New insight into how liquid crystal is formed revealed by Leeds researchers

A new study which investigates how liquid crystal droplets can change their appearance in the presence of certain drugs has given insight that could lead to advances in pharmaceutical knowledge.

Liquid crystals, or more specifically, ‘liquid crystal colloids’ – which are clusters of liquid crystals grouped together – have sparked interest among scientists, mathematicians, biologists, engineers, and chemists due to the diversity of possibilities they present.

Professor Cliff Jones and postgraduate researcher Nikita Solodkov from the School of Physics and Astronomy have authored a new paper, published in Nature Communications. Their study gives insight into how the symmetry properties of liquid crystals determine how colloids, which are made up of specific patterns of molecules, assemble.

The colloids can be built by adding particles to the original sample of liquid crystal: in Solodkov and Jones’ case, they put droplets water into the liquid crystal sample. The resulting shapes can range from linear chains to complex ‘fractals’, all depending on the order in which the particles are added and the relative size distributions.

Solodkov and Jones aim to use their research to improve applications such as sensors, biological systems and drug control.

Complex fractals

Adding particles into liquid crystal can result in configurations that range from linear chains to complex fractals depending on their size and the order in which they are distributed.

Illuminating technology

Application of liquid crystals to technology has dominated the entertainment industry and beyond, being used to control screens on electronic devices from tablets, smartphones, and TVs to operating photonic computers and more. However, there’s a big move to see how the self-assembly of liquid crystal colloids can be applied more widely.

Solodkov and Jones’ insight into manipulating the properties of liquid crystals is a first step for physical scientists who are investigating the use of liquid crystals in drug delivery and control.

The researchers acknowledge that, currently, this work is in its early stages and further development is needed to establish how it can be transferred to a commercial pharmaceutical setting.

Detecting toxins

The toxicity of a substance can be tested by exposing it to coated liquid crystal (LC) droplets suspended in a solution. When the substance is released into the solution containing the droplets, it may cause a chemical reaction to take place on the LC’s surface, dissolving the coating.

This changes the ‘boundary conditions’ on the liquid crystal droplets, and the ‘director’ (the average pointing direction of the liquid crystal molecules) changes its orientation. Researchers may use this method to test glucose, bacteria, or toxins, for example, by investigating whether the orientation of the molecules will allow the substance to pass through.

Jones and Solodkov aim to use their insight into manipulating liquid crystal colloid patterns to test the toxicity of certain drugs by observing chemical reactions and the resulting boundary conditions of the liquid crystal droplets.

Solodkov said:

“Our paper explores the use of ‘point defects’ and the elastic properties of liquid crystals to trap particles in particular configurations. Note that this is nothing new, the new part is the shapes that the particles make: in particular, the self-assembly of fractal structures.”

We explore switching between these configurations with the aim of detecting on a molecular level how drugs may release toxins, for example, in order to determine if a substance is safe.

Jones and Solodkov’s discovery is in its early stages: at the moment the researchers hope to be able to switch the systems from one pattern to another in order act as a ‘microscopic scale sensor,’ which will make it possible to detect the configurations optically.

Jones said:

There’s a vast similarity between biological systems and liquid crystals: The properties of a cell wall are similar to that of a liquid crystal molecule.

“Mitosis occurs because of the liquid crystal-like behaviour of molecules in human chromosomes."

He added:

“General molecular self-assembly interests biologists as much as liquid-crystal scientists. What we do is relevant to biological scientists as well as device physicists such as myself and Nikita.”