Optical trapping with low numerical aperture objective lens

High numerical aperture (NA) objective lenses used in optical tweezers typically limit the axial working range below 100 μm and since these lenses have magnification at the higher end (typically 100X) offer a narrow field of view resulting studies possible only over a small sample volume. Therefore, the light gradient field of phase engineered multiple plane wave three dimensional interference patterns generated at the focal plane of a low NA objective lens was used to stably trap particles in three dimensions. By employing a spatial light modulator to phase engineer the interfering plane waves the approach could be used to generate single or multiple trap points. Objective lens with NA 0.55, working distance as long as ~ 9 mm and magnification of 50x could be used to optically trap objects allowing for manipulation as well as imaging over a large sample volume using this technique.