11-Mercaptoundecyloxytrimethylsilane is a bifunctional molecule used as a surface modifier in nanotechnology, materials science, and biosensor applications. The thiol (-SH) group enables strong chemisorption to gold or other noble metal surfaces, forming self-assembled monolayers (SAMs) that provide a stable, ordered platform for functionalization. The trimethylsilyloxy (-O-Si(CH3)₃) group serves as a protecting group for the underlying alcohol functionality, which can be deprotected under mild conditions to yield a hydroxyl-terminated SAM for further chemical modification or attachment of biomolecules, ligands, or polymers. This makes it valuable for immobilizing thiol-reactive or hydroxy-compatible molecules on gold-coated oxide substrates in biosensors and diagnostic devices. In microelectronics and MEMS, it reduces stiction, controls wettability, and modifies interfacial energy by creating anti-adhesive coatings on metallic components. Unlike traditional silane coupling agents, it does not form covalent bonds to silica or oxide surfaces directly but is often used in hybrid systems combining gold and oxide layers.