Recent Patents on Nanotechnology - Volume 14, Issue 1, 2020

Due to their unique properties, nanofibers have been widely used in various areas, for example, information industry, pharmaceutical application, environmental industry, textile and clothing, etc. Bubble electrospinning is one of the most important non-needle electrospinning methods for nanofiber fabrication. It usually uses polymer bubbles for the production of nanomaterials by using electrostatic force, flowing air or mechanical force to overcome the surface tension of bubbles. Bubble electrospinning mainly includes bubble electrospinning and blown bubble electrospinning. History of the development of bubble electrospinning is briefly introduced in this article, and the most promising patents on the technology are elucidated. The methods of bubble electrospinning are single bubble electrospinning, porous bubble electrospinning, blown bubble electrospinning, electrostatic-fieldassisted blown bubble spinning and others. These different bubble electrospinning methods are also discussed in this paper.

Electrospinning is a highly efficient technology for fabrication of a wide variety of polymeric nanofibers. However, the development of traditional needle-based electrospinning has been hampered by its low productivity and need of tedious work dealing with needles cleaning, installation and uninstallation. As one of the most promising needleless electrospinning means, bubble electrospinning is known for its advantages of high productivity and relatively low energy consumption due to the introduction of a third force, air flow, as a major force overcoming the surface tension. In this paper, the restrictions of conventional electrospinning and the advantages of needleless electrospinning, especially the bubble electrospinning were elaborated. Reports and patents on bubble-spun nanofibers with unique surface morphologies were also reviewed in respect of their potential applications.

Background: Though there are many patents on silk, patents on sea silk are rare. Sea silk is one of the most coveted materials in the world, and the technology to make sea silk is at an extremely high risk of extinction. Unlike spider dragline silk and silkworm silk, this natural silk has been forgotten in the academic commune for millennia, though it has many fascinating properties: high strength, remarkable adhesion, extreme lightweight, and others. Methods: Here we report that mussel-derived silk fibers can be fabricated by electrospinning. Instead of extracting proteins from byssus, we directly use the protein solution from alive blue mussels, which are intensely commercially used. The protein solution and the polyvinyl alcohol solution are mixed together to produce mussel-based silk fibers. Results: The mussel-based silk fibers have many special properties like high mechanical strength, remarkable super-contraction and good wetting properties. Conclusion: The electrospinning mussel-based silk fibers have the potential for use as a replacement for the rarest sea silk and as a new bio-inspired material with multi-functions.

Background and Objective: Some patents have reported the centrifugal spinning method which utilizes the centrifugal force produced by a high speed rotating device to fabricate fibers from polymer melts or solutions. Recently, with the development of technologies, centrifugal spinning was employed to produce ultrafine fibers and nanofibers. In order to improve the equipment and technology of centrifugal spinning and obtain finer fibers, it is important to model the polymer drawing of the centrifugal spinning. Methods: The polymer drawing in the centrifugal spinning is modeled and simulated. The force balance equation and heat transfer balance equation are established after analyzing the motion and heat transfer of the polymer melts. These nonlinear equations are solved based on the least square method to obtain the radius of excircle and the shape of streamline. A fourth order Runge-Kutta method is utilized to obtain the diameter and temperature of the threadline because there are initial value problems of first order ordinary differential equations. Streamlines and diameter of polymer melts at different viscoelasticities and different spinning temperatures are obtained. The simulation results are compared with the measured results to verify the polymer drawing model. Results: The viscoelastic force in the centrifugal spinning changes constantly at a fixed rotation speed of the rotating spinneret. As the spinneret is rotating, the radius of excircle R1 increases slowly when the time passes, which means the viscoelastic force decreases slowly. The change of the viscoelastic force accelerates the increase of the radius vector. The simulation results show that the threadline diameter under the condition of changing viscoelastic forces is smaller than that under the condition of fixed visoelastic forces. The temperature of the polymer melts decreases faster under the condition of changing viscoelastic forces than that under the condition of fixed visoelastic forces. The threadline diameter decreases with the increase of the rotation speed. Higher initial polymer temperatures yield smaller fiber diameters. Conclusion: The polymer drawing in the centrifugal spinning is modeled and simulated. The simulation results tally with the measured results confirming the effectiveness of the polymer drawing model. The simulation results show that the change of the viscoelastic force is favorable to the polymer drawing and both larger rotation speeds and higher initial polymer temperatures can produce finer fibers, which lays a good foundation for the computer-assisted design of the centrifugal spinning.

Background: As a relatively novel and promising method, the bubble electrospinning is to fabricate continuous and uniform nanowires using an aerated polymer solution in an electric field. A large number of oxidized docking nanowires were established on a silicon substrate using the bubble electrospinning, and then using Tungsten Oxide Ammonium (AMT) as an appropriate calcined air with the WO3 sources. WO3 production can enhance its catalytic activity, stability, and can raise its rhodamine B degradation rate as well; the prospect of its wide application. Methods: The high aspect ratio of WO3 nanowires is successfully prepared by a lightweight bubble electrospinning technique using Polyoxyethylene (PEO) and Ammonium-Tungstate (AMT) as the WO3 precursor after annealing in air at 400, 450 and 500°C, respectively. The products were characterized by SEM, FTIR, XRD, and TG analysis. This Paper reviews the related patents on bubble electrospinning and WO3 nanowires. Results: The results were shown that the diameter of WO3 nanowires ranges from 2μm to 450nm, which varies with the calcination temperature. XRD diffraction and infrared spectroscopy showed that monoclinic crystals were prepared at different calcination temperatures (400, 450 and 500°C). Conclusion: In addition, the UV-vis diffuse reflectance spectroscopy showed that the fiber had a bandgap energy of 2.63 eV after calcination at 450oC, showing excellent photocatalytic activity in the degradation of Rh B at 245 nm. The preparation of WO3 nanowires by bubble electrospinning method is a feasible patented technology.

Background: The electrospinning and the bubble electrospinning provide facile ways for the fabrication of functional nanofibers by incorporating rutin/hydroxypropyl-β-cyclodextrin inclusion complex (RT/HP-β-CD-IC) in Polyvinyl Alcohol (PVA). Few patents on incorporation of rutin and cyclodextrin in nanofibers has been reported. Objective: The study aimed at increasing the loading amount of rutin in the electrospun nanofibers to obtain ultraviolet resistant property. Methods: Rutin was encapsulated in the cavity of RT/HP-β-CD and formed an inclusion complex. Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimeter (DSC) was used to verify the formation of inclusion complexes. Results: The results showed that the inclusion between rutin and HP-β-CD had been successfully formed. The surface morphologies of nanofibrous membranes were characterized by Scanning Electron Microscope (SEM), which indicated that adding RT/HP-β-CD inclusion complexes had little influence on the morphologies and diameters of the fibers. Ultraviolet resistant results also confirmed the inclusion complex had increased the loading amount in the final nanofibrous mats, and thus had good ultraviolet resistant properties. Conclusion: The formed inclusion complexes had obviously enhanced the loading amount of rutin in electrospun PVA nanofibers, indicating that encapsulation of rutin in the cavity of HP-β-CD is a good way to increase the loading amount.

Background: The patented bubble electrospinning, which is a simple and effective technique for mass-production of polymer nanofibers, has been studying extensively, but it is still under development. In the bubble electrospinning, multiple jets move from the positive electrode to the receptor, a long distance between the two electrodes is needed to guarantee complete solvent evaporation, as a result a relative high voltage is needed. Objective: The aim of the present study is to use an auxiliary electrode and an auxiliary air flow to improve bubble electrospinning with lower voltage and higher output than those by its traditional one. Methods: The modification of the bubble electrospinning with an auxiliary electrode and an auxiliary airflow is used to fabricate nanofibers. The auxiliary electrode is close to the positive electrode. The experiment was carried out at room temperature with 8%PVA solution. The result was analyzed with a S4800 cold field scanning electron microscope (SEM, Hitachi S-4800, Tokyo, Japan). Results: The auxiliary electrode can generate a strong induced electric field force. With the action of airflow, the jets will fly to the receptor instead of the auxiliary electrode. Conclusion: Both auxiliary electrode and auxiliary airflow are two important factors affecting the spinning process. It can reduce the spinning voltage and improve spinning efficiency.

Background: Nanofiber’s productivity plagues nanofibrous membranes’ applications in many areas. Herein, we present the needle-disk electrospinning to improve throughput. In this method, multiple high-curvature mentals are used as the spinning electrode. Methods: Three aspects were investigated: 1) mechanism elucidation of the needle-disk electrospinning; 2) parameter optimization of the needle-disk electrospinning; 3) productivity improvement of the needle-disk electrospinning. Results: Results show that high-curvature electrode evokes high electric field intensity, making lower voltage supply in spinning process. The needle number, needle length and needle curvature synergistically affect the spinning process and nanofiber morphology. Additionally, higher disk rotation velocity and higher voltage supply can also result in higher nanofiber’s productivity. Conclusion: Compared with previous patents related to this topic, the needle-disk electrospinning is featured with the merits of high throughput, low voltage supply, controllable spinning process and nanofiber morphology, benefiting the nanofiber practical industrial employment and further applications of nanofiber-based materials.

Background: Wastewater involving a lot of contaminants like organic dyes from the textile finishing industry causes a greater adverse impact on human beings. There are many patents on nanofibers involved metallic oxides, this paper studies photocatalytic degradation of free-pollution Zinc Oxide (ZnO) nanomaterials on dye decontamination. Objective: Polyacrylonitrile (PAN) nanofibrous membranes loaded with Zinc Oxide (ZnO) nanowires were fabricated and evaluated for photocatalytic degradation. Methods: In this work, Polyacrylonitrile (PAN) nanofibrous membranes loaded with ZnO seeds were prepared by electrospinning PAN/Zn (Ac)2 solution followed by a thermal decomposition process. ZnO nanowires were hydrothermally grown on the surface of PAN nanofibers. The effects of the ratio of PAN and zinc acetate in a solution, decomposition temperature and ammonia (NH4OH) on the morphologies of ZnO nanowires were observed. ZnO nanowires showed the optimum morphologies when the ratio of PAN/Zn (Ac)2 was 10:1.5. The decomposition temperature was 150oC, and NH4OH was added in the hydrothermal reaction. The photocatalytic degradation of Rhodamine B solution under UV irradiation was used as a model reaction. The photodegradation ability of the ZnO @PAN membrane doped with cerium (Sm) was also investigated. Results: Slight Sm doping increased the photocatalytic degradation rate from 57% to 89% under ultraviolet light irradiation for 2h. After 5 times of cycling under the same conditions, it still maintained the dye decolorization rate that was above 65%. Conclusion: Sm doped ZnO nanowires @PAN nanofibrous membranes were easily produced and could provide a novel process for the degradation of dye decontamination.

Background: There are many patents on design of a material surface with special wetting property, however, theoretical methods are lacked. The wetting property of a nanofiber member has attracted much attention. A material with different sizes or with different structures possesses different wetting properties. No theory can explain the phenomenon. Methods: The contact angle, fiber fineness, pore size and layer of the nanofiber membrane were tested. The contact angles were measured for membranes with different thicknesses. The geometrical potential is used to explain the experimental phenomenon. Results: The wetting property of a nanofiber membrane mainly depends on fiber diameter and thickness. Conclusion: Wetting property of a PVA nanofiber membrane depends upon not only the hydrophilic groups, but also the geometrical structure of its surface, the latter prevails when the porous size of the membrane tends to a nanoscale, and the wetting property can be inverted from hydrophilicity to hydrophobicity.

Background: Bubble electrospinning patent has been commercially used for the massproduction of various nanofibers, but its application to the fabrication of nanofiber yarns is less studied. We assume that there is great potential in this direction. Objective: This paper focuses on bubble electrospinning with an emphasis on new technologies for the fabrication of fascinated nanofiber yarns by the bubble electrospinning. Methods: The paper begins with the mechanism of the bubble electrospinning to introduce how it produces fascinated nanofiber yarns experimentally, then the industrialization of fascinated nanofiber yarns is illustrated. Results: The bubble electrospinning is extremely suitable for the fabrication of fascinated nanofiber yarns with a hierarchical structure, and the hierarchy can be designed biomimetically according to some natural fibers. Conclusion: This paper sheds light on both experimental study and industrial applications of fascinated nanofiber yarns.

Background: Currently, the most important challenge in the development of therapeutics and actives is their poor aqueous solubility and bioavailability. Objective: The low aqueous solubility, poor pharmacokinetic properties, and bioavailability associated with novel actives manifest in numerous challenges in the formulation of conventional dosage forms like tablets, capsules, suspensions, emulsions, etc. Nanosponges are a novel class of drug delivery system capable of encapsulating or entrapping both lipophilic and hydrophilic drugs. Target-specific drug delivery and controlled drug release are the advantages offered by nanosponges which make them a promising anti-tumor drug delivery system. Methods: Nanosponges are colloidal structures comprising solid nanoparticles with cavities and meshlike structures for encapsulation of wide varieties of substances like antineoplastic agents, proteins and peptides, volatile oils, genetic material, etc. The methods of preparation of β-cyclodextrin-based nanosponges include solvent evaporation method, emulsion solvent evaporation method, ultrasound-assisted synthesis, hyper cross-linked cyclodextrin and interfacial phenomenon method. A large variety of nanosponges- based formulations are available in the market and some formulations of prostavastin, brexin, glymesason, mena-gargle, etc. are under clinical trials. Results: Nanosponges possess potential applications in target site-specific drug delivery to liver, spleen, and lungs. Due to the surface functionalization, nanosponges show broad applications in water purification, protein delivery, chemical sensors, detection of explosives, agriculture, etc. In the near future, nanosponges-based products will capture a huge market for commercialization due to their improved properties and advantages. Conclusion: This review provides an account of the patents related to nanosponges (2006-2018) and covers the broad applications of β-cyclodextrin-based nanosponges, their roles in vaccine delivery, cancer therapy, fire engineering, water purification, etc.