The microplasma generator consists of a microstrip split-ring resonator (MSRR) operated at its first odd resonant mode. As in other microwave designs, the frequency of operation is determined by the size of the resonator that in this case is only one half-wavelength in circumference. In a MSRR microplasma source, the plasma is ignited in the small gap region of the split ring. Given the circular geometry of the microstrip, the maximum voltage difference in the device occurs across the gap, favoring the discharge breakdown in this region while minimizing the losses in the rest of the device. 

MSRR microplasma sources can be operated in a large pressure range. When operated at low pressure, the discharge extends beyond the gap region creating a large diffused plasma (~0.5 cm³ at 400 mtorr ). As pressure is increased the discharge self-confines to the gap region forming a filament-like structure. Despite the high luminescence that is reminiscent of an arc, the discharges are found to be close to room temperature (T_rotational < 100C) even at atmospheric pressure.

Given the low power needed to run the MSRR-MIP source (<3W) , the power supply can be integrated into the microsystem using low-cost off-the-self IC chips manufactured for telecommunication applications. Small size and low-power air-cooled operation at atmospheric pressure make the MSRR-MIP source a well-suited device for portable applications.

Three MSRR microplasma sources

500 um gap MSRR microplasma source operating in argon @ 1W - 900MHz

Click here to see MSRR sources in operation

• J. Hopwood, F. Iza, et al. A microfabricated atmospheric-pressure microplasma source operating in air, J. Phys D: Applied Physics 38, 1698 (2005).

• Iza F. and Hopwood J., Low-power microwave plasma source based on a microstrip split-ring  resonator, IEEE Transactions on Plasma Science, Vol. 31, No. 4, pp 782-787, August 2003

• Iza F. and Hopwood J., Rotational, vibrational and excitation temperatures of a microwave- frequency microplasma, IEEE Transactions on Plasma Science, Vol. 32 No. 2, pp. 498-504, April 2004

• Iza F. and Hopwood J., Self-Organized Filaments, Striations and Other Non-Uniformities in Non-Thermal Atmospheric Microwave Excited Microdischarges, Submitted for publications in IEEE Transactions on plasma science - Special Issue of Images in Plasma Science, 2005

• Iza F. and Hopwood J., Low-Power mwave Plasma Source for Microsystems - Oral presentation - ICOPS 2003, Jeju (S. Korea)

• Iza F. and Hopwood J., Atmospheric Microplasma Source Based on a Microstrip Split-ring Resonator - Poster presentation - GRC 2004, Plymouth, NH

• "Low- Power Plasma Generator," F. Iza and J. Hopwood. US Patent 6,917,165, (July 12, 2005).