Stretchable pressure sensor based on stress decoupling and preparation method thereof

Abstract

The application relates to the technical field of pressure sensors, and discloses a stretchable pressure sensor based on stress decoupling and a preparation method thereof, which comprises, from top to bottom, an upper packaging layer, an upper metal electrode, a patterned PVDF piezoelectric film, a lower metal electrode and a lower packaging layer; the upper metal electrode and the lower metal electrode are arranged on the upper surface and the lower surface of the patterned PVDF piezoelectric film respectively, and the stretchable performance and the piezoelectric performance of the patterned PVDF piezoelectric film are regulated through patterned design; the stretchable performance of the pressure sensor is realized by using a snake-shaped structure design; single signal sensing of the piezoelectric unit is realized through the snake-shaped interconnection wire design, and the interference of the tensile strain on the piezoelectric unit assembly is eliminated; the balance adjustment between the stretchability and the piezoelectric performance of the flexible pressure sensor can be effectively adjusted through adjustment of several parameters of the patterned design.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor technology, specifically to a stretchable pressure sensor based on stress decoupling and its fabrication method. Background Technology

[0002] In recent years, pressure sensors, as an important component of flexible electronic devices, have attracted widespread research interest and have significant research value in many fields such as health monitoring, wearable medical devices, human-computer interaction, and robotics.

[0003] Piezoelectric flexible pressure sensors are a type of sensor technology based on the piezoelectric effect. They mainly utilize the properties of piezoelectric materials to generate charge or voltage through the compression or deformation of the material under external force, thereby realizing the sensing and measurement of pressure signals.

[0004] With the continuous development of flexible material technology, such as polymers, rubber, and nanomaterials, flexible pressure sensors can be fabricated on soft, flexible, and stretchable substrates, enabling them to adapt to application scenarios with different shapes and curvatures and possess good mechanical properties.

[0005] Among them, piezoelectric materials are a key component of piezoelectric flexible pressure sensors, and their performance plays a vital role in the sensor's sensitivity, stability, and reliability.

[0006] With the continuous development of piezoelectric materials such as piezoelectric polymers and piezoelectric nanocomposites, the sensitivity and performance of sensors have been significantly improved. In practical applications, flexible pressure sensors are usually attached to the surface of human skin. However, the operating environment of electronic devices on the human skin surface is extremely harsh, requiring them to withstand various degrees of physical interference such as stretching, torsion, and friction. This leads to a decline in the accuracy, stability, reliability, and dynamic response of pressure sensors. Therefore, the development of stress-resistant pressure sensors is of great research significance for improving sensor accuracy and reliability, expanding the application range of sensors, and providing long-term stability.

[0007] Current research strategies for enhancing the strain interference resistance of flexible pressure sensors mainly focus on optimizing structural design and signal processing algorithms. Structural design of flexible pressure sensors also plays a role in enhancing their strain interference resistance. Several structural design strategies, such as mesh structures and multilayer structures, have been developed to improve this resistance, but issues such as decreased sensitivity or reduced mechanical strength still exist. Structural engineering is an effective strategy that enhances the strain interference resistance of pressure sensors through structural design. Designs such as serpentine, wave, and paper-cut structures can impart unique mechanical properties to non-stretchable materials. This design allows the material structure to deform under stress / strain, thereby absorbing stress / strain and preventing a sharp decline in the performance of the sensing area. However, it is important to note that while strain engineering strategies can improve the strain interference resistance of pressure sensors, they also limit the overall tensile strength of the device. Therefore, a trade-off must be struck between device performance and strain resistance during structural engineering design to ensure that the pressure sensor possesses both high-precision sensing performance and stable operation under strain conditions in practical applications. Therefore, it is necessary to design a strain-resistant stretchable pressure sensor and its fabrication method to address the shortcomings of existing technologies and solve or alleviate the above problems.

[0008] Based on this, we propose a stress-decoupling-based tensile pressure sensor in order to address the shortcomings of existing technologies. Summary of the Invention

[0009] (a) Technical problems to be solved

[0010] To address the shortcomings of existing technologies, this invention provides a tensile pressure sensor based on stress decoupling and its fabrication method.

[0011] (II) Technical Solution

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] A stretchable pressure sensor based on stress decoupling includes, from top to bottom, an upper encapsulation layer, an upper metal electrode, a patterned PVDF piezoelectric film, a lower metal electrode, and a lower encapsulation layer;

[0014] The patterned PVDF piezoelectric film has an upper metal electrode and a lower metal electrode respectively on its top and bottom. The patterned PVDF piezoelectric film controls its stretchability and piezoelectric properties through pattern design.

[0015] As a further technical solution, the Young's modulus of the upper and lower encapsulation layers is 0.1-1 MPa.

[0016] As a further technical solution, the patterned PVDF piezoelectric film is a serpentine mesh, and the PVDF piezoelectric film includes a circular pressure sensing area, serpentine interconnecting wires, and an external wire interface.

[0017] As a further technical solution: based on the structure of the serpentine network, each serpentine unit cell includes two identical arcs, whose geometric parameters include arc angle, width, and span.

[0018] As a further technical solution: the arc angle θ of the serpentine interconnecting wire includes 130°, 180° and 230°, the width-to-span ratio W / L is 0.15, and the width is 0.3mm.

[0019] As a further technical solution, both the upper metal electrode and the lower metal electrode are made of copper-nickel alloy;

[0020] The patterned PVDF piezoelectric film has a thickness of 110 μm.

[0021] As a further technical solution, the encapsulation material used for the upper and lower encapsulation layers is polydimethylsiloxane;

[0022] The upper and lower encapsulation layers have the same thickness, ranging from 300μm to 500μm.

[0023] A method for fabricating a tensile pressure sensor based on stress decoupling, comprising:

[0024] (1) Select a PVDF film with a thickness of 110μm. The PVDF film is coated with an upper metal electrode and a lower metal electrode on the top and bottom respectively. The thickness of the upper metal electrode and the lower metal electrode is 80-100nm.

[0025] (2) Design a stretchable pattern. The thin film graphic design includes a circular pressure sensing area, a serpentine interconnecting wire and an external electrode interface. According to the structure of the serpentine network, the diameter of the pressure sensing area is set to 10 mm. Each serpentine unit includes two identical arcs. The arc angle θ of the serpentine interconnecting wire includes 130°, 180° and 230°. The ratio of width to span W / L is 0.15 and the width is 0.3 mm.

[0026] (3) A layer of water-soluble adhesive tape is attached to the top surface of the PVDF film, and the bottom surface is laser-scanned and cut. The laser power is 2W and the scanning speed is 700mm / s.

[0027] (4) Weigh 10 ml of polydimethylsiloxane precursor liquid as liquid B, add 1 ml of polydimethylsiloxane curing agent as liquid A, and then mechanically stir at room temperature for 30 min at a stirring speed of 500 rpm. The mass ratio of liquid B to liquid A is 10:0.5-1.5. Let it stand at room temperature for 2 h to remove bubbles and obtain PDMS prepreg.

[0028] (5) Spin-coat a layer of the PDMS pre-prepared liquid prepared in step (4) onto the bottom surface of the PVDF film, and then place it in an oven and cure it at 55-65℃ for 2 hours.

[0029] (6) Remove the water-soluble tape and remove the excess to obtain a PVDF film with a stretchable structure;

[0030] (7) A layer of PDMS pre-formed liquid is spin-coated onto the top surface of the PVDF film for encapsulation. After the same operation as in step (5) above, a stretchable pressure sensor is obtained.

[0031] (III) Beneficial Effects

[0032] Compared with the prior art, the present invention provides a tensile pressure sensor based on stress decoupling, which has the following advantages:

[0033] (1) The stretchability of the pressure sensor was achieved by using a serpentine structure design;

[0034] (2) The design of the serpentine interconnecting wires enables the single signal sensing of the piezoelectric unit, eliminating the interference of tensile strain on the piezoelectric unit components;

[0035] (3) By adjusting several parameters through patterned design, the balance between the stretchability and piezoelectric properties of the flexible pressure sensor can be effectively adjusted. Attached Figure Description

[0036] Figure 1 This is a three-dimensional schematic diagram of the stretchable PVDF film of the present invention;

[0037] Figure 2 This is a cross-sectional schematic diagram of the PVDF film in this invention;

[0038] Figure 3 Schematic diagram of the stretchable planar structure in this invention;

[0039] Figure 4 This is a schematic diagram of the device in the embodiment (before and after stretching). Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0041] A stretchable pressure sensor based on stress decoupling includes, from top to bottom, an upper encapsulation layer, an upper metal electrode, a patterned PVDF piezoelectric film, a lower metal electrode, and a lower encapsulation layer;

[0042] The patterned PVDF piezoelectric film has an upper metal electrode and a lower metal electrode respectively on its top and bottom. The patterned PVDF piezoelectric film controls its stretchability and piezoelectric properties through pattern design.

[0043] The Young's modulus of the upper and lower encapsulation layers is 0.1-1 MPa.

[0044] The patterned PVDF piezoelectric film is a serpentine mesh, and the PVDF piezoelectric film includes a circular pressure sensing area (10), serpentine interconnecting wires (20), and an external wire interface (30).

[0045] Based on the structure of the serpentine network, each serpentine unit consists of two identical arcs, whose geometric parameters include arc angle (θ), width (W), and span (L).

[0046] The arc angle θ of the serpentine interconnecting conductor includes 130°, 180° and 230°, the width-to-span ratio W / L is 0.15, and the width is 0.3mm.

[0047] Both the upper metal electrode (11) and the lower metal electrode (11) are made of copper-nickel alloy;

[0048] The patterned PVDF piezoelectric film (22) has a thickness of 110 μm.

[0049] The encapsulation material used for both the upper and lower encapsulation layers is polydimethylsiloxane;

[0050] The upper and lower encapsulation layers have the same thickness, ranging from 300μm to 500μm.

[0051] A method for fabricating a tensile pressure sensor based on stress decoupling, comprising:

[0052] (1) Select a PVDF film with a thickness of 110μm. The PVDF film is coated with an upper metal electrode and a lower metal electrode on the top and bottom respectively. The thickness of the upper metal electrode and the lower metal electrode is 80-100nm.

[0053] (2) Design a stretchable pattern. The thin film graphic design includes a circular pressure sensing area, a serpentine interconnecting wire and an external electrode interface. According to the structure of the serpentine network, the diameter of the pressure sensing area is set to 10 mm. Each serpentine unit includes two identical arcs. The arc angle θ of the serpentine interconnecting wire includes 130°, 180° and 230°. The ratio of width to span W / L is 0.15 and the width is 0.3 mm.

[0054] (3) A layer of water-soluble adhesive tape is attached to the top surface of the PVDF film, and the bottom surface is laser-scanned and cut. The laser power is 2W and the scanning speed is 700mm / s.

[0055] (4) Weigh 10 ml of polydimethylsiloxane (PDMS) precursor solution as solution B, add 1 ml of polydimethylsiloxane curing agent as solution A, and then mechanically stir at room temperature for 30 min at a stirring speed of 500 rpm. The mass ratio of solution B to solution A is 10:0.5-1.5. Let it stand at room temperature for 2 h to remove bubbles and obtain PDMS prepreg.

[0056] The polydimethylsiloxane curing agent is DBP.

[0057] (5) Spin-coat a layer of the PDMS pre-prepared liquid prepared in step (4) onto the bottom surface of the PVDF film, and then place it in an oven and cure it at 55-65℃ for 2 hours.

[0058] (6) Remove the water-soluble tape and remove the excess to obtain a PVDF film with a stretchable structure;

[0059] (7) A layer of PDMS pre-formed liquid is spin-coated onto the top surface of the PVDF film for encapsulation. After the same operation as in step (5) above, a stretchable pressure sensor is obtained.

[0060] The following are specific examples:

[0061] Example 1

[0062] A method for fabricating a tensile pressure sensor based on stress decoupling includes the following steps:

[0063] (1) Select a PVDF film with a thickness of 110 μm, and deposit a copper-nickel alloy electrode 11 with a thickness of 100 nm on the surface of the film.

[0064] (2) Design stretchable patterns, such as Figure 1As shown, the thin-film pattern design includes a circular pressure sensing area 10, a serpentine interconnecting wire 20, and an external electrode interface 30. According to the structure of the serpentine network, the diameter (D) of the pressure sensing area is set to 10 mm. Each serpentine unit includes two identical arcs. The arc angle θ of the serpentine interconnecting wire is 130°, the width-to-span ratio W / L is 0.15, and the width is 0.3 mm.

[0065] (3) A layer of water-soluble adhesive tape is attached to the top surface of the PVDF film, and the bottom surface is laser-scanned and cut. The laser power is 2W and the scanning speed is 700mm / s.

[0066] (4) Weigh 10 ml of polydimethylsiloxane precursor solution B, add 1 ml of polydimethylsiloxane curing agent A, and mechanically stir at room temperature for 30 min at a stirring speed of 500 rpm. The mass ratio of polydimethylsiloxane PDMS solution B to solution A is 10:1.0. Let it stand at room temperature for 2 h to remove air bubbles.

[0067] (5) Spin-coat a layer of the PDMS pre-prepared liquid prepared in step (4) onto the B side of the PVDF film, and then place it in an oven to cure at 60°C for 2 hours.

[0068] The thickness of the upper and lower encapsulation layers is 400 μm; the Young's modulus of the upper and lower encapsulation layers is 0.55 MPa.

[0069] (6) Remove the water-soluble tape and remove the excess to obtain a PVDF film with a stretchable structure;

[0070] (7) A layer of PDMS pre-formed liquid is spin-coated onto the top surface of the PVDF film for encapsulation. After the same operation as in step (5), a stretchable pressure sensor is obtained.

[0071] Example 2:

[0072] The method for preparing the stress-decoupling-based stretchable pressure sensor in this embodiment is based on Embodiment 1, except that the angle θ value in the stretchable pattern design in step (2) is set to 180°, and the rest of the technical solutions are the same as in Embodiment 1.

[0073] Example 3:

[0074] The method for preparing the stress-decoupling-based stretchable pressure sensor in this embodiment is based on Embodiment 1, except that the angle θ value in the stretchable pattern design in step (2) is 230°, and the rest of the technical solutions are the same as in Embodiment 1.

[0075] 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 tensile pressure sensor based on stress decoupling, characterized in that, include: From top to bottom, the layers are: upper encapsulation layer, upper metal electrode, patterned PVDF piezoelectric film, lower metal electrode, and lower encapsulation layer. The patterned PVDF piezoelectric film is provided with an upper metal electrode and a lower metal electrode on its top and bottom, respectively. The patterned PVDF piezoelectric film controls its stretchability and piezoelectric properties through pattern design. The patterned PVDF piezoelectric film is a serpentine mesh, and the PVDF piezoelectric film includes a circular pressure sensing area (10), serpentine interconnecting wires (20), and an external wire interface (30). Based on the structure of the serpentine network, each serpentine unit consists of two identical arcs, whose geometric parameters include arc angle, width, and span; The arc angle θ of the serpentine interconnecting wire includes 130°, 180° and 230°, the width-to-span ratio W / L is 0.15 and the width is 0.3 mm.

2. The tensile pressure sensor based on stress decoupling according to claim 1, characterized in that, The Young's modulus of the upper and lower encapsulation layers is 0.1-1 MPa.

3. A tensile pressure sensor based on stress decoupling according to claim 1, characterized in that, Both the upper metal electrode (11) and the lower metal electrode (11) are made of copper-nickel alloy; The patterned PVDF piezoelectric film (22) has a thickness of 110 μm.

4. A tensile pressure sensor based on stress decoupling according to claim 1, characterized in that, The encapsulation material used for the upper and lower encapsulation layers is polydimethylsiloxane; The upper and lower encapsulation layers have the same thickness, ranging from 300μm to 500μm.

5. The method for fabricating a tensile pressure sensor based on stress decoupling according to claim 1, characterized in that: include: (1) A PVDF film with a thickness of 110 μm is selected. An upper metal electrode and a lower metal electrode are deposited on the top and bottom of the PVDF film, respectively. The thickness of the upper metal electrode and the lower metal electrode is 80-100 nm. (2) Design a stretchable pattern. The thin film graphic design includes a circular pressure sensing area, a serpentine interconnecting wire and an external electrode interface. According to the structure of the serpentine network, the diameter of the pressure sensing area is set to 10 mm. Each serpentine unit includes two identical arcs. The arc angle θ of the serpentine interconnecting wire includes 130°, 180° and 230°. The ratio of width to span W / L is 0.15 and the width is 0.3 mm. (3) A layer of water-soluble adhesive tape is attached to the top surface of the PVDF film, and the bottom surface is laser-scanned and cut. The laser power is 2W and the scanning speed is 700 mm / s. (4) Weigh 10 ml of polydimethylsiloxane precursor liquid as liquid B, add 1 ml of polydimethylsiloxane curing agent as liquid A, and then mechanically stir at room temperature for 30 min at a stirring speed of 500 rpm. The mass ratio of liquid B to liquid A is 10:0.5-1.

5. Let it stand at room temperature for 2 h to remove bubbles and obtain PDMS prepreg. (5) Spin-coat a layer of the PDMS pre-formed liquid prepared in step (4) onto the bottom surface of the PVDF film, and then place it in an oven and cure it at 55-65℃ for 2 h. (6) Remove the water-soluble tape and remove the excess to obtain a PVDF film with a stretchable structure; (7) A layer of PDMS pre-formed liquid is spin-coated onto the top surface of the PVDF film for encapsulation. After the same operation as in step (5) above, a stretchable pressure sensor is obtained.

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