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Full-Text Articles in Engineering
Electrospinning Jets And Polymer Nanofibers, Darrell Reneker, Alexander Yarin
Electrospinning Jets And Polymer Nanofibers, Darrell Reneker, Alexander Yarin
Darrell Hyson Reneker
In electrospinning, polymer nanofibers are formed by the creation and elongation of an electrified fluid jet. The path of the jet is from a fluid surface that is often, but not necessarily constrained by an orifice, through a straight segment of a tapering cone, then through a series of successively smaller electrically driven bending coils, with each bending coil having turns of increasing radius, and finally solidifying into a continuous thin fiber. Control of the process produces fibers with nanometer scale diameters, along with various cross-sectional shapes, beads, branches and buckling coils or zigzags. Additions to the fluid being spun, …
How Super Is Supercontraction? Persistent Versus Cyclic Responses To Humidity In Spider Dragline Silk, Todd Blackledge, Cecilia Bountry, Shing-Chung Wong, Avinash Baji, Ali Dhinojwala, Vasav Sahni, Ingi Agnarsson
How Super Is Supercontraction? Persistent Versus Cyclic Responses To Humidity In Spider Dragline Silk, Todd Blackledge, Cecilia Bountry, Shing-Chung Wong, Avinash Baji, Ali Dhinojwala, Vasav Sahni, Ingi Agnarsson
Ali Dhinojwala
Spider dragline silk has enormous potential for the development of biomimetic fibers that combine strength and elasticity in low density polymers. These applications necessitate understanding how silk reacts to different environmental conditions. For instance, spider dragline silk ;supercontracts' in high humidity. During supercontraction, unrestrained dragline silk contracts up to 50% of its original length and restrained fibers generate substantial stress. Here we characterize the response of dragline silk to changes in humidity before, during and after supercontraction. Our findings demonstrate that dragline silk exhibits two qualitatively different responses to humidity. First, silk undergoes a previously unknown cyclic relaxation-contraction response to …
Supercontraction Forces In Spider Dragline Silk Depend On Hydration Rate, Ingi Agnarsson, Cecilia Boutry, Shing-Chung Wong, Avinash Baji, Ali Dhinojwala, Andrew Sensenig, Todd Blackledge
Supercontraction Forces In Spider Dragline Silk Depend On Hydration Rate, Ingi Agnarsson, Cecilia Boutry, Shing-Chung Wong, Avinash Baji, Ali Dhinojwala, Andrew Sensenig, Todd Blackledge
Ali Dhinojwala
Spider dragline silk is a model biological polymer for biomimetic research due to its many desirable and unusual properties. 'Supercontraction' describes the dramatic shrinking of dragline silk fibers when wetted. In restrained silk fibers, supercontraction generates substantial stresses of 40-50 MPa above a critical humidity of approximately 70% relative humidity (RH). This stress may maintain tension in webs under the weight of rain or dew and could be used in industry for robotics, sensor technology, and other applications. Our own findings indicate that supercontraction can generate stress over a much broader range than previously reported, from 10 to 140 MPa. …