Metamaterial tweezers for trapping and distinguishing nanoparticles

We have previously reported Fano resonance assisted plasmonic tweezers for ultrastable nanoparticle trapping based on fabricating an array of asymmetrical split nano-apertures on a 50 nm gold thin film. Here, we show that these tiny noble asymmetrical nano-apertures, with dimensions of a few tens of nanometers, serve as nanosources of heat generating large temperature gradients at Fano resonant excitation. As a result, thermophoresis occurs, leading to particle drift induced by temperature gradients in fluid mixtures. This thermophoretic trapping process plays an important role in controlling particle trapping location and thermal kinetic energies. Our findings could be relevant for downsizing microfluidics to the nanometric manipulation range, allowing us to distinguish between different types of nanoparticles such as single enzymes and dielectric particles.