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Electrospinning uses an electrical charge to form a mat of fine fibers. Electrospinning shares characteristics of both the commercial electrospray technique and the commercial spinning of fibers. The standard setup for electrospinning consists of a spinneret with a metallic needle, a syringe pump, a high-voltage power supply, and a grounded collector. A polymer, sol-gel, composite solution (or melt) is loaded into the syringe and this liquid is driven to the needle tip by a syringe pump, forming a droplet at the tip. When a voltage is applied to the needle, the droplet is first stretched into a structure called the Taylor cone. If the viscosity of the material is sufficiently high, varicose breakup does not occur (if it does, droplets are electrosprayed) and an electrified liquid jet is formed. The jet is then elongated and whipped continuously by electrostatic repulsion until it is deposited on the grounded collector. Whipping due to a bending instability in the electrified jet and concomitant evaporation of solvent (and, in some cases reaction of the materials in the jet with the environment) allow this jet to be stretched to nanometer-scale diameters. The elongation by bending instability results in the fabrication of uniform fibers with nanometer-scale diameters. Hollow nanofibers were first produced by electrospinning by Dan Li and Younan Xia at the University of Washington in 2003.
This process was patented by Antonin Formhals in 1934. About 50 patents for electrospinning polymer melts and solutions have been filed in the past 60 years.
Electrospinlacing is the use of electrospinning to combine different fibers and coatings to form three dimensional shapes, e.g. clothing.
Electrospinning can produce seamless garments by integrating advanced manufacturing with fiber electrospinning. This would introduce multi-functionality (flame, chemical, environmental protection) by blending fibers into electrospinlaced layers in combination with polymer coatings. High-tech applications for multifunctional fabrics warrant the investigation of novel textile manufacturing technologies, such as electrospinning, which has the capability of lacing together numerous types of polymers and fibers in a direct one step operation to produce ultrathin layers of protection. These fibers are also expected to be excellent substrates for immobilized enzymes and other catalyst systems to break down toxic chemicals. Recent results show that these fiber webs are efficient aerosol filters. Electrospinning also has potential for computer aided manufacturing of garments by spraying fiber layers onto advanced 3-D forms generated from laser scanning.
Electrospinning of Nanofibers: Reinventing the Wheel? Li, D. and Xia, Y., Adv. Mater. 2004, 16, 1151-1170
Categories: Industrial processes | Nanotechnology