All-fiber-shaped SF NF-Ag NWs composite wearable electronic skin and preparation method thereof

Abstract

The invention discloses a full-fiber-shaped SF NF-Ag NWs composite wearable electronic skin and a preparation method thereof, and the preparation method comprises the following steps: forming a large-area full-fiber-shaped composite film (SF NF-Ag NWs) by adopting a silk fibroin fiber film (SF) prepared by an electrostatic spinning technology and a silver nanowire conducting medium (Ag NWS) through vacuum filtration; the ultrathin porous SF NF-Ag NWs material is designed into an electrode patch of a portable electrocardiogram monitoring instrument to be attached to a healthy human body, and can be used for human body movement health monitoring application expansion and portable electrocardiogram monitoring.

Description

Technical Field

[0001] The present invention relates to the field of new material technology, and more specifically to a fully fibrous SF NF-Ag NWs composite wearable electronic skin and a preparation method thereof. Background Art

[0002] Wearable sensing technology is an essential part of personalized medicine in the future. Such sensors need to overcome the mismatch between typical rigid silicon-based sensors and soft, elastic organisms, so as to perfectly fit onto biological interfaces such as the epidermis, eyes and teeth to assess health levels. As the largest organ in the human body, the skin not only has the basic functions of protection, secretion and breathing, but is also an important somatosensory system for humans to perceive, interact and communicate with the physical world.

[0003] With the continuous development of wearable electronic technology, people's demand for continuous monitoring of physiological signals is growing. There is an increasing demand for wearable flexible sensors with real-time health monitoring and synchronous feedback functions. At present, electrocardiogram (ECG), electromyogram (EMG) and electroencephalogram (EEG) are widely used in clinical practice. However, traditional biopotential electrodes must be used with conductive gel, and patients are connected to bulky instruments through a large number of wires with the help of medical staff, which not only restricts the natural movement of the patient's body and causes great discomfort, but also fails to detect the patient's health at any time. In addition, gels and adhesives may cause skin irritation, which has aroused concerns about how to monitor biosignals over a long period of time and how to improve the comfort and breathability of wearable devices.

[0004] Surface enhanced Raman scattering (SERS) is a powerful non-invasive spectroscopic technique that has been widely used in bio / chemical sensing. SERS characteristics contain the inherent fingerprint vibration information of the target analyte and can be used to identify and quantify the analyte. SERS utilizes the optical properties of nanostructures with plasmonic properties, which significantly enhances the Raman signal of the target molecule located near the plasmonic metal nanostructure. The extremely high sensitivity, molecular specificity of plasmonic nanomaterials and the synergistic effect of Raman spectroscopy make SERS a sensitive, fast, non-destructive and powerful analytical technique. Flexible SERS sensors can adapt to non-planar surfaces and allow swab sampling or in-situ detection of analytes, which is not possible with rigid SERS sensors, greatly meeting the needs of on-site and real-time detection.

[0005] Flexible sensor devices refer to bendable or stretchable sensor devices that can convert human body signals or environmental stimulus signals into detectable signals (mainly electrical signals). Silk fibers can provide support for sensor devices with their inherent flexibility and excellent mechanical properties. Silk fibroin (SF) is a natural and ideal biocompatible material that is safe, non-toxic, and non-immunogenic. SF has excellent mechanical properties and shows good application prospects in the fields of flexible electronics, optics, and electrical sensors. SF can be converted into a stable silk fibroin crystal structure by ethanol reagents, thereby greatly improving its mechanical properties. More importantly, it also has excellent hygroscopicity and produces a humidity-driven effect when it encounters water molecules. The silk fibroin chain of the silk fibroin film is composed of hydrophilic and hydrophobic amino acid sequences. The interaction between water molecules and SF chains is promoted by functional groups and secondary structures (such as β-sheet and α-helix). At the same time, the SF chain adapts to water molecules by changing its conformation, resulting in the adhesion of the membrane to the surface of biological samples such as skin and gloves.

[0006] Based on the above, there is an urgent need to design reasonable, safe and stable wearable material structures to achieve simple, low-cost, large-scale preparation of wearable multifunctional sensing materials, and to construct multimodal mechanical sensors that can monitor multiple mechanical stimuli to meet the flexibility and good biocompatibility required by current wearable mechanical sensors. Summary of the invention

[0007] In view of this, the technical solution of the present invention adopts electrospinning technology, uses silk cocoons to prepare regenerated silk protein solution as a flexible substrate, and prepares a silk protein nanofiber membrane with a three-dimensional elastic porous structure.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] First, the present invention provides a method for preparing a fully fibrous SF NF-Ag NWs composite wearable electronic skin, comprising the following steps:

[0010] Step 1: Extraction of silk fibroin

[0011] Cut the cocoons into pieces and place them in Na 2 CO 3 After boiling the cocoons in the solution for 30 minutes, the cocoons were washed with clean water, the excess water was squeezed out, and then dried at 60°C. A certain amount of LiBr was added to the dried silk fibroin, dissolved at 60°C for 4 hours, dialyzed with ultrapure water for 3 days, and then centrifuged at 8000 rpm to remove impurities to obtain a regenerated silk fibroin solution with a mass fraction of 7-8%;

[0012] Step 2: Preparation of silk fibroin fiber membrane

[0013] (2.1) slowly stirring the obtained regenerated silk fibroin solution and the spinning aid in a volume ratio of 1:3 at a rotation speed of 100 rpm for 10 minutes in an environment of 4°C to obtain a mixed solution;

[0014] (2.2) electrospinning the mixed solution to obtain a composite film, then soaking the composite film in a 90% by volume methanol solution for 10-30 min to obtain a SF membrane, then soaking the SF membrane in deionized water for 10 min, taking it out and drying it at room temperature;

[0015] Step 3: Preparation of SF NF-Ag NWs fiber membrane

[0016] Silver nanowires were deposited on the surface of the SF membrane prepared in step 2 by suction filtration to obtain a fully fibrous SF NF-AgNWs composite wearable electronic skin.

[0017] Preferably, in step 1, Na 2 CO 3 The solution concentration is 0.02 mol / L, the LiBr concentration is 9.3 mol / L, and the ratio of silk fibroin to LiBr is 1 g:4 mL.

[0018] Preferably, the spinning aid in step (2.1) is a PEO solution with a volume fraction of 1.5%.

[0019] Preferably, the electrospinning parameters in step (2.2) are as follows: using an 18-gauge needle and applying a voltage of 10.6 kV to the needle.

[0020] Preferably, the filtration in step 3 is specifically:

[0021] Take deionized water to soak the filter element of the vacuum filtration equipment, take the filter membrane to cover the filter element, then place the SF membrane prepared in step 2 on the filter membrane and fix the filter cup and filter element, pour the silver nanowire solution into the filter cup and start filtering to load the silver nanowires on the SF membrane.

[0022] Preferably, in step 3, the amount of silver nanowires deposited on the surface of the SF film is 0.02 mg / cm 2 .

[0023] In addition, the present invention also provides a fully fibrous SFNF-Ag NWs composite wearable electronic skin prepared by the method described in the above technical solution.

[0024] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a fully fibrous SFNF-Ag NWs composite wearable electronic skin and a preparation method thereof, which has the following beneficial effects:

[0025] The present invention adopts electrospinning technology, uses cocoons to prepare regenerated silk protein solution as a flexible substrate, and prepares a silk protein nanofiber membrane with a three-dimensional elastic porous structure. Due to the structure of silk protein and silver nanowires, the electronic skin of the present invention has extremely high biocompatibility, good adhesion performance, excellent moisture absorption and tensile properties, good conductivity, antibacterial properties and high sensitivity. The all-nanofiber electronic skin of the present invention effectively avoids the accumulation of sweat through the humidity driving effect of silk protein and the capillary effect of fiber. The preparation method adopted by the present invention is simple, low in operability, and low in cost. It can be used as a method for preparing ultra-thin porous flexible wearable electronic skin materials on a large area. The preparation method is easy to industrialize and has strong universality. The electronic skin prepared by the preparation method in the present invention can be further combined with intelligent portable ECG monitoring, and human sports health monitoring and biomedical testing can be directly performed through mobile phone software. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 Optical image and SEM image of silk fibroin fiber membrane;

[0028] Figure 2 is the SEM image of SF NF-AgNWs;

[0029] Figure 3 This is the electrocardiogram of SF NF-AgNWs;

[0030] Figure 4 Figure 2 shows the SERS activity of SF NF-AgNWs. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] First, the silk fibroin is extracted and the silk fibroin fiber membrane is prepared, specifically:

[0034] First, 5g natural silkworm cocoons were cut and then mixed with 0.02M Na 2 CO 3 Boil the cocoons for 30 minutes, then wash the fibers, squeeze out excess water and dry in an oven at 60°C, add 9.3M LiBr to the silk fibers, SF:LiBr=1:4 (1 g:4 mL), dissolve at 60°C for 4 hours, dialyze with 1L ultrapure water for 3 days, centrifuge at 8000rpm to remove impurities, and obtain a regenerated silk protein solution with a mass fraction of 7-8%, which is stored at 4°C;

[0035] The obtained regenerated silk fibroin solution and a spinning aid PEO with a volume fraction of 1.5% were stirred at a low speed of 100 rpm for 10 minutes in a volume ratio of 1:3 to obtain a mixed solution. The mixed solution was electrospun using an 18-gauge needle and a voltage of 10.6 kV was applied to the needle. The successfully electrospun PEO@SF film was soaked in 90% methanol by volume for 10-30 minutes to remove PEO. The SF membrane from which PEO was removed was soaked in deionized water for 10 minutes. Finally, the SF fiber membrane was dried at room temperature to obtain a silk fibroin fiber membrane. Figure 1 Optical and SEM images of silk fibroin fibers.

[0036] Then the SF NF-AgNWs fiber membrane was prepared, specifically:

[0037] Take deionized water to soak the filter element of the vacuum filtration equipment, take the filter membrane to cover the filter element, and then cut the SF membrane prepared in step 2 into 4×4cm 2 The square was placed on the filter membrane and the filter cup and filter element were fixed. The silver nanowire solution was poured into the filter cup and then filtered to load the silver nanowires on the SF membrane. The concentration of the silver nanowire solution was obtained by filtering the silver nanowire solution on the surface of the SF membrane (the final silver nanowire deposition amount on the surface of the SF membrane was 0.02 mg / cm 2 Finally, the obtained SF NF-AgNWs fiber membrane was stored at room temperature. Figure 2 SEM image of SF NF-AgNWs.

[0038] Finally, the SF NF-AgNWs fiber membrane was subjected to a wearing experiment, specifically:

[0039] Before the experiment, volunteers need to thoroughly clean the skin area to be attached with deionized water and spray a small amount of water on the skin surface, and then use the humidity-driven properties of the SF membrane to attach the SF NF-Ag NWs layer to the skin surface. During the motion detection process, it is necessary to add a connecting wire between the electrochemical workstation and the fiber membrane to facilitate the collection of electrical signals during exercise.

[0040] Figure 3 and Figure 4 The ECG detection and SERS activity diagram of SF NF-AgNWs. As can be seen from the figure, SF NF-AgNWs electronic skin can obtain stable ECG signals and good SERS signals.

[0041] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0042] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a fully fibrous SF NF-Ag NWs composite wearable electronic skin, characterized in that: The following steps are involved: Step 1: Extraction of silk fibroin Cut the silk cocoons into pieces, boil them in a Na2CO3 solution for 30 minutes, wash them with clean water, squeeze out excess water, and then dry them at 60°C. Add a certain amount of LiBr to the dried silk fibroin, dissolve it at 60°C for 4 hours, dialyze it with ultrapure water for 3 days, and then centrifuge it at 8000rpm to remove impurities to obtain a regenerated silk fibroin solution with a mass fraction of 7-8%; Step 2: Preparation of silk fibroin fiber membrane (2.1) slowly stirring the obtained regenerated silk fibroin solution and the spinning aid in a volume ratio of 1:3 at a rotation speed of 100 rpm for 10 minutes in an environment of 4°C to obtain a mixed solution; (2.2) electrospinning the mixed solution to obtain a composite film, then soaking the composite film in a 90% by volume methanol solution for 10-30 min to obtain a SF membrane, then soaking the SF membrane in deionized water for 10 min, taking it out and drying it at room temperature; Step 3: Preparation of SF NF-Ag NWs fiber membrane Silver nanowires were deposited on the surface of the SF membrane prepared in step 2 by suction filtration to obtain a fully fibrous SF NF-Ag NWs composite wearable electronic skin.

2. The method for preparing a fully fibrous SF NF-Ag NWs composite wearable electronic skin according to claim 1, characterized in that: In step 1, the concentration of the Na2CO3 solution is 0.02 mol / L, the concentration of the LiBr is 9.3 mol / L, and the ratio of silk fibroin to LiBr is 1 g:4 mL.

3. The method for preparing a fully fibrous SF NF-Ag NWs composite wearable electronic skin according to claim 1, characterized in that: The spinning aid in step (2.1) is a PEO solution with a volume fraction of 1.5%.

4. The method for preparing a fully fibrous SF NF-Ag NWs composite wearable electronic skin according to claim 1, characterized in that: The electrospinning parameters in step (2.2) are as follows: using an 18-gauge needle and applying a voltage of 10.6 kV to the needle.

5. The method for preparing a fully fibrous SF NF-Ag NWs composite wearable electronic skin according to claim 1, characterized in that: The filtration described in step 3 is specifically as follows: Take deionized water to soak the filter element of the vacuum filtration equipment, take the filter membrane to cover the filter element, then place the SF membrane prepared in step 2 on the filter membrane and fix the filter cup and filter element, pour the silver nanowire solution into the filter cup and start filtering to load the silver nanowires on the SF membrane.

6. The method for preparing a fully fibrous SF NF-Ag NWs composite wearable electronic skin according to claim 1, characterized in that: In step 3, the amount of silver nanowires deposited on the surface of the SF film is 0.02 mg / cm 2 .

7. A fully fibrous SF NF-Ag NWs composite wearable electronic skin prepared by the method according to any one of claims 1 to 6.

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