Fountain pen for scanning electrochemical microscopy

A fountain pen probe has been developed to extend the scope of scanning electrochemical microscopy (SECM) experiments to dry surfaces. The fountain pen is fabricated by UV-photoablation of a polyethylene terephthalate (PET) film and consists on one side of one microchannel for flowing an electrolyte solution to the open tip, integrating a reference/counter electrode and on the other side a carbon track. The exposed tip of the track forms the working electrode located close to the microchannel outlet. The fountain pen can operate in a pointillist mode where a nanolitre droplet at the bottom of the probe connects it to a well-defined surface area to study locally the substrate, but can also operate in a scanning mode leaving a linear wet track of solution behind it to monitor the surface activity. The electrochemical characterization of the proposed fountain pen probe was performed by cyclic voltammetry, approach curves and lateral line scans over insulating and conductive substrates, showing that the flow rate and the probe-substrate distance have a major influence on its electrochemical behavior. An SECM image of a gold on glass EPFL logo is presented as a proof-of-concept that fountain pen probes can be employed for the detection of surface activity when scanning in a contact regime.