The team, comprising scientists from SISSA, the University of Edinburgh and the University of Padova, introduced flaws into liquid crystals by inserting microspheres and then controlling them with an electric field.
"Generally, flaws are the last thing you want in a liquid crystal," said Giuseppe D'Adamo, a postdoctoral fellow at SISSA. "However, this new method allows us to exploit defects in the material to our advantage." Whilst the optical properties of such composite materials have been attracting attention, the team says the use of electric fields to modify them at will is 'an absolute novelty'.
"Our simulations demonstrate that, by switching on or off an electric field of appropriate intensity, we can reorder the colloids by arranging them into columns or planes," noted SISSA researcher Cristian Micheletti. "This easy to control plasticity could make the material suitable for optical-electronic devices, such as e-readers."
According to the team, the natural tendency of liquid crystal molecules to arrange themselves spontaneously in a certain pattern can be counteracted by introducing colloids in the fluid. "In our case," D'Adamo explained, "we used microscopic spherical particles, which 'force' the molecules coming into contact with their surface to adapt and rotate in a different direction. This creates 'defect lines' in the material which bring a local change in its optical properties."
"By switching the field on and off," Micheletti continued, "we create competition between the spontaneous order of the liquid crystal, the order dictated by the surface of the colloidal particles and, finally, the order created by the electrical potential. This competition produces many defect lines that act on the colloids by moving them or clustering them.
"In this respect, the method works like the electronic ink used in digital readers and it would be interesting to explore its applicability in this sense," Micheletti concluded.
