Nest building with fibers: Controlling micron-scale coiling and sedimentation in Jet-Assisted Wet Spinning*

Thin, elastic threads falling vertically through a quiescent medium will coil differently depending on system parameters like feed rate, falling height, and fiber thickness. We work with a novel unconfined microfluidic setup to produce elastic fibers using fast, assistive jets to entrain, bend, and thin a nearby, slow pre-fiber jet. Photo-polymerizing the thinned pre-fiber jet yields fibers of sub-100 micron thickness. The length and number of fibers can be tuned using on-off pulses of UV light. In addition, we can also produce looped and meandering fibers by oscillating the assistive jet transverse to the flow direction before polymerizing it. The enforced shapes will influence the settling speed and hence, the coiling nature itself. As the coiling/sedimentation progresses, the fibers pile up into mounds. The morphology and properties of these mounds will be discussed.