A New Method of Accurately Controlling Defect Movement in Active Liquid Crystals
Aug 6 2021
Liquid crystals contain small defects that exhibit the ability to host chemical reactions or transport cargo, which makes them useful for exciting new technologies, such as synthetic platforms for completely new drug delivery systems, sensors and materials.
Researchers have shown in simulations that they can precisely control the movement of defects within active liquid crystals, which makes the crystals candidates for technologies like drug delivery systems and sensors. Image Credit: Wikimedia Commons.
Scientists at the
University of Chicago
’s Pritzker School of Molecular Engineering (PME) earlier took a step toward such technologies by making liquid crystals that could move independently.
Currently, the same team has demonstrated, through simulations, that it is possible to accurately regulate the movement of defects inside such active liquid crystals by altering the gradient of activity about them. Theoretically, this can be performed by discharging pulses of light or varying the chemical composition in several areas of the system.
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The study findings were published in the
Physical Review Letters
journal on June 2
, 2021. The other study authors include postdoctoral researchers Rui Zhang, Ali Mozaffari, and Noe Atzin.
Controlling Movements, Creating Patterns
When compared to conventional liquids, liquid crystals display an even molecular order. Such crystals have been utilized in optical technologies, such as communications or displays. However, they can be utilized in highly sophisticated technologies, like capsules implanted in the body to automatically discharge antibodies in response to a virus, or clothing that senses and captures hazardous contaminants present in the air.
One step ahead of developing such technologies is engineering autonomous materials that could be regulated remotely. Earlier, de Pablo and collaborators at UChicago and Stanford University created autonomous liquid crystals by blending in actin filaments — the same filaments that are responsible for the formation of a cell’s cytoskeleton — and “motor” proteins, the proteins used by biological systems to apply force on actin filaments.
In this specific case, the proteins were designed to be light-sensitive, implying their activity increases upon exposure to light.
Through computer simulations, the team discovered that the motion of the liquid crystals can be regulated in circular domains by altering the gradient of low and high activity.
Thus, the researchers concluded they could alter the material’s dynamic states while also making the defects act in certain periodic ways like cruising, dancing, bouncing or holding a steady rotation. The outcomes of such movements can be mapped as complex geometric designs that are reminiscent of drawings made using a Spirograph.
Understanding Dynamics Within Cells
As a next step, the team is collaborating with experimentalists to test if the same outcomes are obtained in physical systems. Gaining better insights into ways to control such dynamic systems could be a leap toward sensing technologies and also give researchers a hint as to how to comprehend or control materials inside similar systems, like cells.
. (2021) Defect Spirograph: Dynamical Behavior of Defects in Spatially Patterned Active Nematics.
Physical Review Letters