Plasmonic-Based Impedance Microspectroscopy of Optically Heterogeneous Samples

An optical label-free microscopy technique for high resolution imaging of electrical impedance is presented. To achieve this, surface plasmon resonance sensors are used to detect surface charge density modulation optically. Therefore, they provide the basis for computing electrical current and impedance. However, one of the major challenges of plasmonic-based impedance imaging is the contribution from the optical properties of the sample. Here, a correction method is presented as an effective way for isolating the effect of the optical heterogeneity. Using this technique, capacitance of bovine serum albumin (BSA) patterns was mapped with submicroscopic resolution. The work reported will enable electrical characterisation of cells and biomolecules with promising biophysical applications.