Nanoscale fluorescent electrostatic spinning yarn and preparation method thereof

Abstract

The invention discloses nanoscale fluorescent electrostatic spinning and a preparation method thereof, and particularly relates to the technical field of high-performance fiber products, and the nanoscale fluorescent electrostatic spinning comprises a flexible supporting layer and an electrostatic spinning nanofiber layer. According to the nanoscale fluorescent electrostatic spinning yarn and the preparation method thereof, an electrostatic spinning process based on cellulose acetate and other cellulose derivatives is adopted, so that good biocompatibility, degradability and film-forming property of a cellulose material are utilized; the problems of uniform dispersion and high-load compounding of the inorganic fluorescent powder in a high-molecular-weight cellulose solution are successfully solved, and the conduction efficiency and distribution uniformity of stress are remarkably improved. Experiments show that the force sensitivity of the prepared electronic skin device reaches 10.5 mV / MPa or above, the pressure threshold value is reduced to 380 kPa or below, the response time does not exceed 15 ms, the sensitivity is improved by 30% or above compared with that of a device prepared through a traditional coating method, and the requirement for high-precision touch sensing can be met.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber products technology, and in particular to a nanoscale fluorescent electrospinning method and its preparation method. Background Technology

[0002] Flexible electronic skin, as a novel electronic device capable of simulating the sensory functions of human skin, has shown broad application prospects in fields such as humanoid robots, smart wearables, and medical monitoring. Among them, stress-luminescent electronic skin, due to its ability to directly convert mechanical stimulation into light signals, possesses advantages such as non-contact signal reading and strong resistance to electromagnetic interference, making it one of the current research hotspots. The performance of stress-luminescent materials, especially their luminescence intensity, spectral characteristics, and response sensitivity to mechanical stress, directly determines the sensing capability of the device. Currently, the fabrication of stress-luminescent flexible electronic skin mostly employs traditional processes such as coating, spin coating, or lamination, mixing bulk or powder stress-luminescent materials with a polymer matrix to form a functional thin film. However, these methods have significant shortcomings: First, the prepared thin films are often dense in structure and have low porosity, leading to uneven stress transmission within the material and a significant stress concentration effect, making it difficult for the device's force sensitivity and pressure detection threshold to meet the requirements of high-precision tactile sensing. Second, traditional processes struggle to achieve uniform dispersion and ordered structural control of materials at the nanoscale, resulting in uneven distribution of luminescence centers, affecting the uniformity and stability of luminescence, and making the material prone to cracking or performance degradation under repeated bending.

[0003] Electrospinning is an advanced method for the direct and continuous fabrication of polymer nanofibers. The resulting fiber membranes possess high specific surface area, high porosity, good flexibility, and structural designability, providing a new approach to improving the performance of stress-emitting layers. Theoretically, incorporating stress-emitting materials into electrospun nanofibers can construct a three-dimensional interconnected porous network, which is beneficial for efficient stress conduction and uniform distribution. Simultaneously, the nanofiber structure can effectively disperse stress, enhancing the mechanical durability of the device. However, applying electrospinning technology to the fabrication of stress-emitting-optocoupled flexible electronic skin faces several challenges: First, there is a lack of systematic research on the compatibility of inorganic stress-luminescent materials with biocompatible and fiber-forming polymers such as cellulose derivatives (e.g., cellulose acetate), making it difficult to obtain stable, uniform, and high-load spinning solutions. Cellulose and its derivative solutions, as classic spinning systems, have the advantages of well-defined solution behavior and easy fiber processing. However, research on combining them with high-performance inorganic phosphors for electrospinning while simultaneously satisfying high phosphor loading, uniform dispersion, and excellent fiber-forming properties is still lacking. Second, existing electrospinning process parameters such as voltage, flow rate, and receiving distance are mostly optimized for pure polymers or simple composite materials. For spinning solutions incorporating phosphors and cellulose-based materials with unique rheological properties, their rheological and electrical properties change, requiring the development of suitable process windows to ensure the uniformity of fiber morphology, diameter, and luminescent material distribution. Third, how to achieve high flexibility and high porosity while ensuring optimal matching of stress luminescence efficiency, spectrum, and back-end photodetector through the synergistic design of material systems and fiber structures, and to construct effective signal feedback and coupling mechanisms, remains a pressing technical challenge.

[0004] While some existing technologies have attempted to combine fluorescent materials with electrospinning, these efforts have largely focused on fluorescent labeling or simple sensing, failing to address the crucial material-process-structure-mechanism synergy issues encountered when applying them to high-sensitivity, high-reliability dual-mode sensing electronic skin. For instance, although existing technologies have proposed the concept of photoelectric dual response, manufacturing still relies on coating-bonding processes, failing to utilize the structural advantages of electrospun nanofibers. Furthermore, limitations exist in doping systems and photoelectric coupling mechanisms, resulting in significant room for improvement in the overall performance of devices, including sensitivity, uniformity, and environmental stability. Summary of the Invention

[0005] The main objective of this invention is to provide a nanoscale fluorescent electrospinning method for preparing the same, which can effectively solve the problems of uneven stress distribution, poor dispersion of luminescent materials, low photoelectric coupling efficiency, and insufficient structural flexibility in existing stress-emitting flexible electronic skin.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A nanoscale fluorescent electrospun material comprises a flexible support layer and an electrospun nanofiber layer. The electrospun nanofiber layer is formed by electrospun process from a spinning solution containing a composite matrix stress-luminescent material and a spinning polymer. The composite matrix is ​​a composite of ScBO3 and Al2O3, and the composite matrix stress-luminescent material is Cr doped into the composite matrix. 3+ Yb 3+ and Nd 3+ The resulting ternary doped fluorescent material has the general chemical formula (Sc0). 9-x-The electrospun nanofiber layer is composed of α-Al0.1BO3:Crˣ,Ybʸ,Ndᶻ, where 0.015≤x≤0.035, 0.008≤y≤0.012, and 0.003≤z≤0.007; the spinning polymer is a cellulose derivative, preferably cellulose acetate; the fiber diameter of the electrospun nanofiber layer is 500nm to 2μm, and the porosity is 30% to 50%.

[0007] Preferably, the mass ratio of ScBO3 to Al2O3 in the composite matrix is ​​7:3.

[0008] Preferably, in the electrospun nanofiber layer, the mass ratio of the composite matrix stress luminescent material to the polyvinylidene fluoride is 1:1.5 to 1:2.5.

[0009] Preferably, the flexible support layer is a composite film of polylactic acid and polydimethylsiloxane with a thickness of 80 μm to 150 μm.

[0010] Preferably, the thickness of the electrospun nanofiber layer is 50 μm to 100 μm.

[0011] A method for preparing nanoscale fluorescent electrospinning as described above includes the following steps: S1. Preparation of spinning solution: Weigh out the chemical formula (Sc0) according to the specified proportion. 9-x- Phosphors of Al0.1(BO3):Crˣ,Ybʸ,Ndᵧ are mixed with cellulose acetate and suitable solvents such as a mixture of acetone and water or acetic acid. The mixture is then ultrasonically dispersed and magnetically stirred to obtain a homogeneous spinning solution. The spinning solution is formulated based on the solubility characteristics of cellulose derivatives in specific solvents. By optimizing the solvent ratio and solid content, the phosphors are highly dispersed while ensuring the solution has a viscosity and conductivity suitable for electrospinning, ranging from 150 mPa·s to 300 mPa·s. S2. Pretreatment of flexible support layer: Plasma cleaning of the flexible support layer; S3. Electrospinning: The spinning solution obtained in step S1 is electrospinned and received on a pretreated flexible support layer to form a nanofiber membrane, which is then dried. The electrospinning process parameters are optimized for the characteristics of the cellulose-based composite spinning solution, including voltage, receiving distance, ambient temperature and humidity, to ensure continuous and uniform fiber deposition. S4. Encapsulation: A flexible encapsulation layer is covered on the surface of the nanofiber membrane and then heat-pressed for encapsulation.

[0012] Preferably, in step S1, the mass ratio of N,N-dimethylformamide to acetone is 7:3; and the mass ratio of phosphor to polyvinylidene fluoride is 1:1.5 to 1:2.5.

[0013] Preferably, in step S1, the ultrasonic dispersion power is 300W and the time is 30min to 40min; the magnetic stirring speed is 600r / min and the time is 6h to 8h; the viscosity of the spinning solution is 150mPa·s to 300mPa·s.

[0014] Preferably, in step S3, the electrospinning process parameters are: voltage 15kV to 25kV, receiving distance 10cm to 15cm, spinning solution flow rate 0.5mL / h to 1.5mL / h, ambient temperature 20℃ to 25℃, ambient humidity 30% to 50%; a roller receiving device is used, the roller speed is 50r / min to 100r / min, and the spinning time is 60min to 120min.

[0015] Preferably, the drying conditions in step S3 are: drying in a vacuum drying oven at 80°C to 90°C for 4 to 6 hours; in step S4, the flexible encapsulation layer is a polycaprolactone film, and the hot-press encapsulation conditions are: temperature 70°C to 80°C, pressure 0.3MPa to 0.5MPa, and time 20 to 30 minutes.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a nanoscale fluorescent electrospinning method and its preparation. By employing an electrospinning process based on cellulose derivatives such as cellulose acetate, it not only utilizes the excellent biocompatibility, biodegradability, and film-forming properties of cellulose materials, but also successfully solves the problem of uniform dispersion and high-load composite of inorganic phosphors in high molecular weight cellulose solutions, significantly improving stress transmission efficiency and distribution uniformity. Experiments show that the prepared electronic skin device achieves a force sensitivity of over 10.5 mV / MPa, a pressure threshold reduced to below 380 kPa, and a response time of no more than 15 ms. Compared with devices prepared by traditional coating methods, the sensitivity is improved by more than 30%, meeting the requirements of high-precision tactile sensing.

[0017] 2. This invention provides a nanoscale fluorescent electrospinning method and its preparation method, which involves designing a ScBO3-Al2O3 composite matrix and using Cr 3+ / Yb 3+ / Nd 3+ The ternary doped system optimizes the matching of the emission spectrum with the response band of the silicon-based photodetector. The device achieves a spectral matching degree of ≥75%, a photoelectric conversion efficiency of 55.2%, and a signal-to-noise ratio of over 50dB. Compared with the existing binary doped system, the photoelectric coupling efficiency is improved by 25%, significantly enhancing the stability and reliability of signal acquisition.

[0018] 3. This invention provides a nanoscale fluorescent electrospinning method for its preparation. The electrospinning process used can achieve a nanofiber layer thickness error of ≤±5%, controllable porosity within the range of 30%–50%, and the device as a whole can be bent to a radius of curvature of 3mm with an elongation at break of ≥180%. In addition, the performance difference between batches is ≤3%, exhibiting good process consistency and structural flexibility, making it suitable for complex curved surface bonding and dynamic strain scenarios.

[0019] 4. This invention provides a nanoscale fluorescent electrospinning method for its preparation. The resulting electronic skin device exhibits excellent stability over a wide humidity range of 30%–95%RH and a dynamic stress frequency range of 0–20Hz. After 500 cycles of testing, the performance retention rate is ≥92%; under strong light conditions of 10000 lux, the performance fluctuation is ≤4%, demonstrating good environmental adaptability and long-term reliability, making it suitable for demanding applications such as medical monitoring and robotic tactile sensing. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation process of the present invention. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0022] Example 1 This embodiment provides a specific preparation method for nanoscale fluorescent electrospinning, including the following steps: Step 1: Preparation of spinning solution The chemical formula is (Sc0). 87 Al0.1)BO3:Cr0. 02 ,Yb0. 01 ,Nd0. 005 The following materials were prepared: 3g of phosphor, 5g of cellulose acetate (acetyl content approximately 39.8%), and 13.5g of a mixed solvent of acetone and water (mass ratio 8:2). These materials were placed in a container and first ultrasonically dispersed for 35 minutes at 300W, followed by magnetic stirring for 10 hours at 600 rpm, resulting in a uniform and stable spinning solution with a viscosity of approximately 200 mPa·s. Cellulose acetate was chosen because of its good solubility and fiber-forming properties in the acetone / water system, and the polar groups on its molecular chain facilitate interaction with the surface of the inorganic phosphor, promoting dispersion stability.

[0023] Step 2: Pre-treatment of the flexible support layer A composite film of polylactic acid and polydimethylsiloxane with a mass ratio of 4:6 and a thickness of 100μm was used as a flexible support layer. The film was placed in a plasma cleaner and cleaned for 6 minutes at a power of 100W to improve the surface hydrophilicity and adhesion.

[0024] Step 3: Electrospinning The above spinning solution was injected into the electrospinning apparatus, and the process parameters were set as follows: Voltage: 20kV Reception distance: 12cm Spinning solution flow rate: 1.0 mL / h Ambient temperature: 22℃ Ambient humidity: 40% Rotation speed of the drum receiving device: 80 r / min Spinning continued for 90 minutes to form a nanofiber membrane on the pretreated flexible support layer. The sample was then dried in a vacuum drying oven at 85°C for 5 hours to completely remove residual solvent. The above process parameters were optimized and determined as follows: a voltage of 20kV can ensure stable fiber formation during spinning; a receiving distance of 12cm is conducive to uniform fiber deposition; a flow rate of 1.0 mL / h can control the fiber diameter to around 800 nm; and environmental temperature and humidity control is conducive to solvent evaporation and fiber formation.

[0025] Step 4: Packaging A 20 μm thick polycaprolactone film was used as a flexible encapsulation layer to cover the surface of the nanofiber membrane. The membrane was then hot-pressed at 75 °C and 0.4 MPa for 25 min to obtain the final nanoscale fluorescent electrospun sample. The performance of the sample prepared in Example 1 was tested: Force sensitivity: 11.2 mV / MPa Pressure detection threshold: 350 kPa Response time: 14 ms Photoelectric conversion efficiency: 56.1% The bending radius can reach 3 mm, and the performance retention rate is 93% after 500 cycles.

[0026] Example 2 The difference between this embodiment and Embodiment 1 lies in the adjustment of the phosphor doping ratio and the spinning process parameters: The general chemical formula for phosphors is (Sc0). 88 Al0.1)BO3:Cr0. 025 ,Yb0. 01 ,Nd0. 005 .

[0027] The electrospinning parameters were adjusted as follows: voltage 18kV, receiving distance 14cm, flow rate 0.8mL / h, and spinning time 120min.

[0028] The remaining steps are the same as in Example 1; The performance of the sample prepared in Example 2 was tested: Force sensitivity: 10.8 mV / MPa Pressure detection threshold: 370 kPa Response time: 15 ms Photoelectric conversion efficiency: 54.7% Spectral matching degree: 76% The bending radius can reach 3.5 mm, and the performance retention rate is 91% after 500 cycles. Fiber diameter distribution: 600 nm–1.2 μm Porosity: 45%.

[0029] Example 3 The difference between this embodiment and Embodiment 1 lies in the material and thickness of the flexible support layer: It uses a pure PDMS flexible film with a thickness of 80μm.

[0030] The mass ratio of phosphor to PVDF in the spinning solution was adjusted to 1:2.

[0031] The remaining steps are the same as in Example 1; The performance of the sample prepared in Example 3 was tested: Force sensitivity: 9.8 mV / MPa Pressure detection threshold: 390 kPa Response time: 16 ms Photoelectric conversion efficiency: 52.3% Elongation at break: 195% It has a bending radius of up to 2.8 mm and retains 94% of its performance after 500 cycles. Fiber diameter distribution: 700 nm–1.5 μm Porosity: 40%.

[0032] The performance test results of the three embodiments above show that the present invention can achieve synergistic optimization of force sensitivity, photoelectric conversion efficiency, flexibility, and environmental stability by adjusting the phosphor doping ratio, spinning process parameters, and support layer structure. Embodiment 1 exhibits the best overall performance and is suitable for high-precision tactile sensing; Embodiment 2 demonstrates outstanding performance in spectral matching and process stability; and Embodiment 3 has advantages in flexibility and cycle durability, making it suitable for dynamic bending scenarios.

[0033] Application test examples The fluorescent electrospun fiber prepared in Example 1 was bonded to the surface of a mechanical finger, and pressure distribution tests were conducted. Within a pressure range of 0–500 kPa, the device exhibited good linear response and spatial resolution, making it suitable for robot tactile sensing.

[0034] The working principle of this nanoscale fluorescent electrospinning will be explained in detail below.

[0035] like Figure 1 As shown, the nanoscale fluorescent electrospinning provided by this invention includes a flexible support layer and an electrospinned nanofiber layer; the nanofiber layer is composed of Cr-doped nanofibers. 3+ Yb 3+ 、Nd 3+ The ScBO3-Al2O3 composite matrix phosphor is made by combining it with cellulose acetate. The cellulose acetate matrix not only provides a flexible three-dimensional network support, but also has a certain polarity and good compatibility with the phosphor interface, which helps to efficiently transfer stress from the polymer matrix to the phosphor particles and reduce light scattering loss at the interface. In addition, by controlling the degree of substitution of cellulose derivatives and solution properties, the mechanical properties of the fiber and the coating state of the luminescent material can be further optimized.

[0036] When external mechanical stress is applied to this spun structure, the stress can be rapidly and uniformly transmitted to the phosphor particles due to the high-porosity three-dimensional interconnected network structure of the nanofiber layer; the Cr in the composite matrix 3+ Occurs under stress excitation 4 T2→ 4 The A2 level transition produces near-infrared emission in the 700–900 nm range. Simultaneously, Nd... 3+ Yb enhances luminescence intensity through energy transfer mechanisms. 3+ Furthermore, the emission spectrum is redshifted to the 980–1020 nm range, which is highly matched with the response band of commonly used silicon-based photodetectors, thereby improving the photoelectric coupling efficiency.

[0037] Nanofiber structures not only improve the flexibility and stress distribution uniformity of materials, but also enhance the interfacial bonding between luminescent materials and polymers due to their high specific surface area and porous characteristics, thus avoiding cracks or performance degradation under bending or dynamic loads. In addition, polyvinylidene fluoride itself has certain piezoelectric properties, which can generate a micro-electric field under stress, further modulating the luminescence behavior and realizing a multimodal response of stress, light, and electricity.

[0038] In summary, this invention achieves the fabrication of highly sensitive, highly uniform, and highly flexible stress-luminescent nanofibers through the synergistic design of material composition, fiber structure, and fabrication process. These nanofibers are suitable for precision sensing fields such as high-performance flexible electronic skin and tactile sensing.

[0039] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A nanoscale fluorescent electrospun fiber comprising a flexible support layer and an electrospun nanofiber layer made from a spinning solution comprising a composite matrix stress luminescent material and a spinning polymer by an electrospinning process, characterized in that, The composite matrix is a composite of ScBO3 and Al2O3, and the composite matrix stress luminescence material is a ternary doped fluorescent material formed by doping Cr in the composite matrix, and the chemical general formula is (Sc0. 3+ , Yb 3+ , and Nd 3+ , and the chemical general formula is (Sc0. 9-x- ᵧAl0.1)BO3:Crˣ,Ybʸ,Ndᶻ, wherein 0.015≤x≤0.035, 0.008≤y≤0.012, and 0.003≤z≤0.007; the spinning polymer is a cellulose derivative, preferably cellulose acetate; the fiber diameter of the electrospun nanofiber layer is 500 nm to 2 μm, and the porosity is 30% to 50%.

2. The nanoscale fluorescent electrospun fiber of claim 1, wherein: The mass ratio of ScBO3 to Al2O3 in the composite matrix is 7:

3.

3. The nanoscale fluorescent electrospun fiber of claim 1, wherein: In the electrospinning nanofiber layer, the mass ratio of the composite matrix stress luminescent material to the polyvinylidene fluoride is 1:1.5 to 1:2.

5.

4. The nanoscale fluorescent electrospun fiber of claim 1, wherein: The flexible support layer is a composite film of polylactic acid and polydimethylsiloxane, with a thickness of 80 to 150 μm.

5. The nanoscale fluorescent electrospun fiber of claim 1, wherein: The thickness of the electrospinning nanofiber layer is 50 to 100 μm.

6. A method of producing nanofluorescent electrospun fibers as claimed in any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1, preparing a spinning solution: ingredients with chemical formula (Sc0. 9-x- The fluorescent powder of (Sc0.1)BO3:Cr3+, Yb2+, Nd3+, cellulose acetate, a suitable solvent such as a mixed solvent of acetone and water or acetic acid, etc. are mixed, ultrasonic dispersion and magnetic stirring are performed, and a uniform spinning solution is obtained; the preparation of the spinning solution is based on the solubility of the cellulose derivative in a specific solvent, by optimizing the solvent ratio and solid content, the highly dispersed fluorescent powder is realized, and the solution has a suitable viscosity of 150 mPa·s to 300 mPa·s and conductivity for electrospinning. S2, pretreatment of the flexible support layer: plasma cleaning of the flexible support layer; S3, electrospinning: electrospinning of the spinning solution obtained in step S1, receiving on the pretreated flexible support layer to form a nanofiber film, followed by drying; The electrospinning process parameters are optimized according to the characteristics of the cellulose-based composite spinning solution, including voltage, receiving distance, ambient temperature and humidity, etc., to ensure continuous and uniform deposition of fibers; S4, packaging: covering the flexible packaging layer on the surface of the nanofiber film and hot pressing packaging.

7. The method according to claim 6, wherein the method is characterized by: In step S1, the mass ratio of N,N-dimethylformamide to acetone is 7:3; the mass ratio of the fluorescent powder to the polyvinylidene fluoride is 1:1.5 to 1:2.

5.

8. The method according to claim 6, wherein the method is characterized by: In step S1, the power of ultrasonic dispersion is 300 W, and the time is 30 to 40 min; the stirring speed of magnetic stirring is 600 r / min, and the time is 6 to 8 h; the viscosity of the spinning solution is 150 to 300 mPa·s.

9. The method of claim 6, wherein the nanofiber is a fluorescent electrospun nanofiber. In step S3, the process parameters of electrospinning are as follows: voltage 15 to 25 kV, receiving distance 10 to 15 cm, spinning solution flow rate 0.5 to 1.5 mL / h, ambient temperature 20 to 25℃, and ambient humidity 30 to 50%; a drum receiving device is used, the drum rotating speed is 50 to 100 r / min, and the spinning time is 60 to 120 min.

10. The method of claim 6, wherein the nanofiber is a fluorescent electrospun nanofiber. The drying conditions in step S3 are as follows: drying in a vacuum drying oven at 80 to 90℃ for 4 to 6 h; in step S4, the flexible packaging layer is a polycaprolactone film, and the hot pressing packaging conditions are as follows: temperature 70 to 80℃, pressure 0.3 to 0.5 MPa, and time 20 to 30 min.

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