Jessica Vermeer
25 August 2020

A team of researchers from Utrecht University and Oxford University has developed a new system of micrometer-sized banana-shaped particles. With these bananas, they’ve experimentally confirmed the existence of the so-called “splay-bend nematic” liquid crystal phase, which was predicted forty years ago.

Liquid crystals have unique properties that make them easily respond to external stimuli such as electric fields. They’re therefore often used in TV and computer displays. Simple rod-like molecules can form just five liquid crystal phases, whereas the banana-shaped ones form over fifty.

Scanning electron microscopy image of the colloidal bananas. Some particles are colored in, to emphasize their shape. The scale bar is 5 micrometers. Credit: Utrecht University

The banana phases were discovered twenty years ago, initiating ‘banana mania’ in the field of liquid crystals. The researchers are the first to look inside these phases and directly visualize the way the banana particles pack or move. They expect their results to be a cornerstone for further development of liquid crystals.

Since molecular systems are extremely small and move very fast; direct imaging of these systems is extremely challenging. Using image analysis techniques, the researchers directly determined positions and orientations of the banana-shaped particles, enabling them to identify a range of different banana phases.