Flexible piezoelectric sensor based on porous microstructure PDMS and preparation method thereof

Abstract

The invention relates to the technical field of flexible piezoelectric sensor preparation, and particularly discloses a flexible piezoelectric sensor based on porous microstructure PDMS and a preparation method thereof, and the preparation method comprises the following steps: S1, preparing an organic-inorganic composite cured body; s2, obtaining a solidified block containing a uniformly dispersed sucrose template inside; s3, obtaining the PDMS sponge with the communicated porous microstructure; s4, obtaining a dry sponge with a porous morphology; s5, obtaining a precursor film covering body; and S6, obtaining the porous microstructure ZnO / PDMS composite membrane. S7, forming flexible upper and lower electrode layers; and S8, completing device packaging and obtaining the flexible piezoelectric sensor. Interconnected pore channels are introduced into a PDMS matrix through a sucrose template method, so that the overall specific surface area of the material is remarkably increased, and piezoelectric active ZnO nanowire networks are grown in situ in pore walls, so that external pressure can excite piezoelectric polarization response in a larger range and a deeper level; therefore, the conversion efficiency of the mechanical stress to the electric signal is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of flexible piezoelectric sensor fabrication technology, specifically relating to a flexible piezoelectric sensor based on porous microstructure PDMS and its fabrication method. Background Technology

[0002] In the field of flexible piezoelectric sensors, the demand for high-performance flexible piezoelectric sensors is becoming increasingly urgent with the rapid development of technologies such as the Internet of Things, artificial intelligence, and wearable devices. These sensors need to possess characteristics such as high sensitivity, wide detection range, good stability, and biocompatibility to adapt to complex and diverse application scenarios such as skin-fit monitoring, wearable health monitoring, and artificial intelligence interaction.

[0003] Currently, the fabrication of traditional flexible piezoelectric sensors has some shortcomings. In terms of material structure, many existing technologies use matrix materials with simple structures and limited specific surface areas. For example, the common planar thin film structure results in a small contact area between the material and the external environment, making it difficult to excite an effective piezoelectric polarization response over a large range and at a deeper level when external pressure is applied. This limits the conversion efficiency of mechanical stress into electrical signals, leading to low sensor sensitivity and an inability to meet the requirements for accurate detection of minute pressure changes.

[0004] To address this issue, this application proposes a flexible piezoelectric sensor based on porous microstructure PDMS and its fabrication method. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible piezoelectric sensor based on porous microstructure PDMS and its fabrication method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for fabricating a flexible piezoelectric sensor based on porous microstructured PDMS, comprising:

[0008] S1. PDMS prepolymer and curing agent are mixed evenly with crystalline sucrose particles at a weight ratio of 10:1 to prepare an organic-inorganic composite cured body.

[0009] S2. The composite cured body is placed in an oven at 75-85°C and cured for 1.5-2.5 hours to obtain a cured block containing a uniformly dispersed sucrose template inside.

[0010] S3. Soak the solidified block in 40°C warm water and gently shake for 2-3 hours to dissolve the sucrose template and obtain a connected porous microstructured PDMS sponge.

[0011] S4. Place the porous sponge in a vacuum drying oven at 60°C for 30 minutes to dehydrate it, thereby obtaining a dry sponge that retains its porous morphology.

[0012] S5. The sponge is immersed in a 0.1M zinc acetate solution and subjected to ultrasonic treatment at 20kHz for 5-15 minutes to allow the Zn to... 2+ The precursor fully penetrates into the pore wall to obtain a precursor membrane covering.

[0013] S6. The precursor membrane cover is first pre-baked at 100°C for 30 min to remove the solvent, and then hydrothermally reacted at 140-160°C for 0.5-2 h to grow a ZnO nanowire network in situ on the pore wall of PDMS, thereby obtaining a porous microstructure ZnO / PDMS composite membrane.

[0014] S7. Spray silver nanowire conductive paste onto both sides of the composite film and cure it at room temperature for 4 hours to form flexible upper and lower electrode layers.

[0015] S8. Spray the surface of the electrode layer with PDMS encapsulation solution (PDMS: curing agent = 20:1) and cure at 60°C for 1 hour to complete device encapsulation and obtain a flexible piezoelectric sensor.

[0016] Preferably, in step S1, the particle size of the crystalline sucrose particles is 100–200 μm.

[0017] Preferably, in step S2, the curing temperature is 80℃ and the curing time is 2h.

[0018] Preferably, in step S3, the oscillation frequency is 100-200 rpm.

[0019] Preferably, in step S5, the ultrasonic power is 100-200W and the ultrasonic time is 10min.

[0020] Preferably, in step S6, the composite film is subjected to polarization treatment: a 2kV / mm electric field is applied at 100°C for 30 minutes to polarize it, in order to enhance the piezoelectric properties of ZnO nanowires.

[0021] Preferably, in step S7, the solid content of the silver nanowire conductive paste is 5wt% to 15wt%.

[0022] Preferably, in step S8, the curing temperature range of the encapsulation solution is 50–70°C, and the curing time is 0.5–2 hours.

[0023] The PDMS prepolymer is silane-modified polydimethylsiloxane.

[0024] A flexible piezoelectric sensor based on porous microstructure PDMS is obtained by the above-described preparation method.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] (1) The present invention introduces interconnected channels inside the PDMS matrix by means of sucrose template, which not only significantly increases the overall specific surface area of ​​the material, but also grows a piezoelectric active ZnO nanowire network in situ in the pore wall, so that the applied pressure can excite the piezoelectric polarization response on a larger scale and at a deeper level, thereby enhancing the conversion efficiency of mechanical stress into electrical signal.

[0027] (2) The ultrasonic-assisted permeation and hydrothermal growth process in this invention ensures that the ZnO nanowires are uniformly and densely distributed in the porous PDMS framework, avoiding the phenomenon of local stress concentration or peeling failure of the active layer in traditional planar thin films, so that the sensor can obtain stable and repeatable electrical output under low-pressure micro-motion and high-frequency vibration scenarios.

[0028] (3) Both PDMS and ZnO of the present invention have good chemical stability and biocompatibility. The sensor can maintain its performance without degradation in a variety of complex environments (such as humid heat, high salt or slightly corrosive media) and is suitable for skin contact, wearable monitoring or artificial intelligence interaction scenarios. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating a method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1:

[0032] Please see Figure 1 As shown, a method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS includes:

[0033] S1. PDMS prepolymer and curing agent are mixed evenly with crystalline sucrose particles at a weight ratio of 10:1 to prepare an organic-inorganic composite cured body.

[0034] The particle size of the crystalline sucrose particles is 100–200 μm;

[0035] S2. The composite cured body is placed in an oven at 80°C for 2 hours to obtain a cured block containing a uniformly dispersed sucrose template inside.

[0036] S3. Soak the solidified block in 40°C warm water and vibrate at 200 rpm for 2 hours to dissolve the sucrose template and obtain a connected porous microstructured PDMS sponge.

[0037] S4. Place the porous sponge in a vacuum drying oven at 60°C for 30 minutes to dehydrate it, thereby obtaining a dry sponge that retains its porous morphology.

[0038] S5. The sponge is immersed in a 0.1M zinc acetate solution and subjected to ultrasonic treatment at 20kHz for 10 minutes to allow the Zn to... 2+ The precursor fully penetrates into the pore wall to obtain a precursor membrane covering.

[0039] S6. The precursor film cover is first pre-baked at 100°C for 30 min to remove the solvent, and then hydrothermally reacted at 150°C for 1 h to grow a ZnO nanowire network in situ on the pore walls of PDMS, thereby obtaining a porous microstructure ZnO / PDMS composite film. The composite film is further polarized by applying a 2 kV / mm electric field at 100°C for 30 min to enhance the piezoelectric properties of the ZnO nanowires.

[0040] S7. Spray silver nanowire conductive paste onto both sides of the composite film and cure it at room temperature for 4 hours to form a flexible upper and lower electrode layer, wherein the solid content of the silver nanowire conductive paste is 12wt%.

[0041] S8. Spray the surface of the electrode layer with PDMS encapsulation solution (PDMS: curing agent = 20:1) and cure at 60°C for 1 hour to complete device encapsulation and obtain a flexible piezoelectric sensor.

[0042] As can be seen from the above, the introduction of interconnected channels inside the PDMS matrix by the sucrose template method not only significantly increases the overall specific surface area of ​​the material, but also allows for the in-situ growth of a piezoelectric active ZnO nanowire network within the pore walls. This enables the applied pressure to excite the piezoelectric polarization response over a wider range and at a deeper level, thereby enhancing the conversion efficiency of mechanical stress into electrical signals.

[0043] Example 2:

[0044] Preparation of porous PDMS sponge:

[0045] Raw materials: PDMS prepolymer (Sylgard 184), curing agent, sucrose granules (100μm±20μm, mass ratio 10∶1∶3)

[0046] Mixing: Mix at 200 rpm for 5 min with a mechanical stirrer at room temperature, degas under -0.09 MPa vacuum for 10 min, then pour into Silicone mold;

[0047] Curing: Cur in an 80℃ oven for 2.0 h (±0.2 h);

[0048] Dissolving sugar: Remove the solidified block and immerse it in 40℃ deionized water, gently agitating at 150 rpm for 2.0 hours;

[0049] Drying: Dehydrated in a vacuum chamber at 60℃ (–0.08MPa) for 30 min to obtain a connected porous microstructured PDMS sponge.

[0050] In-situ growth of ZnO nanowires

[0051] Precursor membrane: Immerse the interconnected porous microstructured PDMS sponge in a 0.1M zinc acetate solution, sonicate at 100W for 10 minutes (cycle: 5s on / 5s off), remove and spin dry;

[0052] Pre-baking: Bake on a hot plate at 100℃ for 30 minutes;

[0053] Hydrothermal synthesis: The sample was placed in a reaction vessel containing 10 mL of an equal volume of zinc acetate and ammonia (pH 10) and hydrothermally synthesized at 150 °C for 1.0 h.

[0054] Cleaning / Drying: After the reaction, the membrane was ultrasonically cleaned with deionized water for 3×5 min and vacuum dried at 60℃ for 20 min to obtain a porous microstructured ZnO / PDMS composite membrane.

[0055] Electrode fabrication and packaging

[0056] Electrode spraying: Using a spray gun (0.2mm nozzle, 0.2MPa air pressure), 10wt% AgNWs slurry was uniformly sprayed on both sides of the porous microstructure ZnO / PDMS composite membrane, with each layer being approximately 5μm thick, and cured at room temperature for 4h.

[0057] Encapsulation: Prepare an encapsulation solution with a PDMS:curing agent ratio of 20:1, spray a 10μm thick layer, and cure at 60℃ for 1.0h to obtain a flexible piezoelectric sensor.

[0058] As can be seen from the above, the ultrasonic-assisted infiltration and hydrothermal growth process ensures the uniform and dense distribution of ZnO nanowires in the porous PDMS framework, avoiding the phenomenon of local stress concentration or peeling failure of the active layer in traditional planar thin films, so that the sensor can obtain stable and repeatable electrical output under low-pressure micro-motion and high-frequency vibration scenarios.

[0059] Example 3:

[0060] Preparation of porous PDMS sponge:

[0061] The sucrose particles were changed to 150μm±30μm, and other conditions were the same as in Example 2, to obtain sponge C2.

[0062] ZnO nanowire growth:

[0063] The ultrasonic power was 150W and the time was 12min; the rest was the same as in Example 2, and the composite membrane F2 was obtained.

[0064] Electrodes and Packaging:

[0065] The AgNWs slurry has a solid content of 12wt% and a spraying thickness of 7μm; the rest is the same as in Example 2, resulting in S2.

[0066] Characterization and testing:

[0067] SEM: Focus on observing the distribution of ZnO in larger pores;

[0068] Tensile test: Using a flat plate tensile fixture, the stability of the electrical signal under strain of 0–20% was tested;

[0069] Temperature stability: Cycled between 25℃ and 60℃, and record voltage drift;

[0070] Frequency response: 10Hz–1kHz dynamic piezoelectric test.

[0071] Comparative example:

[0072] Preparation of dense matrix: template and vacuum drying are omitted, the rest is the same as in Example 2;

[0073] ZnO nucleation and growth: Same as in Example 2;

[0074] Electrodes and packaging: Same as in Example 2, finally obtaining the sensor;

[0075] The sensors prepared in Examples 2, 3, and the comparative example were characterized and tested as follows:

[0076] SEM: 7300F scanning electron microscope, 5kV voltage, to capture porous structures and endogenous ZnO nanowires;

[0077] XRD: D8 Advance, CuKα, 2θ=20–60°, confirming the characteristic peak of wurtzite ZnO;

[0078] Dielectric constant: tested with an LCR meter (100kHz), frequency scan 10kHz–1MHz;

[0079] Force-Electrical Measurement: A universal testing machine (loading rate 1N / s) combined with an oscilloscope and a high-precision pressure sensor synchronously records the 0–20kPa voltage output;

[0080] Response / Recovery Time: Step loading (10 kPa) and release tests were used to extract 90% rise / 10% fall time;

[0081] Cyclic life: 5000 cycles of 10kPa loading / unloading on a cellular fatigue testing bench, recording peak values ​​at the 1st, 1000th, 3000th, and 5000th cycles.

[0082] Characterization and testing: The testing process of Example 2 was completely replicated. The non-porous structure caused ZnO to mainly accumulate on the surface.

[0083] The characterization results of Examples 2, 3, and the comparative examples are shown in Table 1 below:

[0084] Table 1:

[0085]

[0086]

[0087] As can be seen from the above, the combination of the high elasticity of PDMS itself and the weakened stiffness of the porous structure enables the device to uniformly distribute stress when subjected to bending, torsion or stretching, without causing thin film cracks or conductive layer peeling off, thus ensuring stable performance during long-term, multi-angle wearing and fitting applications.

[0088] The use of silver nanowire spraying technology to replace traditional metal evaporation or foil bonding not only reduces processing temperature and equipment costs, but also creates a good permeation interlocking structure between the electrode layer and the porous substrate, avoiding problems such as metal layer cracking, peeling and increased interfacial impedance.

[0089] Both PDMS and ZnO have good chemical stability and biocompatibility. The sensors can maintain their performance without degradation in a variety of complex environments (such as humid heat, high salt or slightly corrosive media) and are suitable for skin-fitting, wearable monitoring or artificial intelligence interaction scenarios.

[0090] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0091] The accompanying drawings of the embodiments disclosed in this invention only involve structures relevant to the embodiments disclosed in this invention. Other structures can be referred to with common designs. Unless otherwise specified, the same embodiment and different embodiments of this invention can be combined with each other.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for fabricating a flexible piezoelectric sensor based on porous microstructured PDMS, characterized in that, Includes the following steps: S1. PDMS prepolymer and curing agent are mixed evenly with crystalline sucrose particles at a weight ratio of 10:1 to prepare an organic-inorganic composite cured body. S2. The composite cured body is placed in an oven at 75-85°C and cured for 1.5-2.5 hours to obtain a cured block containing a uniformly dispersed sucrose template inside. S3. Soak the solidified block in 40°C warm water and shake for 2-3 hours to dissolve the sucrose template and obtain a connected porous microstructured PDMS sponge. S4. Place the porous sponge in a vacuum drying oven at 60°C for 30 minutes to dehydrate it, thereby obtaining a dry sponge that retains its porous morphology. S5. The sponge is immersed in a 0.1M zinc acetate solution and subjected to ultrasonic treatment at 20kHz for 5-15 minutes to allow the Zn to... 2+ The precursor fully penetrates into the pore wall to obtain a precursor membrane covering. S6. The precursor membrane cover is first pre-baked at 100°C for 30 min to remove the solvent, and then hydrothermally reacted at 140-160°C for 0.5-2 h to grow a ZnO nanowire network in situ on the pore wall of PDMS, thereby obtaining a porous microstructure ZnO / PDMS composite membrane. S7. Spray silver nanowire conductive paste onto both sides of the composite film and cure it at room temperature for 4-5 hours to form flexible upper and lower electrode layers. S8. Spray PDMS encapsulation solution onto the surface of the electrode layer and cure it at 50-70°C for 0.5-2 hours to complete device encapsulation and obtain a flexible piezoelectric sensor.

2. The method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to claim 1, characterized in that, In step S1, the particle size of the crystalline sucrose particles is 100-200 μm.

3. The method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to claim 1, characterized in that, In step S2, the curing temperature is 80℃ and the curing time is 2 hours.

4. The method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to claim 1, characterized in that, In step S3, the oscillation frequency is 100-200 rpm.

5. The method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to claim 1, characterized in that, In step S5, the ultrasonic power is 100-200W and the ultrasonic time is 10min.

6. The method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to claim 1, characterized in that, In step S6, the composite film is polarized: a 2kV / mm electric field is applied at 100℃ for 30 min to enhance the piezoelectric properties of ZnO nanowires.

7. The method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to claim 1, characterized in that, In step S7, the solid content of the silver nanowire conductive paste is 5wt% to 15wt%.

8. The method for fabricating a flexible piezoelectric sensor based on porous microstructure PDMS according to claim 1, characterized in that, In step S8, the ratio of PDMS to curing agent is 20:1, the curing temperature range of the encapsulation solution is 60℃, and the curing time is 1 hour. The PDMS prepolymer is silane-modified polydimethylsiloxane.

9. A flexible piezoelectric sensor based on porous microstructured PDMS, characterized in that, The sensor is prepared by the preparation method according to any one of claims 1-8.

Images