Combined Super-Resolution Fluorescence and Coaxial 3-D Scanning Microwave Microscopy: Proof-of-Concept In-Liquid Live-Cell Imaging: Toward a Biological Nano-Radar

We present a proof-of-concept 3-D scanning microwave microscope based on a miniaturized coaxial probe combined with high-resolution fluorescence microscopy for in-liquid operation and live-cell imaging. The system simultaneously provides electric (GHz) and optical (super-resolution) imaging of live cells for broad applications in life sciences. It combines advantages offered by both open-ended coaxial probing and near-field scanning microwave microscopy (SMM) for accurate and quantitative local microwave measurements. The shielded tip minimizes unwanted absorption of microwaves by the biological media as compared to fringe fields of unshielded tips which we previously showed absorb over 90% of the signal and mask the true imaging signal. A proof-of-concept system built up with commercial off-the-shelf (COTS) components is demonstrated in the frequency range 0.01–6 GHz with micrometric spatial resolution, only limited by the coaxial probe geometry. Our work at the microscale lays the technological foundation for a true nano-radar in liquid cell imaging system that will come with further advances in nanofabrication technologies applied to coaxial probes and can be integrated with super-resolution optical microscopy, for an integrated full electromagnetic spectrum to probe biology at the nanoscale, from dc to lightwave.