Improving charge-sensitive biomolecule sensors with the right choice of electrolyte

[Display omitted] •Signal optimization in FET-based sensors with electrolytic analytes is modeled.•Having large monovalent ions in the background electrolyte increases signal.•Low millimolar concentrations increases sensitivity of electrolyte flow sensors. Biomolecule detectors are crucial to many fields, from medicine to environmental conservation. One type of sensor detects charged biomolecules in solution by flowing an electrolyte over a receptor-functionalized surface (e.g., a transistor) before and after the analyte binds to the surface. This changes the surface charge, and a change in a device property like a conductance is measured. The change in the device property correlates with the concentration of analyte in the solution. While many groups have tested this method, most studies have only used electrolytes with small cations like potassium and calcium. Here, we use density functional theory of electrolytes to calculate how different electrolytes affect the output of these detectors. We determined that the signal of these devices could be improved by using electrolytes with a minimal concentration of large, monovalent cations. Likewise, the sensitivity of these devices can be improved with a moderate-to-low concentration of large, monovalent cations. Therefore, using electrolytes with large (∼0.9nm diameter), monovalent ions may increase the sensitivity of currently-used sensors.