Two-layered metallic film induced surface plasmons for enhanced optical propulsion of microparticles

We demonstrate the use of surface plasmons (SPs) excited on a two-layered metallic film for enhanced particle propulsion. The extended SP field is predominantly attributed to propel particles with increased speed along metal-deposited regions. Various silver-gold combinations were used to quantify for the SP field enhancement. The underlying silver yields better SP evanescent field enhancement, while the overlying gold ensures that the stability of the sensing surface is not compromised. In comparison to the conventional single gold film SP resonance configuration for particle manipulation, the two-layered metallic structure enhances the propulsive force, as verified experimentally by $∼2.0$ times increase in particle velocities.