Towards microwave and millimter wave biosensors

Bio-sensing by electromagnetic waves from GHz towards THz frequencies, although not yet established as a common method for biomedical applications, offers challenging opportunities, which are complementary to the established optical methods, often based on plasmonic waves and resonances. The longer wavelength - in comparison to visible and IR provides a disadvantage in terms of the smallest possible interaction volume, which can be partially overcome by evanescent field methods. However, the high absorption of micro- and millimetre waves by liquid water, which is the most abundant component of biological substances, provides a unique observation window, which is substantially different and therefore complementary to the other parts of the electromagnetic spectrum.