Multifunctional microfluidic papers and ionic liquids as basis for selective and sensitive electrochemical sensors

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Objective of the project extension is to realize a new paper sandwich structure as a platform for a multifunctional element (microfluidic, emulsion-separating, locally temperature-controllable with phase change materials, electrochemical). This platform will leverage the efficient use of minimal amounts of ILs (ionic liquids) to enhance the selectivity and sensitivity of electrochemical heavy metal sensors. For an efficient extraction of heavy metal ions from aqueous solutions, ILs/water mixtures with a critical solution temperature between room temperature and water boiling temperature are to be used. Above the critical temperature, the IL mixes rapidly in the homogeneous solution. After falling beneath the critical temperature, an emulsion is formed in which the heavy metals are enriched in the IL phase. The slow settling behavior of the two phases should be improved by paper microfluidics. The emulsion is broken by contact with paper surface and then the IL phase is to be selectively transported further, where it is required for the electrochemical analysis. Furthermore, the negative influence of the low conductivity of the IL should be enhanced by increasing the temperature and minimizing the distance between the electrodes. Especially for the last point, tailor made papers are ideal, as they act simultaneously as spacer in the µm range and as fluid channel for the IL. In order to achieve sufficient locally variable temperature control in the paper sandwich structure, phase change material sandwich elements in combination with graphite paper heaters are being investigated. In the longer term, the objective is to establish a new platform for paper-based and electrochemical applications using the novel paper-sandwich structures.