Modular Optical Tweezers (Thorlabs) provide users with a tool for trapping and manipulating microscopic-sized objects. These laser-based tweezers, or traps, have been employed in numerous biological experiments. Biological applications for optical tweezers include trapping viruses and bacteria, manipulating cellular structures, patterning of surfaces, and measuring forces of molecular motors and biological molecules such as DNA and proteins.
See the article "Optical trapping for undergraduates"