In 1927, the term plasma was adopted by Nobel Prize-winning chemist Irving Langmuir to describe the properties of gases in which atoms have been ionized by high voltage to form free negatively charged electrons and positive ions (in a neutral background gas). These ionized gases conduct electricity and are strongly affected by magnetic fields . Although quite common in nature – it is estimated that more than 99% of the matter in the universe is in the form of plasma – only two forms of plasma occur naturally on Earth, within lightning and flames.

Early Studies    

Most early studies on man-made plasmas were performed in low-pressure or vacuum vessels filled with inert gases to provide ready sources of electrons and positive ions. When high-voltage power is applied to metal electrodes within these vessels, a plasma containing high-energy particles if formed. High-energy, accelerating electrons collide with other atoms, thus sustaining a steady-state plasma. Some of these collisions are sufficiently energetic that light, such as the characteristic dark violet-blue from plasma in the air, is emitted from the bombarded atoms. These experiments ultimately led to the development of neon signs, streetlights, and fluorescent light bulbs.

Recent Developments

Over the past twenty to thirty years, attention has turned to atmospheric-pressure plasmas and their use in technological applications. Although originally reported by Werner von Siemens in 1857 for the generation of ozone, the technology remained underdeveloped until modern materials were used to produce more effective and efficient ‘dielectric barrier discharges’. The plasma-inducing electrodes in a dielectric barrier discharge device are coated with or embedded into specialized ceramic materials, thus providing an insulating layer between the electrodes that suppresses arcing while allowing glowing micro discharges to form. Dielectric barrier discharges exist in many shapes and forms, a property leveraged by IonField products , and can thus easily ‘shape’ the geometry of the resulting plasma as needed.

 Cold Plasma

 The term atmospheric pressure plasma or “cold plasma” refers to air that has been disassociated into positive and negative species, without the need for vacuum or high temperatures . Photos taken looking into our plasma generation station show a dark blue color from nitrogen emission peaks. Although heat can be a significant byproduct of the plasma generation process, IonField’s process is optimized to maximize plasma production and minimize heat gain, thereby increasing the potential number of labware reuses.

Plasma from IonField’s design is generated by a dielectric barrier discharge methodology that produces short-lived (1/6000th second) micro discharges which dissociate oxygen and nitrogen molecules. The method is simple: air is blown through a gap between a pair of oppositely charged alumina ceramic-surfaced electrodes with a few thousand-volt differential charge across the gap. Streamers of electrons flow back and forth each time the applied charge is reversed

Each dielectric barrier discharge is unidirectional. To obtain a steady-state plasma, the alternating current frequency of discharges maintains plasma in space between the electrodes. Dielectric barrier discharges do not have current flow or create sparks.  As a result, an optimized design produces very little heat.

Successfully balancing voltage, frequency, and gap distance produces a stable, non-thermal (“cold”) plasma that turns on and off like a light bulb.