Reconfigurable flexible pressure sensor based on magnetic ion droplets and its preparation method

Abstract

The present invention provides a reconfigurable flexible pressure sensor based on magnetic ion droplets and a preparation method thereof, wherein superparamagnetic nanoparticles are combined with ion droplets to prepare magnetic ion droplets with high fluidity and magnetic controllability, and the magnetic ion droplets are used as the pressure sensitive layer of the pressure sensor device to construct a flexible stretchable pressure sensor based on the magnetic ion droplet array. The present invention also provides a distributed / combined non-contact multi-element in-situ reversible reconstruction method of the flexible pressure sensor, which uses an external magnetic field to control the magnetic ion droplets in the sensor to perform programmable low-resistance rapid movement and deformation between the super-hydrophobic interconnected microfluidic channels and chamber arrays, so as to regulate the spatial distribution, composition / volume and geometric shape changes of the magnetic ion droplets in the array, and achieve the distributed / combined non-contact multi-element in-situ reversible reconstruction of the performance of the flexible stretchable pressure sensor in terms of spatial resolution, sensitivity, detection limit and pressure response mode through one or more combinations of changes.

Description

Technical Field

[0001] The present invention belongs to the field of flexible pressure sensors, and in particular relates to a reconfigurable flexible pressure sensor based on magnetic ion droplets and a preparation method thereof. Background Art

[0002] Flexible pressure sensors can be tightly attached to a variety of complex curved surfaces, and can achieve stable and accurate physiological signal detection. They are widely used in tactile perception, fingerprint recognition, human-computer interaction, and medical monitoring. The recyclability, self-healing, and reusability of flexible electronic sensor devices have also become key issues that developers need to consider. As an important component of many biomedical diagnosis and treatment systems, flexible pressure sensors with single performance and fixed electronic materials have been unable to meet complex task environments and rapidly changing detection needs. For example, lesions will change in position, shape, and mechanical sensitivity as the disease progresses. This requires flexible pressure sensors with different spatial resolutions, sensitivities, geometric shapes, and other performances to meet the corresponding detection needs. Therefore, in order to further improve the scene adaptability, reusability, and diversity and differences in the use of flexible pressure sensors, it is necessary to reconstruct the performance of flexible pressure sensors.

[0003] At present, there are two main reconfigurable methods for flexible pressure sensors: (1) Designing multifunctional sensing modules on the same flexible substrate, such as pressure, temperature, humidity and electrochemical sensing modules. This method integrates multiple types of sensing elements to achieve multi-environmental parameter perception of the working scene, which can not only meet the detection of mechanical signals in the environment, but also detect other physical signals and biochemical signals, and to a certain extent realize the functional reconstruction of flexible pressure sensors. However, this method is difficult to regulate the performance of a single sensor. Once the sensor device is prepared, it cannot be changed. Although the multi-sensing chamber brings the function of multi-environmental parameter detection, it also leads to an increase in the area, volume and weight of the entire device, which limits its development in the field of wearable and especially implantable medical devices. (2) Reconstructing the performance of the sensor in terms of sensitivity, detection limit, response speed, etc. by regulating the pressure-sensitive layer of the sensor. One is to reconstruct the sensitivity and function of the sensor by regulating the geometric deformation of the sensitive layer with mechanical external force. This method is a contact reconstruction method that requires mechanical external force to act directly on the sensitive layer. It is mostly suitable for the performance reconstruction of off-body pressure sensors, which limits its application in the field of wearable / implantable medical monitoring. Therefore, it is necessary to develop a non-contact reconfigurable method for flexible pressure sensors. Another method is to regulate the physical properties of the sensitive layer such as stiffness and conductivity through a magnetic field, and ultimately achieve changes in the detection range and sensitivity. Although this method realizes the non-contact in-situ reconstruction of the flexible pressure sensor, and the magnetic field regulation is also fast and efficient, the method of reconstructing the sensor performance based on stiffness regulation and conductivity regulation is relatively simple, and the latter reconstruction method is unidirectional and irreversible, requiring extreme conditions (such as high temperature) to demagnetize the magnetized particles and regress the overall performance. Therefore, it is necessary to develop a flexible pressure sensor with multi-element in-situ reversible reconstruction. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a reconfigurable flexible pressure sensor based on magnetic ion droplets and a preparation method thereof, which can solve the main problems in the prior art that the reconfigurable flexible pressure sensor is difficult to take into account multiple, non-contact in-situ and rapid reversibility, as well as the problem that it cannot meet complex and unknown task environments and rapidly changing detection requirements.

[0005] To solve the above technical problems, the present invention provides the following technical solution: a reconfigurable flexible pressure sensor based on magnetic ion droplets, comprising: a flexible stretchable pressure sensor device, and a magnetic ion droplet placed inside the flexible stretchable pressure sensor device.

[0006] The flexible and stretchable pressure sensor device includes: an upper flexible substrate layer, a row contact electrode layer, electrical breakpoints between rows, an interconnected microfluidic layer, a magnetic ion droplet, a column contact electrode layer, electrical breakpoints between columns, and a lower flexible substrate layer.

[0007] The upper surface of the upper flexible substrate layer serves as the first direct action layer of the external pressure signal of the flexible stretchable pressure sensor device. The row contact electrode layer is an island-bridge structure, the electrode is the island, the serpentine wire is the bridge, and the upper surface of the electrode of the row contact electrode layer is bonded to the bottom surface of the upper flexible substrate layer; the inter-row electrical breakpoint is located on the serpentine wire of the row contact electrode layer, which can meet the mechanical stretching requirements of the row contact electrode layer and block the electrical interconnection between the electrodes of the row contact electrode layer.

[0008] The interconnected microfluidic layer is bonded to the lower surface of the row contact electrode layer; a plurality of circular chambers are arranged on the interconnected microfluidic layer, each chamber is connected by a microfluidic channel, and the circular chamber contains magnetic ion droplets for accommodating pressure detection; the lower surface of the electrode of the row contact electrode layer is in direct contact with the magnetic ion droplets on the interconnected microfluidic layer, and the magnetic ion droplets flow and transport between the chambers through the microfluidic channel; the cross-sectional size of the channel is smaller than the diameter of the magnetic ion droplets, so as to avoid uncontrolled contact of the droplets between the chambers.

[0009] The column contact electrode layer is an island-bridge structure, in which the electrode is the island and the serpentine wire is the bridge. The upper surface of the electrode of the column contact electrode layer is in direct contact with the magnetic ion droplets on the interconnected microfluidic layer, and the lower surface of the electrode of the column contact electrode layer is bonded to the top surface of the lower flexible substrate layer. The electrical breakpoint between columns is located on the serpentine wire of the column contact electrode layer, which can meet the mechanical stretching requirements of the column contact electrode layer and block the electrical interconnection between the electrodes of the column contact electrode layer. The interconnected microfluidic layer is bonded to the upper surface of the column contact electrode layer.

[0010] The lower surface of the lower flexible substrate layer serves as the second direct acting layer for external pressure signals of the flexible and stretchable pressure sensor device.

[0011] Furthermore, the aforementioned upper flexible substrate layer and lower flexible substrate layer are made of flexible and stretchable polymer materials.

[0012] Furthermore, the upper surface of the electrodes of the row contact electrode layer and the lower surface of the electrodes of the column contact electrode layer are both covered with a flexible insulating layer.

[0013] Furthermore, the electrodes of the aforementioned row contact electrode layer and the electrodes of the column contact electrode layer are both circular.

[0014] Furthermore, the chambers arranged on the aforementioned interconnected microfluidic layer are made of a flexible and stretchable polymer material.

[0015] Furthermore, the aforementioned magnetic ion droplets are a uniform and stable mixture of a base liquid, a surfactant and superparamagnetic nanoparticles.

[0016] Another aspect of the present invention provides a method for preparing a reconfigurable flexible pressure sensor based on magnetic ion droplets, comprising the following steps:

[0017] S1. Spin-coat and cure a layer of polydimethylsiloxane on a glass sheet to form a flexible transparent film, and then spin-coat a layer of polyimide after UV modification to form an insulating layer film; magnetron sputter a chromium / gold metal film on the polyimide, and form contact electrodes, serpentine wires and electrical breakpoints after photolithography and etching processes, then spin-coat a layer of polyimide and etch to expose the electrode, and finally sputter a silicon dioxide film on the back of the electrode and bond it to the pre-prepared polydimethylsiloxane flexible substrate. Prepare a photosensitive resin mold for the interconnected microfluidic layer by 3D printing technology, pour polydimethylsiloxane and heat and cure to form a microfluidic channel and a circular chamber film, and prepare the interconnected microfluidic layer after demolding. Carboxylate the surface of the interconnected microfluidic layer and the row and column contact electrodes, and hydrophobically modify the surface of the electrode and the interconnected microfluidic layer using polydimethylsiloxane and super-hydrophobic nanocomposites. Finally, the flexible substrate, row contact electrodes, column contact electrodes, and interconnected microfluidic layer are aligned and bonded together to prepare a flexible stretchable pressure sensor device with a closed interconnected microfluidic circular chamber;

[0018] S2, weighing a base liquid, a surfactant, and superparamagnetic nanoparticles respectively, mixing the base liquid and the surfactant and oscillating them to form a stable and uniform solution A, then mixing the superparamagnetic nanoparticles into the prepared solution A, oscillating and stirring to form a dispersion B, and finally ultrasonically dispersing the prepared dispersion B to form magnetic ion droplets;

[0019] S3. Injecting the magnetic ion droplets prepared in step S2 into the flexible stretchable pressure sensor device prepared in step S1 to form a multi-element in-situ reversible reconstructible flexible pressure sensor based on the magnetic ion droplet array.

[0020] The present invention also provides a multi-element reconstruction method of magnetic ion droplets for use in a reconfigurable flexible pressure sensor, including reconstruction of magnetic ion droplet spatial distribution, reconstruction of magnetic ion droplet components and volume, and reconstruction of magnetic ion droplet geometry;

[0021] The spatial distribution reconstruction of magnetic ion droplets is specifically: using magnetic field to drive magnetic ion droplets to shuttle between different array chambers, thereby changing the density and arrangement pattern of droplets in the local area, and then regulating the spatial detection resolution and target detection pattern of the sensor;

[0022] The composition and volume reconstruction of magnetic ion droplets is specifically as follows: using a magnetic field to drive magnetic ion droplets with different ion concentrations, ion types, quantities and volumes to mix between the array chambers, thereby changing the ion concentration, type and volume of the magnetic ion droplets in the target array chamber, and then regulating the sensitivity of the sensor;

[0023] The geometric shape reconstruction of magnetic ion droplets is specifically: using the magnetic field to control the change of the geometric shape of the magnetic ion droplets, thereby changing the contact mode and morphology between the droplets and the row / column contact electrodes, and then controlling the sensitivity and pressure response mode performance of the sensor.

[0024] Compared with the prior art, the beneficial technical effects of the present invention using the above technical solution are as follows:

[0025] 1. Combine superparamagnetic nanoparticles with ionic droplets to prepare magnetic ionic droplets, and achieve programmable low-resistance rapid movement and deformation in superhydrophobic microfluidic channels and chambers through magnetic field regulation.

[0026] 2. Introduce magnetic ion droplets into flexible pressure sensors and use the remote control characteristics of the magnetic field to achieve non-contact in-situ regulation of the pressure-sensitive layer.

[0027] 3. By regulating the position and number of magnetic ion droplets in the array chamber, spatial distribution reconstruction can be achieved, and then the sensing pattern and spatial resolution of the flexible pressure sensor can be reconstructed.

[0028] 4. Magnetic ion droplets of different viscosities, ion types and volumes are merged through magnetic field control to achieve reconstruction of the composition and volume of the magnetic ion droplets in the target array chamber.

[0029] 5. Use complex magnetic fields to reconstruct the geometric shape of magnetic ion droplets, thereby changing the contact mode between the magnetic ion droplets and the electrodes and affecting the pressure response.

[0030] 6. The reconfigurable flexible pressure sensor can be manufactured by micro-nano processing methods such as lithography, etching, sputtering, bonding and transfer. It has high precision, small size and mature technology. The entire sensor is flexible and stretchable.

[0031] 7. Relevant researchers in this field have not yet applied magnetic ion droplets to the sensitive layer of flexible pressure sensors and simultaneously achieved non-contact multivariate, in-situ, and reversible reconstruction of flexible pressure sensors under magnetic field regulation. The present invention provides a new idea for constructing a new type of reconfigurable flexible pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structure of the reconfigurable flexible pressure sensor based on magnetic ion droplets in the present invention.

[0033] Figure 2 It is a schematic diagram of the processing of the flexible and stretchable pressure sensor device in the present invention.

[0034] Figure 3 It is a schematic diagram of the hydrophobic treatment process of the interconnected microfluid layer and the contact electrode surface in the present invention.

[0035] Figure 4 It is a schematic diagram of the composition and preparation process of the magnetic ion droplets in the present invention.

[0036] Figure 5 This is a schematic diagram of the assembly of the reconfigurable flexible pressure sensor based on magnetic ion droplets in the present invention.

[0037] Figure 6 It is a schematic diagram of the distributed / combined multi-reconstruction method of magnetic ion droplets in the present invention.

[0038] In the figure, 1-flexible stretchable pressure sensor device, 2-magnetic ion droplet, 3-upper flexible substrate layer, 4-row contact electrode layer, 5-electrical breakpoints between rows, 6-interconnected microfluidic layer, 7-column contact electrode layer, 8-electrical breakpoints between columns, 9-lower flexible substrate layer, 10-base liquid, 11-surfactant, 12-superparamagnetic nanoparticles. DETAILED DESCRIPTION

[0039] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0040] Various aspects of the invention are described herein with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the invention are not limited to those described in the accompanying drawings. It should be understood that the invention is implemented by any of the various concepts and embodiments described above, as well as the concepts and embodiments described in detail below, because the concepts and embodiments disclosed in the invention are not limited to any implementation. In addition, some aspects disclosed in the invention may be used alone or in any appropriate combination with other aspects disclosed in the invention.

[0041] The present invention provides a reconfigurable flexible pressure sensor based on magnetic ion droplets, constructs highly fluid and magnetically controllable magnetic ion droplets as the pressure-sensitive layer of a flexible and stretchable pressure sensor device, and uses magnetic fields to control the magnetic ion droplets to perform programmable movement and deformation between array chambers, thereby achieving rapid, multivariate, in-situ, and reversible reconstruction of the pressure sensor's performance in terms of spatial resolution, detection pattern, sensitivity, and detection limit.

[0042] refer to Figure 1 A reconfigurable flexible pressure sensor based on magnetic ion droplets comprises: a flexible stretchable pressure sensor device 1, and a magnetic ion droplet 2 placed inside the flexible stretchable pressure sensor device 1, wherein the overall size of the flexible stretchable pressure sensor device 1 is 50 mm × 50 mm × 4 mm.

[0043] The flexible stretchable pressure sensor device 1 includes: an upper flexible substrate layer 3, a row contact electrode layer 4, electrical breakpoints between rows 5, an interconnected microfluidic layer 6, magnetic ion droplets 2, a column contact electrode layer 7, electrical breakpoints between columns 8, and a lower flexible substrate layer 9; a plurality of circular chambers are arranged on the interconnected microfluidic layer 6, each chamber is connected by a microfluidic channel, and the circular chamber contains a magnetic ion droplet 2 for pressure detection.

[0044] The upper surface of the upper flexible substrate layer 3 serves as the first direct action layer of the external pressure signal of the flexible stretchable pressure sensor device 1. In this embodiment, the upper flexible substrate layer 3 is a flexible stretchable polymer material and is a direct action layer of the external pressure signal. The overall thickness of the upper flexible substrate layer 3 is less than 1 mm, and a flexible polymer material such as polyimide (PI), polyethylene succinate (EcoFlex), Dragon Skin or polydimethylsiloxane (PDMS) is used. Transparent PDMS material is preferred to facilitate observation of the controlled state of the magnetic ion droplet 2.

[0045] In this embodiment, the row contact electrode layer 4 is an electrode layer with an island-bridge structure, bonded to the bottom surface of the upper flexible substrate layer 3, and the circular electrode is an island, and the serpentine wire is a bridge; the lower surface of the circular electrode is an exposed electrode surface, which is in direct contact with the magnetic ion droplet 2, and the upper surface of the circular electrode is covered with a flexible polyimide (PI) insulating layer, and the upper surface of the row contact electrode layer 4 is bonded to the lower surface of the upper flexible substrate layer 3. The circular electrode is designed as a 10 × 11 array (one column is a row lead electrode), the electrode diameter is 4mm, the thickness is 1µm, the serpentine electrode bending angle is 240°, the line width is 100µm, and the electrode material is chromium / copper (Cr / Cu, 5nm / 50nm) and chromium / gold (Cr / Au, 5nm / 50nm).

[0046] In this embodiment, the inter-row electrical breakpoint 5 is located on the serpentine conductor of the row contact electrode layer 4 and is made of flexible polyimide (PI) insulating material, which can meet the mechanical stretching requirements of the row contact electrode layer 4 and block the electrical interconnection between the electrodes of the row contact electrode layer 4.

[0047] The interconnected microfluidic layer 6 is bonded to the lower surface of the row contact electrode layer 4, and the lower surface of the electrode of the row contact electrode layer 4 is in direct contact with the magnetic ion droplets 2 on the interconnected microfluidic layer 6. In this embodiment, the interconnected microfluidic layer 6 is composed of a microfluidic channel and a circular chamber. The circular chamber is a pressure-sensitive layer space for accommodating the magnetic ion droplets 2, and the microfluidic channel is a transitional channel for magnetic ion droplets, which is used for droplet transport between chambers. The interconnected microfluidic circular chamber is a flexible polymer material. The circular chamber is designed as a 10 × 10 array, and each chamber is directly opposite to the circular contact electrode up and down. The diameter of each circular chamber is 5 mm and the depth is 2 mm. The circular chambers are interconnected by microfluidic channels, which can allow the magnetic ion droplets 2 to move through. The cross-sectional size of the channel is 2 mm × 2 mm, which needs to be lower than the diameter of the magnetic ion droplets 2, so as to avoid uncontrolled contact of droplets between chambers.

[0048] In this embodiment, the column contact electrode layer 7 is an electrode layer with an island-bridge structure, bonded to the top surface of the lower flexible substrate layer 9, and the circular electrode is an island, and the serpentine wire is a bridge; the upper surface of the circular electrode is an exposed electrode surface, which is in direct contact with the magnetic ion droplet 2, and the lower surface of the circular electrode is covered with a flexible polyimide (PI) insulating layer, and the lower surface of the electrode of the column contact electrode layer 7 is bonded to the upper surface of the lower flexible substrate layer 9. The circular electrode is designed as an 11 × 10 array (one row is a column lead electrode), the electrode diameter is 4mm, the thickness is 1µm, the serpentine electrode bending angle is 240°, the line width is 100µm, and the electrode material is titanium / copper (Ti / Cu, 5nm / 50nm) or chromium / gold (Cr / Au, 5nm / 50nm).

[0049] The interconnected microfluidic layer 6 is bonded to the upper surface of the column contact electrode layer 7 , and the upper surface of the electrode of the column contact electrode layer 7 is in direct contact with the magnetic ion droplets 2 on the interconnected microfluidic layer 6 .

[0050] In this embodiment, the inter-column electrical breakpoint 8 is located on the serpentine wire of the column contact electrode layer 7 and is composed of a flexible polyimide (PI) insulating material, which can meet the mechanical stretching requirements of the column contact electrode layer 7 and block the electrical interconnection between the electrodes of the column contact electrode layer 7.

[0051] The lower surface of the lower flexible substrate layer 9 serves as the second direct action layer of the external pressure signal of the flexible stretchable pressure sensor device 1. In this embodiment, the lower flexible substrate layer 9 is a flexible stretchable polymer material and is a direct action layer of the external pressure signal. The overall thickness of the lower flexible substrate layer 9 is less than 1 mm, and a flexible polymer material such as polyimide (PI), polyethylene succinate (EcoFlex), Dragon Skin or polydimethylsiloxane (PDMS) is used. Transparent PDMS material is preferred to facilitate observation of the controlled state of the magnetic ion droplet 2.

[0052] In this embodiment, the magnetic ion droplet 2 comprises:

[0053] Base liquid 10, surfactant 11 and superparamagnetic nanoparticles 12.

[0054] In this embodiment, the base liquid 10 is an ionic droplet, which is composed of a water-based electrolyte solution or a non-aqueous electrolyte solution. The water-based electrolyte solution is a neutral electrolyte solution, and one of the liquids such as a sodium chloride electrolyte base liquid with a high ion concentration of mixed glycerol, a sodium chloride electrolyte base liquid, deionized water, a phosphate buffer solution PBS, a hydrogel and a mixture thereof is used. The non-aqueous electrolyte solution is an ionic liquid (ILs) and a mixture thereof, including: imidazole ionic liquids, such as 1-ethyl-3-methylimidazolium acetate; pyridine ionic liquids, such as 1-butylpyridinium hexafluorophosphate; quaternary ammonium salt ionic liquids, such as 1-butyl-3-methylimidazolium tetrafluoroborate; quaternary phosphonium salt ionic liquids, such as trihexyltetradecylphosphine tetrafluoroborate; guanidine ionic liquids, such as 1-butylguanidine hexafluorophosphate. The non-aqueous electrolyte solution in this embodiment uses one or more mixed liquids of the above ionic liquids.

[0055] In this embodiment, the surfactant 11 is one of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), oleic acid (OA), citric acid (CA), sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium salt (CTAB), betaine (Bet), tetramethylammonium hydroxide (TMAH) or soy lecithin (SL) organic solution, which is used to reduce the interfacial tension between the magnetic nanoparticles and the base liquid, so that the magnetic particles are better dispersed in the base liquid, prevent particle agglomeration, and improve the fluidity and stability of the magnetic ionic liquid.

[0056] In this embodiment, the superparamagnetic nanoparticles 12 are at least one of Fe3O4, Au / Fe3O4, Fe3O4 adsorbed with carbon nanotubes or graphene, and Au / Fe3O4 adsorbed with carbon nanotubes or graphene, and the particle size is 10-200 nm.

[0057] In this embodiment, the magnetic ion droplets 2 are a uniform and stable mixture of a base liquid 10 , a surfactant 11 and superparamagnetic nanoparticles 12 .

[0058] Another aspect of the present invention provides a method for preparing a reconfigurable flexible pressure sensor based on magnetic ion droplets, which involves micromachining processes such as photolithography, etching, sputtering, bonding and transfer, and includes the following steps:

[0059] S1: Prepare a flexible and stretchable pressure sensor device 1.

[0060] S2: preparing magnetic ionic droplets 2.

[0061] S3: injecting the magnetic ion droplets prepared in step S2 into the flexible stretchable pressure sensor device prepared in step S1 to form a reconfigurable flexible pressure sensor based on magnetic ion droplets.

[0062] Step S1 includes the following steps S11 to S14:

[0063] S11: preparing a row contact electrode layer 4, a column contact electrode layer 7, an upper flexible substrate layer 3, and a lower flexible substrate layer 9

[0064] like Figure 2 As shown in the figure, a layer of polydimethylsiloxane (PDMS) is spin-coated on a glass sheet at a speed of 500 rpm, and cured on a hot plate at 80 ° C for half an hour to form a flexible transparent film; the glass sheet and the flexible transparent film on it are placed in a UV light box for irradiation for 3 minutes to modify the surface of the transparent film and facilitate the subsequent bonding of the PI insulating layer; a layer of polyimide (PI) is spin-coated on the surface of the surface-modified flexible transparent film at a speed of 2000 rpm, and cured in a glove box at 250 ° C for 2 hours to form a PI insulating layer film; a layer of chromium / gold (Cr / Au, 5nm / 50nm) metal film is sputtered on the surface of the PI insulating layer film by magnetron sputtering technology; the chromium / gold metal film is patterned by photolithography and wet etching processes to form a row / column contact electrode layer composed of circular electrodes and serpentine wires and electrical breakpoints between rows / columns; a layer of PI is spin-coated on the surface of the electrode layer as an insulating layer, and after curing, photolithography and plasma etching processes are used to form a PI insulating layer on the surface of the PI The circular contact electrode is exposed separately on the insulating layer, and the PI of the area other than the serpentine wire is etched; the above-mentioned electrode is peeled off from the PDMS substrate using a water-soluble tape, transferred to a temporary glass substrate and fixed with tape, at this time, the exposed contact electrode faces the glass substrate, and the back of the contact electrode faces upward, and the water-soluble tape faces downward; a layer of silicon dioxide film (5nm) is sputtered on the back of the contact electrode by magnetron sputtering technology, and a flexible substrate layer (PDMS film) is prepared by a demolding process for standby use; the back of the contact electrode sputtered with silicon dioxide and the PDMS flexible substrate layer are bonded together after being treated with oxygen plasma to form a row contact electrode layer 4, a column contact electrode layer 7, an upper flexible substrate layer 3, and a lower flexible substrate layer 9.

[0065] S12: Preparation of interconnected microfluidic layer 6

[0066] like Figure 3As shown, a photosensitive resin mold of the interconnected microfluidic layer 6 is designed and prepared by 3D printing technology; uncured PDMS (10:1 ratio) is poured into the mold and cured on a hot plate at 80°C for half an hour to form the microfluidic channels and circular chamber films of the interconnected microfluidic layer 6; finally, the cured circular chamber film is taken out to obtain the desired interconnected microfluidic layer 6.

[0067] S13: Surface hydrophobic treatment of the interconnected microfluidic layer 6 and the contact electrodes

[0068] like Figure 3 As shown, first, an oxygen plasma cleaner is used to perform surface hydroxylation on the interconnected microfluidic layer 6 and the required areas of the row contact electrodes and column contact electrodes; then a flexible PDMS stamp (10:1 ratio) is physically pressed onto the surface of the hydroxylated row / column contact electrodes and the interconnected microfluidic layer for 15 minutes, during which a layer of nanometer-thick PDMS oligomer is transferred and fixed on the surface of the electrode and the interconnected microfluidic layer; a superhydrophobic nanocomposite material (PFCM1604V, FluoroPelTM) is sprayed on the PDMS oligomer-modified electrode and interconnected microfluidic layer surface to further improve the surface hydrophobicity, thereby reducing the droplet response time.

[0069] S14: Assemble and bond the various parts to construct a flexible and stretchable pressure sensor device 1

[0070] like Figure 1 As shown, the row contact electrode layer 4, column contact electrode layer 7, upper flexible substrate layer 3, lower flexible substrate layer 9, and interconnected microfluidic layer 6 prepared in steps S11 to S13 and subjected to surface hydrophobic treatment are placed in an oxygen plasma cleaning machine for surface hydroxylation treatment, and then the above parts are physically aligned and pressed in the upper flexible substrate layer 3, row contact electrode layer 4, interconnected microfluidic layer 6, column contact electrode layer 7 and lower flexible substrate layer 9 in the upper and lower order, and heated at 80°C for 30 minutes for bonding, and finally a flexible stretchable pressure sensor device 1 with a closed interconnected microfluidic circular chamber is obtained.

[0071] In this embodiment, the step S2 is as follows: Figure 4 As shown, including:

[0072] S21: Weigh the base liquid 10, surfactant 11, and superparamagnetic nanoparticles 12 respectively, and weigh the corresponding base liquid 10, surfactant 11, and superparamagnetic nanoparticles 12 respectively according to a mass ratio of 4:1:1. The above mass ratio, nanoparticle size, etc. can be adjusted according to actual needs.

[0073] S22: mixing and oscillating the surfactant 11 and the base liquid 10 to fully dissolve the surfactant 11 in the base liquid to form a stable and uniform solution A;

[0074] S23: mixing the superparamagnetic nanoparticles 12 weighed in step S21 with the solution A prepared in step S22, and forming a stable dispersion B after oscillation and stirring;

[0075] S24: Finally, the dispersion B is ultrasonically dispersed by an ultrasonic disperser for 30 min, and a stable and uniform nanomagnetic fluid dispersion, namely, magnetic ion droplets 2, is finally formed.

[0076] In this embodiment, the step S3 is as follows: Figure 5 As shown, including:

[0077] Under the control of a magnetic field and a microfluidic injection pump, 2 drops of magnetic ionic liquid obtained in step S2 are injected into the circular chamber of the flexible stretchable pressure sensor device 1 prepared in step S1, and finally a reconfigurable flexible pressure sensor based on magnetic ionic liquid droplets is constructed.

[0078] Based on the reconfigurable flexible pressure sensor of magnetic ion droplets, this embodiment also provides three distributed / combined multi-reconstruction methods of magnetic ion droplets, and the performance of the sensor is changed by adjusting the magnetic ion droplets. Figure 6 As shown, the three reconstruction methods include: reconstruction of the spatial distribution of magnetic ion droplets, reconstruction of the components and volume of magnetic ion droplets, and reconstruction of the geometric shape of magnetic ion droplets.

[0079] In this embodiment, the spatial distribution of the magnetic ion droplets is reconstructed: the spatial distribution of the magnetic ion droplets is reconstructed, and the spatial resolution and detection of the flexible pressure sensor can be dynamically controlled. The magnetic ion droplets in the array chamber are programmably controlled by a gradient magnetic field, and the magnetic ion droplets are driven to shuttle between different array chambers, so that each array chamber changes between "no" droplets and "with" droplets, thereby using the density of droplets in the local area to control the spatial detection resolution of the sensor. In addition, since the geometric shape of the detected target varies from person to person and changes with the diagnosis and treatment process in actual application scenarios, such as venous ulcer and varicose vein interface pressure detection, in order to improve the scope of application of the sensor, this embodiment is not limited to a single graphic, and a variety of detection patterns are designed, including "square", "circular", "L-shaped" and "snake-shaped", etc., and the feasibility and accuracy of patterning operations of magnetic droplets are verified. The selection of the control route for the spatial distribution of droplets will directly affect the control efficiency. To this end, this embodiment designs different control routes for time characterization according to the distribution of magnetic ion droplets around the control area in the initial state, and determines the optimal control route for each density and pattern to achieve fast and efficient control.

[0080] In this embodiment, the magnetic ion droplet component and volume reconstruction: the ion concentration of the magnetic ion droplet is reconstructed, and the sensitivity and detection range of the flexible pressure sensor can be adjusted. In this embodiment, at least two magnetic ion droplets of ion concentrations are encapsulated in the initial state of the sensor, wherein the mass proportion of sodium chloride is 10% and 20% respectively, the droplet volume is 50~100μL, and the magnetic ion droplets of the two concentrations are distributed in different array chambers. Through gradient magnetic field control, the two droplets of different concentrations and quantities are merged and mixed to achieve the regulation of the droplet ion concentration between 10%~20%. According to the unit area capacitance between the droplet and the contact electrode at different frequencies (101Hz~105Hz) and concentrations, the change law between the ion concentration and the unit area capacitance is obtained. At the same time, after two or more droplets are mixed, the volume of the new droplet and its contact area with the contact electrode also change, so the mixing between the droplets ultimately affects the performance of the sensor. In this embodiment, the droplet ion concentration and the number of droplets before reconstruction can be customized and pre-packaged according to actual needs.

[0081] In this embodiment, the geometric shape of the magnetic ion droplets is reconstructed: the geometric shape of the magnetic ion droplets is reconstructed, which directly affects the contact area with the contact electrode, and then the sensitivity and other performance of the flexible pressure sensor can be adjusted. In this embodiment, three types of geometric shape reconstructions are designed under the premise that the cavity structure design and material selection remain unchanged. The first type is a conventional spherical magnetic droplet. After the droplet is driven to the target array chamber by a gradient magnetic field and the magnetic field is removed, a spherical droplet can be obtained. The second type is a conical magnetic droplet, which is obtained by "stretching" the droplet by applying a gradient magnetic field in the vertical direction of the droplet. This type of conical magnetic droplet has a small initial contact area with the upper contact electrode and has a higher sensitivity. The third type is a patterned magnetic droplet, such as a long strip, a ring, a star, etc., which is obtained by adjusting the magnetic field at the bottom of the droplet for patterned distribution.

[0082] It should be noted that this embodiment combines the above three reconstruction forms to form distributed multi-reconstruction and combined multi-reconstruction. Distributed multi-reconstruction is a one-dimensional reconstruction between different sensor array units, and each unit represents a reconstruction form; combined reconstruction is to perform two or more reconstruction forms in the same sensor array unit at the same time.

[0083] Although the present invention has been described above with preferred embodiments, it is not intended to limit the present invention. A person skilled in the art of the present invention may make various modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the definition of the claims.

Claims

1. A reconfigurable flexible pressure sensor based on magnetic ion droplets, characterized in that: It comprises: a flexible and stretchable pressure sensor device (1), and a magnetic ion droplet (2) placed inside the flexible and stretchable pressure sensor device (1); The flexible stretchable pressure sensor device (1) comprises: an upper flexible substrate layer (3), a row contact electrode layer (4), electrical breakpoints between rows (5), an interconnected microfluidic layer (6), magnetic ion droplets (2), a column contact electrode layer (7), electrical breakpoints between columns (8), and a lower flexible substrate layer (9); The upper surface of the upper flexible substrate layer (3) serves as the first direct action layer of the external pressure signal of the flexible stretchable pressure sensor device (1); the row contact electrode layer (4) is an island-bridge structure, the electrode is the island, the serpentine wire is the bridge, and the electrode upper surface of the row contact electrode layer (4) is bonded to the bottom surface of the upper flexible substrate layer (3); the inter-row electrical breakpoint (5) is located on the serpentine wire of the row contact electrode layer (4), which can meet the mechanical stretching requirements of the row contact electrode layer (4) and block the electrical interconnection between the electrodes of the row contact electrode layer (4); The interconnected microfluidic layer (6) is bonded to the lower surface of the row contact electrode layer (4); a plurality of circular chambers are arranged on the interconnected microfluidic layer (6), each chamber is connected by a microfluidic channel, and the circular chamber contains a magnetic ion droplet (2) for accommodating pressure detection; the lower surface of the electrode of the row contact electrode layer (4) is in direct contact with the magnetic ion droplet (2) on the interconnected microfluidic layer (6), and the magnetic ion droplet (2) flows and is transported between the chambers through the microfluidic channel; the cross-sectional size of the channel is smaller than the diameter of the magnetic ion droplet (2), so as to avoid uncontrolled contact of the droplets between the chambers; The column contact electrode layer (7) is an island-bridge structure, wherein the electrode is an island and the serpentine wire is a bridge; the upper surface of the electrode of the column contact electrode layer (7) is in direct contact with the magnetic ion droplet (2) on the interconnected microfluidic layer (6), and the lower surface of the electrode of the column contact electrode layer (7) is bonded to the top surface of the lower flexible substrate layer (9); the inter-column electrical breakpoint (8) is located on the serpentine wire of the column contact electrode layer (7), which can meet the mechanical stretching requirements of the column contact electrode layer (7) and block the electrical interconnection between the electrodes of the column contact electrode layer (7); the interconnected microfluidic layer (6) is bonded to the upper surface of the column contact electrode layer (7); The lower surface of the lower flexible base layer (9) serves as the second direct action layer for external pressure signals of the flexible and stretchable pressure sensor device (1).

2. The reconfigurable flexible pressure sensor based on magnetic ion droplets according to claim 1 is characterized in that: The upper flexible substrate layer (3) and the lower flexible substrate layer (9) are made of flexible and stretchable polymer materials.

3. The reconfigurable flexible pressure sensor based on magnetic ion droplets according to claim 1 is characterized in that: The upper surface of the electrodes of the row contact electrode layer (4) and the lower surface of the electrodes of the column contact electrode layer (7) are both covered with a flexible insulating layer.

4. The reconfigurable flexible pressure sensor based on magnetic ion droplets according to claim 1 is characterized in that: The electrodes of the row contact electrode layer (4) and the electrodes of the column contact electrode layer (7) are both circular.

5. The reconfigurable flexible pressure sensor based on magnetic ion droplets according to claim 1, characterized in that: The chambers arranged on the interconnected microfluidic layer (6) are made of a flexible and stretchable polymer material.

6. The reconfigurable flexible pressure sensor based on magnetic ion droplets according to claim 1, characterized in that: The magnetic ion droplets (2) are a uniform and stable mixture of a base liquid (10), a surfactant (11) and superparamagnetic nanoparticles (12).

7. A method for preparing a reconfigurable flexible pressure sensor based on magnetic ion droplets, characterized in that: The following steps are involved: S1, spin coating and curing a layer of polydimethylsiloxane on a glass sheet to form a flexible transparent film, and spin coating a layer of polyimide after UV modification to form an insulating layer film; A chromium / gold metal film is magnetron sputtered on polyimide, and contact electrodes, serpentine wires and electrical breakpoints are formed after photolithography and etching processes. A layer of polyimide is then spin-coated and etched to expose the electrode. Finally, a silicon dioxide film is sputtered on the back of the electrode and bonded to a pre-prepared polydimethylsiloxane flexible substrate. A photosensitive resin mold of the interconnected microfluidic layer is prepared by 3D printing technology, polydimethylsiloxane is poured and heated to cure to form a microfluidic channel and a circular chamber film, and the interconnected microfluidic layer is prepared after demoulding. The surfaces of the interconnected microfluidic layer and the row and column contact electrodes and the column contact electrodes are carboxylated, and the surfaces of the electrodes and the interconnected microfluidic layer are hydrophobically modified using polydimethylsiloxane and super-hydrophobic nanocomposites. Finally, the flexible substrate, the row contact electrodes, the column contact electrodes and the interconnected microfluidic layer are aligned and bonded together to prepare a flexible and stretchable pressure sensor device with a closed interconnected microfluidic circular chamber (1). S2, weighing a base liquid (10), a surfactant (11), and superparamagnetic nanoparticles (12) respectively, mixing the base liquid (10) and the surfactant (11) and oscillating them to form a stable and uniform solution A, then mixing the superparamagnetic nanoparticles (12) into the prepared solution A, oscillating and stirring to form a dispersion B, and finally ultrasonically dispersing the prepared dispersion B to form magnetic ion droplets (2); S3, injecting the magnetic ion droplets prepared in step S2 into the flexible stretchable pressure sensor device (1) prepared in step S1, to form a multi-element in-situ reversibly reconstructible flexible pressure sensor based on the magnetic ion droplet array.

8. A multi-element reconstruction method for magnetic ionic droplets according to claim 1, characterized in that: Including reconstruction of the spatial distribution of magnetic ion droplets (2), reconstruction of the composition and volume of magnetic ion droplets (2), and reconstruction of the geometric shape of magnetic ion droplets (2); The spatial distribution reconstruction of magnetic ion droplets (2) is specifically: using a magnetic field to drive the magnetic ion droplets to shuttle between different array chambers, thereby changing the density and arrangement pattern of the droplets in the local area, and then regulating the spatial detection resolution and target detection pattern of the sensor; The composition and volume reconstruction of magnetic ion droplets (2) is specifically as follows: using a magnetic field to drive magnetic ion droplets with different ion concentrations, ion types, quantities and volumes to mix between the array chambers, thereby changing the ion concentration, type and volume of the magnetic ion droplets in the target array chamber, thereby regulating the sensitivity of the sensor; The geometrical shape reconstruction of the magnetic ion droplet (2) is specifically: using a magnetic field to control the change in the geometrical shape of the magnetic ion droplet, thereby changing the contact mode and morphology between the droplet and the row / column contact electrodes, and then controlling the sensitivity and pressure response mode performance of the sensor.

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