Surfaces and Materials
Plasmas are an indispensable tool for material synthesis and targeted surface modification. They can impart additional new properties to materials and allow the complete modification of the interfacial properties of components.
The research program Surfaces and Materials explores plasmas under low pressure and atmospheric pressure conditions to create materials with tailored material and surface properties. Bundling competencies in surface modification, thin film deposition and material synthesis based on low-temperature plasma technology, the research program designs customized solutions for the implementation of socially highly relevant topics such as energy materials, bioactive surfaces, biosensors as well as sustainable surface treatment & material synthesis. Surfaces and Materials bridges material synthesis, organization, functionalization, deposition, exfoliation and etching to explore emerging topics such as materials & processes for bio-inspired electronics.

With the aim to create application-centric solutions, INP provides expertise and competences in:

The wide range of applications is based on a number of method-related advantages of plasma technology, such as low thermal load on the components, environmental friendliness, controllability and low direct influence on the basic material properties. Since process costs and simple integration of plasma technology into existing production lines are of great importance, especially in industrial applications, INP offers many processes both at low pressure for highest purity and at atmospheric pressure for short process times.
INP has a long-standing experience in the development of plasma-assisted processes for the refinement of product surfaces, both in the life science sector and in the field of thin-film technology in general. Plasma- and ion-assisted processes span the spectrum from structured material deposition and the targeted adjustment of interface properties to the production of functional layers.
Research & Application Areas
Plasma-based deposition techniques open up versatile routes to create functional nanocomposites which contain an arrangement of multiple nanoscale components, such as nanoparticles. At INP, the research programme Surfaces and Materials develops innovative approaches to fabricate functional nanocomposites with applications in bio-inspired electronics, sensing and photonics.
Nanogranular matter, employing a network of distributed metal nanoparticles, is of particular interest for bio-inspired electronics and potential applications as physical reservoirs for in-materia reservoir computing. State-of-the-art gas phase synthesis and nanoparticle beam deposition is used to create nanogranular networks, which are poised at the threshold of percolation. These nanogranular networks exhibit collective resistive switching with dynamic transitions between multiple resistance states, which trace back to local rearrangements in the current paths throughout the network. To tailor stability and spatio-temporal properties of resistive switching, nanoparticulate systems can be combined with solid encapsulation or liquid host media.
Plasma-polymerized nanocomposites, created by combining monomeric precursors with metal and non-metal nanoparticles, are of interest for fields such as biosensors, optics and microelectronics. In particular, the incorporation of metal nanoparticles, like gold, into plasma-polymerized (pp) thin films can enhance signal amplification for biosensors. This enhancement is due to the nanoparticles' high conductivity, catalytic properties, stability, and biocompatibility, which complement the inherent function of the pp films in immobilizing bioreceptors.

→ Materials for Energy Technologies
Advanced materials are at the heart of hydrogen and ammonia technologies for the energy transition. Within Materials for Energy Technology, high performance nanomaterials are developed for storage and conversion of renewable energy such as electrolysis, battery and fuel cell technologies. INP core expertise in vacuum deposition and atmospheric plasma synthesis from liquid and solid precursors are utilized to develop cost-efficient and scalable synthesis processes, electroceramic thin films and redoxactive 2D nanohybrids. Another important pillar of our work is the characterization of the crystal and nano- or microstructure of the materials by means of XRD, TEM/SEM, EDX, XPS, gas adsorption, thermal gravimetric analysis, UV/Vis, FT-IR and Raman spectroscopy as well as a screening of the electrochemical properties, e.g. by cyclic voltammetry and impedance measurements.

Solar materials are materials for converting sunlight into usable electrical energy or heat in photovoltaic or solar thermal systems. To do this, they must effectively absorb the incident light and have a high conductivity in order to transport the absorbed energy. Due to their outdoor environment, they require high resistance to environmental conditions such as humidity and UV radiation. Solar materials are designed as thin film stacks, combining the properties of semiconductors, metals and dielectrics for specific applications. Their performance can be further optimized through plasma surface treatments to enhance durability and absorption characteristics. Spin coating processes and magnetron sputtering are mainly used for their fabrication.

For a variety of applications, it is important that proteins are immobilized on surfaces. Whether a protein that is anchored to a surface shows its natural activity depends strongly on the type of anchoring. For example, linkers and spacers, are used for the covalent coupling of proteins to surfaces. The decisive factor is that the protein retains its natural activity. Although enzymes are sometimes very specific and selective, in many cases they do not fulfil the process stability required in industrial applications. To improve stability, the enzyme or biocatalyst can be immobilized and the yield increased by plasma-assisted surface modification of the carrier material.
The surface determines the adhesion properties when a work piece is brought into contact with organic, inorganic or living matter. Adhesion to different media can be tailored to a large extent by precise control over the surface properties, e.g. by modifying surface roughness or its chemical composition. Plasma polymer surface coatings, both from low pressure plasmas and atmospheric pressure plasmas, offer an interesting pathway to precisely tune adhesion behaviour, ranging from hydrophilic, hydrophobic, oleophilic or oleophobic surfaces towards cell-attracting and cell-repelling surfaces. The key to obtain targeted surface modifications lies in precise control over precursor chemistry and plasma parameters, enabling e.g., to achieve PFAS-free antiadhesive coatings even without the use of fluorine-containing precursors.
Microfluidic systems are of great importance for bioanalysis and integrate analytical functions such as sample introduction, chemical and biochemical reaction and detection on one chip. With the help of plasmas and masked/maskless approaches, chemically different microstructures can be created on a variety of materials in a targeted manner. Multi-step plasma process sequences can be used to create a combination of cell-attracting and cell-repelling areas on the surface.
Application of thin films enables controlled enhancement in material properties. Depending on the application, the coatings fulfil special functions: in the case of tribologically stressed components, they reduce mechanical abrasion or, in the case of metals, the tendency to corrosion. They serve to improve the adhesion of material composites, have a decorative character, make it easier to keep clean or can give the surface of plastics increased scratch protection. As a structurally conformal, low-porosity and transparent barrier layer, they prevent the permeation of gases (e.g. in PET bottles) or protect sensitive goods from the diffusion of solvents from the wall of plastic containers. In semiconductor technology and optics, coatings take on functions as dielectrics, EMC shielding or anti-reflective layers. A particular interest lies in photocatalytic and ceramic surfaces:
Photocatalytic surfaces are characterized by a layer of a transition metal oxide, usually TiO2, which is activated by irradiation. Thus, in combination with a naturally present thin film of water, for example, OH radicals are produced, which then interact with cells, microorganisms, fats and other liquids. Such surfaces are particularly advantageous for implants. TiO2 is approved as a material for medical implants, so that there are no major hurdles to overcome with regard to the approval of such a refined implant as a medical product.
Ceramic surfaces are often used in technical as well as biomedical applications. Compared to conventional processes, the already established method of plasma spraying allows the creation and development of unique coatings with complex property portfolio. The uniqueness of the process lies in the almost arbitrary combination possibilities and mixtures of powders (metals, glasses, ceramics, polymers, etc.) and the high material deposition rate or layer thickness. In the biomedical field, coatings with TiO2, CaCO3, Cu, Ag, ZnO and their mixtures are the core competence of the INP. The system used at INP is an industrial system with a very common plasma source. This has the advantage that coatings and coating systems developed with it can be directly used by the customer or ordered from established contract coaters without process scaling.
Competence Portfolio
The research programme Surfaces & Materials focuses on plasma-technology to create tailored thin films & coatings via its expertise in
- physical vapor deposition (e.g., magnetron sputtering in DC, RF and HiPIMS mode)
- chemical vapor deposition approaches (e.g., plasmapolymerization via low-pressure microwave plasmas)
- deposition processes at atmospheric pressure conditions (e.g., atmospheric plasma spraying)
To control the thin film’s microstructure as well as its morphological, electrical, mechanical and compositional properties, INP approaches a deeper understanding of process-property relations by intertwining plasma technology, plasma characterization (diagnostics and modeling) and surface & material characterization.
Utilizing water-based electrolytes, plasma-electrolytic processes provide a versatile and eco-friendly solution for fine cleaning, polishing and deburring of metallic surfaces, which traces back to the creation of local plasma discharges in the vapor-gaseous envelope at the surface of the work piece. Apart from tailored material removal in plasma-electrolytic polishing, in plasma-electrolytic oxidation also the chemical composition of the surface can be modified.
Nanomaterials, owing to their nanoscopic dimensions, offer unique physico-chemical properties, which make them promising for applications in fields such as plasmonics, sensing and catalysis. At INP, complementary plasma-based approaches are pursued to create a large range of nanomaterials.
Nanoparticles from nanoparticle beam deposition can be obtained from a supersaturated metal vapor via a magnetron-based gas aggregation source, resulting in a high-purity, surfactant-free deposition with good process control on all vacuum-compatible substrates, ranging from solid substrates, over fabrics and fibers, flexible and soft substrates towards liquids. Gas phase synthesis enables fabrication of complex nanoparticles with tailored composition (controlled alloying) and morphology (core-shell, core-satellite, multicore-shell). To gain a deeper understanding of the processes involved in nanoparticle formation within the gas aggregation source, we have introduced a variety of in-situ diagnostic techniques that allow for enhanced monitoring and control of the deposition process.

In-liquid plasma processing (ILP) is a new eco-friendly and single-step process for the production of nanomaterials at high cost-efficiency. ILP synthesis exhibit attractive advantages, such as a simple reactor design and rapid processing times, no need of toxic chemicals and can easily be upscaled and operated as a continuous process. Production of nanoparticles by ILP can be carried out from solid and liquid precursors and enable production routes via exfoliation, pyrolysis, fragmentation or crystallization of nanomaterials. Also, hydration, intercalation, functionalization, and phase transitions may occur in ILP synthesis, giving rise to a large range of new structures formed. Charged and neutral species with different energies, lifetimes, and densities may be produced by specific adaption of the electrode setup, precursor solution or suspension, applied voltage, frequency, pulse width, and process time.

To design plasma-derived surfaces and materials for functional applications requires intricate understanding of process-property-function relations. Therefore, a through characterization of Surfaces and Materials is at the heart of the competences of research programme. The analytic competencies span state-of-the art methods to determine the compositional, morphological, structural, electrical and mechanical properties of materials and surfaces. The core competences and analytical set-ups are collected in the Laboratory for Surface Diagnostics and Laboratory for Materials Characterization.
Project Topics
The spread of electric vehicles is increasing and their market share is growing rapidly. However, there are still limitations to electric mobility in terms of range compared to conventional combustion engines. In addition to larger battery capacities, improvements can be achieved through increased efficiency and lower vehicle weight.
To this end, the Leibniz Institute for Plasma Research and Technology (INP) has conducted research in the joint project 'Integrative Layer Heating Module' together with the partners
- Webasto Thermo & Comfort SE; Webasto Neubrandenburg GmbH
- Fraunhofer Institute for Large Structures in Production Engineering IGP
- Welding Technology Training and Testing Institute Mecklenburg-Vorpommern GmbH
on technical solutions for electric vehicle heaters. The core component is a heating module that uses thin layer structures for heating. This allows the high-voltage components in electric vehicles to be used effectively at their optimal operating point while saving moving mass. The introduction of such heating modules thus brings both economic and ecological advantages.
Essential for the quality of the product is the production of thin ceramic and metallic layers. These are applied by means of atmospheric pressure plasma spraying. Although this process has already proven itself for years in many areas of thin-film technology, its practical application in industrial manufacturing processes raises questions regarding the homogeneity of the layer thickness to be achieved, the utilisation of the raw material, the material properties to be achieved, the process stability over time or even the life cycle of the plasma torches.
This is where INP comes in with its many years of expertise in the field of plasma diagnostics and plasma technology. Optical methods (spectroscopy and high-speed photography) are used to characterise the plasma properties of the plasma spraying systems involved in production and to visualise layer growth. The experimental findings are complemented by numerical simulations and combined to form a well-founded picture of the plasma process.
From process monitoring to targeted process control, the project contributes to producing products of a consistently high quality and to making the manufacturing process more effective by reducing maintenance.
Particle composites are processed into high-quality components by means of sintering, among other things. The material and form-fit structure of several materials means that the porosity changes in each production step. This is largely dependent on the parameters of the production processes, has a significant influence on the properties of the finished product and therefore makes it necessary to test the density of the workpieces between the individual production steps before tempering/sintering.
Up to now, the density of workpieces has typically been measured in the laboratory, which is time-consuming and cost-intensive. The laboratory measurement methods that represent the state of the art (e.g. micrograph analysis, gas pycnometry) therefore entail practical process times of 1-2 days.
In contrast, the Archimedes' principle measurement method allows non-destructive and rapid density measurement and can also be integrated directly into production processes. However, the application of this method to porous objects that are unstable to moisture, such as green and brown bodies, i.e. ceramic components before the firing or sintering process, has so far been made difficult or impossible by their absorption of liquid during the measurement. This can be remedied by a thin functional coating whose barrier effect effectively suppresses the liquid absorption of the measurement object.
The aim of the joint project with the partners
- Dimensionics Density GmbH
- University of Rostock, Chair of Microfluidics
- Leibniz Institute for Plasma Science and Technology e. V.
is the development of an automated system for the deposition of such a thin functional layer on porous components using plasma-enhanced chemical vapor deposition (PECVD) for non-destructive, production-integrated density measurement according to Archimedes' principle.
The project objective of the Leibniz Institute for Plasma Science and Technology e. V. is the development of such functional layers by means of PECVD, which allow the application of the measurement principle also for porous and sensitive components.
In order to achieve the project goal, different coating processes, plasma sources and chemical starting compounds for coating are being examined for their suitability. In addition to the proven low-pressure processes, the suitability of a locally effective atmospheric pressure plasma for this application is being researched in particular, for which a laboratory model is being set up as part of the project. The results will be evaluated and compared by characterizing the chemical composition and measuring the wettability of the functional layers.
Publications
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