room temperature for 2 hours.

[0103] 2) Making encapsulation layers and base layers

[0104] After mixing the PDMS liquid material with the curing agent in a mass ratio of 10:1 and mixing and stirring in a planetary mixer for 3 minutes, the PDMS composite material is obtained after degassing treatment, and then it is injected into the pre-prepared PDMS upper encapsulation layer mold 25 with pyramid bosses and the PDMS lower encapsulation layer mold 26 with pyramid grooves, and then placed in a vacuum drying box and left to stand at room temperature for degassing. After being taken out, it is cured on a heating table at 90°C for 2 hours, and after complete curing, the PDMS upper encapsulation layer 1 with pyramid bosses and the PDMS lower encapsulation layer 6 with pyramid grooves are obtained by peeling off from the mold. The PDMS composite material configured and degassed is spin-coated on a glass base, and after being cured on a heating table at 90°C for 2 hours, a flexible film is obtained, and the ultrasonic sensing array base layer 3 and the flexible pressure-sensitive sensing array base layer 5 are obtained using a laser cutting machine.

[0105] 3) Configure the sensitive layer and electrode layer materials in the ultrasonic sensing array and flexible pressure-sensitive sensing array.

[0106] PVDF powder was dissolved in dimethylformamide solution, then ultrasonically mixed and dispersed with ZnO and tetrahydrofuran at a mass ratio of 20:1:5 to form a homogeneous mixed solution. The mixed solution was then placed on a heating stage and stirred to promote the volatilization of tetrahydrofuran, resulting in a viscous PVDF composite material. The viscous PVDF composite material was then placed in a polarization device and thermally polarized under a strong electric field, causing the viscous PVDF composite material to exhibit piezoelectricity. This material was then used to fabricate a PVDF sensitive layer that emits and receives ultrasonic waves. Graphene nanosheets were mixed with 30 ml of tetrahydrofuran at 5% of the mass of silicone rubber and ultrasonically dispersed for 30 minutes to obtain a viscous graphene composite material, which was used to fabricate graphene pattern arrays. Silver nanosheets, silicone rubber, and polyvinylpyrrolidone were added to 30 ml of tetrahydrofuran at a mass ratio of 250:100:2.5 and mixed in a planetary mixer for 3 minutes. The mixture was then transferred to a 90°C heating stage and heated and stirred to volatilize the tetrahydrofuran solution, resulting in a viscous silver nanosheet composite material.

[0107] 4) Fabrication of an ultrasonic sensing array

[0108] like Figure 6 As shown, the screen printing plates 17 of the lower electrode layer of the ultrasonic sensing array, 18 of the PVDF sensitive layer that emits and receives ultrasonic waves, 19 of the circular insulating isolation block of the ultrasonic sensing array, and 16 of the upper electrode layer of the ultrasonic sensing array are sequentially aligned and tightly attached to the substrate layer of the ultrasonic sensing array. The silver nanosheet composite material, PVDF composite material, PDMS composite material, and silver nanosheet composite material are respectively scraped into the patterned grooves of the corresponding screen printing plates. After each screen printing plate is peeled off, it is moved to the heating stage for curing before the next layer is scraped.

[0109] 5) Fabrication of a flexible pressure-sensitive array

[0110] like Figure 8 As shown, the graphene pattern array screen printing plate 22, the flexible pressure-sensitive array lower electrode layer screen printing plate 21, the flexible pressure-sensitive array circular insulating isolation block screen printing plate 23, and the flexible pressure-sensitive array upper electrode layer screen printing plate 24 are sequentially aligned and tightly attached to the flexible pressure-sensitive array substrate layer. Then, silver nanosheet composite material, graphene composite material, PDMS composite material, and silver nanosheet composite material are respectively scraped into the patterned grooves of the corresponding screen printing plates. After each screen printing plate is peeled off, it is moved to the heating stage for curing before the next layer is scraped.

[0111] 6) Fabrication of flexible composite sensing array

[0112] The connecting surfaces between the PDMS upper packaging layer 1 with pyramid protrusions, the ultrasonic sensing array 2, the ultrasonic sensing array substrate layer 3, the flexible pressure sensitive sensing array 4, the flexible pressure sensitive sensing array substrate layer 5, the PDMS lower packaging layer 6 with pyramid recesses are subjected to plasma activation treatment, and then aligned and attached under an optical microscope, and packaged after compaction and heating.

[0113] The above specific embodiments are used to explain and illustrate the present application, rather than limiting the present application, and any modifications and changes made to the present application within the spirit and protection scope of the claims of the present application shall fall within the protection scope of the present application.

Claims

1. A flexible composite sensor array with ultrasonic and pressure sensing functions, characterized in that: The flexible composite sensing array includes, from top to bottom, a PDMS upper encapsulation layer (1) with pyramidal protrusions, an ultrasonic sensing array (2), an ultrasonic sensing array base layer (3), a flexible pressure-sensitive sensing array (4), a flexible pressure-sensitive sensing array base layer (5), and a PDMS lower encapsulation layer (6) with pyramidal grooves. Under the action of alternating current, the ultrasonic sensing array (2) emits ultrasonic waves using the inverse piezoelectric effect. After being reflected by an external object, the ultrasonic sensing array (2) receives and outputs a voltage signal. When external pressure is applied to the flexible composite sensing array, the external pressure is transmitted to the flexible pressure-sensitive array (4) through the PDMS upper encapsulation layer (1) with pyramidal protrusions and the ultrasonic sensing array base layer (3), causing the flexible pressure-sensitive array (4) to generate and output a pressure signal. The PDMS upper encapsulation layer (1) with pyramidal protrusions and the PDMS lower encapsulation layer (6) with pyramidal grooves form an interlocking structure. The ultrasonic sensing array (2) is closely attached to the upper surface of the ultrasonic sensing array base layer (3). The ultrasonic sensing array (2) consists of an upper electrode layer (7) of the ultrasonic sensing array, a PVDF sensitive layer (8) that emits and receives ultrasonic waves, a circular insulating isolation block (9) of the ultrasonic sensing array, and a lower electrode layer (10) of the ultrasonic sensing array. The upper electrode layer (7) of the ultrasonic sensing array is composed of ultrasonic sensing upper electrode units arranged in an N-row × N-column array. The PVDF sensitive layer (8) that transmits and receives ultrasonic waves is composed of PVDF sensitive units arranged in an N-row × N-column array. The lower electrode layer (10) of the ultrasonic sensing array is composed of ultrasonic sensing lower electrode units arranged in an N-row × N-column array. Each ultrasonic sensing upper electrode unit, a PVDF sensitive unit, and an ultrasonic sensing lower electrode unit are stacked together from top to bottom to form an ultrasonic sensing unit (15). Multiple ultrasonic sensing units (15) are arranged on the upper surface of the ultrasonic sensing array base layer (3) to form a uniformly spaced N-row × N-column array structure. The PDMS upper encapsulation layer (1) with pyramid protrusions and the PDMS lower encapsulation layer (6) with pyramid grooves both include the same N rows × N columns of uniformly arranged cells, which are consistent with the array arrangement of the ultrasonic sensing unit (15) in the ultrasonic sensing array (2) and the pressure sensing unit (20) in the flexible pressure sensing array (4). In each cell, the bottom surface of the PDMS upper encapsulation layer (1) with pyramid protrusions has multiple pyramid protrusions, and the bottom surface of the PDMS lower encapsulation layer (6) with pyramid grooves has multiple pyramid grooves. The pyramid protrusions and pyramid grooves are arranged in a one-to-one correspondence and nested with each other. The pyramid protrusions and pyramid grooves are located at the location where there is no ultrasonic sensing unit (15), but at the location of the pressure sensing unit (20). Pressing down the pyramid protrusions makes only the ultrasonic sensing array base layer (3), the flexible pressure sensing array (4), and the flexible pressure sensing array base layer (5) be pressed into the pyramid grooves. The PVDF sensitive layer unit (27) that transmits and receives ultrasonic waves in the PVDF sensitive layer (8) that transmits and receives ultrasonic waves adopts a concentric circle structure and is divided into three parts: inner circle, inner ring and outer ring. When AC power is applied to the PVDF sensitive layer unit (27) that transmits and receives ultrasonic waves, the three parts of the inner circle, inner ring and outer ring generate ultrasonic waves of different frequencies. Each cell contains a PVDF sensing unit consisting of a concentric circular area, a pair of small arc-shaped areas, and a pair of large arc-shaped areas. The circular area is located in the center. Each of the small and large arc-shaped areas is composed of two arc-shaped areas located on the same circumference and symmetrically positioned on either side of the circular area. The diameter of the circumference of the pair of small arc-shaped areas is smaller than the diameter of the circumference of the pair of large arc-shaped areas. The ultrasonic sensing upper electrode unit and the ultrasonic sensing lower electrode unit both have figure-eight-shaped electrode patterns. The electrode patterns pass through the pair of small and large arc-shaped areas of the PVDF sensing unit. A bridging area is set in the middle of the electrode patterns, which passes through the circular area. At the same time, four pyramid protrusions or pyramid recesses are arranged at the four corners of the rhombus. The two pyramid protrusions / pyramid recesses located at the two symmetrical corners of the rhombus are respectively located in the gaps on the circumference of the pair of small arc-shaped areas of the PVDF sensing unit. The coverage of the electrode area in the upper electrode layer (7) and lower electrode layer (10) of the ultrasonic sensing array reaches 2 / 3 of the area of ​​the sensitive material in the PVDF sensitive layer (8); The PVDF sensitive layer (8) is made of PVDF material mixed with ZnO.

2. The flexible composite sensor array with ultrasonic and pressure sensing functions according to claim 1, characterized in that: Each ultrasonic sensing upper electrode unit leads out an electrode line, totaling N×N electrode lines. N×N ultrasonic sensing lower electrode units are connected in series and lead out a single electrode line. The electrode lines of each ultrasonic sensing upper electrode unit and the ultrasonic sensing lower electrode unit are connected to the peripheral circuit to collect the ultrasonic sensing signals fed back by each ultrasonic sensing unit (15). A circular insulating block (9) is set at the intersection of the electrode lines led out by the ultrasonic sensing upper electrode unit and the ultrasonic sensing lower electrode unit for insulation and isolation. The ultrasonic sensing array upper electrode layer (7), the ultrasonic sensing array lower electrode layer (10), and the PVDF sensitive layer (8) that emits and receives ultrasonic waves form a closed loop. Alternating current is applied between the electrode lines of the ultrasonic sensing array upper electrode layer (7) and the ultrasonic sensing array lower electrode layer (10). Through the inverse piezoelectric effect, the PVDF sensitive layer (8) that emits and receives ultrasonic waves converts electrical energy into mechanical vibration, thereby exciting ultrasonic waves.

3. The flexible composite sensor array with ultrasonic and pressure sensing functions according to claim 1, characterized in that: The flexible pressure sensing array (4) is closely attached to the upper surface of the flexible pressure sensing array substrate layer (5). The flexible pressure sensing array (4) is composed of a graphene pattern array (11), a flexible pressure sensing array lower electrode layer (12), a circular insulating isolation block (13) of the flexible pressure sensing array, and a flexible pressure sensing array upper electrode layer (14). The graphene pattern array (11) is composed of N rows × N columns of graphene units. Each graphene unit has two output pins. One output pin of N graphene units in the same row is connected in series through the electrode line of the flexible pressure-sensitive lower electrode to form a group of graphene units. The other output pin of N graphene units in the same column is connected in series through the electrode line of the flexible pressure-sensitive lower electrode to form a group of graphene units. There are a total of N+N groups. Each group of graphene units is connected by an electrode line to concentrate the electrode signal and output it through this electrode line. There are a total of N+N electrode lines. The pressure sensing signal of the flexible pressure-sensitive array (4) is collected by row and column scanning. A circular insulating block (13) of the flexible pressure-sensitive array is set at the intersection between the electrode line of the upper electrode layer (14) of the flexible pressure-sensitive array and the electrode line of the lower electrode layer (12) of the flexible pressure-sensitive array for insulation and isolation. Each graphene unit and the electrode wire of the flexible pressure-sensitive lower electrode layer are connected to form a pressure sensing unit (20). Multiple pressure sensing units (20) are arranged on the upper surface of the flexible pressure-sensitive array substrate layer (5) to form an array structure with uniform spacing of N rows × N columns.

4. A flexible composite sensor array with ultrasonic and pressure sensing functions according to claim 3, characterized in that: The graphene pattern array (11) is made of silicone rubber mixed with graphene nanosheets.

5. A flexible composite sensor array with ultrasonic and pressure sensing functions according to claim 1, characterized in that: The ultrasonic sensing array upper electrode layer (7) and ultrasonic sensing array lower electrode layer (10) in the ultrasonic sensing array (2) and the flexible pressure sensing array lower electrode layer (12) and flexible pressure sensing array upper electrode layer (14) in the flexible pressure sensing array (4) are all made of silver nano-conductive particles and silicone rubber composite.

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