A new technique from MIT researchers boosts production of nanofibers fourfold, while cutting energy consumption by more than 90 percent. Potential nanofiber applications include solar cells, water filtration, and fuel cells.
The MIT team used methods common in the manufacture of microelectromechanical systems to produce dense arrays of tiny emitters. The tiny emitters reduce the voltage necessary to drive them and allow more of the components to be packed together, increasing production rate.
Using a technique called deep reactive-ion etching, the researchers etched dense arrays of tiny rectangular columns — tens of micrometers across — on either face of a silicon wafer. The nubbly texture etched into the emitters’ sides regulates the rate at which fluid flows toward their tips, yielding uniform fibers at high manufacturing rates.
Sawtooth patterns were then cut out of the wafer. The sawteeth were mounted vertically, and their bases were immersed in a solution of deionized water, ethanol, and a dissolved polymer.
When an electrode is mounted opposite the sawteeth and a voltage applied between them, the water-ethanol mixture streams upward, dragging chains of polymer with it. The water and ethanol quickly dissolve, leaving a tangle of polymer filaments opposite each emitter, on the electrode.
The researchers were able to pack 225 emitters, several millimeters long, on a square chip about 35 millimeters on a side. At a voltage of 8,000 volts, the device yielded four times as much fiber per unit area as commercial electrospinning devices.
Also: Learn about Photoluminescent Nanofibers for High-Efficiency Solid-State Lighting.