arXiv subjects

Konstantin Georgiev Kostov

Publications and source records attributed to Konstantin Georgiev Kostov.

6 recordsLinked to original sources

arXiv2025

Water activation using Ar-H$_2$ atmospheric pressure plasma jets

Whether for materials processing or medical applications, the use of atmospheric pressure plasma jets (APPJs) has emerged as a relevant alternative to conventional methods. Within the APPJs research field, the search for innovation aims not only to solve existing problems but also to explore novel options for generating plasma jets and find new possible applications. In this work, the properties of Ar-H$_2$ APPJs generated using two plasma sources that differ in the frequency, amplitude, and waveform of the generated voltage signal were studied through electrical, thermal, and optical characterization. The discharge parameters were analyzed as a function of the H$_2$ content in the gas mixture, with this parameter varying from 0\% to 3.5\%. Optical emission spectroscopy revealed that the same reactive species were produced for both plasma sources, except nitric oxide (NO), which was observed only for the source operated at a higher frequency (PS #1). Applications for water activation were performed without H$_2$ and with 3.5% H$_2$ in the gas mixture. The results of water treatment revealed that ammonia is also produced when H$_2$ is added to the working gas. This finding suggests that the water treated by a Ar-H$_2$ plasma jet can be an attractive option for use in agriculture.

physics.plasm-ph↗

arXiv2025

A low-cost plasma source aimed for medical applications using Ar as the working gas

Due to advances in equipment and intense research on plasma biomedical applications over the past few years, plasma devices are now suitable for clinical use. It has been demonstrated that plasma sources can be designed in a way that ensures their safe operation and application whilst preserving the relevant clinical results. However, the manufacturing and operating costs of such plasma devices remain high, which can be decisive for their adoption in medical procedures. In this work, a simple modification of a low-cost plasma jet configuration is proposed in order to evaluate the device's viability for medical applications using argon as working gas. Typically, plasma jets operating with argon (Ar) generate high electrical currents, which makes them unsuitable for medical applications. With the proposed device modification, the treatment is no longer carried out using the plasma jet directly, but rather with the post-discharge effluent enriched with reactive oxygen and nitrogen species. As a result, the electrical current reaching the target remains below the safety threshold established for plasma applications in humans. Tests on water activation by plasma jets with and without the proposed modification indicate that both devices can yield comparable outcomes.

physics.plasm-ph↗

arXiv2025

Measurements of power dissipated in an atmospheric pressure plasma jet device with double plasma discharge ignition

Atmospheric pressure plasma jets (APPJs) are versatile devices with numerous applications. This work focuses on APPJs generated at the tip of long, flexible tubes using the jet transfer technique. The plasma source consists of a primary discharge and a secondary discharge forming the plasma jet. Discharge power measurements were carried out in a way that it was possible to separate the contribution of the primary discharge from the total power dissipated by the plasma source. Both power and effective current were analyzed under different operating conditions. The results show that the variation of the primary discharge power is much lower than the power dissipated by the plasma jet. Additionally, the electrical characteristics of the plasma device were analyzed. Notable differences were observed between the negative and positive phases of the discharge, with a more resistive load in the negative one, which suggests that the electrical equivalent circuit model changes according to the voltage polarity.

physics.plasm-ph↗

arXiv2024

A low cost, flexible atmospheric pressure plasma jet device with good antimicrobial efficiency

Plasma sources suitable to generate low temperature plasmas has been fundamental for the advances in plasma medicine. In this research field, plasma sources must comply with stringent conditions for clinical applications. The main requirement to be met is the patient and operator's safety and the ethical requirement of effectivity, which encompasses the electrical regulations, potential device toxicity and effectiveness in relation to the desired treatment. All these issues are addressed by the German pre-standard DIN SPEC 91315:2014-06 (DINSpec), which deals with the safety limits, risk assessment and biological efficacy of plasma sources aimed for medical applications. In this work, a low cost, user-friendly and flexible atmospheric pressure plasma jet (APPJ) device was characterized following the DINSpec guidelines. The device, which is still under development, proved to be safe for medical applications. It is capable of producing an APPJ with low patient leakage current and UV emission, gas temperature lower than 40 °C, production of harmful gases within the safety limits and low cytotoxicity. The most differentiating feature is that the device presented good antimicrobial efficacy even operating at frequency of the order of just a few hundred Hz, a value below that of most devices reported in the literature.

physics.plasm-ph↗

arXiv2023

On the gas heating effect of helium atmospheric pressure plasma jet

Plasma medicine is an emerging research field which has been driven by the development of plasma sources suitable to generate low temperature plasmas. In many cases, such devices can operate without a gas flow, producing a plasma discharge from the ambient air. However, the most common case is the use of a working gas at a given flow rate to produce a plasma jet. Helium (He) is one of the gases commonly used as the carrier gas to generate cold atmospheric pressure plasma jets (CAPPJs) due mainly to the easiness to ignite a gas discharge with it. However, in this work it was observed that most of the heating of a He CAPPJ can come just from the expansion of the He gas. This was found through measurements of gas temperature ($T_{gas}$), using fiber optic temperature (FOT) sensors, and thermal output, using both FOT and infrared imaging with the He flow impinging on a copper (Cu) plate. Such findings were achieved through comparisons of $T_{gas}$ and the temperature on the Cu ($T_{Cu}$) plate in the conditions with and without discharge ignition, as well as comparing $T_{gas}$ in the free gas/jet mode with and without discharge ignition. It was verified that the $T_{gas}$ values increased as the distance from the gas outlet was enlarged, especially at low He flow rates, even without discharge ignition. Despite the temperature increase with distance, it is possible to produce plasma jets with temperatures lower than 40 $^\circ$C at low He flow rates.

physics.plasm-ph↗

arXiv2023

Different configurations of transferred atmospheric pressure plasma jet and their application to polymer treatment

The employment of atmospheric pressure plasma jets (APPJs) in a large sort of applications is limited by the adversities related to the size of the treated area and the difficulty to reach the target. The use of devices that employ long tubes in their structure has contributed significantly to overcome these challenges. In this work, a comparison between two different plasma systems employing the jet transfer technique is presented. The main difference between the two devices is how the long plastic tube was assembled. The first one uses a copper wire placed inside a long plastic tube. The other device has a metallic mesh installed in a concentric arrangement between two coaxial plastic tubes. As a result, the two APPJ systems exhibit different properties, with the wire assembly being more powerful, also presenting higher values for the electrical current and rotational temperature when compared to the mesh mounting. X-ray photoelectron spectroscopy (XPS) demonstrates that both configurations were capable of inserting O-containing functional groups on the polypropylene (PP) surface. However, the transferred plasma jet with wire assembly was able to add more functional groups on the PP surface. The results from XPS analysis were corroborated with water contact angle measurements (WCA), being that lower WCA values were obtained when the PP surface presented higher amounts of O-containing groups. Surface morphology evaluation showed that the plasma treatment tends to slightly increase the surface roughness of the PP samples with both wire and mesh configurations. Furthermore, the findings in this work suggest that the APPJ with wire configuration is more appropriate for material treatments, while the transferred jet with mesh arrangement tends to present lower electrical current values which makes it more suitable for biological applications.

physics.plasm-ph↗