Applying Magnetic Field to Carbon-Paste Electrodes for Electroanalytical Tape-and-paper-based Devices

The influence of magnetic fields on electrochemical systems is known as magnetoelectrocatalysis1. When an electrochemical reaction is carried out in the presence of an external magnetic field, there are two main sources of magnetic force: (1) the Lorentz force and (2) the force resulting from the magnetic properties of the redox molecules being investigated2. The Lorentz force is defined as the force on charge-carrying ions and is attributed to magnetohydrodynamic (MHD) effects. These MHD effects lead to an increase in the flux, which results in an increase in the current response. In our group, we have developed tape-and-paper-based electrochemical sensors for various applications, which can be improved using the application of external magnetic fields. To demonstrate this, we have applied commercial external magnets to a prototype of our tape-and-paper-based electrochemical devices. These devices are portable, flexible, low-cost and disposable. The prototypes utilize formulations of carbon paste as working and counter electrodes. Two formulations of carbon paste were developed, with and without iron (II, III) oxide magnetite particles. When characterized in potassium ferrocyanide, both types of carbon paste electrodes have a similar current response compared to the devices made with commercial graphite paint electrodes. The electroactive surface area was investigated using different electrochemical techniques and showed to be greater than that of the painted devices. Cyclic voltammetry (CV) was used to demonstrate the current increase in the presence of the external magnet for both types of carbon paste electrodes in two different redox solutions. Additionally, it was demonstrated that the magnet does not need to remain present during the CV scan for the increase to be observed. These devices show promise as well for further improvements in other prototypes used for various sensing applications.