Fig. 3.

(a) Experimental results demonstrating 4D RI reconstruction of three bacteria (S. pombe, ~ 6 μm long and ~ 2 μm wide) while they have been optically manipulated by using a laser ring trap. This example shows real-time motion control achieved by simultaneously exploiting trapping and propelling optical forces. The cell labeled as B1 optically transported along the ring follows a pendulum-like motion (due to switching the rotation direction) as observed in Visualization 3 ^{(537KB, mp4)} . The time-lapse image confirms stable 3D confinement of the cells in the ring. (b) The positions of the confined cells have been tracked revealing their trajectory and velocity distribution during this experiment, see the corresponding local speed map. Note that some of these cells are undergoing division cycle with a clearly visible medial cavity. (c) Experimental 4D RI results demonstrating real-time reconfiguration of the transport trajectory, switching between triangle and ring laser trap. The time-lapse images reveal the corresponding flows of cells transported along the curves while their tracking confirm a nearly uniform velocity distribution for each case as shown in (d), see also Visualization 4 ^{(842.2KB, mp4)} . In these experiments the recording time was 20 s with rate of 10 fps (100 ms each 3D frame).