We aim at laying the foundations of a novel paradigm in optical sensing by introducing molecule-specific strong light-matter interaction at mid-infrared wavelengths through the engineering of plasmonic effects in group-IV semiconductors.The key enabling technology is the novel germanium-on-silicon material platform: heavily-doped Ge films display plasma frequencies in the mid-infrared range. This allows for the complete substitution of metals with CMOS-compatible semiconductors in plasmonic infrared sensors, with enormous advantages in terms of fabrication quality and costs. Moreover, the mid-infrared range offers the unique opportunity of molecule specificity to target gases in the atmosphere, analytes in a solution or biomolecules in a diagnostic assay.We will develop sensing substrates containing infrared antennas and waveguides with antenna-enhanced detectors. Antennas and waveguides will be made of heavily-doped Ge to fully exploit plasmonic effects: high field concentration to increase sensitivity, resonant coupling to vibrational lines for chemical specificity, deeper integration to decrease costs. To achieve our goals we will rely on semiconductor growth by chemical vapor deposition, electromagnetic simulations, micro/nanofabrication of devices and advanced infrared spectroscopy. We aim at studying the fundamental properties of new materials and devices in order to assess their potential for sensing.Impacts of the proposed research go far beyond transforming optical sensing technology. Lab-on-chip disposable biosensors with integrated readout for medical diagnostics would radically cut healthcare costs. The possibility of actively tuning electromagnetic signals by electrical and/or optical control of the plasma frequency in semiconductors holds promises for dramatic opto-electronic integration. Finally, plasmonic semiconductor antennas will impact on photovoltaics, light harvesting and thermal imaging.