Pattern formation using light-actived bacterial swimmers

We have created E. coli bacteria that only swim when illuminated by light, and have \’tuned\’ the genetics to obtain the shortest possible \’stopping distance\’ when illumination ceases. I will describe protocols for creating bespoke patterns using these bacteria by applying static and dynamic light fields, and explain the physical bases underlying these protocols. The same bacteria also allow us to prove a theorem for active particles, viz., that the product of their velocity and density should be constant in a region where both quantities are spatially dependent.