Abstract: Force exerted on a microobject by the focused laser beam can be as high as the gravity force acting on the object or even significantly higher. This implies that the laser light can be used to manipulate small objects (range size approximately 0.1 - 100 $mu@m) within a suitable immersion medium. This possibility is of a great practical importance, for example, for microbiology and molecular biology (manipulation of single living cells, cell organelles, chromosomes, etc.) as well as for micromachinery and other technical branches. We use a ray-optics-based model to determine the magnitude of forces exerted by laser light as the functions of laser beam, object and surrounding medium parameters. We study the influence of these parameters on the total force in order to find the optimal parameter combination for the most effective manipulation. We have employed these theoretical results in practice and succeeded in building up a 3D laser trap which we use to manipulate divinylbenzen spherical particles (10 - 35 $mu@m sized) and also irregularly shaped living protozoa cells in water medium.!5
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