Plasmonic Nanotweezers for Biophysics
There are some pretty interesting tools in science, and among them are optical tweezers. By focusing laser light correctly, it is possible to hold a transparent microscopic object, such as a living cell. For most microscopic cells, this tool is great, but you cannot go too small with them. Lens can only focus light to half the wavelength, and scientists cannot simply use a smaller wavelength of light, as this may lead to damaging or killing the cell. Fortunately, researchers at Harvard University have improved upon the design of plasmonic tweezers. Plasmons, a virtual particle created when light shines on a metal, can be focused down to a much smaller point than regular photons, but using them in tweezers have been difficult. The laser would be aimed at gold nano-disks on a sheet of glass, but the brightest point would actually be beneath the pillar, within the glass. This caused a great deal of heat, and the optimal point to hold a particle or cell to be somewhere unreachable. To solve both of these problems, the researchers replaced the glass with silicon topped with copper and gold. This substrate would conduct the heat away and moved the optimal point to around the gold nano-disks. This may lead to the next-generation of optical tweezers with its ability to capture smaller objects.