NASA recently announced $100k grant to study the possibility of using laser tractor beams. What tractor beam concepts have been published but not been dis-proven?
Most of these effects are simply thermal gradients in air (or some other atmopshere).
Heat an area to the left of a molecule with a laser and the gas expands moving the sample right, a bit of careful control and you can move a dust particle into a sensor. Pulling it toward you is tricky, but you could have a very dispersed beam which comes to focus on the other side of the particle and blows it toward you.
It's not really star-wars tractor beams but Nasa's particular expertise these days is getting media attention.