Precise determination of electric field applied to charged materials in liquid via van der Pauw technique

The electric field is a fundamental physical quantity that determines the characteristics or behavior of charged materials in liquids. The precise characterization of charged materials involving nanoparticles or biomaterials such as cells and extracellular vesicles (EVs) requires a rigorous calculation of the electric field applied to these materials. However, unlike solid-state materials, the precise measurement of the electric field applied in liquids is challenging because of liquid-electrode interface resistance and non-uniform electric-field regions near electrodes. This study proposes a method for determining the precise electric field in liquids using the van der Pauw measurement technique. The conductivity of the liquid was measured using a microfluidic channel with a van der Pauw configuration. The electric field in the liquid was then calculated based on the relationship between the conductivity and current density. The accuracy of the proposed method was verified by measuring the conductivity of standard solutions and phosphate-buffered saline (PBS), followed by determining the electric field applied to the nanoparticles in these solutions. In addition, the proposed method was used to determine the zeta potential of charged nanoparticles. This simple method for determining liquid conductivity and calculating electric fields in liquids could be effectively used for various electrochemical studies.