Light Trap for Nanoparticles ⚡ экспресс
An approach based on density-based topological optimization is proposed for designing plasmonic metasurfaces intended for optical trapping of nanoparticles. The forces acting on particles of various sizes and materials are calculated via the Maxwell stress tensor. The objective function is the maximization of the gradient (attractive) force under normal incidence of monochromatic light. First, free-form designs are explored, then fabrication constraints are imposed to obtain realizable planar structures. It is found that the topology of the optimal metasurfaces depends on the nanoparticle size and material, with greater trapping stiffness achieved for small particles. The resulting structures can enable selective mass trapping of particles, which is promising for biosensing, microfabrication, and the assembly of quantum systems.
Light flows like an invisible river. If you place an obstacle in the stream, the water whirls into eddies. Likewise, specially designed surfaces create light 'whirlpools' that catch nanoparticles like wood chips. Maxwell derived the formulas for light pressure back in the 19th century, and today algorithms based on them design a relief of the tiniest features, like a riverbed for this flow.
Such traps are embedded into aqueous solutions to capture and sort carbon nanotubes, viruses, and bacteria. They assemble microchips without mechanical contact and hold single atoms for quantum circuits. The designs are efficient and suitable for mass production.
🎯 Light can lift and hold a particle in the air, like an invisible tweezer. This phenomenon has been recognized with a Nobel Prize.
🎬 These light traps work like a 'tractor beam' from science fiction, attracting objects without touching them.