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A Preliminary Study on Water Collection Ability of Nanofibers Derived from Electrospun Polymers

LIU, XIAOXIAO
http://rave.ohiolink.edu/etdc/view?acc_num=akron1573050761831223

Abstract Details

2019, Doctor of Philosophy, University of Akron, Mechanical Engineering.
As inspired by the fog-collecting behavior of Namib Desert beetle and spider silk, artificial hydrophobic/hydrophilic patterned surface and bead-on-string fibers are fabricated for high-efficient water collection ability in this study via facial one-step electrospinning process. Water collection test is applied to evaluate the water harvesting efficiency (WHE) of electrospun membrane. Poly(vinylidene fluoride) (PVDF), Polystyrene (PS), Thermoplastic Polyurethane (TPU) and Polyacrylonitrile (PAN) are electrospun into bead-free fibers with an average fiber diameter in range of 400 nm to 3000 μm varies with different polymer material. In wetting behavior characterization, electrospun membrane exhibits enhanced wettability (super-hydrophobicity for PS and PVDF, and super-hydrophilicity for TPU and PAN) as compared with cast film derived from the same polymer solution, which is due to its fibrous structure with high porosity. The results of water collection test show that the hydrophobic cast film exhibits relative lower water collection ability than hydrophilic cast film, while the hydrophobic electrospun membrane obtains much higher water harvesting efficiency than hydrophilic electrospun membrane. Hydrophobic/hydrophilic membrane is derived from electrospun PS/TPU, PVDF/TPU and PVDF/PAN solutions. Ultrafine nanofibers without obvious phase separation is observed by morphological analyses. By changing the weight ratio of hydrophilic content in the composite polymer solution, the fiber diameter changes resulted from the different solution viscosity. The wetting phenomenon and FTIR spectrum for surface of as-spun membranes is studied and the results demonstrate the formation of novel wettability including super-hydrophobicity and super-hydrophilicity simultaneously. Highest WHE is exhibited at 161.6 ± 11.7 mg/cm2/h after we add hydrophilic content into hydrophobic fibers and formed the beetle-inspired membranes. This value is 1.63 and 2.98 times larger than WEH obtained from pure hydrophobic and pure hydrophilic electrospun membranes, respectively. The water collection capability is a parabolic relationship with super-hydrophilic density in which the maximum efficiency reach is at 30% hydrophilic. Multi-cycle water harvesting experiment is applied to report the high durability of the as-spun membranes. Effect of distribution of hydrophobic/hydrophilic content on water collection ability is studied by fabricating composite membrane via dual-syringe electrospinning process for comparison. Relative low water harvesting efficiency for the dual-syringe-electrospun membrane demonstrates that closer distribution of hydrophobic and hydrophilic content on the single fiber derived from composite polymer solution enables high water harvesting efficiency. In the end, a novel multi-scale structured membrane with beaded fiber derived from electrospun dilute PVDF solution is designed and fabricated for mimicking the joints and spindle-knot structure of spider silk, which will enable directional movement of water droplets on the fiber. The result of water collection test demonstrates a proper shape of bead, with aspect ratio of 3.74 in this study, leads to the highest water harvesting efficiency up to approximate 20% improvement as compared with smooth electrospun nanofiber. Overall, bio-inspired artificial hydrophobic/hydrophilic and beaded nanofibers fabricated by novel one-step electrospinning process exhibit enhanced water collection ability. Weight ratio of hydrophobic and hydrophilic parts, distribution of the bio-component and shape of bead are the considered parameters in this study. Contribution is made to provide a novel approach for fabrication of hydrophobic-hydrophilic patterned surface. Applications of the electrospun membrane are developed for potential highly efficient water harvester.
Shing-Chung "Josh" Wong (Advisor)
Xiaosheng Gao (Committee Member)
Shengyong Wang (Committee Member)
Ernian Pan (Committee Member)
Todd Blackledge (Committee Member)
210 p.
Mechanical Engineering; Polymer Chemistry
electrospinning, composite polymer membranes, bead-on-string nanofiber, water harvesting efficiency

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Citations

  • LIU, X. (2019). A Preliminary Study on Water Collection Ability of Nanofibers Derived from Electrospun Polymers [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1573050761831223

    APA Style (7th edition)

  • LIU, XIAOXIAO. A Preliminary Study on Water Collection Ability of Nanofibers Derived from Electrospun Polymers. 2019. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1573050761831223.

    MLA Style (8th edition)

  • LIU, XIAOXIAO. "A Preliminary Study on Water Collection Ability of Nanofibers Derived from Electrospun Polymers." Doctoral dissertation, University of Akron, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1573050761831223

    Chicago Manual of Style (17th edition)

akron1573050761831223
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This open access ETD is published by University of Akron and OhioLINK.