Dual-layer Fiber Research Articles

Dual-layer orthogonal fiber Bragg grating mesh based soft sensor for 3-dimensional shape sensing.

A soft shape sensor for 3-dimensional object shape measurement is demonstrated. The proposed sensor is based on dual-layer fiber Bragg grating arrays with an orthogonal mesh structure, which enables multi-point bi-directional shape sensing. The 3D shape reconstruction is based on a bi-directional curvature measurement at each sensing point, which is achieved through measuring the direction and amount of wavelength shift of each off-center embedded FBG. The conversion coefficient between the wavelength shift and bending curvatures is acquired and is used to convert the change in FBG to the corresponding bending curvatures and bending direction. The measurement error on the bending radius of each sensing point is about 2.7%. A 3D shape of the object surface is reconstructed with the help of a curve fitting method based on the curvature information across the whole FBG mesh. This design successfully achieved visualized 3D shape sensing, which has great practical value in soft robotics and biomedical applications.

Robust CO2 and H2 resistant triple-layered (Ag-YSZ)/YSZ/(La0.8Sr0.2MnO3-δ-YSZ) hollow fiber membranes with short-circuit for oxygen permeation

Oxygen selective ceramic membranes have many important applications, not only for air separation but also as membrane reactors for cost-effective chemical synthesis. However, the prerequisite to realize these potentials is their stability in the presence of acid gases of CO2 and reducing atmosphere containing H2 and CH4. This work seeks to validate the applicability of robust triple layer hollow fiber membranes consisting of (Ag+YSZ)/YSZ/La0.8Sr0.2MnO3-δ (LSM)+YSZ to separate O2 from air in the presence of these unavoidable gases for more advanced applications. To prepare the triple layer hollow fiber, the dual-layer fiber was firstly synthesized via a combined phase inversion and sintering method where the dense YSZ layer was present on top of the porous LSM-YSZ layer. We further deposited either porous Ag or its mixture with YSZ layer above the dense YSZ surface. The final fiber consists of three layers in sequence from outside surface to inside surface of Ag+YSZ/YSZ/LSM+YSZ. The dense central YSZ layer acts as the ionic conducting phase to prevent gas diffusion while the other two porous layers serve as the electronic conducting phase with catalytic effect to enhance the surface reaction kinetics. To overcome the electronic conductivity limitation of YSZ, silver (Ag) short circuit paste was additionally used to seal the membrane and electronically connect the outer and inner surfaces for electron shuttle for the two surface O2 exchange reactions. Ag-YSZ coated fiber performed better than Ag coated fiber and showed increasing fluxes from 0.1 to 0.53mLmin−1cm−2 upon increasing temperature from 700 to 900°C. The O2 fluxes remained constant irrespective of changing the sweep gas from pure He to its mixtures containing CO2, H2, or CH4; mirroring the membrane robustness to tolerate these gases at high temperatures.

Hydrophobic/hydrophilic PVDF/Ultem® dual-layer hollow fiber membranes with enhanced mechanical properties for vacuum membrane distillation

Dual-layer hydrophobic/hydrophilic PVDF/Ultem® hollow fiber membranes with superior mechanical and water transport properties have been prepared via co-extrusion method for vacuum membrane distillation (VMD) of seawater. To fabricate such high-performance dual-layer hollow fibers consisting of two different materials, one must overcome the issues of delamination between the two polymer layers and dense interface morphology. The former would result in a defective membrane, while the latter could significantly increase the substructure resistance for vapor transport. By properly manipulating dope formulation and spinning conditions, we have overcome the first challenge and produced delamination free dual-layer fibers. The second problem is resolved by the addition of Al2O3 nanoparticles into the inner layer dope, which creates micro-porosity on the outer surface of the inner layer. The resultant dual-layer fibers show good mechanical properties, permeation flux and wetting resistance simultaneously under VMD operations. Comparing to the conventional single layer MD fibers, the newly developed VMD hollow fiber containing 15wt% Al2O3 has 4.5- fold tensile strength (i.e., about 350% increment) with a VMD flux of 45.8kg/m2-h at 70°C. This study may provide valuable guidelines in designing superior dual-layer PVDF membranes for practical VMD applications of seawater desalination.

Direct dual layer spinning of aminosilica/Torlon® hollow fiber sorbents with a lumen layer for CO2 separation by rapid temperature swing adsorption

ABSTRACTThe direct dual layer spinning of Torlon®/silica hollow fibers with a neat Torlon® lumen layer is reported here for the first time. The dual layer fibers containing a porous Torlon®/silica main structure and a dense, pure Torlon® polymer bore‐side coating provide a simplified, scalable platform from which to construct hollow fiber amine sorbents for postcombustion CO2 capture. After fiber spinning, an amine infusion process is applied to incorporate PEI into the silica pores. After combining dilute Neoprene treatment followed by poly(aramid)/PDMS treatment, a helium permeance of the fiber sorbents of 2 GPU with a He/N2 selectivity of 7.4 is achieved. Ten of the optimized amine‐containing hollow fibers are incorporated into a 22‐inch long, 1/2 inch OD shell‐and‐tube module and the module is then exposed on the shell side to simulated flue gas with an inert tracer (14 mol % CO2, 72 mol % N2, 14 mol % He [at 100% R.H.]) at 1 atm and 35°C in a RTSA system for preliminary CO2 sorption experiments. The fibers are found to have a breakthrough and equilibrium CO2 capacity of 0.8 and 1.2 mmol/g‐ dry fiber sorbent, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41845.

Nitrofurazone-loaded electrospun PLLA/sericin-based dual-layer fiber mats for wound dressing applications

Dual-layer nitrofurazone-loaded nanofiber mats are fabricated by electrospinning with good antibacterial activity and the mats perform well in wound healing.

Morphological architecture of dual-layer hollow fiber for membrane distillation with higher desalination performance

A new strategy to enhance the desalination performance of polyvinylidene fluoride (PVDF) hollow fiber membrane for membrane distillation (MD) via architecture of morphological characteristics is explored in this study. It is proposed that a dual-layer hollow fiber consisting of a fully finger-like macrovoid inner-layer and a sponge-like outer-layer may effectively enhance the permeation flux while maintaining the wetting resistance. Dual-layer fibers with the proposed morphology have been fabricated by the dry-jet wet spinning process via careful choice of dopes composition and coagulation conditions. In addition to high energy efficiency ( EE) of 94%, a superior flux of 98.6 L m −2 h −1 is obtained during the direct contact membrane distillation (DCMD) desalination experiments. Moreover, the liquid entry pressure ( LEP) and long-term DCMD performance test show high wetting resistance and long-term stability. Mathematical modeling has been conducted to investigate the membrane mass transfer properties in terms of temperature profile and apparent diffusivity of the membranes. It is concluded that the enhancement in permeation flux arises from the coupling effect of two mechanisms; namely, a higher driving force and a lower mass transfer resistance, while the later is the major contribution. This work provides an insight on MD fundamentals and strategy to tailor making ideal membranes for DCMD application in desalination industry.

Co-Extrusion / Phase Inversion / Co-Sintering for Fabrication of Hollow Fiber Solid Oxide Fuel Cells

We have used a co-extrusion / phase inversion process, followed by co-sintering and then NiO reduction with hydrogen, to fabricate anode (Ni-CGO) / cerium-gadolinium oxide electrolyte (CGO) dual-layer hollow fibers (HFs) with inner diameters < 1 mm. This is the first time such dual-layer fibers have been produced as components of SOFCs, thereby decreasing the number of fabrication steps compared with single layer extrusion, while ensuring a gas-tight electrolyte layer of controlled thickness (ca. 60-80 μm). A La0.6Sr0.4Fe0.8Co0.2O3 (LSCF)-CGO cathode ca. 100 μm thick was deposited using slurry coating. Preliminary measurements of the performance of the dual-layer microtubular HF-SOFCs were made with hydrogen flowing at 5 cm3 min-1 and air at 40 cm3 min-1, achieving maximum power densities of 420 W m-2, 800 W m-2 and 1000 W m-2 at 450 oC, 550 oC and 580 oC, respectively. A proposed stack design shows how these micro-tubular SOFCs could be connected in parallel to increase currents and in series for scaling up voltages, aiming at the design of practical stacks.