Paper Dynamics

Paper Dynamics

Gaining better understanding of the mechanisms using wet strength agents for paper production

M.Sc. Jan-Lukas Schäfer (2018 – )

Wet strength paper has a broad range of application from tissue paper at home to lateral flow tests in paper-based analytics. Since paper built entirely out of cellulose fibres has no intrinsic strength in the wet state, the papermaking industry uses wet strength agents. Commonly used are polymers which attach to the fibers and shield them from water. After the papermaking process the papers are thermally annealed to attach the polymers to the fibers, which requires a lot of energy and has a high environmental impact. That’s why the research and development of new wet strength agents is of great importance. Photoreactive copolymers which are activated by UV-light can be used to covalently bond the fibers in the paper to each other and induce wet strength. Furthermore using fluorescently labeled polymer systems should allow for a better understanding of the mechanisms behind wet strength agents and how to improve their use in the papermaking process.

Towards reducing sensitivity loss in microfluidic paper-based analytical devices

M.Sc. Alexander Ritter von Stockert (2018 – )

Paper-based analytics provide a large array of potential uses, ranging from medicine, over environmental studies, to quality control in the food industry. While those devices excel in fields such as availability, cost and stability, they often lack the desired sensitivity that is needed to detect trace amounts. This can be due to unspecific adsorption to cellulose fibers, or to diffraction of light of colorimetric displays. To combat the unspecific adsorption of proteins to the fibers, the interactions need to be determined first and later suppressed, by the use of specific polymer coatings. The second block is accompanied by the principle of diffraction between two media with different diffraction indices. By changing that of the paper, to be closer to the one of air, a lower detection limit could be reached. The use of different fiber sources and paper porosities should yield a further understanding of their impact on fluid transport and unspecific adsorption.

Immobilization of ionic liquids in microfluidic papers as basis for electrochemical sensors

M.Sc. Tizian Venter (2018 – )

Functional composites of IL (ionic liquids) and microfluidic paper represent a new platform for electrochemical applications, especially sensors. These composites have the potential to circumvent the disadvantages of systems based on aqueous electrolytes (low potential window, evaporation losses and resulting measurement errors) and may additionally exploit the solubility properties of the IL for the selective enrichment of analytes. A possible application example may be the qualitative and quantitative analysis of heavy metal ions. Heavy metal contaminants can not biodegrade, posing a long-term problem for the ecosystem. Current standard procedures for analyzing such pressures require laborious laboratory studies. Simple methods for on-site diagnosis, such as paper-based electrochemical sensors, which can be carried out with little outlay on equipment, therefore have tremendous innovation potential. Due to the possibility of local control of paper properties such as e.g. the surface functionalization or porosity can be realized in microfluidic papers a defined liquid transport for the sensors.

Techniques to produce and analyse microfluidic channels

M.Sc. Niels Postulka (2017 – )

Microfluidic devices gained a growing interest over the last decades, especially their potential in point of care diagnostics, food safety, environment monitoring and veterinary medicine. The aim of the devices is to analyse an analyte for selected substances. Therefore, the compounds could be divided into a substrate to transport the analyte to one or several detectors to qualify and in some cases quantify the substance. One possibility is using paper-based substrates. This material provides interesting properties including porosity, through which liquid transport is possible, without using external pump systems. Since for microfluidic just small amounts of analyte are needed, it is necessary to modify the paper in structured hydrophobic and hydrophilic areas. To archive those properties there are several methods e.g. printing hydrophobic substances like wax onto paper, photolithography or 3D deformation of paper.

Tailorable fluid flow speed in paper using polymers

Tailoring the fluid flow speed by introducing polymers to paper.
Tailoring the fluid flow speed by introducing polymers to paper.

M.Sc. Marcel Krauße (2016 – )

Within the Merck Lab we are focused on the development of novel paper- based, low- instrumented analytical devices. This implies an extensive understanding of the interactions between paper and analytes, the fluid flow properties and ways how paper can be functionalized with antigens, enzymes etc. Newly developed paper based (hybrid) materials have to be tailored, functionalized and investigated. Well- established platform which are widely used in diagnostics and life science, as e.g. the home-use pregnancy test, are used for benchmarking.

The combination of cellulose (paper) and polymers enables the tuneability of fluid flow properties in tailor-made materials. The fluid flow is defined by the inherent porosity and surface chemistry of cellulose fibers and can be modified by using polymers. Those defined materials can be used to tune the fluid imbibition and could be applied as e.g. µPADs (Microfluidic Paper-Based Analytical Devices).