Rino Morent

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.

Non-thermal plasmas for non-catalytic and catalytic VOC abatement

This paper reviews recent achievements and the current status of non-thermal plasma (NTP) technology for the abatement of volatile organic compounds (VOCs). Many reactor configurations have been developed to generate a NTP at atmospheric pressure. Therefore in this review article, the principles of generating NTPs are outlined. Further on, this paper is divided in two equally important parts: plasma-alone and plasma-catalytic systems. Combination of NTP with heterogeneous catalysis has attracted increased attention in order to overcome the weaknesses of plasma-alone systems. An overview is given of the present understanding of the mechanisms involved in plasma-catalytic processes. In both parts (plasma-alone systems and plasma-catalysis), literature on the abatement of VOCs is reviewed in close detail. Special attention is given to the influence of critical process parameters on the removal process.

Adhesion enhancement by a dielectric barrier discharge of PDMS used for flexible and stretchable electronics

Currently, there is a strong tendency to replace rigid electronic assemblies by mechanically flexible and stretchable equivalents. This emerging technology can be applied for biomedical electronics, such as implantable devices and electronics on skin. In the first step of the production process of stretchable electronics, electronic interconnections and components are encapsulated into a thin layer of polydimethylsiloxane (PDMS). Afterwards, the electronic structures are completely embedded by placing another PDMS layer on top. It is very important that the metals inside the electronic circuit do not leak out in order to obtain a highly biocompatible system. Therefore, an excellent adhesion between the 2 PDMS layers is of great importance. However, PDMS has a very low surface energy, resulting in poor adhesion properties. Therefore, in this paper, PDMS films are plasma treated with a dielectric barrier discharge (DBD) operating in air at medium pressure (5.0 kPa). Contact angle and XPS measurements reveal that plasma treatment increases the hydrophilicity of the PDMS films due to the incorporation of silanol groups at the expense of methyl groups. T-peel tests show that plasma treatment rapidly imparts adhesion enhancement, but only when both PDMS layers are plasma treated. Results also reveal that it is very important to bond the plasma-treated PDMS films immediately after treatment. In this case, an excellent adhesion is maintained several days after treatment. The ageing behaviour of the plasma-treated PDMS films is also studied in detail: contact angle measurements show that the contact angle increases during storage in air and angle-resolved XPS reveals that this hydrophobic recovery is due to the migration of low molar mass PDMS species to the surface.

Penetration of a dielectric barrier discharge plasma into textile structures at medium pressure

Plasma treatment of textiles is becoming more and more popular as a surface modification technique. Plasma treatment changes the outermost layer of a material without interfering with the bulk properties. However, textiles are several millimetres thick and need to be treated homogeneously throughout the entire thickness. To control the penetration depth of the plasma effect, it is necessary to study the influence of operating parameters. Three layers of a 100% polyester non-woven are treated in the medium pressure range (0.3?7?kPa) with a dielectric barrier discharge to study the influence of pressure and treatment time. Current and voltage waveforms and Lichtenberg figures are used to characterize the discharge. Process pressure proved to have an important effect on the penetration of the plasma through the textile layers. This is caused not only by the pressure dependence of diffusive transport of textile modifying particles but also by a different behaviour of the barrier discharge.

Nonthermal Plasma Sterilization of Living and Nonliving Surfaces

The recent tremendous progress in understanding physical plasma phenomena, together with the development of new plasma sources, has put a growing focus on the application of nonthermal plasmas in the biomedical domain. Among several novel applications, the inactivation of bacteria by nonthermal plasmas (so-called plasma sterilization) is particularly interesting. This introductory review provides a summary of the current status of this emerging research field. In addition to the inactivation of bacteria on nonliving surfaces, this review also focuses on the sterilization of living surfaces, such as animal and human tissues. Clearly, nonthermal plasmas have undoubtedly great potential as a novel method for low-temperature sterilization.

Surface Modification of Non-woven Textiles using a Dielectric Barrier Discharge Operating in Air, Helium and Argon at Medium Pressure

In this paper, polyethylene terephthalate (PET) and polypropylene (PP) non-wovens were modified by a dielectric barrier discharge in air, helium and argon at medium pressure (5.0 kPa). The helium and argon discharges contained a fraction of air smaller than 0.1 %. Surface analysis and characterization were performed using X-ray photoelectron spectroscopy, liquid absorptive capacity measurements and scanning electron microscopy (SEM). The non-wovens, modified in air, helium and argon, showed a significant increase in liquid absorptive capacity due to the incorporation of oxygen-containing groups, such as C—O, O—C=O and C=O. It was shown that an air plasma was more efficient in incorporating oxygen functionalities than an argon plasma, which was more efficient than a helium plasma. SEM pictures of the plasma-treated nonwovens showed that the hydrophilicity of the nonwovens could be increased to a saturation value without causing physical degradation of the surface. The ageing behavior of the plasma-treated textiles after storage in air was also studied. It was shown that during the ageing process, the induced oxygen-containing groups re-orientated into the bulk of the material. This ageing effect was the smallest for the argon-plasma treated non-wovens, followed by the helium-plasma treated non-wovens, while the air-plasma treated non-wovens showed the largest ageing effect.

Multi-pin-to-plate atmospheric glow discharge for the removal of volatile organic compounds in waste air

A DC-excited atmospheric pressure glow discharge in a multi-pin-to-plate electrode configuration is applied to the removal of trichloroethylene (TCE) in air. A removal fraction of up to 47% is obtained at an energy density of 35 J litre−1 (air flow rate: 60 m3 h−1; residence time: 50 ms; TCE inlet concentration: 120 ppm; temperature: 298 K). The addition of TCE increases the discharge impedance and improves the uniformity of the current distribution in the direction of the gas flow. In the investigated inlet concentration range (0–160 ppm), no influence of the TCE admixture is observed on the corona-to-glow and glow-to-spark threshold currents. Experiments with other volatile organic compounds (VOCs) reveal that molecules containing a double carbon bond have the lowest energy requirement for decomposition.

Antimicrobial nano-silver non-woven polyethylene terephthalate fabric via an atmospheric pressure plasma deposition process

An antimicrobial nano-silver non-woven polyethylene terephthalate (PET) fabric has been prepared in a three step process. The fabrics were first pretreated by depositing a layer of organosilicon thin film using an atmospheric pressure plasma system, then silver nano-particles (AgNPs) were incorporated into the fabrics by a dipping-dry process, and finally the nano-particles were covered by a second organosilicon layer of 10-50 nm, which acts as a barrier layer. Different surface characterization techniques like SEM and XPS have been implemented to study the morphology and the chemical composition of the nano-silver fabrics. Based on these techniques, a uniform immobilization of AgNPs in the PET matrix has been observed. The antimicrobial activity of the treated fabrics has also been tested using P. aeruginosa, S. aureus and C. albicans. It reveals that the thickness of the barrier layer has a strong effect on the bacterial reduction of the fabrics. The durability and stability of the AgNPs on the fabrics has also been investigated in a washing process. By doing so, it is confirmed that the barrier layer can effectively prevent the release of AgNPs and that the thickness of the barrier layer is an important parameter to control the silver ions release.

Decomposition of Toluene with Plasma-catalysis: A Review

Abstract Non-thermal plasma (NTP) generated at atmospheric pressure has been widely applied to abate the harmful emission of gaseous pollutants such as volatile organic compounds (VOCs). These studies have proven the existence of some drawbacks that hinder commercialization, such as a low energy efficiency and mineralization degree with the formation of undesired byproducts as a consequence. Recently, NTP has successfully been combined with catalysis in an attempt to solve these issues through complex interacting mechanisms. Toluene can be regarded as being the most frequent studied VOC for removal with plasma-catalysis on laboratory scale. Therefore, this paper aims at reviewing the current research on this model VOC.

Measuring the wicking behavior of textiles by the combination of a horizontal wicking experiment and image processing

A horizontal wicking experiment is proposed to measure the wicking behavior of textiles. A syringe supplying a continuous flow of distilled water is in contact with the absorbing fabric resulting in a wicking region. The increase in wicking area or the wicking area after a certain time is recorded with a digital camera. The picture analyzing process is automated by the use of two complementary image segmentation algorithms: morphological segmentation and region merging. Where commercial image analyzing software fails due to the specific porous structure of textiles, the developed algorithms succeed in calculating the wicking area semiautomatically. It is shown that the newly developed technique is able to test the wicking behavior of, e.g., a cotton fabric and a plasma treated polyester nonwoven.