Liquid crystals: A shape-shifting object of study
In school, we are taught three states of matter: solid, liquid and gas. Liquid crystals exist almost in a fourth state: between solid and liquid. In nature, liquid crystals are found in plants, shells of beetles, DNA molecules, human bone, wood cellulose and even slug slime.
Most people look at liquid crystals every day without realising it: They are a key component of LCD screens! Liquid crystals do not emit light directly, but by using their light-modulating properties, combined with polarizers, and a backlight they help produce images in colour or monochrome.
The research on liquid crystals transcends scientific fields, such as physics, chemistry, biology, and engineering, to name a few. Scientists such as physicist PhD researcher Anjali Sharma from the University of Luxembourg study them in unusual shapes. Anjali is part of the Experimental Soft Matter Physics (ESMP) group, lead by Prof Jan Lagerwall at the University of Luxembourg.
The ESMP group is well known for its unconventional approach to LC research – the group confines LCs in different geometries, particularly cylindrical (fibers) and spherical (shells and droplets) and assess their usefulness in several applications. Anjali’s focus lies on studying the LCs in spherical geometry.
Using a polarizing microscope, Anjali is able to capture beautiful images of liquid crystals:
Taking research to new heights: Zero gravity
As part of her research, Anjali got an opportunity for a rare experiment: Taking her research into a zero gravity environment!
Anjali explains that an LC shell is often asymmetric, since the inner aqueous droplet and the outer LC droplet are not concentric, meaning they do not have a common centre. Scientists know that gravity plays a role in this, but what role exactly does gravity play, and what role does the liquid crystal itself play? To find out, Anjali and the group removed gravity from the equation.
“We got the opportunity to take our experimental setup [with the shells mounted in an apparatus specially designed for the purpose] on a parabolic flight. The airplane flies along a parabolic trajectory, giving us first about 20 seconds of double gravity (2g), and then about the same time of zero gravity (0g). This is then repeated 25 times, so we have a few hours to collect data. It was a challenge for us and team we worked with to build a setup compatible for this flight.”
In short, the zero g experiment showed that in the absence of gravity, the asymmetry in the shell changes when the temperature is changed.
The goal of Anjali’s PhD is to use microfluidic techniques to confine the liquid crystals in shell geometry so they can be used in bio or chemo sensing: A bio-/chemo-sensor is an analytical device used for the detection of a selected biological or chemical substance.
Anjali's PhD project at the University of Luxembourg is funded in the framework of the FNR's PRIDE programme, through which the FNR awards PhD grants in blocks to researchers united around a coherent research and training programme.
Discover more about the research of the ESMP group on their website, or find out more about Anjali and her research in the FNR campaign Spotlight on Young Researchers.