Electrospinning process for aligned fiber production
An electrospinning process and apparatus for forming aligned electrospun fibers. A time-dependent (AC) voltage is applied to a multi-electrode collector in order to temporally control the location and orientation of fiber deposition.
1. A method for forming aligned electrospun fibers, said method comprising:
forming a fiber stream comprising an electrically conductive fluid, the fiber stream being formed by a fiber-forming module that is biased at a first DC voltage;
directing the fiber stream at a collector, the collector comprising a plurality of electrodes each electrically biased at a second DC voltage of from about 2 to 20 kV;
attracting the fiber stream to successive ones of the electrodes by applying a time-dependent voltage to at least one of the electrodes; and
depositing the fiber stream between successive pairs of the electrodes such that the deposited fibers are aligned between respective electrode pairs, wherein the time-dependent voltage is a 120V/60 Hz single-phase AC voltage.
2. The method according to claim 1 , wherein a product of the first DC voltage and the second DC voltage is negative.
3. The method according to claim 1 , wherein the collector further comprises a substrate positioned proximate to the electrodes and the depositing comprises depositing the fibers on the substrate.
4. The method according to claim 1 , wherein the fiber stream is directed substantially horizontally toward the collector.
5. The method according to claim 1 , wherein the fiber stream is directed substantially vertically toward the collector.
6. The method according to claim 1 , wherein the collector comprises a first electrode and a second electrode, the first electrode being connected to a single-phase AC power supply via a variable transformer and an isolation transformer.
7. The method according to claim 1 , wherein the aligned fibers have an average diameter of between 0.1 and 2 microns.
8. The method according to claim 1 , wherein the aligned fibers have an average diameter of between 0.4 and 1 micron.
9. A method for forming aligned electrospun fibers, said method comprising:
forming a fiber stream comprising an electrically conductive fluid, the fiber stream being formed by a fiber-forming module that is biased at a first DC voltage;
directing the fiber stream at a collector, the collector comprising a plurality of electrodes each electrically biased at a second DC voltage of from about 2 to 20 kV;
attracting the fiber stream to successive ones of the electrodes by applying a time-dependent voltage to at least one of the electrodes; and
depositing the fiber stream between successive pairs of the electrodes such that the deposited fibers are aligned between respective electrode pairs, wherein the time-dependent voltage is a 208V three-phase AC voltage.
10. The method according to claim 1 , wherein the second DC voltage is continuously applied to the electrodes during the acts of directing, attracting and depositing.
11. The method according to claim 9 , wherein the collector comprises a first electrode, a second electrode and a third electrode, each of the electrodes being connected to a DC power supply and to a three-phase AC power supply via a respective variable transformer and a respective isolation transformer.
12. The method according to claim 11 , wherein the three-phase AC power supply includes a first, a second, and a third phase signal and the first isolation transformer is connected to the first and second phase signals, the second isolation transformer is connected to the second and the third phase signals, and the third isolation transformer is connected to the first and third phase signals.