Manipulation of small particles in water using near field optics

The manipulation of small particles in liquid environments is crucial for biomedical research, environmental sensing, and nanotechnology. Plasmonic metamaterials, particularly Fano-resonant nanostructures, enhance trapping efficiency while reducing laser power to 0.5mW. We demonstrate stable trapping of 20nm gold particles with trap stiffnesses of 4.18 ± 0.2(fN/nm)/(mW/μm²). In addition, opto-thermophoretic forces enable rapid lipid vesicle migration at 1.77µm/s under a 7.3% w/v PEG solution with laser power of 1mW. By integrating optical and thermal forces, we achieve precise nanoparticle control, highlighting near-field optics’ potential for nanoscale manipulation, targeted delivery, and particle sorting in fluidic environments.