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Dielectric profile controlled microwave sterilization system

This United States Non-provisional patent application claims the benefit of U.S. Provisional Patent Application No. 60/682,497, filed May 18, 2005, hereby incorporated by reference herein.

Microwave radiation has been used to heat a wide variety of materials to the point where temperatures are sufficient to create sterilization effects. Many materials, especially those which have not absorbed moisture, may require prolonged exposure at high power levels to ensure complete sterilization.

However, the determination of when a material is rendered inactive or destroyed by irradiation with microwaves still relies largely upon observable changes of the irradiated material. This reliance upon observation of the irradiated material may be impractical when the irradiated material is divided among a large number of discrete containers or when the irradiated material is a biological pathogen or toxic chemical, or may be unlawful for example in the case of opening the United States mail to obtain samples of the irradiated material.

Moreover, conventional irradiation devices and irradiation methods suffer from a lack of precision. Conventional material irradiation devices and methods rely upon a fixed frequency microwave source which provides a high intensity, non-specific radiation field that may be many times stronger than is required to sterilize or heat a particular material because determination as to when a material has been rendered inactive remains largely a matter of guesswork in many cases.

As to these problems and other problems related with conventional microwave irradiation of materials for the purpose of sterilization or heating of a material, rendering the material inactive or destroying the material, the instant invention addresses each in practical fashion.

Accordingly, a broad object of the invention can be to provide a dielectric profiler which analyzes the dialect profile of a material over a wide frequency range which allows adjustment of the microwave frequency prior to material irradiation to achieve sterilization or heating.

Another broad object of the invention can be to provide a computer which operates a dielectric profiler application program which compensates for a numerous and wide variety of material variables including without limitation moisture, volume, temperature, density, contaminants, or the like, by use of calibration profiles retrievable from a computer memory element.

Another broad object of the invention can be to operate a dielectric profiler at power levels which avoid or reduce alteration of the target material (the “profiling event”) prior to irradiation for the purpose of sterilization or heating. Many substances display an altered irradiation absorption profile once they have been exposed to any intense radio frequency field. In certain instances, the amount of microwave energy a material can absorb can be altered by increasing wavelength frequency of microwave irradiation. As such, application of a strong irradiation field at one frequency can alter material characteristics and hinder measurement of the dielectric characteristics of the material at a different frequency.

Another broad object of the invention can be to provide a method of microwave irradiation of a material which includes at least a first step of assessing the dielectric profile of a material to determine a frequency (or frequencies) at which to irradiate the material, and can include additional steps of assessing rate of change in temperature of the material at such established frequency (or frequencies) to establish a duration of an irradiation period at such frequency (or frequencies), irradiation of the material at such frequency (or frequencies) for such irradiation period (the “irradiation event”), comparison of the dielectric profile of the material before the irradiation event and the dielectric profile after the irradiation event, assessment based upon such comparison as to the degree to which the material has been altered by the irradiation event, and assessment based upon such comparison as to whether any undesired products have been generated by the irradiation event.

Another broad object of the invention can be to provide automatic detection and selective destruction or inactivation of a first material on the surface of a second material such as a manufacturing material; or of a first material contained inside a space defined by the configuration of a second material such as parcels, envelopes, boxes, containers, or the like; or of a first material such as mold or other pathogen located in the wall space of a building. However, these specific examples are not intended to be limiting with respect to the numerous and wide variety of applications encompassed by the invention.

Another broad object of the invention can be to provide for detection and identification of concealed materials such as bacteria, viruses, pathogens, cells, cell components, chemicals, compositions, or mixtures or combinations thereof, which as to certain embodiments of the invention, can further comprise the generation of 3D images of a concealed materials.

Naturally, further objects of the invention can be understood from the description and drawings.

FIG. 1 shows an embodiment of the invention which operates to provide both a profiling event and a microwave irradiation event of a target material.

FIG. 2 provides non-limiting examples of configurations of microwave cells and arrays of microwave cells which can be used in embodiments of the invention to provide a profiling event or a microwave irradiation event of a target material.

FIG. 3 shows a particular embodiment of the invention used to provide a profiling event or an irradiation event, or both, of a target material such as a letter or package.