Novel Cost-Efficient Graphene-Based Impedance Biosensor for the Analysis of Viral Cytopathogenicity and the Effect of Antiviral Drugs

Biosensors become increasingly relevant for medical diagnostics, pharmaceutical industry, and environmental technology, for example, to test new drugs easily and reliably or to detect cell growth in changing environmental conditions. Novel materials like graphene are promising candidates to produce biosensors on an industrial scale by means of printing processes. To reach this aim, methods for the reliable and automated production of electrode structures and their coating are required. We present an impedance biosensor in the format of a microtiter plate, fabricated by highly efficient roll-to-roll printing of graphene-based microstructures on large-area polymer foils. Proof-of-principle experiments show the evidence of the suitability of the printed graphene biosensors for impedance-based monitoring of viral cytopathogenicity and its inhibition in the presence of antiviral drugs. The developed system is a promising approach toward cost-efficient impedimetric biosensors for high-throughput screening in vaccine research and antiviral drug development.

Optomechanical Processing of Silver Colloids: New Generation of Nanoparticle–Polymer Composites with Bactericidal Effect

The properties of materials at the nanoscale open up new methodologies for engineering prospective materials usable in high-end applications. The preparation of composite materials with a high content of an active component on their surface is one of the current challenges of materials engineering. This concept significantly increases the efficiency of heterogeneous processes moderated by the active component, typically in biological applications, catalysis, or drug delivery. Here we introduce a general approach, based on laser-induced optomechanical processing of silver colloids, for the preparation of polymer surfaces highly enriched with silver nanoparticles (AgNPs). As a result, the AgNPs are firmly immobilized in a thin surface layer without the use of any other chemical mediators. We have shown that our approach is applicable to a broad spectrum of polymer foils, regardless of whether they absorb laser light or not. However, if the laser radiation is absorbed, it is possible to transform smooth surface morphology of the polymer into a roughened one with a higher specific surface area. Analyses of the release of silver from the polymer surface together with antibacterial tests suggested that these materials could be suitable candidates in the fight against nosocomial infections and could inhibit the formation of biofilms with a long-term effect.

Electronic Multiscale Hybrid Materials: Sinter-Free Inks, Printed Transparent Grids, and Soft Devices

Hybrid electronic materials combine the excellent electronic properties of metals and semiconductors with the mechanical flexibility, ease of processing, and optical transparency of polymers. This talk will discuss hybrids that combine organic and inorganic components at different scales. Metallic and semiconductor nanoparticle cores are coated with conductive polymer shells to create “hybrid inks” that can be inkjet-printed and form conductive leads without any sintering step. Transparent electrodes are printed using ultrathin metal nanowires with core diameters below 2 nm. The chemically synthesized wires spontaneously form percolating structures when patterned with a soft stamp; this rapidly yields optically transparent grid electrodes, even on demanding soft substrates. These new hybrid electronic materials enable the fabrication of soft electronics, including flexible sensors on polymer foils, radio-frequency identification (RFID) antennae on cardboard, and soft human–machine interfaces. Selected devices will be covered at the end of the talk.

High-throughput roll-to-roll production of polymer biochips for multiplexed DNA detection in point-of-care diagnostics

Roll-to-roll UV nanoimprint lithography has superior advantages for high-throughput manufacturing of micro- or nano-structures on flexible polymer foils with various geometries and configurations.

Gold Nanopost-Shell Arrays Fabricated by Nanoimprint Lithography as a Flexible Plasmonic Sensing Platform

Plasmonic noble metal nanostructured films have a huge potential for the development of efficient, tunable, miniaturized optical sensors. Herein, we report on the fabrication and characterization of gold-coated nanopost arrays, their use as refractometric sensors, and their optimization through photonics simulations. Monolithic square nanopost arrays having different period and nanopost size are fabricated by nanoimprint lithography on polymer foils, and sputter-coated by gold films. The reflectivity of these gold nanopost-shell arrays present dips in the visible range, which are efficient for refractometric sensing. By finite-difference time-domain (FDTD) simulations we reproduce the experimental spectra, describe the electric fields distribution around the nanopost-shells, and then explain their good sensitivity, around 450 nm/RIU. Furthermore, we determine by simulations the influence of several geometrical parameters, such as array period, nanopost width, gold film thickness, and nanopost side coverage on both reflectivity spectra and sensing capabilities. Fully coated nanoposts provide an extremely deep reflectivity minimum, approaching zero, which makes the relative reflectivity change extremely high, more than two orders of magnitude higher than for partially coated nanoposts. These results contribute to the understanding of the plasmonic properties of metal coated nanopost arrays, and to the development of efficient platforms for sensing and other surface plasmon based applications.

Surface Processing of Polyethylene Terephthalate for Orientation of Nematics in Display Devices

Thermoplastic polymers have found widespread applicability in electronic industry owing to their facile processing and relatively low costs. Transparent polymer foils, like polyethylene terephthalate (PET), can be utilized in manufacturing components for liquid crystal display (LCD) devices. This work is focused on surface processing of PET through different procedures. The induced surface modifications of polymer samples were analyzed by optical microscopy. Contact angles of nematic drops on PET film are measured to evaluate how the method of surface modification reveals that the surface texturing affects the interactions of polymer with the liquid crystal. The influence of created surface anisotropy on the work of adhesion at polymer/liquid crystal interface is analyzed. Preliminary assessment of nematic orientation on the surface of modified PET foils is performed using polarized light. The results were discussed in regard with the used methodology to adapt the surface of the PET films to achieve optimal orientation of nematic molecules. The obtained data will open new perspectives on processing polymer foils as alignment layers used in LCD devices.

Adhesive-Free Bonding of Web-Like Plastic-Metal Combinations at Low Temperatures

A couple of research projects could demonstrate the adhesive-free bonding of metal and polymer foils very well in the past. The remaining issues on the road to industrial usage of this technology focus on higher process velocities, quality management and process behaviour during long-term usage. For this purpose, a new research project was initiated to concentrate on the maximum achievable adhesion between the two bonding partners at line speeds up to 10 m/min

Electron Irradiation Effects on Strength and Ductility of Polymer Foils Studied by Femtosecond Laser-Processed Micro-Tensile Specimens

The influence of irradiation on mechanical properties of polymer foils used in spacecraft applications has widely been studied via macroscopic tensile samples. An increase in the local resolution of this investigation can be achieved by reducing the sample’s dimensions. A femtosecond laser enables a fast fabrication of micro-samples with dimensions from tens of μ m to the mm range, with ideally no influence on the material. Tensile experiments using such micro-tensile samples were conducted on FEP, Upilex-S and PET foils. The influence of the laser processing on the polymer foils was evaluated. Additionally an investigation of degradation due to electron irradiation was performed. Furthermore an outlook to extend this technique to depth-resolved measurements by preparing samples from locally thinned foils is presented. The study demonstrates the feasibility of femtosecond laser processing for rapid fabrication of micro-samples, enabling insights into the effect of electron irradiation on local mechanical properties of polymers.