The project titled Active tuning of plasmon resonances in gold nanoparticle arrays on elastomeric substrates for ultrasensitive dual MEF/SERS biosensing (OPTiGAP) aims to develop a disruptive approach to dual Metal-Enhanced Fluorescence (MEF)/ Surface-Enhanced Raman Spectroscopy (SERS) biosensing: plasmonic nanostructures will be designed such that both MEF and SERS can be excited by a single laser source, based on active tuning of localized surface plasmon resonances (LSPRs) favouring either MEF or SERS process. The dual MEF/SERS molecular sensing platform will exploit real-time mechanical tuning of LSPRs in designed gold nanoparticle arrays, allowing to modulate the electromagnetic field enhancements in nano-gaps such that the fingerprint-like SERS signal can be collected despite the overwhelming MEF intensity. After careful design based on electromagnetic simulations, gold nanoparticle arrays will be fabricated and characterized. Their plasmonic properties will be investigated and understood, in order to apply them for dual MEF/SERS detection of specific biomarkers as are membrane proteins used to differentiate/ classify various metastatic cancer cells (EGFR or EpCAM). The OPTiGAP project can contribute to expanding the use of MEF and SERS beyond proof-of-concepts studies into viable real-life applications, by developing biosensing protocols exploiting a fluorescence read-out for fast imaging and Raman fingerprinting for multiplexed molecular identification.