Electrochemical picobalance: Proof-of-principle for an electrochemical cantilever-based mass balance

Since the introduction of Faraday’s law, the combination of electrochemical methods with gravimetric techniques has been pursued very actively in the field of electrochemistry. Here, we present a proof-of-concept to combine electrochemical methods with the recently introduced picobalance, which originates from atomic force microscopy (AFM). The picobalance is a cantilever-based technique that can measure mass changes in the order of a few picograms. Hence, the development of fully insulated cantilevers with an integrated microelectrode (electrochemical balance probes, EBPs) was an essential prerequisite. The electrochemical deposition of copper allowed for a highly defined and continuous deposition of mass on the EBP. By comparing the faradaic current and the mass signal of the picobalance, the mass sensitivity of the latter has been determined as 4.6 fg⋅µm −2 ⋅Hz −1 (or ∼ 460 ng⋅cm − 2 ⋅Hz − 1 ). This value can be readily compared to the one for the electrochemical quartz microbalance (EQCM), which has been used here as a benchmark under the same conditions (17.5 ng⋅cm −2 ⋅Hz −1 ). However, in contrast to the EQCM, the picobalance is capable of measuring absolute masses as low as one picogram. The here-presented electrochemical picobalance allows for applications in electropolymerization, organic electronics, and bioelectrochemistry.