Janus particles, named after the two-faced Roman god, are solid particles of two halves, each with different physical properties and with applications that include drug delivery. But Shoji Takeuchi and his colleagues at the University of Tokyo have gone beyond Janus's two faces and made gel spheres with up to six distinct sections. The particles are about 100 micrometres in diameter and, when each section is permeated with different fluorescent nanobeads, look like beach balls.

Credit: WILEY

To make them, the researchers injected dyed sodium alginate solutions down a multi-barrelled capillary tube, which they then centrifuged. This forced the liquid streams out to form droplets composed of multiple liquids. The droplets fell into a waiting bath of calcium chloride, turning them to gel before the component solutions could mix.

The researchers also used their method to produce Janus particles holding magnetic particles and living cells in their separate halves (pictured).

Adv. Mater. http://dx.doi.org/10.1002/adma.201102560 (2012)