Optical tweezers use the momentum of photons to capture and manipulate particles in a noncontact way. Although related techniques have been widely used in biology and materials, research on viruses is still relatively limited. It is hard to optically trap viruses because trap stiffness is rather low and the size of viruses is too small. Here, we used an optical tweezers system coupled with a laser confocal fluorescence imaging system, which allows individual viruses to be imaged and trapped in real time and analyzed using multiple parameters in the culture medium. We show that a single virus tagged by quantum dots (QDs) can increase the real part of polarizability, further increasing gradient force and trap stiffness. With this method, we not only can trap and manipulate viruses in real time but also can analyze their interactions with other targets.
Keywords: permittivity; polarizability; quantum dots; trap stiffness; virus.