Proc. Natl Acad. Sci. USA (2015)

Living cells are adept at converting energy into motion. So what if we could borrow some of their genius to make our own tiny machines — systems capable of manipulating form and function with something as simple as an assembly of colloids? Matthew Spellings and co-workers have designed an active colloidal cell: a fluid-filled compartment made up of rotating particles that generate convective flows.

The team proposed and simulated a system comprising particles that could translate and rotate in two dimensions, and were confined by a flexible boundary built from similar particles. The boundary acted to stir the flow inside the cell, interfering with the phase separation expected of these particles in the bulk. They found that this convective activity allowed them to control the cell's shape and structure, simply by altering its physical properties — the flexibility of the boundary and the particles' activity.