Novel Applications of Microwaves

Rani Jindal and Sanjay Bajaj

Abstract: Microwave activation, as a non-conventional energy source, has received considerable attention in various fields in addition to being used for heating or cooking food. Microwaves are being used for diagnosis of various diseases such as diabetes mellitus, dental diagnosis, as well as in the diagnosis and treatment of cancers. Microwave based hyperthermia technique (thermotherapy) has been used for the treatment of patients suffering from prostate and breast cancer where intense microwave generated heat is used to destroy cancerous tissue. Small molecules can be synthesized rapidly due to which this technique has gained wide acceptance as a valuable tool for accelerating drug discovery and development processes. In addition microwaves are also used for drying of fruits, vegetables, flowers, wood, herbs, etc. disinfection of biomedical waste, decrease air pollutants, remediation of soil, and extraction of active constituents. This article enlists various medicinal, pharmaceutical and other applications of microwaves.

Introduction: Microwave activation, as a non-conventional energy source, has received considerable attention in various fields in addition to being used for heating or cooking food. This is mainly because of increasing need for automation and environment friendliness, and in order to increase productivity, safety and quality with highly improved efficiency.1 By “microwaves” we mean the range of radio frequencies between about 300 MHz (one megahertz is one million oscillations per second, one GHz is 1,000 MHz) and about 30 GHz (one gigahertz, or one billion oscillations per second). Although there is no formal definition of the frequency range for “microwaves”, some text books will say all frequencies above 300 MHz as microwaves. People often misuse the term “millimeter waves” to mean any microwaves of higher frequencies than those normally used. Millimeter waves range between 30 GHz to 300 GHz and above 300 GHz waves are considered as “sub-millimeter waves”. Most common applications are within the 1 to 40 GHz range. Microwave frequency bands, as defined by the Radio Society of Great Britain (RSGB) have been explained in Table 1. Wavelengths in the range 1 to 25 centimeter are extensively used for RADAR transmissions and the remaining range is used for telecommunications. In order to avoid interference, the domestic and industrial microwave-ovens are required to operate at either 12.2cm (2.45 GHz) or 33.3cm (0.9 GHz) unless the apparatus is shielded in such a way that no radiation losses occur. Microwaves are very short radio waves that travel in an invisible circular motion through the air. Microwaves go faster than television waves but slower than infrared rays. They are stronger than radio frequency waves, but weaker than X-rays. They can pass through glass, ceramic, paper plastic and similar materials. They are reflected by metal, aluminum foil and absorbed by food.


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