Nonthermal Plasma Technology as a Versatile Strategy for Polymeric Biomaterials Surface Modification: A Review

In modern technology, there is a constant need to solve very complex problems and to fine-tune existing solutions. This is definitely the case in modern medicine with emerging fields such as regenerative medicine and tissue engineering. The problems, which are studied in these fields, set very high demands on the applied materials. In most cases, it is impossible to find a single material that meets all demands such as biocompatibility, mechanical strength, biodegradability (if required), and promotion of cell-adhesion, proliferation, and differentiation. A common strategy to circumvent this problem is the application of composite materials, which combine the properties of the different constituents. Another possible strategy is to selectively modify the surface of a material using different modification techniques. In the past decade, the use of nonthermal plasmas for selective surface modification has been a rapidly growing research field. This will be the highlight of this review. In a first part of this paper, a general introduction in the field of surface engineering will be given. Thereafter, we will focus on plasma-based strategies for surface modification. The purpose of the present review is twofold. First, we wish to provide a tutorial-type review that allows a fast introduction for researchers into the field. Second, we aim to give a comprehensive overview of recent work on surface modification of polymeric biomaterials, with a focus on plasma-based strategies. Some recent trends will be exemplified. On the basis of this literature study, we will conclude with some future trends for research

26th Symposium on Plasma Physics and Technology

List of abstract

Pulsed laser irradiation of plasma sprayed alumina-zirconia coatings

Plasma sprayed alumina and zirconia coatings are widely used coatings for many industrial applications. One of the most important applications is the production of thermal barrier coatings (TBCs). As sprayed alumina-zirconia coatings have relatively high degree of porosity and the properties of these coatings, such as high temperature, corrosion resistance, toughness and abrasion resistance may thereby be reduced. Laser surface treatment is one novel method that has potential for eliminating porosity and producing a homogeneous surface layer. In this research work the effect of excimer laser annealing on the surface of alumina-zirconia coatings was investigated. Alumina-40% zirconia (AZ-40) coatings were sprayed with a water-stabilized plasma spray gun. The coated surface was treated by excimer laser having a wavelength of 248 nm and pulse duration of 24 ns. In the first phase of the work an analytical model was developed in COMSOL Multiphysics 4.2 in order to investigate the effect of the defects on the heat distribution at the surface of samples irradiated by KrF beam. The model revealed that much higher temperatures were localized at areas having defects than at continuous surfaces. A detailed parametric study was carried out to investigate the effects of different laser surface treatment parameters including laser energy density (fluence), pulse repetition rate (PRR), and number of pulses on the microstructure, surface morphology, and mechanical properties of the coatings. The surface structure of the treated coating was examined by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Treating the surface with low laser energy of 200mJ/cm2 etched a very thin layer from the coating, which helped revealing the microstructures initially present but hidden on the surface of as sprayed coatings. High laser energy of 800mJ/cm2 resulted in significant changes in the coat surface morphology where eutectic colonies growing in a pool of zirconia matrix were identified on the surface. The surface of untreated coating was continuously alternating up and down; it had a zigzag nature. After irradiating the surface with high laser fluence of 800mJ/cm2 the zigzag nature of roughness profile of untreated coating disappeared. Also irradiating the surface with high pulse repetition rate exhibited dome-like structures on the surface, which were associated with an increase in surface hardness

NASA thesaurus. Volume 3: Definitions

Publication of NASA Thesaurus definitions began with Supplement 1 to the 1985 NASA Thesaurus. The definitions given here represent the complete file of over 3,200 definitions, complimented by nearly 1,000 use references. Definitions of more common or general scientific terms are given a NASA slant if one exists. Certain terms are not defined as a matter of policy: common names, chemical elements, specific models of computers, and nontechnical terms. The NASA Thesaurus predates by a number of years the systematic effort to define terms, therefore not all Thesaurus terms have been defined. Nevertheless, definitions of older terms are continually being added. The following data are provided for each entry: term in uppercase/lowercase form, definition, source, and year the term (not the definition) was added to the NASA Thesaurus. The NASA History Office is the authority for capitalization in satellite and spacecraft names. Definitions with no source given were constructed by lexicographers at the NASA Scientific and Technical Information (STI) Facility who rely on the following sources for their information: experts in the field, literature searches from the NASA STI database, and specialized references

Gas Discharge Plasmas and Their Applications (GDP 2019): 14th International Conference, September 15–21, 2019, Tomsk, Russia: abstracts

The book contains abstarcts of oral and poster reports presented at the 14th International Conference "Gas Discharge Plasmas and Their Applications" (GDP 2019). This event is a continuation of conferences on gas discharge physics held in Russia since 1984, as well as seminars and conferences on the technological application of low-temperature plasma. The conference is held every 2 years in different cities of the Russian Federation. This year, the wonderful Siberian city of Tomsk, known for its intellectual environment, was chosen as the venue. The program of the Conference covers a wide range of technical areas and modern aspects of the physical processes occurring in generators of lowtemperature plasma, low and high-pressure discharges, pulsed plasma sources, surface modification, and other gas-discharge technologies

Towards a solution of the closure problem for convective atmospheric boundary-layer turbulence

We consider the closure problem for turbulence in the dry convective atmospheric boundary layer (CBL). Transport in the CBL is carried by small scale eddies near the surface and large plumes in the well mixed middle part up to the inversion that separates the CBL from the stably stratified air above. An analytically tractable model based on a multivariate Delta-PDF approach is developed. It is an extension of the model of Gryanik and Hartmann [1] (GH02) that additionally includes a term for background turbulence. Thus an exact solution is derived and all higher order moments (HOMs) are explained by second order moments, correlation coefficients and the skewness. The solution provides a proof of the extended universality hypothesis of GH02 which is the refinement of the Millionshchikov hypothesis (quasi- normality of FOM). This refined hypothesis states that CBL turbulence can be considered as result of a linear interpolation between the Gaussian and the very skewed turbulence regimes. Although the extended universality hypothesis was confirmed by results of field measurements, LES and DNS simulations (see e.g. [2-4]), several questions remained unexplained. These are now answered by the new model including the reasons of the universality of the functional form of the HOMs, the significant scatter of the values of the coefficients and the source of the magic of the linear interpolation. Finally, the closures 61 predicted by the model are tested against measurements and LES data. Some of the other issues of CBL turbulence, e.g. familiar kurtosis-skewness relationships and relation of area coverage parameters of plumes (so called filling factors) with HOM will be discussed also

High Power Laser - Plasma Interactions for Homeland Security Applications

Advance in laser technology over the last few decades have allowed progress in intense laser-plasma interaction research. The relativistic plasma generated by intense laser pulses can generate many different forms of radiation. This radiation, including X-rays, has been studied intensively due to the numerous potential applications of these sources. For example, for Homeland Security, radiation sources are already utilized to detect dangerous materials and hidden items that threaten civil safety. Neutrons and THz radiation have been studied as candidates for next generation screening, which may complement typical X-ray techniques. This thesis contains three experimental studies of high-power laser-plasma interactions as sources of radiation for Homeland Security applications, especially at kilohertz repetition-rates using few- millijoule pulses. First, a neutron generation experiment was conducted using a high repetition-rate laser system (1⁄2 kHz) at the University of Michigan. A heavy water (D2O) stream was irradiated by 40 fs pulses, each containing a few millijoules of energy. Acceleration of deuterons (to E < 1 MeV) was achieved through plasma sheath acceleration. Ensuing DD nuclear fusion reactions, in turn, generated neutron fluxes of up to 10^5 s^−1 into 4π steradians. In order to understand the neutron source characteristics, deuteron spectra were measured with CR39 detectors and compared to particle-in-cell (PIC) relativistic plasma dynamics simulations. The neutron source characteristics were analyzed using various neutron detection techniques, including Time-of-Flight measurements, bubble detectors, and neutron-capture gamma-ray measurements. Second, THz generation from laser filamentation in air was investigated. For security applications, THz can complement X-ray scanning, because THz can detect non-metallic materials and dangerous chemicals while not ionizing the sample. Even though there have been extensive studies on THz generation from laser filamentation processes, the exact generation mechanisms are yet to be determined. In this thesis, optimization of THz radiation using an adaptive optic with active feedback was demonstrated. Using a genetic algorithm, the THz radiation was improved six-fold without the need for detailed knowledge of the mechanisms. In particular, the use of a high repetition-rate laser system accelerated the optimization of the THz signal. Another strength of this optimization system is that it can enhance certain THz generation mechanisms depending on the experimental circumstances. Lastly, using a nanosecond pulsed high-power laser system (10 Hz), a long-range detection technique was developed for detection of special nuclear materials. Although direct detection of radiation from nuclear materials can be defeated by radiation shielding, leakage of radiation-ionized gases can provide an alternative indicator of the existence of nuclear materials. For instance, in the presence of ionizing radiation, the ratio of ionized nitrogen to neutral nitrogen would be higher than in no-source air-plasma conditions. By inducing optical breakdown (plasma) near a sample’s position, the ionization levels of the surrounding air were analyzed. To enhance the detection efficiency, an adaptive-optic feedback system was introduced with this ratio as a figure-of-merit. This resulted in a 50 % enhancement in the spectral ratio of the nitrogen lines. In addition, aerosol-initiated plasma spectra were distinguished from the original air-breakdown plasma, as a step toward practical deployment.PHDNuclear Engineering & Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145909/1/jmhah_1.pd

20th Space Simulation Conference: The Changing Testing Paradigm

The Institute of Environmental Sciences' Twentieth Space Simulation Conference, "The Changing Testing Paradigm" provided participants with a forum to acquire and exchange information on the state-of-the-art in space simulation, test technology, atomic oxygen, program/system testing, dynamics testing, contamination, and materials. The papers presented at this conference and the resulting discussions carried out the conference theme "The Changing Testing Paradigm.

Functional Modification of Materials and Synthesis of Nanostructures by Non-Equilibrium Atmospheric Pressure Plasma Processes

Widely employed for a steadily increasing number of industrial processes and experimental studies, plasma can be considered as one of the most pervasive and promising technology of our time. Differently from thermal plasmas, the potentialities offered by non-equilibrium plasmas, especially if working at atmospheric pressure, are still far away to be totally understood, since the surprising and sometimes unpredictable results, coming from studies carried out all over the world, bring out the growing versatility of this technology and its suitability for many applications intersecting our daily lives. The present dissertation, organized in two parts, is focused to present and discuss the results obtained from the Ph.D research activities carried out in the wide field of plasma and materials. The first part of the work is mainly aimed at investigating the potentialities of cold atmospheric plasmas (CAP) for the modification of materials, coating deposition and crosslinking of polymers. In the first two chapters, the conventional techniques and the CAP approaches most employed to carry out the processes will be briefly summarized. In the other chapters, organized by topic, the results achieved during the Ph.D research activities in the fields of surface material modification, coating deposition and crosslinking of polymers will be presented and discussed. The second part of the dissertation is linked to the investigation of the potentialities of plasma-induced chemistry in a liquid environment for the synthesis of nanostructures. Similarly to the first one, the second part of the dissertation will present an overview on the conventional and CAP assisted methods for nanostructures synthesis; moreover, in the second part of the last chapter, the Ph.D experimental activities aimed at synthesising CuO quantum dots in a liquid environment will be illustrated