Fig. 6. Motion chirality control with L-shaped particles.

a Optical microscopy image of an L-shaped reconfigurable cluster comprising two PS particles and one microgel in MilliQ water at room temperature. The arrow indicates the microgel position b Trajectories of an L-shaped particle at two different levels of fluorescence light power density (ρ_FL = 9 mW(mm)⁻²–blue; ρ_FL = 54 mW(mm)⁻²–magenta). The schematics in the insets show the propulsion direction relative to the PS-microgel combination as a function of ρ_FL and the corresponding angular velocity Ω. Upon changing illumination density, the helical trajectory changes chirality, due to propulsion reversal, and pitch, due to shape reconfiguration. Scale bars: 5 μm. c Orientation angle as a function of time for a self-propelling L-shaped particle at different light illumination levels. Upon tuning ρ_FL up, the rotation changes direction and slows down. The change is fully reversible upon reducing the fluorescent light.