UC San Diego

In many situations there is a need to physically manipulate microscopic objects with as much dexterity as our own hands provide in the macroscopic world. An example would be applying stresses onto cells in order to determine their mechanical properties. Our existing microscope-laser experimental system is capable of manipulating microscopic objects using two optical tweezers and one optical scissors to move and cut these objects, respectively. Despite these capabilities, however, the point-and-click user interface for optical trapping and cutting was cumbersome and hard to use, limiting the system's potential for micro-manipulation. In order to resolve this limitation, a new, more intuitive and hands- on user interface using two joysticks was designed and developed from the ground up in order to provide responsive, real-time control of the optical tweezers and scissors for microscopic manipulation. This new joystick user interface was then used to verify whether or not forces other than those due to microtubule dynamics act upon chromosomes during mitosis, tested in mitotic PtK2 and Indian Muntjac cells by 1) depolymerizing microtubules using nocodazole, and 2) disrupting microtubules using laser ablation with optical scissors, and subsequently attempting to freely manipulate chromosomes using joystick -controlled optical trapping