Molecular scale transporter with a twist, powered by liquid crystal defects (Vol. 48, No. 3)

Twisting effect, called chirogyral, dictated by the handedness of the fibre in a vertical magnetic field

Delivery of biochemical substances is now possible using a novel application of liquid crystal defects, forming a loop enclosing the substance travelling alongside twisted fibres.

Defects that break the symmetry of otherwise orderly material are called topological defects. In solid crystals, they are called dislocations because they interrupt the regularly structured atom lattice. In contrast, topological defects called disclinations take the form of loops in liquid crystals of the nematic variety, whose elongated molecules look like a shoal of fish. New experiments supported by a theoretical model show how defects forming loops around twisted plastic fibres dipped in liquid crystal could be used for the transport of biochemical substances, when controlled by electric and magnetic fields. These findings, published recently, have potential applications in electro-optical micromechanical and microfluidic systems. The loops have the ability to move alongside a translational motion when a magnetic field is applied in a direction oblique to the fibre. This means that by applying such a field, it is possible to control the transport of molecules trapped inside the loops, moving alongside the fibres.

M. Dazza, R. Cabeça, S. Čopar, M. H. Godinho and P. Pieranski, Action of fields on captive disclination loops, Eur. Phys. J. E 40, 28 (2017)