PLASMA ENABLED NANOFABRICATION AND APPLICATIONS – Research
 Plasma Nanotechnology & Applications

Plasma nanotechnology, plasma surface engineering for “smart” multifunctional surfaces, and plasma applications

  1. Our plasma technology and nanotechnology toolbox

Our research activities focus mainly in developing new plasma processes in vacuum and atmospheric conditions, as well as novel plasma processing apparatus for materials processing. These processes and apparatus are used for surface engineering, fabrication of multifunctional surfaces with wetting control, and biological property control, processing of microfluidics, sensors and other devices, food preservation, energy applications, safety, and many more fields.

We have pioneered the plasma micro-nanotexturing technology and have designed and patented a novel related plasma reactor, which we term “nanoinhibit” reactor based on anisotropic ion-enhanced plasma etching with simultaneous controlled flux of co-sputtered etching inhibitors (see Fig. 1.1). The new plasma reactor is based on control of the area of electrode surface which is sputtered by ions. The control is achieved by a variable shield of specific areas of the electrode. This technology has allowed us to spin-out tens of different applications towards smart functional surfaces and devices as we will explain below. Fig. 1.1 shows a picture from our EPO patent application on how to control the amount of texture produced during etching by changing the shielding of the biased electrode and the control in texture achieved by changing the amount of shielding.

Our technology toolbox is not limited to vacuum plasmas. We have been working for several years now on dielectric barrier discharges for larger area surface processing and nanofabrication. A novel patented DBD design has allowed us to process large area samples. Fig. 1.2 shows the patent-pending DBD reactor design. This is again based on selective shielding of the RF fields.  This new experience in atmospheric plasmas has allowed us again to spin-out several applications towards surface engineering, food processing, and “smart” functional surfaces. In addition, we have observed surface nanostructure formation with atmospheric plasma (fig. 1.3), and etching and nanofabrication for the first time using atmospheric pressure plasma

 

 Plasma Nanofabrication

In terms of nanofabrication, we have been active in nanoscale etching of Silicon creating ultrahigh aspect ratio silicon nanowires perpendicular to the Silicon substrate using both cryogenic and nanoscale gas chopping (Bosch-like) processes. We have studied the bundling of these nanowires (Fig. 1.4), their optical properties, and their application for radial or axial junction photovoltaic devices (Fig. 1.5).

Surface engineering for wetting and optical property control

Our group has acquired expertise in wetting control of surfaces at its extremes namely superhydrophobic, superoleophobic, superamphibhobic, and superhydrophilic surfaces, focusing first on polymers. Using our plasma micro-nanotexturing technology, almost all polymers can be rendered superamphiphobic followed by a hydrophobic film deposition. Such surfaces have shown extreme durability on drop impact (up to 30 atm impact pressure), as well as everlasting underwater durability. Such surfaces have been applied for reduced friction, showing almost an order of magnitude reduced static forces compared to simple hydrophobic surfaces, and for optical applications such as antifogging surfaces, or transparent, antireflective and self-cleaning surfaces. Several examples are shown in Fig. 2.1-2.5

Surface engineering for biofunctionality control

Our group has also pioneered the use of micro-nanotextured surfaces for covalent-like biomolecule attachment leading to high density microarrays, or sensitive sensors, and high binding capacity microfluidics for biomolecule and cell capture. This work has been patented and has been the core technology of our spin-out company Nanoplasmas p.c. which develops area selective, highly binding, biomolecule, and bacteria capturing devices, as well as DNA purification, and cancer cell enrichment surfaces. See Fig. 3.1-3.6. A recent application of these smart surfaces has been their use as antibacterial surfaces, with a double action, namely antisticking and bactericidal with both mechanical and chemical bactericidal effects. Recently we have also started to use atmospheric pressure plasma etching of nanocomposite polymers, containing inorganic antibacterial nanomaterials. Plasma etching enriches the surface concentration of antibacterial agents and thus reduces the volume percent that is necessary for adequate antibacterial action.

Recent and running projects

  • Collaboration with BiC  (2017-2020)
    This was an industrial fellowship project co-funded by Stavros Niarchos Foundation and the company with grant holder Dr Kosmas Ellinas for 3 years, targeting low friction coatings for razor blades
  • Collaboration with Fasmatech (2018-2021)
    This was an industrial fellowship project co-funded by Stavros Niarchos Foundation and the company with grant holder Dr Athanasios Smyrnakis for 3 years, targeting the design and development of a hyperthermal hydrogen atom gun for top-down proteomics.
  • NOVISH : Application of High Pressure and Cold Plasma Technologies for the Production of high quality fish fillets with extended shelf life
    A recent application of atmospheric pressure plasmas has been their use for food preservation by reduction of the microbial load of fresh food. Two methods are used: direct plasma processing of the food matrix, and washing of the food matrix with plasma activated water. These routes are explored in a Hellenic funded project involving fish industry called NOVISH.
  • Harmonic : Energy efficient superhydrophobic metallic interfaces for drop-wise condensation-a FET (Future and Emerging Technologies project) funded by Horizon 2020 EU framework.
    We are exploring water condensation and water collection on superhydrophobic surfaces exhibiting dropwise rather than film-wise condensation. We are hoping to increase the heat transfer coefficient and contribute to huge energy savings in energy production. This is achieved by exploring two parallel routes: Texturing of metallic interfaces and rendering them superhydrophobic using durable coatings, or using flat metallic interfaces and coating them with thin micro-nanotextured polymeric interfaces. These two routes are explored in the HARMONIC project, an FET Horizon project.