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To date, reactive oxygen species and reactive nitrogen species have been regarded as the key factors causing the observable cellular death of cold atmospheric plasma (CAP)-treated cancer cells. The chemical basis of the conventional CAP treatment highlights apoptosis as the main CAP-triggered cell death mechanism. However, we recently demonstrated a strong anti-melanoma effect based on physically-based CAP treatment. In this study, we compared the anti-cancer effect of chemically-based versus physically-based CAP treatment on four typical cancer cell lines in vitro. Three of these cancer cell lines were more sensitive to the physical factors in CAP than the chemical factors in CAP, while the fourth cell line followed the original trend of being more sensitive to chemical factors. This study demonstrated that the physically-based CAP treatment could be an effective anti-cancer approach, which might have a deep impact on the future application of CAP in medicine.

Small, lightweight low-power micro-cathode arc thrusters (µCATs) with micronewton thrust are well suited to the altitude control of small satellites like CubeSats. For some applications (orbit raising, maneuvering) their thrust level needs to be improved. A possible approach for this could be the two-staged thruster—a micro-cathode thruster with a magnetoplasmadynamic (MPD) stage and an external magnetic field. In this article, we discuss some discharge features that such a two-stage µCAT-MPD experiences in each configuration of the magnetic field—formed with either a permanent magnet, or a pulsed magnetic coil. We found that in both configurations of the magnetic field, the thrust can be enhanced significantly (up to factor of 10) after some threshold voltage is applied to the second stage. The pulsed magnetic coil ensures better controllability of the magnetic field; however, it causes an undesirable time delay between the plasma generation moments in both stages, which consequently results in a moderate thrust increase. The permanent magnet provides a stable thrust increase; however, it cannot be switched off, which seems to be impractical for its use in micro-satellites. In both magnetic field configurations, the emissive electromagnetic noise level was found to be low-frequency (within tens of kHz) and quite moderate in amplitude, and mechanical noise was found to be two orders of magnitude lower than the thrust generated in the normal working regime.

Cancer treatment is a challenge in modern medicine. Several novel modalities have been invented to selectively treat cancer cells. The reactive species such as reactive oxygen species and reactive nitrogen species play important role in the anti-cancer capacity of several modalities, such as cold atmospheric plasma. In this study, we first demonstrated that a nanosecond-pulsed magnetic field (NMF) generator could sensitize the melanoma cell line B16-F10 to the cytotoxicity of an important ROS, H2O2. The magnetic field strength and the frequency were two key factors to control the activation level of NMF treatment. This study provided a novel strategy to use electromagnetic modality in cancer treatment particularly for the treatment on deep tumors such as brain, pancreatic, etc.

Cold atmospheric plasma (CAP) has shown strong anti-cancer capability in vitro and in vivo. The interaction between CAP and cancer cells build the foundation to understand the anti-cancer effect of a direct CAP treatment. The CAP-based activation phenomenon is a key factor to understand the CAP cancer treatment. The CAP-treated pancreatic adenocarcinoma cells instantaneously entered a specific activation state, in which these cancer cells become very sensitive to the cytotoxicity of both reactive oxygen species and reactive nitrogen species. Here, we present a roadmap of control the basic operational parameters of the CAP jet (the helium flow rate, the discharge voltage, and the discharge frequency) on the activation. Among three parameters, the discharge voltage shows the largest impact on the activation phenomenon. The maximum activation effect occurred when the discharge voltage reached a medium level. A 0D chemical simulation revealed that such maximum activation effect may be due to the maximum densities of several short-lived reactive species in CAP jet at a certain level of discharge voltage.

Plasma devices generating a sequence of streamers over an inert gas jet in ambient air have been widely used recently in anticancer therapy. An enhancement of electric field carried by the streamers to the target surface is a way to intensify the plasma jet impact on a cell life cycle. In this paper, an increase of the surface electric field without a rise of discharge power is provided with an external biased electrode installed between the plasma device and target. The effect of the presence of this biased electrode on cathode-directed streamer dynamics and its interaction with conductive or charged dielectric surfaces are studied in 2D fluid model simulations and in the experiment. Two stages of the ionization process induced by the streamer near the plasma–target interface are observed in the experiment and simulations. The first stage is related to the streamer approaching the surface. The second stage is the stationary self-sustained ionization and lasts much longer during a positive cycle of sinusoidal voltage applied to the electrode inside of the plasma device. A much higher surface electric field is registered on the dielectric surface compared to the conductive one, due to an accumulation of the surface charge, especially with the negative bias on the external electrode. An area on the dielectric surface exposed by the plasma jet is much larger compared to the conductive one, due to spreading the surface ionization wave over the dielectric.

Cold atmospheric plasma (CAP) jet exhibits remarkable properties that trigger cell death in cancer cells. The effect of CAP on cancer cells is influenced by several factors including plasma jet discharge voltages, gas composition and cancer cell type. Consequently in clinics it becomes challenging to plan plasma cancer treatments for a particular cancer types. To address this, we present preliminary results for an in vitro model which includes an optimal feedback control scheme that can adjust treatment conditions based on the actual cancer cell response. Translation to an in vivo model will be the next objective of the presented project. First, a mathematical model is presented for the dynamic response of cancer cells to CAP jets based on experimental data that provide temporal measurements of cancer cell viability after CAP treatments. A differential equation is developed to model the influence of CAP on the viability of two cancer cell lines, U-87 MG and MDA-MB-231, under varying treatment duration and plasma discharge voltages. Subsequently, a control scheme is presented to determine CAP treatment conditions in an optimal fashion by reducing cancer cell viability less than a prescribed goal while minimizing a weighted sum of the treatment duration and the discharge voltage. This is further extended to a model predictive control framework such that a pre-planned CAP treatment schedule is revised according to the actual cancer cell response. The efficacy of the proposed approach is illustrated by numerical simulations based on experimental data.

In this paper a model of single wall carbon nanotube (SWNT) interactions with thermal plasma is developed. Several effects such as momentum, charge and energy transfer between the SWNT and plasma are considered. It is shown that the SWNT charge and potential with respect to the plasma, as well as SWNT aspect ratio, depend on plasma density and electric field in the interelectrode gap. For instance, the SWNT charge changes from negative to positive value with electron density decrease. This model suggests several ways to improve the controllability of SWNT synthesis in arc discharge, such as an increase in plasma density and the application of an electric field. It is predicted that higher plasma density in the SWNT formation region and electric field lead to the formation of SWNT with a very high aspect ratio.

The distribution of an ion current density on a substrate with a discontinuous film consisting of islands of dimension 25–100 nm was studied numerically. It was found that the ion current distribution is highly non-uniform and islands of the discontinuous film are enclosed with sharply defined zones where the current density is very low. The total area of low current zones reaches 30–50% of the substrate area, depending on the voltage applied to the substrate. The ratio of island radius–low current zone width depends on the island size and equals approximately 1.0 for large islands and 0.5 for small islands. It is shown that the island distribution function may be controlled by bias voltage variation.

The cold atmospheric plasma (CAP) is a promising novel anti-cancer method. Our previous study showed that the cold plasma-stimulated medium (PSM) exerted remarkable anti-cancer effect as effectively as the direct CAP treatment did. H2O2 has been identified as a key anti-cancer substance in PSM. However, the mechanisms underlying intracellular H2O2 regulation by cancer cells is largely unknown. Aquaporins (AQPs) are the confirmed membrane channels of H2O2. In this study, we first demonstrated that the anti-glioblastoma capacity of PSM could be inhibited by silencing the expression of AQP8 in glioblastoma cells (U87MG) or using the aquaporins-blocker silver atoms. This discovery illustrates the key intermediate role of AQPs in the toxicity of PSM on cancer cells. Because the expression of AQPs varies significantly among different cancer cell lines, this study may facilitate the understanding on the diverse responses of cancer cells to PSM or the direct CAP treatment.

Electrosurgical cutting is a well-known technique for creating incisions often used for the removal of benign and malignant tumors. The proposed mathematical model suggests that incisions are created due to the localized heating of the tissue. The model estimates a volume of tissue heating in the order of 2 10−4 mm3. This relatively small predicted volume explains why the heat generated from the very tip of the scalpel is unable to cause extensive damage to the tissue adjacent to the incision site. The scalpel exposes the target region to an RF field in 60 ms pulses until a temperature of around 100 °C is reached. This process leads to desiccation where the tissue is characterized by a significantly low electrical conductivity, which prevents further heating and charring. Subsequently, the incision is created from the mechanical scraping process that follows.

Cold atmospheric plasma (CAP) has been emerged as a novel technology for cancer treatment. CAP can directly treat cells and tissue but such direct application is limited to skin or can be invoked as a supplement during open surgery. In this study we report indirect plasma treatment using CAP discharged in DI water using three gases as carriers (argon, helium and nitrogen). Plasma stimulated water was applied to human breast cancer cell line (MDA-MB-231). MTT assay tests showed that using argon plasma had the strongest effect on inducing apoptosis in cultured human breast cancer cells. This result is attributed to the elevated production of the reactive oxygen species and reactive nitrogen species in water in the case of argon plasma., arXiv admin note: text overlap with arXiv:1607.06775

The two-dimensional expansion of a current carrying plasma jet in the interelectrode gap of a vacuum arc with an axial magnetic field is analysed by finding the steady state solution of the fully ionized plasma in the hydrodynamic approximation. Two models are presented: (1) expansion into a duct with known geometry and (2) free jet expansion. The first approach models the plasma jet expansion with a conical shape. In the second model the geometric position of the free boundary was determined by the free hydrodynamic jet expansion into vacuum without and with the influence of a magnetic field. In the case of plasma expanding into a conical guide, it was found that the flow field in the near-axis region does not depend on the cone angle for cone angles . The radial velocity becomes comparable to the axial velocity due to the expansion, depending on the cone angle and the initial axial velocity. A model of the free boundary plasma expansion was developed, based on the jet-like (i.e. axial velocity larger than the radial velocity) plasma flow in the vacuum arc near the cathode spot. The free jet boundary was calculated by solving the equations for the normal and tangential velocity components at the free boundary. It was found that the plasma jet had a conical shape, and for axial distances 3 - 4 times greater than the initial jet radius, the radial velocity becomes comparable with the axial velocity if no magnetic field is imposed. Imposition of a magnetic field reduces the radial component of the plasma velocity. The streamline angle is about for a 0.001 T magnetic field and about for a 0.01 T magnetic field. The plasma remains quasi-neutral in all regions except in the space charge boundary layer, where an outward directed electric field appears for low magnetic fields, and an inward directed field is present for strong magnetic fields.

Material processing techniques utilizing low-temperature plasmas as the main process tool feature many unique capabilities for the fabrication of various nanostructured materials. As compared with the neutral-gas based techniques and methods, the plasma-based approaches offer higher levels of energy and flux controllability, often leading to higher quality of the fabricated nanomaterials and sometimes to the synthesis of the hierarchical materials with interesting properties. Among others, nanoscale biomaterials attract significant attention due to their special properties towards the biological materials (proteins, enzymes), living cells and tissues. This review briefly examines various approaches based on the use of low-temperature plasma environments to fabricate nanoscale biomaterials exhibiting high biological activity, biological inertness for drug delivery system, and other features of the biomaterials make them highly attractive. In particular, we briefly discuss the plasma-assisted fabrication of gold and silicon nanoparticles for bio-applications; carbon nanoparticles for bioimaging and cancer therapy; carbon nanotube-based platforms for enzyme production and bacteria growth control, and other applications of low-temperature plasmas in the production of biologically-active materials.

Plasma-stimulated medium (PSM) shows a remarkable anti-cancer capacity as strong as the direct cold atmospheric plasma (CAP) treatment of cancer cells. PSM is able to effectively resist the growth of several cancer cell lines. To date, the sole approach to strengthen the anti-cancer capacity of PSM is extending the plasma treatment time. In this study, we demonstrated that the anti-glioblastoma capacity of PSM could be significantly increased by adding 20 mM lysine in Dulbecco's modified Eagle's medium (DMEM). This study provides clear evidence that the anti-glioblastoma capacity of PSM could be noticeably enhanced by modifying the composition of medium without increasing the CAP treatment time.

An approach to controlling heat flux based on electron emission in the double layer assembly of two materials with different work functions has been developed. It is shown that this two-electrode assembly promotes the inverse heat flux exhibiting a thermal metamaterial property in a wide range of temperatures. The proposed thermal metamaterial can be used as an active element of a thermal diode, ensuring heat flux in one direction regardless of temperature difference.

A kinetic model is developed of Teflon ablation caused by a plasma. The model takes into account the returned atom flux that forms in the non-equilibrium layer during the ablation. This approach makes it possible to calculate the ablation rate for the case when the Teflon surface temperature and the density and temperature in the plasma bulk are known.

Tumor modeling is a technique that entails using mathematical and physical equations to describe the biological disease, most importantly uncontrolled cell growth and the tumor life cycle. The model utilized in this paper makes use of a three-dimensional hybrid discrete–continuum model to show the apoptotic effect a tumor volume undergoes when treated with reactive oxygen and nitrogen species from the cold atmospheric plasma. The results compare untreated and treated tumors of varying sizes by measuring spatiotemporal data to predict trends of tumor evolution. The simulation results show that the treated tumor death, irrespective of tumor volume, follows an exponential decay and that the untreated tumor follows an expected growth pattern. Future experiments and applications can lead to a predictive tumor model allowing for individualized treatment planning for the cold atmospheric plasma therapy.

Nanoparticle growth in arc discharges is analysed numerically. An analysis is carried out for the root growth method of nanotubes in plasmas. The existing models for estimating the growth of nanoparticles in stationary plasmas are extended to plasmas with variable properties. The distributions of velocity, species density and temperature from numerical simulations are used as input to the growth models. The nickel particle diameter obtained from the numerical model is 9.2 nm and the frequency of finding this size in the experiment is 26 on the larger side. The length of the single-walled carbon nanotube obtained from the model is 2.1 µm, which falls in the upper 10% of the size distribution from experiment. Parametric studies are carried out varying the arc current, inter-electrode gap and background pressure. Results showed 40–95% increment in the nanotube length by increasing the background pressure and the inter-electrode gap. A hot-chamber arc discharge method is proposed to maximize the growth of nanoparticles subjected to the conditions identical to those existing in convectional arc discharges.

In this perspective paper, we critically analyse the state-of-the-art of arc discharge technique of carbon nanoparticle synthesis. We discuss improving controllability of the arc discharge synthesis of carbon nanotubes, synthesis of graphene as well as general understanding of the synthesis process. Fundamental issues related to relationship between plasma parameters and carbon nanostructure characteristics are considered. Effects of electrical and magnetic fields applied during single-wall carbon nanotube synthesis in arc plasma are explored. Finally our personal opinion on what future trends will be in arc discharge synthesis is offered.

International audience; Nanoparticles and low-temperature plasmas have been developed, independently and often along different routes, to tackle the same set of challenges in biomedicine. There are intriguing similarities and contrasts in their interactions with cells and living tissues, and these are reflected directly in the characteristics and scope of their intended therapeutic solutions, in particular their chemical reactivity, selectivity against pathogens and cancer cells, safety to healthy cells and tissues, and targeted delivery to diseased tissues. Time has come to ask the inevitable question of possible plasma-nanoparticle synergy and the related benefits to the development of effective, selective, and safe therapies for modern medicine. This perspective article offers a detailed review of the strengths and weakenesses of nanomedicine and plasma medicine as a stand-alone technology, and then provides a critical analysis of some of the major opportunities enabled by synergising the nanotechnology and the plasma technology. It is shown that the plasma-nanoparticle synergy is best captured through the plasma nanotechnology and its benefits for medicine are highly promising.

The conditions for carbon nanotube synthesis in the bulk of arc discharges and on plasma-exposed solid surfaces are compared to reveal the main distinguishing features of the growth kinetics and explain the striking difference between the growth of the nanotubes in both cases. It is shown that this difference is due to very different exposure of the discharge-synthesized and surface-bound nanotubes to ion fluxes, with the ratio of the ion fluxes collected per nanotube in the two cases reaching up to six orders of magnitude. Depending on the plasma parameters and the sizes of the nanotubes and metal catalyst particles, four distinct growth modes of the nanotubes in the plasma bulk have been identified. These results shed light on why single-walled carbon nanotube growth is more favourable in the bulk of arc plasmas rather than on plasma-exposed surfaces.