The  plasma is a general term for the ionized gas-like material produced by atoms after being deprived of electrons and atoms after being ionized. There are usually a large number of charged particles ( such as OH-, H2O + ), active substances, O2 and N2 in the excited state and ultraviolet light in the plasma products.

According to whether the plasma reaches the equilibrium state as a whole, the plasma that has reached the equilibrium state as a whole is called the equilibrium thermodynamic plasma, and the plasma that cannot reach the overall equilibrium state is called the non-equilibrium thermodynamic plasma, and the plasma that will reach the equilibrium state is called the quasi-thermodynamic plasma. Because the temperature is closely related to the thermal equilibrium state, the classification according to the temperature and the classification according to the thermodynamic equilibrium state are mutually intersecting. The high temperature plasma usually refers to the equilibrium thermodynamic plasma, and the low temperature plasma generally refers to the non-equilibrium thermodynamic plasma. In the process of plasma generation, discharge is usually used. The main idea of this method is to make the electron kinetic energy in the electric field increase rapidly, and the probability and number of gas collisions between the two electrodes increase. The gaseous atoms and molecules are excited from the lower energy state to the higher energy state to generate plasma. In the actual research on the generation of plasma, dielectric barrier discharge ( DBD ), surface dielectric barrier discharge ( SDBD ), atmospheric pressure plasma jet ( APPJ ) and other devices are usually used to obtain plasma.

For the technology of generating plasma in the traditional sense, there are many problems that limit the wide application of plasma technology, such as the need for a higher breakdown voltage to break down the gas to generate plasma ; the discharge gap is relatively short ; the active particles have low energy and cannot handle large objects. And the overall experimental conditions are very harsh. Focusing on these thorny problems that currently limit applications, researchers have designed a new plasma generation method-APPJ by continuously exploring new methods. APPJ technology refers to the discharge technology that can produce a jet-like plasma jet under the open conditions of atmospheric pressure and affected by factors such as high pressure and airflow, and treat the surrounding treatment. Its generating device mainly includes high pressure electrode, nozzle, working gas and other parts.

APPJ plasma jet can be obtained in open space ; the excitation device is flexible and convenient to operate ; high experimental safety ; the gas temperature of the jet is close to room temperature. Lower excitation voltage ; the jet is more uniform and stable ; short processing time and high efficiency ; due to the advantages of non-residual and non-polluting, it has received great attention. It has been widely used in agriculture, material processing, film deposition, biomedicine and other fields, which is of great significance to production and life.

In the field of agriculture, APPJ technology has unique advantages. In breeding, after APPJ treatment, the seed can stimulate the activity of the seed and will not cause gene pollution to the seed.

In terms of material treatment, because the plasma jet is rich in charged particles and active groups produced by ionized air, and different ionized gases can produce different charged particles, APPJ plays an important role in the modification of materials.

In terms of thin film deposition, the active particles produced by the plasma jet can directly treat the treated material, and there is no special requirement for the shape of the treated material, so it has a good application prospect in thin film processing.

In biomedicine, plasma has been applied in many medical fields. Studies have shown that plasma has significant effects in cancer, skin diseases, oral treatment and new coronavirus inactivation.