Programmable flexible pressure sensor based on multi-level konjac sponge and preparation method thereof

Abstract

The application discloses a programmable flexible pressure sensor based on a multistage konjak sponge and a preparation method thereof, which comprises an upper flexible film layer, a row contact electrode layer, a row contact electrode inter-electrical break, a pressure sensitive layer, a microfluid channel layer, a support layer, a column contact electrode layer, a column contact electrode inter-electrical break, a lower flexible film layer, a flow channel inlet, and a flow channel outlet; the row contact electrode layer is composed of contact electrodes and a serpentine wire, and the row contact electrode inter-electrical break is located on the serpentine wire; the pressure sensitive layer has multistage konjak sponges, the microfluid channel layer has a plurality of flow channels, and the flow channels are connected with the multistage konjak sponges; fluid enters the flow channels from the flow channel inlet, acts on the pressure sensitive layer, and then flows out from the flow channel outlet; the column contact electrode layer is composed of contact electrodes and a serpentine wire, and the column contact electrode inter-electrical break is located on the serpentine wire of the column contact electrode layer; the programmable flexible pressure sensor has high sensitivity and a wide detection pressure range, and realizes programmable control of performance.

Description

Technical Field

[0001] This invention relates to the field of flexible pressure sensors, specifically to a programmable flexible pressure sensor based on multi-level konjac sponge and its fabrication method. Background Technology

[0002] Flexible pressure sensors hold immense application potential in wearable technologies such as smart prosthetics, human-computer interaction, electronic skin, and healthcare. In recent years, researchers have developed flexible pressure sensors based on various conduction mechanisms, achieving significant progress in performance aspects such as sensitivity and detection range. However, existing technologies struggle to simultaneously meet high sensitivity requirements and accommodate a wide pressure detection range. Furthermore, increasingly complex task environments and diverse detection objects place new demands on the programmability of sensors. Pressure sensors with single, fixed performance advantages are no longer adequate for current detection needs. Therefore, to enhance the performance advantages of flexible pressure sensors and improve their adaptability to detection environments and objects, a novel flexible pressure sensor combining high sensitivity, a wide pressure detection range, and programmable control is urgently needed.

[0003] Currently, in achieving both high sensitivity and a wide pressure detection range, some studies have explored designing multi-level microstructures (such as domes) on the same substrate. These multi-level structures gradually contact the electrodes under pressure to provide both high sensitivity and a wide pressure detection range. However, once the sensor is fabricated, its performance cannot be altered, making programmable control difficult. Regarding programmable control, some studies utilize magnetic fields to adjust the stiffness of magnetic pressure-sensitive cilia, thereby enabling programmable control of sensor sensitivity and pressure detection range. However, this method, while expanding the pressure detection range, actually reduces sensitivity. Other studies use magnetic ionic droplets as the pressure-sensitive layer, using magnetic fields to control the droplet's geometry, spatial position, volume, and dielectric constant, also achieving programmable control of sensor performance. However, due to the droplet's strong deformation capacity and extremely low yield stress, the detection pressure is low and the range is narrow.

[0004] Therefore, at present, no research has been conducted that achieves both high sensitivity and a wide detection pressure range in flexible pressure sensors while simultaneously enabling programmable control of their performance. Summary of the Invention

[0005] The purpose of this invention is to provide a programmable flexible pressure sensor based on multi-level konjac sponge and its fabrication method, which can solve the problem that existing flexible pressure sensors are difficult to achieve high sensitivity, wide pressure detection range and programmable control of performance, and provide a technical reference for flexible sensors to flexibly adapt to complex task environments and diverse detection objects.

[0006] To achieve the above functions, this invention designs a programmable flexible pressure sensor based on multi-level konjac sponge, including: an upper flexible thin film layer 1, a row contact electrode layer 2, an electrical break point between row contact electrodes 3, a pressure-sensitive layer 4, a microfluidic channel layer 5, a support layer 6, a column contact electrode layer 7, an electrical break point between column contact electrodes 8, a lower flexible thin film layer 9, a flow channel inlet 10, and a flow channel outlet 11.

[0007] The upper flexible thin film layer 1 is rectangular, and its upper surface serves as the first direct layer for the external pressure signal of the flexible pressure sensor. The row contact electrode layer 2 is an electrode layer with a serpentine island-bridge structure, consisting of multiple contact electrodes and serpentine wires arranged periodically in the horizontal and vertical directions. Each contact electrode has the same shape and size, and each row has a row lead-out electrode on its outer side in the horizontal direction. Adjacent contact electrodes are electrically connected through serpentine wires. The upper surface of the contact electrodes of the row contact electrode layer 2 is bonded to the lower surface of the upper flexible thin film layer 1 by oxygen plasma. The electrical break point 3 between the row contact electrodes is located on the serpentine wire of the row contact electrode layer 2.

[0008] The pressure-sensitive layer 4 comprises multiple pressure-sensitive units arranged periodically in the horizontal and vertical directions. Each pressure-sensitive unit has the same shape and size, and each pressure-sensitive unit has a multi-level konjac sponge. Each level of konjac sponge is composed of multiple hemispherical konjac sponges arranged in a ring. The bottom surface of each contact electrode of the row contact electrode layer 2 is in direct contact with the surface of the hemispherical konjac sponge in each pressure-sensitive unit of the pressure-sensitive layer 4. The microfluidic channel layer 5 is provided with multiple microchannels, each microchannel sequentially connecting to each of the ring-arranged multi-level konjac sponges. Fluid enters the microchannel from the inlet 10 of each microchannel, acts on the pressure-sensitive layer 4, and flows out from the outlet 11.

[0009] The upper surface of the support layer 6 is plasma-bonded to the lower surface of the row contact electrode layer 2; the support layer 6 is used to support the edges of the upper flexible film layer 1 and the microfluidic channel layer 5, and the support layer 6 has a preset thickness, the same as the diameter of the outermost konjac sponge; the support layer 6 is in a square ring shape around the edges of the upper flexible film layer 1 and the microfluidic channel layer 5; the column contact electrode layer 7 is an electrode layer with a serpentine island-bridge structure, consisting of multiple contact electrodes and serpentine wires arranged periodically in the horizontal and vertical directions, each contact electrode having the same shape and size, and adjacent contact electrodes... Electrically connected via serpentine wires; each column in the longitudinal direction has a column lead-out electrode on its outer side; the upper surface of the contact electrode of the column contact electrode layer 7 is directly connected to the lower surface of the pressure-sensitive layer 4, and the lower surface of the contact electrode of the column contact electrode layer 7 is bonded to the upper surface of the lower flexible thin film layer 9; the electrical break point 8 between the column contact electrodes is located on the serpentine wires of the column contact electrode layer 7; the lower surface of the microfluidic channel layer 5 is bonded to the upper surface of the column contact electrode layer 7; the lower surface of the rectangular lower flexible thin film layer 9 serves as the second direct layer for external pressure signals of the flexible stretchable pressure sensor.

[0010] As a preferred embodiment of the present invention: the microfluidic channel layer 5 is divided into upper and lower layers, the lower layer being the flow channel layer and the upper layer being the encapsulation layer; the flow channel layer is provided with inner, middle and outer three-level microfluidic channels, and each level of microfluidic channel is provided with the same number of circular chambers, the diameter and width of each level of microfluidic channel and the diameter of the circular chambers gradually increase from the inside to the outside; the encapsulation layer covers the flow channel layer, and only opens circular holes of the same diameter at the corresponding positions above the circular chambers to expose the circular chambers; the inner, middle and outer three-level flow channels in the flow channel layer are provided with corresponding flow channel inlets 10 and flow channel outlets 11 for fluid input and output.

[0011] As a preferred technical solution of the present invention: multiple hemispherical konjac sponges in each pressure-sensitive unit of the pressure-sensitive layer 4 are uniformly placed in the circular chambers of the inner, middle and outer three-level microfluidic channels of the microfluidic channel layer 5; the diameter of the hemispherical konjac sponge is the same as the diameter of the circular chamber, and the bottom of the hemispherical konjac sponge has a channel with the same width and radius as the channel it is located in.

[0012] As a preferred embodiment of the present invention, the upper flexible film layer 1 and the lower flexible film layer 9 are made of flexible and stretchable silicone material.

[0013] As a preferred embodiment of the present invention, the upper surface of the contact electrode of the row contact electrode layer 2 and the lower surface of the contact electrode of the column contact electrode layer 7 are both covered with a flexible insulating layer.

[0014] As a preferred embodiment of the present invention, the contact electrodes of the row contact electrode layer 2 and the contact electrodes of the column contact electrode layer 7 are both circular.

[0015] As a preferred embodiment of the present invention, the electrical break point 3 between the row contact electrodes and the electrical break point 8 between the column contact electrodes are composed of two layers of flexible polyimide insulating material.

[0016] As a preferred technical solution of the present invention: the plurality of hemispherical konjac sponges are prepared by mixing a pre-concentrated alkaline solution, a pore-forming agent, a plasticizer, and konjac flour.

[0017] This invention also designs a method for fabricating a programmable flexible pressure sensor based on multi-level konjac sponge, which involves performing the following steps S1-S6 to complete the fabrication of the programmable flexible pressure sensor based on multi-level konjac sponge:

[0018] Step S1: Spin-coat and cure a layer of polydimethylsiloxane on a glass slide to form a flexible transparent film. After surface hydrophilic modification by oxygen plasma, spin-coat a layer of polyimide to form an insulating film. Magnetron sputter chromium / gold metal layers are then sputtered onto the polyimide film, and contact electrodes, serpentine wires, and electrical breaks are formed after photolithography and wet etching processes. After spin-coating another layer of polyimide film, reactive ion etching is used to expose the contact electrodes that need to contact the pressure-sensitive layer 4. Then, water-soluble tape is used to transfer the contact electrodes from the polydimethylsiloxane flexible transparent film. A layer of silicon dioxide film is then sputtered on the back of the contact electrodes. After the water-soluble tape is completely dissolved in deionized water, the row contact electrode layer 2, the electrical break between the row contact electrodes 3, the column contact electrode layer 7, and the electrical break between the column contact electrodes 8 are finally prepared.

[0019] Step S2: Mix and swell konjac flour, pore-forming agent, and plasticizer according to the preset design ratio, add the preset ratio of alkaline solution and stir evenly, pour into the pre-prepared multi-level hemispherical groove mold, cross-link and stand at room temperature to form, and then freeze overnight in a freezer; after thawing, decolorization with citric acid solution and repeated washing with water, obtain the pressure-sensitive layer 4 with multi-level konjac sponge.

[0020] Step S3: Prepare a photosensitive resin mold for the microfluidic channel layer 5 using 3D printing technology, pour polydimethylsiloxane and heat to cure to form the inner, middle and outer three-level microfluidic channels in the flow channel layer and encapsulation layer, as well as the circular chamber, and prepare the microfluidic channel layer 5 after demolding and bonding.

[0021] Step S4: Prepare a photosensitive resin mold for the support layer 6 using 3D printing technology, pour in polydimethylsiloxane and heat to cure to form the support layer 6;

[0022] Step S5: Prepare a photosensitive resin mold for the upper flexible film layer 1 and the lower flexible film layer 9 using 3D printing technology, pour polydimethylsiloxane into it and heat it to cure to form the upper flexible film layer 1 and the lower flexible film layer 9;

[0023] Step S6: The pressure-sensitive layer 4 prepared in step S2 is added to the circular cavity in the microfluidic channel layer 5 prepared in step S3. Finally, the row contact electrode layer 2, the electrical break point between the row contact electrodes 3, the pressure-sensitive layer 4, the microfluidic channel layer 5, the support layer 6, the column contact electrode layer 7, the electrical break point between the column contact electrodes 8, and the lower flexible film layer 9 are bonded by oxygen plasma to form a programmable flexible pressure sensor based on multi-level konjac sponge.

[0024] The present invention also designs a programmable control method for a programmable flexible pressure sensor based on multi-level konjac sponge. The programmable control of the programmable flexible pressure sensor based on multi-level konjac sponge includes: programmable control of the stiffness of the multi-level konjac sponge and programmable control of the dielectric constant of the multi-level konjac sponge.

[0025] Specifically, the programmable control of the stiffness of the multi-level konjac sponge involves: allowing the hemispherical konjac sponge to absorb water through the three-level microchannels in the microfluidic channel layer 5, controlling the amount of water absorbed by the hemispherical konjac sponge, and adjusting the stiffness of each hemispherical konjac sponge, as detailed below:

[0026] One approach is to control the filling rate of the liquid inside the hemispherical konjac sponge of the same level to maintain consistency, as well as the gradient change in the filling rate of the liquid inside the hemispherical konjac sponge between levels, so that the stiffness of the hemispherical konjac sponge of the same level is the same, while the stiffness of the hemispherical konjac sponge of different levels varies. The other approach is to control the gradient change in the filling rate of the liquid inside the hemispherical konjac sponge in the same level microchannel by adjusting the flow rate and flow rate of the liquid in the same level microchannel, so that the stiffness of the hemispherical konjac sponge of the same level varies.

[0027] The programmable control of the dielectric constant of the multi-level konjac sponge is specifically achieved by introducing fluids with different dielectric constants through the three-level microchannels in the microfluidic channel layer 5 to adjust the dielectric constant of each hemispherical konjac sponge, as detailed below:

[0028] One type involves controlling the inflow of different types of media into the inner, middle, and outer microchannels, as well as maintaining a consistent liquid filling rate within the same-level hemispherical konjac sponge, thus ensuring that the media in the three-level hemispherical konjac sponges differ while the stiffness of the same-level hemispherical konjac sponges remains consistent. The other type involves controlling the inflow of different types of media into the inner, middle, and outer microchannels, as well as the gradient change in the liquid filling rate within the same-level hemispherical konjac sponge, thus ensuring that the media in the three-level hemispherical konjac sponges differ while the stiffness of the same-level hemispherical konjac sponges varies gradient.

[0029] Beneficial effects: Compared with the prior art, the advantages of the present invention include:

[0030] 1. The hemispherical konjac sponge microstructure, through its geometric advantages, efficiently "focuses" and "amplifies" weak pressure signals into significant mechanical deformation within the sensing material, thereby achieving ultra-high sensitivity detection of minute pressures.

[0031] 2. The multi-level (inner, middle, and outer three-level) hemispherical konjac sponge integrates sponge microstructures of different scales into one through a biomimetic design of "space for performance". This allows it to work in stages at different pressure levels, which broadens the pressure detection range of the sensor and cleverly solves the inherent contradiction between high sensitivity and wide pressure detection range.

[0032] 3. By controlling the water absorption of the hemispherical konjac sponge through microchannels, the stiffness of each level of konjac sponge can be adjusted, thereby achieving programmable control of sensor sensitivity and pressure detection range.

[0033] 4. By introducing fluid media with different dielectric constants and different hydrophilicity / hydrophobicity through microchannels, programmable control of sensor sensitivity and pressure detection range can be achieved.

[0034] 5. This flexible pressure sensor, characterized by high sensitivity, wide pressure detection range, and programmable performance, can be fabricated using micro-nano processing methods such as photolithography, etching, sputtering, bonding, and transfer printing. It boasts high precision, mature technology, and the entire sensor is flexible and stretchable.

[0035] 6. Researchers in this field have not yet combined hemispherical konjac sponges with adjustable stiffness and dielectric constant, microchannels, and multi-level konjac sponge microstructures to construct flexible pressure sensors, and simultaneously achieved high sensitivity, wide pressure detection range, and programmable control of performance of flexible pressure sensors under the control of water absorption and fluid medium type. This invention provides a new approach for the development of novel flexible pressure sensors that combine the advantages of high sensitivity, wide pressure detection range, and programmable control. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of a programmable flexible pressure sensor based on multi-level konjac sponge according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of the microfluidic channel layer and pressure-sensitive layer provided in an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of a method for fabricating a programmable flexible pressure sensor based on multi-level konjac sponge according to an embodiment of the present invention;

[0039] Figure 4 This is a programmable control method for a programmable flexible pressure sensor based on multi-level konjac sponge, provided by an embodiment of the present invention;

[0040] In the figure: 1. Upper flexible thin film layer; 2. Row contact electrode layer; 3. Electrical break point between row contact electrodes; 4. Pressure sensitive layer; 5. Microfluidic channel layer; 6. Support layer; 7. Column contact electrode layer; 8. Electrical break point between column contact electrodes; 9. Lower flexible thin film layer; 10. Flow channel inlet; 11. Flow channel outlet. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0042] The programmable flexible pressure sensor based on multi-level konjac sponge provided in this embodiment of the invention refers to... Figure 1 It includes: an upper flexible thin film layer 1, a row contact electrode layer 2, an electrical break point between row contact electrodes 3, a pressure-sensitive layer 4, a microfluidic channel layer 5, a support layer 6, a column contact electrode layer 7, an electrical break point between column contact electrodes 8, a lower flexible thin film layer 9, a flow channel inlet 10, and a flow channel outlet 11.

[0043] The upper flexible film layer 1 is rectangular, and its upper surface serves as the first direct layer for the external pressure signal of the flexible pressure sensor. The upper flexible film layer 1 has an overall thickness of 2 mm and a length and width of 100 mm. It is made of flexible and stretchable silicone material, such as polyethylene succinate (EcoFlex), Dragon Skin, and polydimethylsiloxane (PDMS). Transparent PDMS material is preferred to facilitate observation of fluid transport in the microchannel and the controlled status of the multi-level konjac sponge in the pressure-sensitive layer 4.

[0044] The row contact electrode layer 2 is an electrode layer with a serpentine island-bridge structure, consisting of multiple contact electrodes and serpentine wires arranged periodically in the horizontal and vertical directions. The contact electrodes are islands, and the serpentine wires are bridges. Each contact electrode has the same shape and size. Each row in the horizontal direction has a row lead electrode on its outer side. Adjacent contact electrodes are electrically connected through serpentine wires. The upper surface of the contact electrodes in the row contact electrode layer 2 is ion-bonded to the lower surface of the upper flexible thin film layer 1. The upper surface of the contact electrodes in the row contact electrode layer 2 is covered with a flexible insulating layer. In this embodiment, the flexible insulating layer is a flexible polyimide (PI) insulating layer. The lower surface of the contact electrodes is an exposed electrode surface that is in direct contact with the pressure-sensitive layer 4. The contact electrodes are circular and designed as a 4×5 array. The fifth column from the left is the row lead electrode, which is used for electrical interconnection with external devices or circuits. The contact electrode diameter is 30 mm and the thickness is 10 μm. The serpentine wire has a bending angle of 240° and a line width of 300 μm. The contact electrode material is chromium / gold (Cr / Au, 5 nm / 50 nm).

[0045] The electrical break 3 between the row contact electrodes is located on the serpentine conductor of the row contact electrode layer 2 and is composed of two layers of flexible polyimide (PI) insulating material; it can meet the mechanical stretching requirements of the row contact electrode layer 2 and block the electrical interconnection between the row contact electrodes.

[0046] Reference Figure 2 The pressure-sensitive layer 4 comprises multiple pressure-sensitive units arranged periodically in the horizontal and vertical directions. Each pressure-sensitive unit has the same shape and size, and each pressure-sensitive unit has a multi-level konjac sponge. Each level of konjac sponge is composed of multiple hemispherical konjac sponges arranged in a ring. Its main functional component is konjac flour (KGM). The hemispherical konjac sponge is prepared by mixing a certain concentration of alkaline solution, konjac flour, pore-forming agent, and plasticizer. It has a porous interior, can absorb liquid, and its stiffness changes after absorbing water. The stiffness decreases (i.e., softens) as the amount of water absorbed increases. The multi-level konjac sponge has three levels: inner, middle, and outer, with diameters of 2mm, 3mm, and 4mm, respectively.

[0047] The bottom surface of each contact electrode in the row contact electrode layer 2 is in direct contact with the surface of the hemispherical konjac sponge in each pressure-sensitive unit of the pressure-sensitive layer 4; the microfluidic channel layer 5 is provided with multiple microfluidic channels, each microfluidic channel is connected in sequence to each hemispherical konjac sponge arranged in a ring; fluid enters the channel from the inlet 10 of each microfluidic channel, acts on the pressure-sensitive layer 4 and flows out from the outlet 11 of the channel;

[0048] The upper surface of the support layer 6 is plasma-bonded to the lower surface of the row contact electrode layer 2 to prevent the upper flexible film layer from slipping due to other factors, which would cause ineffective deformation of the pressure-sensitive layer 4 and affect the pressure measurement results. The support layer 6 is used to support the edges of the upper flexible film layer 1 and the microfluidic channel layer 5, and the support layer 6 has a preset thickness, which is the same as the diameter of the outer hemispherical konjac sponge. The support layer 6 is in the shape of a square ring around the edges of the upper flexible film layer 1 and the microfluidic channel layer 5, with an outer ring side length of 100 mm and an inner ring side length of 96 mm, which can avoid errors caused by the weight of the upper flexible film layer 1 and other interference factors on the pressure-sensitive layer 4.

[0049] The column contact electrode layer 7 is an electrode layer with a serpentine island-bridge structure, consisting of multiple contact electrodes and serpentine wires arranged periodically in the horizontal and vertical directions. The contact electrodes are islands, and the serpentine wires are bridges. Each contact electrode has the same shape and size, and adjacent contact electrodes are electrically connected through serpentine wires. Each column in the vertical direction has a column lead-out electrode on its outer side. The upper surface of the contact electrodes in the column contact electrode layer 7 is an exposed electrode surface, directly connected to the lower surface of the pressure-sensitive layer 4. The lower surface of the contact electrodes in the column contact electrode layer 7 is connected to the upper surface of the lower flexible thin film layer 9. Plasma bonding is used, and the lower surface of the contact electrode is covered with a flexible insulating layer. In this embodiment, the flexible insulating layer is a flexible polyimide (PI) insulating layer. The contact electrodes of the column contact electrode layer 7 are circular and designed as a 5×4 array. The fifth row from the top is the column lead electrode, which is used for electrical interconnection with external devices or circuits. The contact electrode diameter is 30 mm, the thickness is 10 μm, the serpentine wire bending angle is 240°, the line width is 300 μm, and the contact electrode material is chromium / gold (Cr / Au, 5 nm / 50 nm).

[0050] The electrical break 8 between the column contact electrodes is located on the serpentine conductor of the column contact electrode layer 7 and is composed of two layers of flexible polyimide (PI) insulating material. This allows it to meet the mechanical stretching requirements of the column contact electrode layer 7 and block the electrical interconnection between the column contact electrodes. The lower surface of the microfluidic channel layer 5 is bonded to the upper surface of the column contact electrode layer 7. The lower surface of the rectangular lower flexible film layer 9 serves as the second direct layer for external pressure signals in the flexible stretchable pressure sensor. In this embodiment, the lower flexible film layer 9 is made of flexible stretchable silicone material and serves as the direct layer for external pressure signals. The lower flexible film layer 9 has an overall thickness of 2 mm and a length and width of 100 mm. It is made of flexible silicone material, such as polyethylene succinate (EcoFlex), Dragon Skin, or polydimethylsiloxane (PDMS), preferably transparent PDMS material to facilitate observation of fluid transport in the microchannels and the controlled status of the konjac sponge pressure-sensitive layer.

[0051] In one embodiment, the programmable flexible pressure sensor has an overall size of 100mm × 100mm × 100mm, is a 4×4 array, and contains a total of 16 pressure-sensitive units.

[0052] Reference Figure 2The microfluidic channel layer 5 is divided into upper and lower layers. The lower layer is the flow channel layer, and the upper layer is the encapsulation layer. The flow channel layer is provided with three levels of microchannels: inner, middle, and outer. Each level of microchannel is provided with the same number of circular chambers. The diameter and width of each level of microchannel and the diameter of the circular chambers gradually increase from the inside to the outside. The encapsulation layer covers the flow channel layer and only opens circular holes of the same diameter at the corresponding positions above the circular chambers to expose the circular chambers. The inner, middle, and outer microchannels in the flow channel layer are provided with corresponding flow channel inlets 10 and flow channel outlets 11 for fluid input and output.

[0053] In this embodiment, the microfluidic channel layer 5 is provided with three levels of microchannels, each level containing 12 circular chambers of the same diameter, each chamber carrying a hemispherical konjac sponge of the same diameter. Fluid enters the microchannel from the inlet 10 of each level, acts on the pressure-sensitive layer 4, and flows out from the outlet 11. The structural parameters of each pressure sensing unit are identical.

[0054] In the pressure-sensitive layer 4, multiple hemispherical konjac sponges in each pressure-sensitive unit are evenly placed in the circular chambers of the inner, middle, and outer three-stage flow channels of the microfluidic channel layer 5. The diameter of the hemispherical konjac sponge is the same as the diameter of the circular chamber, and the bottom of the hemispherical konjac sponge has a channel with the same width and radius as the flow channel it is in, so that the fluid can flow through the hemispherical konjac sponge without clogging. The pressure-sensitive layer 4 and the lower surface of the contact electrode of the row contact electrode layer 2 make contact step by step as the pressure increases.

[0055] This invention also provides a method for fabricating a programmable flexible pressure sensor based on multi-level konjac sponge, involving microfabrication processes such as photolithography, etching, sputtering, bonding, and transfer printing, as described in the following embodiments. Figure 3 Specifically, the following steps S1-S6 are performed to complete the fabrication of the programmable flexible pressure sensor based on multi-level konjac sponge:

[0056] Step S1: A layer of polydimethylsiloxane (PDMS) is spin-coated and cured on a glass slide to form a flexible transparent film. After surface hydrophilic modification by oxygen plasma, a layer of polyimide (PI) is spin-coated to form an insulating layer film. A chromium / gold (Cr / Au) metal layer is then magnetron sputtered onto the polyimide film, and contact electrodes, serpentine wires, and electrical breaks are formed after photolithography and wet etching processes. Another layer of polyimide film is spin-coated, and the contact electrodes that need to contact the pressure-sensitive layer 4 are exposed by reactive ion etching. Then, the contact electrodes are transferred from the PDMS flexible transparent film using water-soluble tape. A layer of silicon dioxide (SiO2) film is sputtered on the back of the contact electrodes. After the water-soluble tape is completely dissolved in deionized water, the row contact electrode layer 2, the electrical break between the row contact electrodes 3, the column contact electrode layer 7, and the electrical break between the column contact electrodes 8 are finally prepared.

[0057] In the embodiments, reference is made to Figure 3 In (a), the specific steps of step S1 are as follows:

[0058] Step S11: Spin-coat a layer of uncured polydimethylsiloxane (PDMS) (prepolymer:curing agent = 10:1) onto a glass slide at 500 rpm, and cure on a hot plate at 80 ℃ for half an hour to form a flexible transparent PDMS film with a thickness of 1 mm; place the glass slide and the PDMS film on it in a UV lamp box for 3 minutes to modify the surface of the transparent film, which will facilitate the subsequent adhesion of the PI insulation layer; spin-coat a layer of polyimide (PI) onto the surface of the surface-modified PDMS film at 2000 rpm, and cure in a glove box at 250 ℃ for 2 minutes. For several hours, a PI insulating layer thin film with a thickness of 1 μm was formed. A chromium / gold (Cr / Au, 5nm / 50nm) metal thin film was sputtered on the surface of the PI insulating layer thin film using magnetron sputtering technology. The chromium / gold metal thin film was patterned using photolithography and wet etching processes to form row contact electrode layer 2 and column contact electrode layer 7, which consist of circular contact electrodes and serpentine wires, as well as electrical breakpoints 3 and 8 between row contact electrodes and between column contact electrodes. A PI thin film was spin-coated on the surface of the electrode layer as an insulating layer. After curing, the circular contact electrodes were exposed separately on the PI insulating layer using photolithography and reactive ion etching processes to facilitate direct contact between the contact electrodes and the pressure-sensitive layer 4. At the same time, the PI in areas other than the serpentine wires was etched away to improve the stretchability of the contact electrode layer. That is, except for the circular contact electrodes and serpentine wires, other areas are hollowed out.

[0059] Step S12: Use water-soluble tape to peel the contact electrode off from the PDMS substrate, transfer it to a temporary glass substrate and fix it with tape. At this time, the exposed contact electrode faces the glass substrate, while the back of the contact electrode faces up and the water-soluble tape faces down. Sputter a silicon dioxide thin film (5nm) on the back of the contact electrode using magnetron sputtering technology.

[0060] Step S13: Place the contact electrode and serpentine wire sputtered with silicon dioxide film in step S12 into deionized water to dissolve the water-soluble tape, and finally obtain the row contact electrode layer 2 and column contact electrode layer 7 with silicon dioxide film sputtered on the back.

[0061] Step S2: Konjac flour (konjac glucomannan), pore-forming agent, and plasticizer are thoroughly mixed and swollen according to the preset design ratio. After adding the preset ratio of alkaline solution, the mixture is quickly stirred evenly and poured into a pre-prepared multi-level hemispherical groove mold. After full cross-linking and standing at room temperature to form the mold, it is placed in a freezer and frozen overnight. After thawing, decolorization with citric acid solution, and repeated washing with a large amount of water, a pressure-sensitive layer 4 with multi-level konjac sponge is obtained.

[0062] In the embodiments, reference is made to Figure 3 In (b), the specific steps of step S2 are as follows:

[0063] Step S21: Mix 1.0g of konjac flour (konjac glutanol content greater than 90%), 0.8g of Na2SO4 (pore-forming agent), 0.3g of glycerol (plasticizer) and 30mL of 0.1mol / L NaOH aqueous solution thoroughly, and stir rapidly for 3-4min to allow the konjac flour to swell and cross-link, forming konjac latex solution.

[0064] Step S22: Design and prepare a multi-level photosensitive resin mold (gradient diameter, 4mm, 3mm and 2mm) for pressure-sensitive layer 4 using 3D printing technology. Add the konjac latex liquid prepared in step S11 into the photosensitive resin mold and let it stand at room temperature for 24 hours to allow the konjac latex liquid to cross-link and form konjac latex.

[0065] Step S23: The molded konjac latex obtained in step S22 is placed in a vacuum freeze dryer for rapid freeze drying at -80℃ for 36 hours. After that, the freeze-dried konjac latex after demolding is placed in a 0.2mol / L citric acid solution for decolorization, and then repeatedly washed with a large amount of water to finally obtain a hemispherical konjac sponge, i.e., pressure-sensitive layer 4.

[0066] Step S3: Prepare a photosensitive resin mold for the microfluidic channel layer 5 using 3D printing technology, pour polydimethylsiloxane and heat to cure to form the inner, middle and outer three-level microfluidic channels in the flow channel layer and encapsulation layer, as well as the circular chamber, and prepare the microfluidic channel layer 5 after demolding and bonding.

[0067] In the embodiments, reference is made to Figure 3 In (c), the specific steps of step S3 are as follows:

[0068] Step S32: Design and fabricate the lower flow channel layer photosensitive resin mold and the upper encapsulation layer mold using 3D printing technology; pour uncured PDMS (prepolymer:curing agent = 10:1) into the flow channel layer mold and cure it on a hot plate at 80 ℃ for half an hour to form the lower flow channel layer of the microfluidic channel layer 5; pour uncured PDMS (prepolymer:curing agent = 10:1) into the encapsulation layer mold and cure it on a hot plate at 80 ℃ for half an hour to form the upper encapsulation layer of the microfluidic channel layer 5;

[0069] Step S32: Place the flow channel layer and the encapsulation layer into an oxygen plasma cleaner at the same time to perform oxygen plasma treatment on the surface. Finally, align and bond the flow channel layer and the encapsulation layer to obtain the required microfluidic channel layer 5.

[0070] Step S4: Prepare a photosensitive resin mold for the support layer 6 using 3D printing technology, pour in polydimethylsiloxane and heat to cure to form the support layer 6;

[0071] Reference Figure 3 In example (d), a photosensitive resin mold for the support layer was designed and prepared using 3D printing technology; uncured PDMS (prepolymer: curing agent = 10:1) was poured into the support layer mold and cured on a hot plate at 80 °C for half an hour to form the support layer 6.

[0072] Step S5: Prepare a photosensitive resin mold for the upper flexible film layer 1 and the lower flexible film layer 9 using 3D printing technology, pour polydimethylsiloxane into it and heat it to cure to form the upper flexible film layer 1 and the lower flexible film layer 9;

[0073] Reference Figure 3 In embodiment (e), a photosensitive resin mold for the thin film layer is designed and prepared using 3D printing technology; uncured PDMS (prepolymer: curing agent = 10:1) is poured into the mold of the thin film layer and cured on a hot plate at 80 °C for half an hour to form the upper flexible thin film layer 1 and the lower flexible thin film layer 9.

[0074] Step S6: The pressure-sensitive layer 4 prepared in step S2 is added to the circular cavity in the microfluidic channel layer 5 prepared in step S3. Finally, the row contact electrode layer 2, the electrical break point between the row contact electrodes 3, the pressure-sensitive layer 4, the microfluidic channel layer 5, the support layer 6, the column contact electrode layer 7, the electrical break point between the column contact electrodes 8, and the lower flexible film layer 9 are bonded by oxygen plasma to form a programmable flexible pressure sensor based on multi-level konjac sponge.

[0075] In this embodiment, the upper flexible thin film layer 1, row contact electrode layer 2, pressure sensitive layer 4, microfluidic channel layer 5, support layer 6, column contact electrode layer 7 and lower flexible thin film layer 9 prepared in steps S1 to S5 are placed in an oxygen plasma cleaning machine for surface treatment. Then, the above parts are physically aligned and pressed in structural order, and bonded by heating at 80°C for 30 minutes, finally obtaining a programmable flexible pressure sensor based on multi-level konjac sponge.

[0076] This invention also provides a programmable control method for a programmable flexible pressure sensor based on multi-level konjac sponge, referring to... Figure 4 The programmable flexible pressure sensor based on multi-level konjac sponge achieves programmable control of sensor performance by adjusting the fluid volume and type, including: programmable control of multi-level konjac sponge stiffness and programmable control of multi-level konjac sponge dielectric constant.

[0077] Specifically, the multi-level konjac sponge stiffness programmable control involves utilizing the characteristics of konjac sponge softening upon water absorption and continuously decreasing stiffness. Water is absorbed by the hemispherical konjac sponge through the three-level microfluidic channels in the microfluidic channel layer 5. The amount of water absorbed by the hemispherical konjac sponge is controlled through the microfluidic channels, thereby adjusting the stiffness of each level of konjac sponge. This allows for both control of the stiffness of a single-level konjac sponge along a circumferential gradient and inter-level combination programming control, ultimately achieving programmable control of sensor sensitivity and pressure detection range.

[0078] This embodiment designs two types of adjustment methods, both based on the initial conditions of consistent stiffness and dielectric constant of the three-stage konjac sponges. One method controls the consistency of the liquid filling rate within the same-stage konjac sponge and the gradient change of the liquid filling rate between stages to achieve the effect of consistent stiffness within the same-stage konjac sponge and gradient changes in stiffness between different stages, i.e., single stiffness within the same stage and multiple stiffness between stages (A1). The other method controls the gradient change of the liquid filling rate within the same-stage microchannel by adjusting the flow rate and flow rate of the liquid in the same-stage microchannel, to achieve the effect of gradient changes in stiffness within the same-stage konjac sponge, i.e., multiple stiffness within the same stage (A2).

[0079] The programmable control of the dielectric constant of the multi-level konjac sponge is specifically achieved by introducing fluids with different dielectric constants through the three-level microfluidic channels in the microfluidic channel layer 5, thereby adjusting the dielectric constant of each hemispherical konjac sponge. This can be done by introducing hydrophobic fluid media to adjust the dielectric constant without changing the sponge stiffness, or by introducing hydrophilic fluid media to adjust both the sponge stiffness and dielectric constant, thus achieving programmable control of the sensor sensitivity and pressure detection range.

[0080] In this embodiment, the dielectric constant of the multi-stage konjac sponge is programmable: the type of liquid in the konjac sponge is adjusted as needed, thereby controlling the change in the dielectric constant of the konjac sponge, and thus realizing programmable control of the sensitivity performance of the flexible pressure sensor. This embodiment designs two types of adjustment methods. One method controls the flow of different types of medium fluids into the inner, middle, and outer flow channels, and maintains a consistent liquid filling rate in the same-stage sponge, achieving the effect of different media in the three-stage sponges and consistent stiffness in the same-stage sponge, i.e., multi-medium between stages, single stiffness in the same stage (B1). The other method controls the flow of different types of medium fluids into the inner, middle, and outer flow channels, and the gradient change in the liquid filling rate in the same-stage sponge, achieving the effect of different media in the three-stage sponges and gradient change in stiffness in the same-stage sponge, i.e., multi-medium between stages, multiple stiffness in the same stage (B2).

[0081] In this embodiment, both programmable control methods achieve programmable control of the sensor sensitivity and detection range performance by precisely changing the liquid flow rate, flow rate, and liquid type in the three-stage microchannel.

[0082] The stiffness and dielectric constant of multi-level konjac sponges can be synergistically controlled to achieve programmable control of sensor sensitivity and pressure detection range.

[0083] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A programmable flexible pressure sensor based on multi-level konjac sponge, characterized in that, include: Upper flexible thin film layer (1), row contact electrode layer (2), electrical break point between row contact electrodes (3), pressure sensitive layer (4), microfluidic channel layer (5), support layer (6), column contact electrode layer (7), electrical break point between column contact electrodes (8), lower flexible thin film layer (9), flow channel inlet (10), flow channel outlet (11). The upper flexible thin film layer (1) is rectangular, and its upper surface serves as the first direct layer for the external pressure signal of the flexible pressure sensor. The row contact electrode layer (2) is an electrode layer with a serpentine island-bridge structure, consisting of multiple contact electrodes and serpentine wires arranged periodically in the horizontal and vertical directions. Each contact electrode has the same shape and size, and each row in the horizontal direction has a row lead-out electrode on its outer side. Adjacent contact electrodes are electrically connected through serpentine wires. The upper surface of the contact electrodes of the row contact electrode layer (2) is bonded to the lower surface of the upper flexible thin film layer (1) by oxygen plasma. The electrical break point (3) between the row contact electrodes is located on the serpentine wire of the row contact electrode layer (2). The pressure-sensitive layer (4) contains multiple pressure-sensitive units arranged periodically in the horizontal and vertical directions. Each pressure-sensitive unit has the same shape and size. Each pressure-sensitive unit has a multi-level konjac sponge. Each level of konjac sponge is composed of multiple hemispherical konjac sponges arranged in a ring. The bottom surface of each contact electrode of the row contact electrode layer (2) is in direct contact with the surface of the hemispherical konjac sponge in each pressure-sensitive unit of the pressure-sensitive layer (4). The microfluidic channel layer (5) is provided with multiple microchannels. Each microchannel is connected to each of the multi-level konjac sponges arranged in a ring in sequence. Fluid enters the microchannel from the inlet (10) of each microchannel, acts on the pressure-sensitive layer (4), and flows out from the outlet (11). The upper surface of the support layer (6) is plasma-bonded to the lower surface of the row contact electrode layer (2); the support layer (6) is used to support the edges of the upper flexible film layer (1) and the microfluidic channel layer (5), and the support layer (6) has a preset thickness, which is the same as the diameter of the outermost konjac sponge; the support layer (6) is arranged in a square ring around the edges of the upper flexible film layer (1) and the microfluidic channel layer (5); the column contact electrode layer (7) is an electrode layer with a serpentine island-bridge structure, consisting of multiple contact electrodes and serpentine wires arranged periodically in the horizontal and vertical directions, with each contact electrode having the same shape and size, and adjacent contact electrodes... The electrodes are electrically connected by a serpentine wire; each column in the longitudinal direction has a column lead-out electrode on its outer side; the upper surface of the contact electrode of the column contact electrode layer (7) is directly connected to the lower surface of the pressure sensitive layer (4), and the lower surface of the contact electrode of the column contact electrode layer (7) is bonded to the upper surface of the lower flexible film layer (9); the electrical break point (8) between the column contact electrodes is located on the serpentine wire of the column contact electrode layer (7); the lower surface of the microfluidic channel layer (5) is bonded to the upper surface of the column contact electrode layer (7); the lower surface of the rectangular lower flexible film layer (9) serves as the second direct acting layer for the external pressure signal of the flexible stretchable pressure sensor.

2. The programmable flexible pressure sensor based on multi-level konjac sponge according to claim 1, characterized in that, The microfluidic channel layer (5) is divided into two layers: the lower layer is the flow channel layer and the upper layer is the encapsulation layer. The flow channel layer is provided with three levels of microfluidic channels: inner, middle and outer. Each level of microfluidic channel is provided with the same number of circular chambers. The diameter and width of each level of microfluidic channel and the diameter of the circular chambers gradually increase from the inside to the outside. The encapsulation layer covers the flow channel layer and only opens circular holes of the same diameter at the corresponding positions above the circular chambers to expose the circular chambers. The inner, middle and outer microfluidic channels in the flow channel layer are provided with corresponding flow channel inlets (10) and flow channel outlets (11) for the input and output of fluid.

3. The programmable flexible pressure sensor based on multi-level konjac sponge according to claim 2, characterized in that, In the pressure-sensitive layer (4), multiple hemispherical konjac sponges in each pressure-sensitive unit are evenly placed in the circular chambers of the inner, middle and outer three-level flow channels of the microfluidic channel layer (5); the diameter of the hemispherical konjac sponge is the same as the diameter of the circular chamber, and the bottom of the hemispherical konjac sponge has a channel with the same width and radius as the microfluidic channel.

4. The programmable flexible pressure sensor based on multi-level konjac sponge according to claim 1, characterized in that, The upper flexible film layer (1) and the lower flexible film layer (9) are made of flexible and stretchable silicone material.

5. The programmable flexible pressure sensor based on multi-level konjac sponge according to claim 1, characterized in that, The upper surface of the contact electrode of the row contact electrode layer (2) and the lower surface of the contact electrode of the column contact electrode layer (7) are covered with a flexible insulating layer.

6. The programmable flexible pressure sensor based on multi-level konjac sponge according to claim 1, characterized in that, The contact electrodes of the row contact electrode layer (2) and the column contact electrode layer (7) are both circular.

7. The programmable flexible pressure sensor based on multi-level konjac sponge according to claim 1, characterized in that, The electrical break point (3) between the row contact electrodes and the electrical break point (8) between the column contact electrodes are composed of two layers of flexible polyimide insulating material.

8. The programmable flexible pressure sensor based on multi-level konjac sponge according to claim 1, characterized in that, The multiple hemispherical konjac sponges are prepared by mixing a pre-concentrated alkaline solution, a pore-forming agent, a plasticizer, and konjac flour.

9. A method for fabricating a programmable flexible pressure sensor based on multi-level konjac sponge, characterized in that, Perform the following steps S1-S6 to complete the fabrication of the programmable flexible pressure sensor based on multi-level konjac sponge as described in any one of claims 1-8: Step S1: Spin-coat and cure a layer of polydimethylsiloxane on a glass slide to form a flexible transparent film. After surface hydrophilic modification by oxygen plasma, spin-coat a layer of polyimide to form an insulating film. A chromium / gold metal layer was magnetron sputtered onto a polyimide film, and after photolithography and wet etching processes, contact electrodes, serpentine wires and electrical breaks were formed. Then, a polyimide film was spin-coated, and the contact electrodes that need to contact the pressure-sensitive layer (4) were exposed by reactive ion etching. Then, the contact electrodes were transferred from the polydimethylsiloxane flexible transparent film with water-soluble tape. Then, a silicon dioxide film was sputtered on the back of the contact electrodes. After the water-soluble tape was completely dissolved in deionized water, the row contact electrode layer (2), the electrical breaks between the row contact electrodes (3), the column contact electrode layer (7) and the electrical breaks between the column contact electrodes (8) were finally prepared. Step S2: Mix konjac flour, pore-forming agent, and plasticizer according to the preset design ratio to swell, add the preset ratio of alkaline solution and stir evenly, pour into the pre-prepared multi-level hemispherical groove mold, cross-link and stand at room temperature to form, and then freeze overnight in a freezer; after thawing, decolorization with citric acid solution and repeated washing with water, obtain a pressure-sensitive layer with multi-level konjac sponge (4). Step S3: Prepare a photosensitive resin mold for the microfluidic channel layer (5) using 3D printing technology, pour polydimethylsiloxane into it and heat it to cure, and then prepare the microfluidic channel layer (5) after demolding and bonding. Step S4: Prepare a photosensitive resin mold for the support layer (6) using 3D printing technology, pour polydimethylsiloxane into it and heat it to cure to form the support layer (6). Step S5: Prepare photosensitive resin molds for upper flexible film layer (1) and lower flexible film layer (9) using 3D printing technology, pour polydimethylsiloxane and heat to cure to form upper flexible film layer (1) and lower flexible film layer (9). Step S6: The pressure-sensitive layer (4) prepared in step S2 is added to the circular cavity in the microfluidic channel layer (5) prepared in step S3. Finally, the row contact electrode layer (2), the electrical break point between the row contact electrodes (3), the pressure-sensitive layer (4), the microfluidic channel layer (5), the support layer (6), the column contact electrode layer (7), the electrical break point between the column contact electrodes (8), and the lower flexible film layer (9) are bonded by oxygen plasma to form a programmable flexible pressure sensor based on multi-level konjac sponge.

10. A programmable control method for a programmable flexible pressure sensor based on multi-level konjac sponge, characterized in that, The programmable flexible pressure sensor based on multi-level konjac sponge as described in any one of claims 2-3 is subject to programmable control, including: programmable control of the stiffness of the multi-level konjac sponge and programmable control of the dielectric constant of the multi-level konjac sponge. Specifically, the multi-level konjac sponge stiffness programmable control involves: using the three-level microfluidic channels in the microfluidic channel layer (5) to allow the hemispherical konjac sponge to absorb water, controlling the amount of water absorbed by the hemispherical konjac sponge, and adjusting the stiffness of each hemispherical konjac sponge, as follows: One approach is to control the filling rate of the liquid inside the hemispherical konjac sponge of the same level to maintain consistency, as well as the gradient change in the filling rate of the liquid inside the hemispherical konjac sponge between levels, so that the stiffness of the hemispherical konjac sponge of the same level is the same, while the stiffness of the hemispherical konjac sponge of different levels varies. The other approach is to control the gradient change in the filling rate of the liquid inside the hemispherical konjac sponge in the same level microchannel by adjusting the flow rate and flow rate of the liquid in the same level microchannel, so that the stiffness of the hemispherical konjac sponge of the same level varies. The programmable control of the dielectric constant of the multi-level konjac sponge is specifically achieved by introducing fluids with different dielectric constants through the three-level microchannels in the microfluidic channel layer (5) to adjust the dielectric constant of each hemispherical konjac sponge, as follows: One type involves controlling the inflow of different types of media into the inner, middle, and outer microchannels, as well as maintaining a consistent liquid filling rate within the same-level hemispherical konjac sponge, thus ensuring that the media in the three-level hemispherical konjac sponges differ while the stiffness of the same-level hemispherical konjac sponges remains consistent. The other type involves controlling the inflow of different types of media into the inner, middle, and outer microchannels, as well as the gradient change in the liquid filling rate within the same-level hemispherical konjac sponge, thus ensuring that the media in the three-level hemispherical konjac sponges differ while the stiffness of the same-level hemispherical konjac sponges varies gradient.

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