Soltani, M. et al. Nat. Nanotechnol. 9, 448–452 (2014).

Optical trapping is a powerful approach for making single-molecule biophysical measurements. These laser-based tools are limited, however, to manipulating one molecule at a time. Soltani et al. describe a new platform that allows high-throughput optical trapping on a chip, based on a nanophotonic standing-wave array. In a fluidic trapping region of the chip, exposed waveguides form stable optical traps at the antinodes of a standing-wave evanescent field. This configuration allows the laser beam to be recycled, forming an array of optical traps, without increasing laser power. An integrated electric microheater enables controlled trapping array repositioning. The researchers demonstrated their platform by sorting single DNA molecules suspended between two trapped beads, showing promise towards high-throughput analysis of single biochemical reactions.