Fluidic Composite Materials

8.jpgIn this research area, we seek to develop and characterise novel materials for optoelectronic and photonic devices. New materials are developed by combining the remarkable properties of two-dimensional materials, with the dynamic reconfigurability of liquid crystals.

For more information about this research topic, contact Ben Hogan.

The liquid crystal phase has been known and studied for over 100 years (Figure 1) with a wide range of modern-day applications- most notably being ubiquitous in displays. But where else could they find applications?

Liquid crystal timeline
Figure 1. Timeline of the development of liquid crystal technologies.

This research topic is focussed on the development of novel liquid crystalline composites incorporating two-dimensional materials (graphene etc.) for applications in optoelectronics and photonics [Hogan et al., 2D Material Liquid Crystals for Optoelectronics and Photonics, J. Mater. Chem. C, 2017]. By utilising the reconfigurability of the orientation of the liquid crystal mesogens under applied fields (electric, magnetic, thermal…) we propose that ‘metastructuring’ can be achieved. That is, two-dimensional nanoparticles dispersed within a liquid crystalline host can be controllably positioned to form metamaterial structures. We have shown that liquid crystalline composites with dispersed two-dimensional material nanoparticles can be readily synthesised and integrated into CMOS-compatible microfluidic systems [Hogan et al., Dynamic in-situ sensing of fluid-dispersed 2D materials integrated on microfluidic Si chip, Scientific Reports, 2017]. As part of this work, we developed a novel characterisation method, using Raman spectroscopy to elucidate the positions of nanoparticles within microfluidic structures (Figure 2). In the (near) future, this novel methodology will allow us to monitor the spatio-temporal evolution of metastructure formation under applied fields.

Microfluidic chip
Figure 2. Schematic of a microfluidic chip, containing metastructured 2D material particles, monitored by Raman spectroscopy.

A further development of great interest is the discovery of lyotropic liquid crystal phases where two-dimensional material particles are the mesogenic material. Dispersions of two-dimensional material particles in a range of organic solvents can show liquid crystallinity (Figure 3).

WS2 Liquid crystal
Figure 3. Optical images of liquid crystal phases formed from tungsten disulfide dispersed in isopropanol, showing clear bright and dark domains.