title: An optical conveyor for molecules.
abstract: Trapping single ions under vacuum allows for precise spectroscopy in atomic physics. The confinement of biological molecules in bulk water is hindered by the lack of comparably strong forces. Molecules have been immobilized to surfaces, however often with detrimental effects on their function. Here, we optically trap molecules by creating the microscale analogue of a conveyor belt: a bidirectional flow is combined with a perpendicular thermophoretic molecule drift. Arranged in a toroidal geometry, the conveyor accumulates a hundredfold excess of 5-base DNA within seconds. The concentrations of the trapped DNA scale exponentially with length, reaching trapping potential depths of 14 kT for 50 bases. The mechanism does not require microfluidics, electrodes, or surface modifications. As a result, the trap can be dynamically relocated. The optical conveyor can be used to enhance diffusion-limited surface reactions, redirect cellular signaling, observe individual biomolecules over a prolonged time, or approach single-molecule chemistry in bulk water.
authors.affiliation: Physics Department, Ludwig Maximilians Universität München, Center for Nanoscience, Amalienstrasse 54, 80799 München, Germany.
authors.forename: Franz M
authors.initials: FM
authors.lastname: Weinert
authors.forename: Dieter
authors.initials: D
authors.lastname: Braun
mesh_terms: D003460:Crystallization / Q000379:methods*; D004247:DNA / Q000737:chemistry* / Q000528:radiation effects* / Q000648:ultrastructure; D046911:Macromolecular Substances / Q000737:chemistry / Q000528:radiation effects; D008422:Materials Testing; D008968:Molecular Conformation / Q000528:radiation effects; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods*; D052898:Optical Tweezers; D010316:Particle Size; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D046911:Macromolecular Substances; D004247:DNA