WO2023201183A1 - Nanostructures électrofilées bien régulées et procédés associés - Google Patents

Nanostructures électrofilées bien régulées et procédés associés Download PDF

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Publication number
WO2023201183A1
WO2023201183A1 PCT/US2023/065431 US2023065431W WO2023201183A1 WO 2023201183 A1 WO2023201183 A1 WO 2023201183A1 US 2023065431 W US2023065431 W US 2023065431W WO 2023201183 A1 WO2023201183 A1 WO 2023201183A1
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approximately
fibrous network
network film
electrospun
electrospun fibers
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PCT/US2023/065431
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English (en)
Inventor
Sang Eon Han
Sang M. HAN
Bokyung PARK
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Unm Rainforest Innovations
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Publication of WO2023201183A1 publication Critical patent/WO2023201183A1/fr

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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/0007—Electro-spinning
    • D01D5/0015—Electro-spinning characterised by the initial state of the material
    • D01D5/003—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F4/00—Monocomponent artificial filaments or the like of proteins; Manufacture thereof
    • D01F4/02—Monocomponent artificial filaments or the like of proteins; Manufacture thereof from fibroin
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4266—Natural fibres not provided for in group D04H1/425
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4382—Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
    • D04H1/72—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged
    • D04H1/728—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged by electro-spinning
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01C—CHEMICAL OR BIOLOGICAL TREATMENT OF NATURAL FILAMENTARY OR FIBROUS MATERIAL TO OBTAIN FILAMENTS OR FIBRES FOR SPINNING; CARBONISING RAGS TO RECOVER ANIMAL FIBRES
    • D01C3/00—Treatment of animal material, e.g. chemical scouring of wool
    • D01C3/02—De-gumming silk
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D1/00—Treatment of filament-forming or like material
    • D01D1/02—Preparation of spinning solutions

Definitions

  • the present teachings relate generally to fibrous network films and, more particularly, to methods for generating nanostructured fibrous network films.
  • the scales of the white beetle genus, Cyphochilus can be magnified to reveal the fibrillar nanostructure, which is strongly anisotropic, as depicted in FIG. IB, which makes it one of the most efficient light-scattering biological structures known today.
  • the fibrils in the nanostructure are made of a low-index chitin and mostly oriented in transverse directions with near isotropy in the lateral plane. Combined with the anisotropy originating from the fibril orientations, a mean fibril diameter of -0.25 mm and a filling fraction of -31.5% achieve the exceptionally strong optical scattering.
  • Cyphochilus scales preserve structural regularity with relatively uniform length scales, while not strictly minimizing the surface free energy.
  • one of the remaining challenges is how to create strongly scattering anisotropic nanostructures of relatively low surface free energy, such that they share the key structural parameters with Cyphochilus scales, using fabrication techniques that are amenable to mass production.
  • a method of generating a fibrous network film includes preparing a fibroin solution.
  • the method of generating a fibrous network film also includes loading the fibroin solution into a syringe with a conductive needle or nozzle.
  • the method of generating a fibrous network film also includes applying a high voltage to the needle or nozzle and grounding a conductive surface of a collector.
  • the method of generating a fibrous network film also includes electrospinning the fibroin solution from the syringe or nozzle with the conductive needle or nozzle to the grounded conductive surface of the collector to generate the fibrous network film on the grounded conductive surface.
  • Implementations of the method of generating a fibrous network film may include where the collector moves in lateral motion relative to the conductive needle during the electrospinning or where the collector is rotated.
  • the conductive needle can be a 21 -gauge stainless-steel needle.
  • the collector can be drum-shaped with a diameter of about 1 cm to about 15 cm and the grounded conductive surface may include stainless steel.
  • the collector can be rotated about an axis at of about 20 to about 45 rpm during the electrospinning.
  • a distance between a tip of the conductive needle and the grounded conductive surface can be 15 cm.
  • the high voltage can be approximately 21 kv.
  • Using the regenerated silk fibroin powder to produce the fibroin solution may include dissolving the regenerated silk fibroin powder in 98% formic acid for three hours at a concentration varying from 8 to 15 wt% to produce an unfiltered solution of silk fibroin, and filtering the unfiltered solution of silk fibroin through a polyethylene porous membrane to produce the fibroin solution.
  • the preparing the fibroin solution may include preparing a powder of regenerated silk fibroin, and using the powder of regenerated silk fibroin to produce the fibroin solution.
  • the preparing the powder of regenerated silk fibroin may include removing sericin from white silk cocoons to produce degummed silk cocoons, rinsing the degummed silk cocoons with distilled water at 100c for 150 seconds, further rinsing the rinsed degummed silk cocoons with cold distilled water, drying the further rinsed degummed silk cocoons at 80°C for approximately 24 hours, dissolving the dried silk cocoons at a liquor ratio of 1:20 in a CaC12/H2O/EtOH (1/8/2 molar ratio) mixture solvent at 85°C for approximately 30 minutes to produce a silk fibroin solution, placing the silk fibroin solution in a tube of a cellulose membrane and dialyzing the silk fibroin solution for 4 days by circulating distilled water around the tube, filtering the dialyzed silk fibroin solution through a polyethylene porous membrane to produce a filtered solution of regenerated silk fibroin, drying the filtered solution of regenerated silk
  • Removing sericin from white silk cocoons to produce degummed silk cocoons may include preparing an aqueous solution of 0.2% w/v sodium carbonate and 0.3% w/v sodium oleate; heating the aqueous solution to 105°C, and heating the white silk cocoons in the aqueous solution for approximately 90 minutes to produce the degummed silk cocoons.
  • the white silk cocoons can be Bombyx Mori (geumokjam) white silk cocoons.
  • the cold distilled water can be distilled water at approximately 10°C.
  • the fibrous network film generated by any of the method can include where the electrospinning the fibroin solution from the syringe with the conductive needle to the grounded conductive surface of the collector to generate the fibrous network film on the grounded conductive surface may include generating a plurality of electrospun fibers, where each of the plurality of electrospun fibers exhibits a fiber diameter value as a function of fiber length such that a relative standard deviation o of fiber diameter values for each of the plurality of electrospun fibers is approximately 0.32, the plurality of electrospun fibers, taken together, exhibit a mean fiber diameter value that is one of approximately 0.30 pm and approximately 0.32 pm, and the plurality of electrospun fibers in the fibrous network film exhibit a filling fraction from approximately 10% to approximately 60%.
  • the filling fraction can be between approximately 31% and approximately 45%.
  • the mean fiber diameter value is approximately 0.32 pm and the filling fraction is approximately 38%.
  • the filling fraction can be between approximately 31% and approximately 45%.
  • An index of refraction of the fibrous network film can be from about 1.4 to about 1.6.
  • electrospinning the fibroin solution from the syringe with the conductive needle to the grounded conductive surface of the collector to generate the fibrous network film on the grounded conductive surface may include generating a plurality of electrospun fibers, where each of the plurality of electrospun fibers exhibits a fiber diameter value as a function of fiber length such that a relative standard deviation o of fiber diameter values for each of the plurality of electrospun fibers is approximately 0.35, the plurality of electrospun fibers, taken together, exhibit a mean fiber diameter value that is approximately 0.20 pm, and the plurality of electrospun fibers in the fibrous network film exhibit a filling fraction from approximately 10% to approximately 60%.
  • Implementations can include an optical film that can include the fibrous network film.
  • Implementations can include a clothing item that can include the fibrous network film.
  • a method of generating a fibrous network film includes preparing a polymer solution.
  • the method of generating a fibrous network film also includes loading the polymer solution into a syringe with a conductive needle or nozzle, applying a high voltage to the needle and grounding a conductive surface of a collector, electrospinning the polymer solution from the syringe with the conductive needle to the grounded conductive surface of the collector to generate the fibrous network film on the grounded conductive surface, and where an index of refraction of the fibrous network film can be from about 1.4 to about 1.6, and the fibrous network film may include a plurality of electrospun polymer fibers.
  • a fibrous network film can include of a plurality of electrospun fibers.
  • the fibrous network film can also include where each of the plurality of electrospun fibers exhibits a fiber diameter value as a function of fiber length such that a relative standard deviation o of fiber diameter values for each of the plurality of electrospun fibers is approximately 0.32, the plurality of electrospun fibers, taken together, exhibit a mean fiber diameter value that is one of: approximately 0.30 pm and approximately 0.32 pm, and the plurality of electrospun fibers in the fibrous network film exhibit a filling fraction from approximately 10% to approximately 60%. Implementations may include where the filling fraction is between approximately 31% and approximately 45%. The mean fiber diameter value is approximately 0.32 pm and the filling fraction is approximately 38%.
  • a fibrous network film may include of a plurality of electrospun fibers.
  • the fibrous network film can include where each of the plurality of electrospun fibers exhibits a fiber diameter value as a function of fiber length such that a relative standard deviation o of fiber diameter values for each of the plurality of electrospun fibers is approximately 0.35, the plurality of electrospun fibers, taken together, exhibit a mean fiber diameter value that is approximately 0.20 pm, and the plurality of electrospun fibers in the fibrous network film exhibit a filling fraction from approximately 10% to approximately 60%.
  • the fibrous network film can include where the filling fraction is between approximately 31% and approximately 45%.
  • FIGS. 1A and IB are photographs of a Cyphochilus white beetle and an SEM image of a cross-section of its scale, respectively, in accordance to the present disclosure.
  • FIG. 2A is a schematic of an effective medium model for fibrous random media.
  • FIG. 2C is a plot depicting effective transport mean free path (L zz *' ⁇ spectra for anisotropic (random orientation only in the plane perpendicular to the incident light) and isotropic (random orientation in all directions) fibrous media for the same key structural parameters (except anisotropy) and the refractive index of the fibers as those in Cyphochilus scales.
  • FIG. 4A is a composite SEM image of top and cross-sectional views of an electrospun silk film.
  • FIG. 4E is a plot depicting effective transport mean free path (L zz *') spectra obtained by model calculation.
  • FIG. 4F is a plot depicting effective transport mean free path (L zz *') spectra obtained experimentally.
  • FIG. 5B is a plot depicting an average cosine of scattering angle (cos 9 ⁇ as a function of the cosine of incident angle cos 9' for a scattering unit of Cyphochilus scales as compared to the model, where the model calculation assumed the same d 0 , f, a. and refractive index as those in naturally occurring Cyphochilus scales.
  • FIG. 61 is a plot depicting reflectivity as a function of wavelength for a purple structural color 600 transitioning to a whiter color 602 as a becomes larger.
  • FIG. 7 is a flow chart illustrating a method of generating a fibrous network film, in accordance with the present disclosure.
  • Cyphochilus white beetles present one of the strongest optical scattering materials in nature.
  • the intricate optical fibrillar network nanostructure inside the scales has been difficult to mimic without using complicated templating techniques.
  • characteristic structural parameters inside Cyphochilus scales - mean fiber diameter, diameter distribution, filling fraction, and structural anisotropy - are replicated in synthetic nanofibrous materials to functionally mimic the biological material.
  • electrospinning is used because this conventional technique is amenable to nanomanufacturing and scale up.
  • the present teachings provide a method including electrospinning, a well-established technique for mass production of nanoscale fibers, used in the creation of highly anisotropic fibrous networks where fiber diameter is relatively uniform around a quarter micrometer and filling fraction is near 30-40%, in agreement with those in Cyphochilus scales.
  • the electrospinning method enables precise control of the nanostructural parameters.
  • it is expected that the exceptionally strong scattering can be achieved in an electrospun structure by replicating the key structural parameters found in Cyphochilus scales.
  • optical modeling is performed based on effective medium theory and the structural parameters are optimized by modeling calculations.
  • the optimized parameters in electrospun structures are found to be only slightly different from those in Cyphochilus scales. At the optimum, electrospun structures exhibit even stronger optical scattering than Cyphochilus scales, as confirmed by experimental measurements that match well with modeling calculations.
  • the present teachings reveal that electrospun films of nonwoven silk nanofibers, when appropriately structured, can surpass Cyphochilus scales in scattering strength for the entire visible spectrum. Furthermore, the detailed modeling study disclosed herein demonstrates how the key structural parameters affect scattering properties in the electrospun films.
  • An electrospun film with the similar characteristic structural parameters as those in Cyphochilus scales gives two resonance peaks in the visible reflectance spectrum in the limit of a uniform fiber diameter. The stronger resonance is located in the blue and the weaker resonance in the red, giving a purple structural color. As the distribution of diameter increases appreciably to experimentally achievable degrees, the resonance peaks broaden and the reflectance spectrum becomes relatively flat with stronger scattering in shorter wavelengths, resulting in disappearance of the structural color.
  • the dimensions of the electrospun fibers can be approximated as a collection of infinitely long cylinders to model their optical properties.
  • the Mie solutions for single cylinders can be used to predict the optical properties of the media.
  • the optical behavior becomes complicated due to interactions between the cylinders.
  • resonant modes tend to spread out of the cylinder, increasing and complicating the interactions.
  • weak interactions are assumed, so that the distant region surrounding the cylinder is regarded as being occupied by a uniform medium with an effective refractive index represented by the Maxwell-Garnett mixing rule.
  • FIG. 2A is a schematic of an effective medium model for fibrous random media.
  • FIG. 2C is a plot depicting effective transport mean free path (L zz *') spectra for anisotropic (random orientation only in the plane perpendicular to the incident light) and isotropic (random orientation in all directions) fibrous media for the same key structural parameters (except anisotropy) and the refractive index of the fibers as those in Cyphochilus scales.
  • L zz *' for Cyphochilus scales adapted from literature is shown for comparison.
  • FIG. 2C L zz *' for Cyphochilus scales adapted from literature is shown for comparison.
  • FIG. 2A An effective medium model for a fibrous random media is shown in FIG. 2A.
  • a medium filling fraction f a cylinder representing a fiber 200 with a diameter d is assumed to be surrounded by a concentric air cylinder 202 with a diameter d/ ⁇ Ff so that the filling fraction in the space occupied by the two concentric cylinders 200, 202 is f [FIG. 2(A)] .
  • the region outside the air cylinder is treated as an effective medium 204.
  • the Mie solutions for the concentric cylinders 200, 202 in an effective medium 204 are integrated over their orientations and diameter distributions to give the scattering cross section and the phase function.
  • a more accurate model while not used in the present disclosure, can also be used where the effective index is determined self-consistently by imposing a condition that an average optical energy density in the two concentric cylinders 200, 202 is the same as that in the effective medium 204.
  • the z-axis 206 is indicative of the incident light propagation.
  • Optical scattering in dense electrospun fibrous media can be calculated following a radiative transfer approach. In this approach, the scattering cross section and the phase function are used in the radiative transfer equation (RTE) to calculate specific intensity as a function of spatial position and direction. RTE can be simplified into the diffusion equation when the angular dependence of specific intensity is assumed to be small.
  • FIG. 2C depicts an effective transport mean free path (L zz *') spectra for anisotropic (random orientation only in the plane perpendicular to the incident light) and isotropic (random orientation in all directions) fibrous media for the same key structural parameters.
  • L zz *' effective transport mean free path
  • transmissivity and reflectivity of a thick film for normal incidence are determined by a single characteristic length.
  • This length is called the effective transport mean free path L zz ', which is the vertical thickness direction component (zz) of its tensorial form £*' .
  • L zz *' is the z-length over which the direction of light propagation becomes randomized, so that ⁇ -I zz ' represents scattering strength in the z-direction.
  • the assumption of small angular dependence for the diffusion approximation can be problematic for fibrous media because of their strongly forward-scattering nature. Nevertheless, transmissivity and reflectivity for electrospun media are calculated with negligible errors by the diffusion model.
  • the fibers are randomly oriented over all directions in the isotropic structure, whereas they are oriented only in transverse directions in the anisotropic structure.
  • the phase function in the anisotropic structure contributes to increasing scattering strength or decreasing L zz *' compared to that in the isotropic structure.
  • FIG. 2C shows that this behavior is maintained throughout the visible spectrum.
  • L zz *' in the Cyphochilus structure is located between L zz *'’s of the two structures. This is pronounced of a previous study where it is argued that, in the biological structure, scattering would become stronger as its anisotropy increases.
  • the anisotropic structure considered in FIG. 2B and FIG. 2C has the maximum desired anisotropy among rotationally symmetric random fibrous structures because its fibers are oriented strictly in the transverse directions.
  • FIGS. 3A and 3B show P( e )/ e for the free-standing and coating samples, respectively, where P is the transmitted light power and cos -1 p e is the angle from the normal as the light exits the samples.
  • the calculated P(pg)lp e spectra match well with experiments. The exact reasons for small deviations between the two are difficult to identify. However, a likely reason is that the model is limited in describing optical scattering at interfaces, as it assumes a unit in FIG. 2A derived from bulk structures and the fibers near interfaces have a different environment from the bulk.
  • FIG. 4A is a composite SEM image of top and cross-sectional views of an electrospun silk film.
  • FIGS. 4E and 4F are plot depicting effective transport mean free path (L zz *') spectra obtained by model calculation.
  • FIG. 4F is a plot depicting effective transport mean free path (L zz *') spectra obtained experimentally.
  • L zz *' for Cyphochilus scales adapted from literature values is presented for comparison.
  • FIGS. 4C - 4F the model calculation assumed experimentally determined o.
  • filing fraction % is similar to and can be considered as essentially an inverse of porosity.
  • the filling fraction percent can be defined as a ratio of unoccupied volume to occupied volume.
  • the filling fraction is typically measured by volume displacement. Where density differences are present, the density of different solvents can be utilized to determine filling fractions or porosity.
  • reducing the filling fraction can be achieved by other means known to those skilled in the art in alternate examples, such as varying solvent properties, polymer properties, processing additives, flow rate, voltage applied, nozzle size or needle gauge, distance from tip to collector, and the like.
  • a needle-less dispensing system may be utilized.
  • ambient temperature and humidity can modify the porosity as well, as these parameters are known to influence the fiber diameter, density, and therefore the porosity.
  • FIG. 4(B) The optimum /is located roughly in the middle because the density of scattering centers vanishes as / approaches 0 or 100%.
  • L zz *' From extract L zz *' from the samples, linear regression on plots of inverse transmissivity vs. film thickness was performed.
  • L zz *' As evidenced by lower L zz *' curves in FIG. 4F the electrospun structures of the present examples outperform Cyphochilus scales in optical scattering. Specifically, L zz *' is approximately 0.9 pm - 2.1 pm for the two electrospun structures in FIG. 4F, whereas it is 1.5 pm - 2.4 pm for Cyphochilus scales in the visible spectrum. Thus, the enhancement factor in the scattering strength by electrospun fibers from Cyphochilus scales is 1. 1 - 1.7 in the visible spectrum. For all the structures, L zz *' increases with A.
  • FIG. 5B is a plot depicting an average cosine of scattering angle (cos 0) as a function of the cosine of incident angle cos 9' for a scattering unit of Cyphochilus scales as compared to the model, where the model calculation assumed the same d 0 , f, a. and refractive index as those in naturally occurring Cyphochilus scales.
  • the FIG. 5B, inset further depicts a definition of 9 and 9’.
  • a normal incident angle, z 502 is shown, with an incoming variable incident angle, 9’ 504 and the outgoing, scattered angle, 9 506 in relation to the oriented plane of the surface 500.
  • its scattering characteristics may also be different, despite similar magnitudes and spectral dependence in L zz *' .
  • Scattering characteristics in an electrospun film can be investigated using our model based on infinitely long cylinders. In this case, the scattering characteristics can be represented by the differential scattering cross section, which gives the angular distribution of scattered intensity. However, this quantity is not trivial to obtain for the structure in Cyphochilus scales.
  • a scattering unit has to be defined for such intricate continuous structure to determine this quantity.
  • FIG. 5A shows a comparison between the results on the electrospun structure and the results on Cyphochilus scales known in literature. The sign of (cos 9) determines whether the scattering is overall in the positive or negative z-direction, as depicted in the inset of FIG. 5B.
  • the structures in the electrospun fdm and Cyphochilus scales exhibit different scattering behaviors from each other.
  • the colors shown for the two spectra are those under CIE standard illuminant D65.
  • the general trend of dQ/L ⁇ ' is captured more closely by Q sca than by (cos 0), also referring to Eq. (2).
  • a resonance appears at d 0 0.33 pm as o -> 0 based on the peak in Q sca , shown in FIG. 6B.
  • the resonance peak broadens as the fiber diameter distribution increases.
  • the peak in Q sca as o -> 0 at d 0 « 0.34 pm is stronger than that at d 0 « 0.20 pm.
  • the incident light is polarized with its electric fields parallel to the fiber axis because this polarization dominates the resonances.
  • resonant modes exhibit a greater number of nodal planes, and interference between the modes and the incident field induces stronger local electric fields.
  • the fiber when diameter distribution is negligible, such as in a single fiber, as shown in FIGS. 6G and 6H, the fiber possesses a structural color. Upon reflection a color is observed, but the color has a a spectral dependence, for example, generating a purple color, as shown in FIG. 61. As wavelength increases, the color disappears and becomes whiteish with a larger distribution of length scales of fibers.
  • the present teachings provide fibrous nanostructures that surpass Cyphochilus scales in light scattering strength by focusing on key structural parameters found in the scales, i.e., mean fiber diameter, diameter distribution, filling fraction, and anisotropy. These nanostructures were fabricated by electrospinning, which is amenable to mass production, and scattering characteristics in these structures were investigated by both experiment and optical modeling. Our modeling revealed that, despite large nanostructural difference between Cyphochilus scales and electrospun films, the mean diameter and filling fraction at the optimum point for electrospun films are similar to those in Cyphochilus scales. With the optimized parameters in electrospun films, their optical scattering is even stronger than that in Cyphochilus scales.
  • fibrous optical films can be flexible with high curvatures for a variety of practical use, unlike other common scattering materials such as paint, optical diffusers, or solid foams.
  • Applications of the present electrospun fibers and films designed according to the present disclosure can have applications in optical films, wound healing films, potentially for use in treating bums, beauty items, patches for outdoor activity that counter sunlight exposure with radiative cooling, delivery packages requiring temperature control for temp sensitive goods, or clothing items having optical radiative cooling properties.
  • FIG. 7 is a flow chart illustrating a method of generating a fibrous network film, in accordance with the present disclosure.
  • a method of generating a fibrous network film 700 includes preparing a fibroin solution 702, loading the fibroin solution into a syringe with a conductive needle 704, applying a high voltage to the needle and grounding a conductive surface of a collector 706, and electrospinning the fibroin solution from the syringe with the conductive needle to the grounded conductive surface of the collector to generate the fibrous network film on the grounded conductive surface 708.
  • the method of generating a fibrous network film 700 can include the use of a collector that is in motion relative to the conductive needle during the electrospinning, such as, but not limited to lateral motion.
  • the collector is rotated, moved transversely, moved in one direction or moved in multiple directions in succession.
  • a collector may be a belt or flat substrate moving laterally in a roll-to-roll process.
  • the conductive needle is a 21 -gauge stainless-steel needle, although other sizes of needle are applicable and known to one skilled in the art, provided they are configured to dispense the solution or dispersion used the electrospinning.
  • the collector is drum-shaped with a diameter of about 1 cm to about 15 cm and the grounded conductive surface comprises stainless steel.
  • the grounded conductive surface can be or include other metals or alloys.
  • the collector is rotated about an axis at of about 20 to about 45 rpm during the electrospinning, where a distance between a tip of the conductive needle and the grounded conductive surface is nominally 15 cm.
  • the high voltage used in the method of generating a fibrous network film 700 is approximately 21 kV, although various parameters in the method 700 can influence a suitable high voltage value to be use in the electrospinning process.
  • Preparing the powder of regenerated silk fibroin can further include removing sericin from white silk cocoons to produce degummed silk cocoons, rinsing the degummed silk cocoons with distilled water at 100°C for 150 seconds, further rinsing the rinsed degummed silk cocoons with cold distilled water, drying the further rinsed degummed silk cocoons at 80°C for approximately 24 hours, dissolving the dried silk cocoons at a liquor ratio of 1:20 in a CaC12/H2O/EtOH (1/8/2 molar ratio) mixture solvent at 85 °C for approximately 30 minutes to produce a silk fibroin solution, placing the silk fibroin solution in a tube of a cellulose membrane and dialyzing the silk fibroin solution for 4 days by circulating distilled water
  • Removing sericin from white silk cocoons to produce degummed silk cocoons can include preparing an aqueous solution of 0.2% w/v sodium carbonate and 0.3% w/v sodium oleate, heating the aqueous solution to 105°C, and heating the white silk cocoons in the aqueous solution for approximately 90 minutes to produce the degummed silk cocoons.
  • the cold distilled water can be distilled water at approximately 10°C.
  • Using the regenerated silk fibroin powder to produce the fibroin solution can include dissolving the regenerated silk fibroin powder in 98% formic acid for three hours at a concentration varying from 8 to 15 wt% to produce an unfiltered solution of silk fibroin, and filtering the unfiltered solution of silk fibroin through a polyethylene porous membrane to produce the fibroin solution.
  • the preparation of silk powders can be employed using silk powders derived from materials including, but not limited to, Bombyx mori (Geumokjam) white silk cocoons, or any species of silk cocoons which is mainly comprised of silk fibroin and silk sericin.
  • alternate reagents may be used in a similar procedure as described previously, such as specific solvents required for dissolution or processing of applicable polymers or reactant materials.
  • alternate polymeric starting materials can include, but are not limited to, polyesters, polyacrylics, polyamides, and polyethylenes, as well as alginate, chitosan, collagen, fibrinogen, gelatin, hyaluronic acid, cellulose acetate (CA), cellulose triacetate (CTA), polybutylenesuccinate (PBS), nylon, polyacrylonitrile (PAN), polycaprolactone (PCL), polydioxanone (PDO), polyethersulfone (PES), polyethylene oxide (PEO), polyethylene terephthalate (PET), polyglycolic acid (PGA), polyhydroxybutyrate (PHB), polylactic acid (PLA), polylactic-co-glycolic acid (PLGA), poly(lact
  • Another example method of generating a fibrous network film can include the preparation of a polymer solution, loading the polymer solution into a syringe with a conductive needle, applying a high voltage to the needle and grounding a conductive surface of a collector, and electrospinning the polymer solution from the syringe with the conductive needle to the grounded conductive surface of the collector to generate the fibrous network film on the grounded conductive surface, wherein an index of refraction of the fibrous network film is from about 1.4 to about 1.6 and the fibrous network film comprises a plurality of electrospun polymer fibers.
  • polymers having a polymer refractive index around 1.4-1.6 when used make similar electrospun film structures, provide similar performance in terms of optical scattering.
  • the use of different polymers can provide similar scattering strengths, as described herein when fabricated using electrospinning. While a solution preparation may be different for a different polymer, electrospinning can still produce similar structural parameters as described in the present teachings. In addition to other polymer or starting materials described herein, any raw polymer materials having refractive indices in range between about 1.4 to about 1.6 will show similar performance.
  • the present teachings provide a fibrous network film consisting of a plurality of electrospun fibers, wherein each of the plurality of electrospun fibers exhibits a fiber diameter value as a function of fiber length such that a relative standard deviation o of fiber diameter values for each of the plurality of electrospun fibers is approximately 0.32, but ranging from 0 to about 0.6, or from about 0.1 to about 0.5, or from about 0.3 to about 0.4. Furthermore, the plurality of electrospun fibers, taken together, can exhibit a mean fiber diameter value that is one of approximately 0.30 pm and approximately 0.32 pm, ranging from about 0.10 pm to about 0.40 pm, from about 0.25 pm to about 0.35 pm, or from about 0.30 pm to about 0.32 pm. Moreover, the plurality of electrospun fibers in the fibrous network film exhibit a filling fraction from approximately 10% to approximately 60%, from about 10 % to about 50%, or from about 30% to about 45%.
  • Silk solutions were prepared by our previously reported methods using Bombyx mori (Geumokjam) white cocoons. For electrospinning, the solutions were loaded into a syringe with a 21-gauge stainless steel needle (0.495 mm inner diameter). A high voltage (21 kV) was applied to the tip of the needle and a stainless steel collector was grounded. Distance between the tip and the collector was kept at 15 cm. Filling fraction was controlled by changing the sizes of square-shaped collectors (3, 3.5, 4, 4.5, and 5 cm).
  • Silk cocoons were heated in the solution for 90 min to ensure almost complete removal of sericin from the cocoons.
  • the weight ratio between the silk cocoons and the aqueous solution (liquor ratio) was 1:25.
  • the degummed silk cocoons, which were comprised mostly of fibroin, were rinsed with distilled water at 100°C for 150 s to remove degumming agents (i.e., sodium carbonate and sodium oleate) and residual sericin from the silk cocoons. After further rinsing with cold distilled water, the silk cocoons were dried at 80°C for a day.
  • the degummed silk was dissolved at a liquor ratio of 1 : 20 in a CaCE/FF /EtOH (1/8/2 molar ratio) mixture solvent at 85°C for 30 min.
  • a CaCE/FF /EtOH (1/8/2 molar ratio) mixture solvent at 85°C for 30 min.
  • the solution was placed in a tube of a cellulose membrane and was dialyzed for 4 days by circulating distilled water around the tube.
  • the membrane was impenetrable to fibroin of molecular weight over 12,000-14,000.
  • the dialyzed silk fibroin solution was filtered through a polyethylene porous membrane to remove any extraneous dirt.
  • the filtered solution of regenerated silk fibroin was dried and ground into powder.
  • Electrospinning of Regenerated Silk Fibroin Regenerated silk fibroin powder was dissolved in 98% formic acid for 3 h at a concentration varying from 8 to 15 wt% and filtered through a polyethylene porous membrane. The fibroin solution was loaded into a syringe with a 21-gauge stainless steel needle (inner diameter of 0.495 mm) for electrospinning. Next, 22.5 kV was applied to the needle and a 9 cm diameter drum-shaped collector was electrically grounded. The distance between the needle tip and the collector surface was 15 cm. The drum collector was rotated about its axis at 34 rpm.
  • a drum-shaped collector can have a diameter of from about 1 cm to about 15 cm, or from about 5 cm to about 10 cm, or from about 6 cm to about 9 cm.
  • the distance between the needle tip and the collector surface can be from about 1 cm to about 15 cm, or from about 5 cm to about 10 cm, or from about 6 cm to about 9 cm 15 cm.
  • applied voltage should at least surpass a threshold voltage of about 1 kV/cm, or in examples, can be from about 1 kV/cm to about 50 kV/cm, or from about 5 kV/cm to about 35 kV/cm, or from about 10 kV/cm to about 25 kV/cm.
  • the collector may be stationary, while in some examples, the collector is in motion.
  • a drum or cylindrical collector can be in motion from about 20 rpm to about 45 rpm rpm, from about 5 rpm to about 100 rpm, or from about 20 to about 35 rpm.
  • the translational speed can range from about 1 m/min to about 50 m/min, or from about 5 m/min to about 40 m/min, or from about 10 m/min to about 25 m/min.
  • Optical and Structural Characterization Transmissivity spectra of electrospun silk films were measured by a spectrophotometer (USB4000VIS-NIR, Ocean Optics) with an integrating sphere (ISP-50-8R, Ocean Optics). Nanostructures in electrospun silk films were characterized by scanning electron microscopy (SEM) (FEI, Helios Nanolab 660) after Au-Pd coating. Mean values and standard deviations in fiber diameters were calculated from measurements over 1100 - 1200 fibers based on the SEM images.
  • SEM scanning electron microscopy
  • one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.
  • the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”
  • the term “at least one of’ is used to mean one or more of the listed items may be selected.
  • the term “on” used with respect to two materials, one “on” the other means at least some contact between the materials, while “over” means the materials are in proximity, but possibly with one or more additional intervening materials such that contact is possible but not required.

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)

Abstract

Des films électrofilés de nanofibres de soie non tissées, lorsqu'ils sont structurés de manière appropriée, peuvent surpasser des échelles de Cyphochilus dans la résistance à la diffusion pour l'ensemble du spectre visible. Des études de modélisation détaillées démontrent comment les paramètres structuraux clés influencent les propriétés de diffusion dans les films électrofilés. Un film électrofilé présentant les paramètres structuraux caractéristiques similaires à ceux des échelles de Cyphochilus fournit deux pics de résonance dans le spectre de réflectance visible dans la limite d'un diamètre de fibre uniforme. Lorsque la distribution de diamètre augmente sensiblement jusqu'à des degrés pouvant être obtenus expérimentalement, les pics de résonance s'élargissent et le spectre de réflectance devient relativement plat, une diffusion plus forte étant présente dans des longueurs d'onde plus courtes, ce qui aboutit à une disparition de la couleur structurale. Cela soutient le concept selon lequel des nanostructures fibreuses pouvant être régulées qui dépassent la diffusion optique à large bande exceptionnellement forte présente parmi des organismes vivants peuvent être produites en volume.
PCT/US2023/065431 2022-04-15 2023-04-06 Nanostructures électrofilées bien régulées et procédés associés WO2023201183A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010102533A1 (fr) * 2009-03-10 2010-09-16 广州迈普再生医学科技有限公司 Dure-mère artificielle et son procédé de fabrication
WO2011068389A2 (fr) * 2009-12-04 2011-06-09 주식회사 아모그린텍 Poudre d'oxyde de nanocomposite multicomposant et procédé de préparation de celle-ci, procédé de fabrication d'une électrode utilisant celle-ci, batterie à film mince munie de l'électrode et procédé de fabrication de la batterie
EP3412682A1 (fr) * 2013-03-15 2018-12-12 Trustees Of Tufts College Compositions de soie à faible poids moléculaire et compositions de soie de stabilisation
WO2021081393A1 (fr) * 2019-10-24 2021-04-29 Unm Rainforest Innovations Techniques d'évolution et de restructuration accélérées pour le développement de structures évoluées
WO2021102523A1 (fr) * 2019-11-29 2021-06-03 Royal Melbourne Institute Of Technology Poudre de graphène redispersible dans l'eau

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010102533A1 (fr) * 2009-03-10 2010-09-16 广州迈普再生医学科技有限公司 Dure-mère artificielle et son procédé de fabrication
WO2011068389A2 (fr) * 2009-12-04 2011-06-09 주식회사 아모그린텍 Poudre d'oxyde de nanocomposite multicomposant et procédé de préparation de celle-ci, procédé de fabrication d'une électrode utilisant celle-ci, batterie à film mince munie de l'électrode et procédé de fabrication de la batterie
EP3412682A1 (fr) * 2013-03-15 2018-12-12 Trustees Of Tufts College Compositions de soie à faible poids moléculaire et compositions de soie de stabilisation
WO2021081393A1 (fr) * 2019-10-24 2021-04-29 Unm Rainforest Innovations Techniques d'évolution et de restructuration accélérées pour le développement de structures évoluées
WO2021102523A1 (fr) * 2019-11-29 2021-06-03 Royal Melbourne Institute Of Technology Poudre de graphène redispersible dans l'eau

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