Pull Spinning in Action
Video: Leila Deravi
Journal Cover Image
Pull Spinning is a novel nanofiber manufacturing process developed in the Disease Biophysics Group at Harvard SEAS. The original inspiration for the method was the motion of a cat's tongue as it draws milk from a saucer, and the technique has evolved to a portable, point-of-use fiber fabrication system that supports a wide range of polymer and protein materials.
Unlike many other nanofiber fabrication systems, pull spinning does not rely on a high electric field to extrude nanofibers. Instead, a combination of viscous and centrifugal forces contribute to nanofiber formation:
First, a polymer, protein, or biohybrid solution is infused through a needle reservoir.
Then, a rotating bristle attached to a high-speed motor strikes the droplet that forms at the top of the needle. The bristle pulls and elongates the droplet into a polymer jet within 35 milliseconds.
As the bristle pulls the jet through one revolution, the solvent evaporates from the polymer solution, forming a single nanofiber.
As the bristle subsequently contacts the polymer reservoir, the nanofiber is projected linearly toward a collector. This process continues until a network of nanofibers have formed.
Pull spun nanofabrics can be used for a variety of applications, including muscle tissue engineering and point-of-wear apparel. The combination of minimal processing parameters, portability, high control of fiber deposition, flexible substrate materials distinguish pull spinning as a robust and easy- to-use platform for nanofiber manufacturing.
Image: Karaghen Hudson
Anisotropic polyester nanofibers manufactured using pull spinning. The surface of the fibers is smooth, with no visible defects.
We envision that pull spinning may one day be used as a method for depositing apparel or medical fabrics on-the-go. This concept is illustrated here by spinning a polymer nanofiber "bandage" onto a doll.
Immunofluorescence staining of murine skeletal muscle, cultured on pull spun fiber muscular thin films. Nanofiber scaffolds support myoblast fusion and maturation into functional muscle tissue. Moreover, it was possible to measure dynamic stress values with quantifiable twitch and tetanus curves - key clinical metrics for skeletal muscle. Adapted from Deravi and Sinatra et al, 2017
The capability of a lab-scale pull spinning device to fabricate point-of-wear apparel was demonstrated by spinning a dress onto a doll.
This schematic illustrates the formation of nanofibers using pull spinning. Adapted from Deravi and Sinatra et al., 2017
Pull spun nanofibers can be manufactured in a variety of conformations, including: anisotropic, cross-hatched, and threaded. Nonwoven nanofiber sheets can also be laser-cut and woven into multi-layer structures. Adapted from Deravi and Sinatra, et al., 2017
Image: Christophe Chantre
Image: Christophe Chantre