Sterilization system employing low frequency plasma

Abstract

A method and system for sterilizing an article is provided that includes use of a low frequency (LF) gas discharge plasma. The method includes placing the article in a vacuum chamber and evacuating the vacuum chamber to a predetermined pressure. Gas or vapor species are introduced into the vacuum chamber, and a low frequency plasma is generated within the vacuum chamber, the low frequency plasma having a frequency of from 0 to approximately 200 kHz. The low frequency plasma is maintained for a time period sufficient to substantially remove gas or vapor species from the article. The sterilization system includes a vacuum chamber coupled to a vacuum pump and a vent, a first electrode, and a second electrode. The sterilization system further includes a second region within the vacuum chamber, the second region including a region between the first and second electrodes, and a first region within the vacuum chamber, the first region being in fluid communication with the second region. The sterilization system further includes a source of reactive agent species coupled to the vacuum chamber, a process control monitor, and a low frequency power module including components adapted to apply a low frequency voltage between the first electrode and second electrode to generate a low frequency plasma in the vacuum chamber, the low frequency voltage having a frequency of from 0 to approximately 200 kHz.

What is claimed is:  
     
         1 . A method of sterilization of an article, the method comprising: 
 placing the article in a first region;    introducing gas or vapor species into a second region;    generating a plasma by applying an applied electric field in the second region, the second region in fluid communication with the first region, the first region having an electric field weaker than the applied electric field in the second region, the applied electric field having a frequency of less than 10 kHz; and    maintaining the plasma for a time period sufficient to substantially remove gas or vapor species from the article.    
     
     
         2 . The method as defined in  claim 1 , wherein the gas or vapor species comprises hydrogen peroxide.  
     
     
         3 . The method as defined in  claim 2 , wherein an amount of hydrogen peroxide remaining on the article after maintaining the plasma is less than approximately 8000 ppm.  
     
     
         4 . The method as defined in  claim 1 , wherein the applied electric field is applied in the second region by applying a voltage between two electrodes.  
     
     
         5 . The method as defined in  claim 1 , wherein the voltage has a frequency from 0 to approximately 1 kHz.  
     
     
         6 . The method as defined in  claim 1 , wherein the voltage has a frequency from 0 to approximately 400 Hz.  
     
     
         7 . The method as defined in  claim 1 , wherein the plasma has a plasma decay time and the applied electric field has a half-period greater than said plasma decay time.  
     
     
         8 . A system for sterilizing an article, the system comprising: 
 a first electrode;    a second electrode;    a first region comprising a region between the first and second electrodes;    a second region in fluid communication with the first region, the second region adapted to receive the article;    a source of reactive agent species, the source in fluid communication with the first region;    a process control module; and    a power module comprising components adapted to apply a voltage between the first electrode and second electrode so as to generate a plasma in the first region, the voltage having a frequency of less than 10 kHz.    
     
     
         9 . The system as described in  claim 8 , wherein the reactive agent species comprises hydrogen peroxide.  
     
     
         10 . The system as described in  claim 8 , wherein the power module comprises a power controller, a flyback current shunt element, a current monitor, a voltage monitor, an inductor, a capacitor, and a power control module.  
     
     
         11 . The system as described in  claim 10 , wherein the power control module is coupled to the process control module and the power controller, and the power controller is adapted to adjust the duty cycle of the voltage applied between the first and second electrodes in response to the power control module.  
     
     
         12 . The system as described in  claim 10 , wherein the power control module is coupled to the process control module and the power controller, and the power controller is adapted to adjust the amplitude of the voltage applied between the first and second electrodes in response to the power control module.  
     
     
         13 . The system as described in  claim 10 , wherein the inductor and capacitor comprise an LC circuit connected in series with the power controller.  
     
     
         14 . The system as described in  claim 13 , wherein an inductance and a capacitance of the LC circuit are chosen to match a resonant frequency of the LC circuit to the frequency of the voltage applied between the first and second electrodes.  
     
     
         15 . The system as described in  claim 8 , wherein the voltage is above a threshold voltage required to ignite a plasma.  
     
     
         16 . The system as described in  claim 8 , wherein the voltage has a frequency from 0 to approximately 1 kHz.  
     
     
         17 . The system as described in  claim 8 , wherein the voltage has a frequency from 0 to approximately 400 Hz.  
     
     
         18 . The system as defined in  claim 8 , wherein the plasma has a plasma decay time and the voltage has a half-period greater than said plasma decay time.  
     
     
         19 . The system as described in  claim 8 , wherein the power module further comprises a switching module that in response to an input voltage provides an output voltage with a frequency different from the frequency of the input voltage.