Agent illumination

Volvox samples (Blades Biological, UK) were maintained at room temperature. For imaging, 75 µL of the Volvox suspension was added to the sample arena, comprised of 3D printed walls attached to a microscope slide (Figure \ref{172910}). This sample arena was constructed to allow the free movement of Volvox colonies. A square chip of outer dimensions 25 × 25 mm with a 7.75 × 7.75 mm square cut from the middle was 3D printed in PLA and attached to a standard glass microscope slide using superglue adhesive. This square well has depth of 1.5 mm, allowing Volvox colonies of 350–500 µm in diameter to move freely in the x-y plane, with some limited movement in the z plane.