Tailoring the Morphology of Responsive Bioinspired Bicomponent Fibers

Abstract

and morphologies, are highly promising materials for water collection, smart textiles for moisture management, dual drug release, actuation, etc.Electrospinning is a versatile method for the production of thin fibers with a high surface-to-volume-ratio from a multitude of materials in a simple and straightforward way. [4] Various fiber morphologies have been realized by either controlling the spinning parameters or by using special spinning nozzles, e.g., homogenous fibers, particles, or particles immobilized on fibers (also called beaded fibers) as well as fibers with bead-on-string or pearl-necklace morphology. [5] Beaded fibers, in which beads of different shapes (i.e., spherical, spindle shape) and the joints (fiber segment between the two beads) are made up of the same polymer, already gained an edge over conventional nanofibers in providing superhydrophobicity as well as encapsulation and release of microparticle drugs from the beads. [6] Complex fiber morphologies with precisely defined composition and properties are accessible employing special spinning nozzles, which combine two or more components in either s-b-s or core-shell (c-s) fashion. [7] This method also allows to combine bioinspired structures with appropriate material properties to achieve complex functional materials with unique properties. For example, wool-like crimps were generated by spinning polymers with different mechanical properties in an s-b-s fashion, both by melt and solution electrospinning. [7b,8] Bicomponent fibers with core-shell-type beads (coaxial beadon-string morphology) are another example. The formation of these fibers is not trivial and can be realized by using a polymer solution, which contains swollen crosslinked polymeric colloids. Applying a simple spinning nozzle produced beaded fibers, in which a row of colloidal particles is embedded in the matrix polymer. [9] Alternatively, bicomponent fibers with coaxial bead-on-string structure can be obtained by combining electrospraying with electrospinning in a coaxial electrospinning setup. [10] Similar fibers have also been produced employing a coating method. [11] In this approach, a polymer solution is coated onto a supporting fiber, which further on breaks up into droplets driven by Rayleigh instability. Fibers with coaxial beadon-string morphology are very promising materials for water harvesting applications, which demands for the development of efficient large-scale production methods. [12] Bioinspired Electrospun Bicomponent Fibers Nature is an intriguing inspiration for designing a myriad of functional materials. However, artificial mimicking of bioinspired structures usually requires different specialized procedures and setups. In this study, a new upscalable concept is presented that allows to produce two bioinspired, bicomponent fiber morphologies (side-by-side and coaxial bead-on-string) using the same electrospinning setup, just by changing the employed spinning solvent. The generated fiber morphologies are highly attractive for thermoresponsive actuat...

Progress in the Field of Water‐ and/or Temperature‐Triggered Polymer Actuators

“…One side of the fiber was a hydrophobic polymer (TPU or a poly(methyl methacrylate) copolymer), and the other side was PNIPAM. The straight side‐by‐side fibers showed immediate reversible curling motions in water at different temperatures ( Figure ) …”

“…This effect was achieved by producing hinges at appropriate places by printing black toner (light absorber) and exposing the entire printed film to IR light ( Figure 5). Black toner absorbs IR light and converts it to thermal energy, Polyacrylamide [40] Poly(acrylic acid) [55] Poly(sodium acrylate) [8] Poly(vinyl alcohol) [16] Polystyrene [6,17,49] Polydimethylsiloxane [18,25] Polycarbonate [19,20] Poly(N-isopropylacrylamide) [20,31,32,40,41,[43][44][45]49,50,52,60,[62][63][64][65][66]73,77] Poly(ethylene glycol) methacrylate [37] Chitosan [37] Poly(hydroxyethyl acrylamide) [46] (Continued ) raising the local temperature. Therefore, the PS directly underneath the black toner will be heated above its T g , relaxing stresses at that particular area and hence leading to bendingtype actuation.…”

“…The straight sideby-side fibers showed immediate reversible curling motions in water at different temperatures (Figure 21). [62] The formation of a side-by-side microspring is possible by extrusion of a mixed alginate and poly(N-isopropylacrylamideco-acrylic acid) (PNIPAM-co-AAc) pre-gel in CaCl 2 solution using a bevel-tip capillary. The anisotropic gelation around the bevel tip of the capillary led to the microspring morphology.…”

“…Reproduced with permission. [62] Copyright 2018, Wiley-VCH. Interestingly, PNIPAM fibrous membranes with different alignment angles of fibers could also be combined together in the form of a bilayer structure.…”

Mechanical Reinforcement of Low‐Concentration Alginate Fibers by Microfluidic Embedding of Multiple Cores

“…[15,16] Recently, biological applications have also benefited from fibrous materials, and physical/chemical or dry/wet spinning methods have been developed for the control of the fiber morphology. [17][18][19] The fibers were not only used as biological scaffolds, but also used as direct cell encapsulated materials. However, because of the long process time, harsh coating www.advancedsciencenews.com www.mme-journal.de…”