Hybrid Sterilization: UV-C, cold plasma, and H2O2

Context: Scientists have developed a portable sterilisation unit using a new technology called the hybrid sterilization system that can decontaminate personal protective equipment (PPE) necessary for combating COVID 19, easily and rapidly, allowing them to be used multiple times.

Analysis

  • UV radiation is a proven method for sterilization. However, the lower penetration depth of UV-C and faster divergence from the source can result in nonuniform treatment. The team of scientists have developed this hybrid sterilization system consisting of a UV radiation cavity, cold plasma, and H2O2 spray.
  • Unlike the traditional UV systems, this system confines the UV radiation and enhances photon-flux and sterilization efficacy. The coherent operation of UV-C, cold plasma, and H2O2 spray further strengthens the sterilization efficiency.

Cold Plasma

“What is the fourth state of matter?” 

  • Matter has a fourth state other than the three, everyone knows about – solid, liquid and gas. This fourth state of matter is called Plasma.
  • When heated, the ice (for example) changes into water. On further heating, the liquid water changes into water vapour, the gaseous state. With sufficient heating, heated gas changes into plasma.
  1. So, in essence, plasma is an exotic state consisting of a mixture of electrons, charged atoms and neutral atoms.
  • As a matter of fact, we are surrounded by plasma, since plasma is a common component of the universe.
  1. In our daily life, we meet plasma in the form of beautiful auroras (northern lights) and lighting in the sky.
  2. In addition, when leaving the atmosphere of our planet, we encounter plasma in the Sun, Stars and solar winds,which are all compose of plasma.
  3. Almost 99 percent of all known matter in the Universe is plasma, leaving the three ordinary states of matter with merely 1 percent.

What is cold plasma?

  • To understand cold plasma, we need to refresh our knowledge of temperature and heat.
  • It is a common misconception that higher temperature should always mean a lot of heat.
  • When defining the hotness or coldness of a given substance, one must not only consider its actual temperature but also its heat capacity.
  • For example: You might have experienced accidentally dropping the ash of a cigarette on your hand. Even though the temperature of the ash is very high, you were probably not immediately burned. This is because the total amount of heat involved is very low.
  • Cold plasma (or non-equilibrium plasma) is the plasma where the temperature of the individual constituents are different from each other.
  1. Electrons are at higher temperature (more than 10,000K) and neutral atoms are at room temperature.
  • However, the density of the electrons in the plasma is very low compared to the density of the neutral atoms.
  • In the laboratory, cold plasmas are generally produced by the provision of electrical energy to different inert gases. This can be done at room temperature and at atmospheric pressure.

What are the applications of Cold Plasma?

  • Cold plasma is a source of high-temperature electrons at ambient conditions (room temperature & pressure). 
  • In Biomedicine, cold plasma is used for the treatment of teeth, skin and sterilization of medical devices.
  • In material science, it is used for surface modifications (computer chip production).
  • In food industry, cold plasma finds applications in the packaging process as well as in food production.
  • In environmental sciences, it is used in air and water purification and many more.

Hydrogen peroxide, H2O2

  • Hydrogen peroxide works as a disinfectant by destroying essential components of germ cells, and can deactivate a wide range of microorganisms, including bacteria, viruses, fungi, and spores. 
  • Hydrogen peroxide works by producing destructive hydroxyl free radicals that can attack membrane lipids, DNA, and other essential cell components. 

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