Fiber having dielectric polymeric layer on electrically conductive surface

1. An apparatus, comprising:

a fiber having an electrically conductive outer surface and having an average diameter of less than about 5 millimeters; and

a dielectric polymeric layer comprising a polymer having a main polymer chain on said outer surface, said dielectric polymeric layer having a thickness of less than about 50 microns, said main polymer chain comprising carbon.

2. The apparatus of claim 1 , in which said dielectric polymeric layer comprises dipolar moieties having a dipole moment of at least about 1 Debye.

3. The apparatus of claim 2 , in which said dielectric polymeric layer comprises a polymer selected from the group consisting of polycarbonates, polyimides, poly (ethersulfones) and polyacrylates.

4. A method for making a coated fiber, comprising the steps of:

providing a fiber having an electrically conductive outer surface and an average diameter of less than about 5 millimeters; and

forming a dielectric polymeric layer comprising a polymer having a main polymer chain on said outer surface, said dielectric polymeric layer having a thickness of less than about 50 microns, said main polymer chain comprising carbon.

5. The method of claim 4 comprising the further steps of:

providing a solution of a polymer comprising dipolar moieties having a dipole moment of at least about 1 Debye; and

forming said dielectric polymeric layer from said solution.

6. The method of claim 4 , further comprising the step of forming said dielectric polymeric layer on said outer surface by dip-coating said fiber with a solution, the solution comprising a precursor for said dielectric polymeric layer.

7. The method of claim 5 , in which said dielectric polymeric layer comprises a polymer selected from the group consisting of polycarbonates, polyimides, poly (ethersulfones) and polyacrylates.

8. A fiber transistor, comprising:

an insulating fiber having an average diameter of less than about 5 millimeters;

a gate electrode on said insulating fiber;

a dielectric polymeric layer comprising a polymer having a main polymer chain on said gate electrode, the dielectric polymeric layer having a thickness of less than about 50 microns, said main polymer chain comprising carbon;

a semiconductor layer and source and drain electrodes on said dielectric polymeric layer, said source and drain electrodes being in contact with said semiconductor layer;

said fiber transistor having an on/off ratio of at least about 10.

9. The fiber transistor of claim 8 , in which said dielectric polymeric layer comprises dipolar moieties having a dipole moment of at least about 1 Debye.

10. The fiber transistor of claim 8 , in which said source and drain electrodes form spaced apart spirals around a circumference of said dielectric polymeric layer, said source and drain electrodes being in contact with said semiconductor layer.

11. The fiber transistor of claim 8 , in which the semiconductor layer has a charge carrier mobility of at least about 0.01 cm 2 /Vs.

12. The fiber transistor of claim 9 , in which said dielectric polymeric layer comprises a polymer selected from the group consisting of polycarbonates, polyimides, poly (ethersulfones) and polyacrylates.

13. A fiber transistor, comprising:

an insulating fiber having an average diameter of less than about 5 millimeters;

a semiconductor layer and source and drain electrodes on said insulating fiber, said source and drain electrodes being in contact with said semiconductor layer;

a dielectric polymeric layer comprising a polymer having a main polymer chain on said semiconductor layer, the dielectric polymeric layer having a thickness of less than about 50 microns, said main polymer chain comprising carbon; and

a gate electrode on said dielectric polymeric layer;

said fiber transistor having an on/off ratio of at least about 10.

14. A method for making a fiber transistor, comprising the steps of:

providing an insulating fiber having an average diameter of less than about 5 millimeters;

forming a gate electrode on said insulating fiber;

forming a dielectric polymeric layer comprising a polymer having a main polymer chain on said gate electrode, the dielectric polymeric layer having a thickness of less than about 50 microns, said main polymer chain comprising carbon;

forming a semiconductor layer and a source electrode and a drain electrode on said dielectric layer, said source and drain electrodes being in contact with said semiconductor layer;

in which said fiber transistor has an on/off ratio of at least about 10.

15. The method of claim 14 comprising the further steps of:

providing a solution of a polymer comprising dipolar moieties having a dipole moment of at least about 1 Debye; and

forming said dielectric polymeric layer from said solution.

16. The method of claim 14 , comprising the further step of forming said dielectric polymeric layer on said gate electrode by dip-coating said fiber in a solution, the solution comprising a precursor for said dielectric polymeric layer.

17. The method of claim 14 , comprising the further step of forming source and drain electrodes as spaced apart spirals around a circumference of said dielectric polymeric layer, the semiconductor layer forming a channel region between said source and drain electrodes.

18. The method of claim 15 , in which said dielectric polymeric layer comprises a polymer selected from the group consisting of polycarbonates, polyimides, poly (ethersulfones) and polyacrylates.

19. The method of claim 17 , comprising the further step of masking said dielectric polymeric layer prior to said step of forming source and drain electrodes, the step of masking including spirally winding a plurality of masking filaments onto said dielectric polymeric layer.

20. A method for making a fiber transistor, comprising the steps of:

providing an insulating fiber having an average diameter of less than about 5 millimeters;

forming a semiconductor layer and source and drain electrodes on said insulating fiber, said source and drain electrodes being in contact with said semiconductor layer;

forming a dielectric polymeric layer comprising a polymer having a main polymer chain on said semiconductor layer, the dielectric polymeric layer having a thickness of less than about 50 microns, said main polymer chain comprising carbon; and

forming a gate electrode on said dielectric polymeric layer;

said fiber transistor having an on/off ratio of at least about 10.