WiSys Technologies

Nanoscale Corona Discharge Electrode

WiSys Technology Number: T05014US
Patent Number: 7,504,628
Patent Issued Date: March 17, 2009 (PDF)
Stage of Development:


Corona discharge is a process by which an electric field near a discharge electrode ionizes air to produce an electrical current between two electrodes. It has many industrial applications, including manufacturing ozone, scrubbing air particles in air-conditioning systems, removing unwanted volatile organics, and photocopying. But electrostatic photocopiers and other office machines that utilize corona discharge produce small amounts of ozone, which can be a health hazard. Current techniques to reduce ozone production and power consumption employ wire electrodes with radii as small as one micrometer; however, the ability to further decrease wire size is limited by practical considerations of wire strength and durability.


This invention describes the use of nanotubes and other nano-objects as corona discharge electrodes. A metal wire or plate, or other conductive substrate can be coated with nanostructures, such as carbon nanotubes, to produce a robust discharge electrode with a small radius of curvature. These novel corona ion sources provide high ion concentration and high charging efficiency with minimal ozone production.


Useful in indoor air cleaners, photocopiers, printers, and nanofabricators


  • Extremely small (less than 100 nanometers) electrode radii
  • Low ozone production
  • Saves energy—can be operated with a lower corona discharge initiation voltage
  • Produces high ion concentration
  • High charging efficiency
  • Improved resistance to erosion
  • Simple to fabricate
  • Provides a flexible electrode design to fit particular applications
Junhong Chen
Professor of Mechanical Engineering