Fig. 3

Symmetrization of the scan pattern resolves distortions of the flow field. Maximum intensity projections over time show flow trajectories of fluorescent beads driven by different scan patterns. a Diagram of the temporal scanning units used to compose the ISO-FLUCS patterns. b Distorted flow field obtained by scanning a pattern with x and y broken symmetry. c Asymmetric flow field obtained by scanning a pattern with x broken symmetry. d Asymmetric flow field obtained by scanning a symmetric pattern. e Asymmetric flow field obtained by scanning a symmetric pattern with minimal cost. f Theoretical leading-order trajectories of tracers induced by a Gaussian heat spot scanning the same pattern as for panel e, but with an offset of 2 μm included between the forward and reverse paths. The dimensionless speed of the tracers (see Sect. 4.7 for details), averaged over the total time taken for the scan pattern, is indicated as a color map. g Quadrupolar flow field obtained by experimentally scanning a single line (33-μm long) back and forth. h Theoretical leading-order trajectories of tracers induced by a Gaussian heat spot scanning the same pattern as for panel g, but with an offset of 2 μm included between the forward and reverse paths. The dimensionless predicted speed of the tracers (see Sect. 4.7 for details), averaged over the time taken for the scan pattern, is indicated as a color map. i Montage of the dipolar fields obtained by scanning a line (11-μm long) RL (green) and LR (red). j Distorted flow field obtained by scanning the pattern with x and y broken symmetry and 4.6-μm offset between the forward and reverse paths. k Asymmetric flow field obtained by scanning the pattern with x broken symmetry and 4.6-μm offset. l Asymmetric flow field obtained by scanning the symmetric pattern e and 4.6-μm offset. m Symmetric flow field obtained by scanning the symmetric pattern with minimal cost and 4.6-μm offset. Scale bar: 20 μm. LR, left to right; RL, right to left