Molecular diagnostic tools need to be capable of detecting specific biomolecules that serve as an indicator for a disease state, ideally in a robust and easy to use format, enabling implementation as a point-of-care device. As sample collection should be minimally invasive and not require specific medical expertise or qualifications, blood fingerprick samples (~20 ÂµL) are particularly attractive. Nanoscale field effect transistors are being explored as disposable point-of-care molecular diagnostic devices in the TSB/EPSRC-funded project "Low cost nanowire diagnostic platform" (see link below). However, nanoFET assays require a low, 1 mM or less, salt concentration to avoid Debye screening of antibody-bound analyte molecules and hence require a sample preparation step. For nanoFET analysis of blood biomarkers, this cannot be achieved by dilution of the sample because this could result in biomarker concentrations below the detection limit of the assay. In this project we are developing a simple dialysis cell which can remove a desired amount of salt by adjustment of the sample and water flow rates, while biomarkers with a molecular weight exceeding a set threshold value are retained. The cell is based on a cross-flow dialysis configuration with millifluidic channels on both sides of a track-etched membrane, enabling low sample volumes as required for fingerprick blood samples.