Microfluidic induced self-assembly core-shell structure cellulose-based structural color fiber and preparation method thereof

Abstract

The invention discloses a microfluidic induced self-assembly core-shell structure cellulose-based structural color fiber and a preparation method thereof, and relates to the technical field of structural color fibers.The preparation method of the structural color fiber comprises the following steps that S1, a cellulose-based cholesteric liquid crystal polymer is dissolved in a first solvent to obtain a core-layer liquid crystal phase solution; dissolving the shell polymer or the polymer precursor solution in a second solvent to obtain a shell solution; s2, conveying the core layer liquid crystal phase solution through an inner layer channel of the coaxial micro-fluidic chip, conveying the shell layer solution through a middle layer channel, conveying the sheath layer solution through an outer layer channel, and collecting in a coagulating bath to obtain the structural color fiber. The size of the fiber is accurately regulated and controlled through a microfluidic platform, the fiber is endowed with tunable structural color and excellent mechanical properties by combining rapid self-assembly and an in-situ curing mechanism, the process is high in controllability and environmentally friendly, and the prepared structural color fiber has wide application prospects in the fields of intelligent sensing, flexible display, biomedicine and the like.

Description

Technical Field

[0001] This invention relates to the field of structural color fiber technology, and more particularly to microfluidic-induced self-assembled core-shell structured cellulose-based structural color fibers and their preparation methods. Background Technology

[0002] Structural color is the color produced by the interaction of light with the periodic arrangement of a material's microstructure. Unlike traditional chemical dyes, it offers advantages such as being environmentally friendly, fading-free, and responsive to external stimuli. Cellulose-based polymers, as a natural polymer derivative, possess excellent green renewability, biocompatibility, and self-assembly properties. At specific concentrations, they can spontaneously form cholesteric liquid crystal structures, whose periodic helical arrangement selectively reflects specific wavelengths of visible light, generating structural color. Currently, methods for preparing cellulose-based structural color materials mainly include solution casting and electrospinning, but these methods suffer from low assembly efficiency, low structural color intensity, poor uniformity, and narrow tunable range. Therefore, exploring a technical solution for large-scale, high-efficiency assembly of structural color fibers is a major challenge in this field.

[0003] Microfluidics is an emerging technology that precisely manipulates microfluidics through microchannels. It utilizes coaxial shearing, mass diffusion, energy exchange, and chemical reactions to govern fluid flow behavior, enabling the fabrication of nano- to micron-sized fibers. These fibers offer advantages such as high size uniformity, designable structures, high raw material utilization, and ease of integrating multiple components, promising to enable continuous assembly and mass production of materials. They are widely applied in tissue engineering, optoelectronic materials, smart fabrics, and flexible sensing. However, single-phase cellulose-based structural color fibers often suffer from low mechanical properties, poor flexibility, and susceptibility to structural color degradation. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, this invention proposes microfluidic-induced self-assembly core-shell structured cellulose-based structural color fibers and their preparation method. The prepared cellulose-based structural color fibers have the characteristics of bright and uniform structural color, high strength and good flexibility.

[0005] This invention proposes a method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers, the method steps of which are as follows:

[0006] S1: Dissolve the cellulose-based cholesteric liquid crystal polymer in a first solvent to obtain a core liquid crystal phase solution; dissolve the shell polymer or polymer precursor solution in a second solvent to obtain a shell solution;

[0007] S2: The core liquid crystal phase solution is delivered through the inner channel of the coaxial microfluidic chip, the shell solution is delivered through the middle channel, and the sheath solution is delivered through the outer channel. The solution is then collected in a coagulation bath to obtain structural color fibers.

[0008] Preferably, the cellulose-based cholesteric liquid crystal polymer is one or more of hydroxypropyl cellulose, cellulose acetate, carbamoyl ethyl cellulose, ethyl cellulose, acetylacetoethyl cellulose, acetoxypropyl cellulose, acetylacetohydroxypropyl cellulose, ethyl cyanoethyl cellulose, and cellulose nanocrystals.

[0009] Preferably, the first solvent is one or more polar solvents such as deionized water, ethanol, acetone, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide.

[0010] Preferably, the shell polymer is one or more of polyvinyl alcohol, polyacrylic acid, chitosan, sodium alginate, gelatin, silk fibroin, and polyurethane.

[0011] Preferably, the second solvent is one or more of water, acetic acid, formic acid and glycerol.

[0012] Preferably, the polymer precursor solution is composed of a polymer monomer, a crosslinking agent, an initiator, and a third solvent.

[0013] Preferably, the polymeric monomer is one or more of acrylic acid, gelatin methacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, hexanediol diacrylate, hydroxybutyl acrylate, isopropyl acrylamide, glycidyl methacrylate, and polyurethane oligomers.

[0014] Preferably, the third solvent is one or more of water, acetic acid, and formic acid.

[0015] Preferably, the crosslinking agent is one or more of ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, trimethylolpropane triacrylate, and methylenebisacrylamide.

[0016] Preferably, the crosslinking agent has a mass fraction of 0-5% in the polymer precursor solution, and the amount of crosslinking agent added is not 0.

[0017] Preferably, the initiator is a photoinitiator such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone.

[0018] Preferably, the initiator has a mass fraction of 0-5% in the polymer precursor solution, and the amount of initiator added is not zero.

[0019] Preferably, the inner diameter ratio of the inner channel, the middle channel, and the outer channel is 1:1.5-5:3-10; the flow velocity ratio of the inner channel, the middle channel, and the outer channel is 1:1-8:10-30.

[0020] Preferably, the sheath solution is one or more of ethanol, methanol, water, alkanes, and metal ion solutions.

[0021] Preferably, the metal ion is Ca. 2+ Ba 2+ 、Sr 2+ Cu 2+ and Zn 2+ One or more of them, with a metal ion concentration of 0.1-5%.

[0022] The present invention proposes a microfluidic-induced self-assembled core-shell structured cellulose-based structural color fiber, which is prepared by the above-described preparation method.

[0023] Beneficial technical effects of the present invention:

[0024] This invention uses a cellulose-based cholesteric liquid crystal polymer solution as the core phase and a polymer solution or polymer precursor solution with a high curing rate as the shell phase. Based on the multiple physical interactions and microscale effects between the two phases, the core layer cellulose-based cholesteric liquid crystal polymer is induced to self-assemble to form a cholesteric liquid crystal structure. At the same time, the shell phase solution is rapidly cured in situ and continuously formed. By precisely controlling the size and velocity of the two-phase fluids through microfluidic technology, functional fibers with uniform structural color, good mechanical properties, and high flexibility are prepared.

[0025] This invention achieves precise control of fiber size through a microfluidic platform, and combines rapid self-assembly and in-situ curing mechanisms to endow the fibers with tunable structural color and excellent mechanical properties. The process is highly controllable, green and environmentally friendly, and the prepared structural color fibers have broad application prospects in fields such as intelligent sensing, flexible display, and biomedicine. Attached Figure Description

[0026] Figure 1 The images shown are of the cellulose-based structural color fibers proposed in this invention; (a) is the product obtained in Example 1, (b) is the product obtained in Example 2, and (c) is the product obtained in Example 3.

[0027] Figure 2 This is a scanning electron microscope image of the cellulose-based structural color fiber of Example 1 proposed in this invention;

[0028] Figure 3 The reflectance spectrum of cellulose-based structural color fiber proposed in Example 1 of this invention;

[0029] Figure 4 The tensile test results are for the cellulose-based structural color fiber of Example 1 proposed in this invention. Detailed Implementation

[0030] The present invention will be further explained below with reference to specific embodiments.

[0031] Example 1

[0032] Hydroxypropyl cellulose (HCP) and deionized water were mixed and stirred until homogeneous to form a liquid crystal phase stock solution, wherein the HCP content was 50%. Polyvinyl alcohol (PVA) and a solvent were mixed and stirred until homogeneous to form a shell spinning solution, wherein the HCP content was 10%. Methanol was selected as the sheath fluid. The liquid crystal phase stock solution, shell spinning solution, and sheath fluid were simultaneously injected into a three-phase coaxial flow focusing microfluidic chip as the inner phase, intermediate phase, and outer phase, respectively. The inner diameters of the inner, intermediate, and outer phases were 100 μm, 160 μm, and 500 μm, respectively, and the flow rates were 5 μL / min, 10 μL / min, and 50 μL / min, respectively. After flowing out of the microfluidic chip, the fibers were immediately collected in a coagulation bath and solidified for 30 min to obtain HCP fibers with a red structural color.

[0033] Figure 1 Part (a) is a physical image of the hydroxypropyl cellulose structural color fiber prepared in this embodiment. The fiber diameter is 450 μm, and it displays a bright red structural color with uniform color.

[0034] The prepared hydroxypropyl cellulose structural color fibers were subjected to scanning electron microscopy. The results are shown in [reference needed]. Figure 2 The results showed that the prepared hydroxypropyl cellulose structural color fiber had a uniform layered structure with a pitch of 665 nm.

[0035] The reflectance spectra of hydroxypropyl cellulose structural color fibers were measured, and the results are shown in [reference needed]. Figure 3 The results showed that the prepared hydroxypropyl cellulose structural color fiber had a photonic bandgap of 685 nm and high reflection intensity.

[0036] Tensile tests were performed on the hydroxypropyl cellulose structural color fibers, and the results are shown below. Figure 4 The results showed that the prepared hydroxypropyl cellulose structural color fiber had a tensile strength of 2.2 MPa, an elongation at break of 990%, good mechanical properties, and high flexibility.

[0037] Example 2

[0038] Hydroxypropyl cellulose and deionized water were mixed and stirred until homogeneous to form a liquid crystal phase stock solution, wherein the hydroxypropyl cellulose content was 55%. Sodium alginate and a solvent were mixed and stirred until homogeneous to form a shell spinning solution, wherein the sodium alginate content was 2%. Calcium chloride was selected as the sheath fluid, wherein the calcium chloride content was 3%. The liquid crystal phase stock solution, shell spinning solution, and sheath fluid were simultaneously injected into a three-phase coaxial flow focusing microfluidic chip as the inner phase, intermediate phase, and outer phase, respectively. The inner diameters of the inner phase, intermediate phase, and outer phase were 120 μm, 400 μm, and 800 μm, respectively, and the flow rates were 8 μL / min, 50 μL / min, and 200 μL / min, respectively. After flowing out of the microfluidic chip, the fiber was immediately collected in a coagulation bath. After 10 min of solidification, hydroxypropyl cellulose fibers with a green structural color, a photon band gap of 550 nm, and high reflection intensity were obtained.

[0039] Figure 1 Part (b) is a physical image of the hydroxypropyl cellulose structural color fiber prepared in this embodiment. The fiber diameter is 340 μm, and it displays a bright green structural color with uniform color.

[0040] Example 3

[0041] Cellulose nanocrystals and deionized water were mixed and stirred until homogeneous to form a liquid crystal phase stock solution, in which the hydroxypropyl cellulose content was 58%. Polyethylene glycol diacrylate, methylenebisacrylamide, 2-hydroxy-2-methyl-1-phenylpropanone, and water were mixed and stirred until homogeneous to form a shell spinning solution, in which the polyethylene glycol diacrylate content was 50%. Hexadecane was selected as the sheath fluid. The liquid crystal phase stock solution, shell spinning solution, and sheath fluid were simultaneously injected into a three-phase coaxial flow focusing microfluidic chip as the inner phase, intermediate phase, and outer phase, respectively. The inner diameters of the inner, intermediate, and outer phases were 100 μm, 200 μm, and 400 μm, and the flow rates were 5 μL / min, 5 μL / min, and 100 μL / min, respectively. The fibers flowed out of the microfluidic chip and were immediately collected in a coagulation bath. After 10 min of solidification, cellulose nanocrystal fibers with a blue structural color, a photon bandgap at 490 nm, and high reflectivity were obtained.

[0042] Figure 1 Part (c) is a physical image of the cellulose nanocrystalline structured color fiber prepared in this embodiment. The fiber diameter is 235 μm, and it displays a blue structural color with uniform color.

[0043] As can be seen from Examples 1-3, this invention utilizes microfluidic-induced self-assembly technology to prepare patterned photonic crystal films with structural colors. Leveraging the simplicity, controllability, and continuous fabrication capabilities of microfluidic technology, it achieves efficient preparation of cellulose-based fibers with bright and uniform structural colors. These cellulose-based structural color fibers have broad application prospects in fields such as smart clothing, biosensing, and flexible displays.

[0044] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that several variations, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers, characterized in that, The steps are as follows: S1: Dissolve the cellulose-based cholesteric liquid crystal polymer in a first solvent to obtain a core liquid crystal phase solution; dissolve the shell polymer or polymer precursor solution in a second solvent to obtain a shell solution; S2: The core liquid crystal phase solution is delivered through the inner channel of the coaxial microfluidic chip, the shell solution is delivered through the middle channel, and the sheath solution is delivered through the outer channel. The solution is then collected in a coagulation bath to obtain structural color fibers.

2. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 1, characterized in that, The cellulose-based cholesteric liquid crystal polymer is one or more of hydroxypropyl cellulose, cellulose acetate, carbamoyl ethyl cellulose, ethyl cellulose, acetylacetoethyl cellulose, acetoxypropyl cellulose, acetylacetohydroxypropyl cellulose, ethyl cyanoethyl cellulose, and cellulose nanocrystals. The first solvent is one or more of deionized water, ethanol, acetone, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide.

3. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 1, characterized in that, The shell polymer is one or more of polyvinyl alcohol, polyacrylic acid, chitosan, sodium alginate, gelatin, silk fibroin, and polyurethane. The second solvent is one or more of water, acetic acid, formic acid, and glycerol.

4. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 1, characterized in that, The polymer precursor solution consists of polymeric monomers, crosslinking agents, initiators, and a third solvent.

5. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 4, characterized in that, The polymeric monomer is one or more of the following: acrylic acid, gelatin methacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, hexanediol diacrylate, hydroxybutyl acrylate, isopropyl acrylamide, glycidyl methacrylate, and polyurethane oligomers. The polymeric monomer has a mass fraction of 40%-70% in the polymer precursor solution; The third solvent is one or more of water, acetic acid, and formic acid.

6. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 4, characterized in that, The crosslinking agent is one or more of ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, trimethylolpropane triacrylate, and methylenebisacrylamide; The crosslinking agent has a mass fraction of 0-5% in the polymer precursor solution, and the amount of crosslinking agent added is not 0.

7. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 4, characterized in that, The initiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone; The initiator has a mass fraction of 0-5% in the polymer precursor solution, and the amount of initiator added is not 0.

8. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 1, characterized in that, The inner diameter ratio of the inner channel, middle channel, and outer channel is 1:1.5-5:3-10; The flow rate ratio of the inner, middle and outer channels is 1:1-8:10-30.

9. The method for preparing microfluidically induced self-assembled core-shell structured cellulose-based structural color fibers according to claim 1, characterized in that, The sheath solution is one or more of ethanol, methanol, water, alkanes, and metal ion solutions; The metal ion is Ca. 2+ Ba 2+ 、Sr 2+ Cu 2+ and Zn 2+ One or more of them, with a metal ion concentration of 0.1-5%.

10. A microfluidic-induced self-assembled core-shell structured cellulose-based structural color fiber, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

Images