Manipulation of large, irregular-shape particles using contour-tracking optical tweezers

While the optical tweezers technique is a promising tool for manipulation of microparticles, its application to large (>50 µm) particles and irregular-shape ones is still a hard task. In this Letter, we propose what is to our knowledge a novel concept of contour-tracking optical tweezers (CTOTs), which extract the contour of the objective particle to form the illumination pattern of the trapping laser into the contour shape in real time. We demonstrated the trapping of polystyrene particles of irregular shape with the size of over 100 µm with CTOTs. Our approach has potential to open the way for expanding the applicability of optical tweezers by enabling manipulation of a variety of samples.