a. Chiral Polymer Scaffolds
Our research in this area involves the fabrication and characterisation on new photonic and meta-materials based upon chiral nematic and blue phase liquid crystals that have been ‘templated’ using a polymer scaffold that has been created by a cross-linked polymer network. The aim of this work is to harness the self-organising feature of liquid crystalline phases that naturally assemble to form a structure with a periodic modulation of the refractive index that is on the order of the wavelength of visible light. Furthermore, depending upon the liquid crystal phase, this periodicity can exist in either 1-dimension (chiral nematic) or 3-dimensions (blue phase). By forming a template of these structures with a polymer network it is then possible to impart this macroscopic structure onto other materials. An example of the 'templating' process of a blue phase is shown in Figure 1. This work is carried out in collaboration with Dr Flynn Castles in the Department of Materials at the University of Oxford and also previously with the Centre of Molecular Materials for Photonics and Electronics at the University of Cambridge.
Figure 1. A Blue phase template (a self-assembled 3D photonic crystal).
b. Stretchable Photonic Crystal-like Gels
In addition, we are also studying the mechanochromic and electro-optic properties of chiral nematic blue phase liquid crystalline gels, which have recently been demonstrated as a result of research carried out at the Departments of Engineering at both Oxford and Cambridge. Examples of free-standing blue phase gels from a recent publication in Nature Materials are shown in Figure 2.
Figure 2. Stretchable liquid crystalline blue phase gels.
We are also working on stretchable laser gels based upon chiral nematic and blue phase liquid crystals. An example of wavelength tuning of the laser emission from a liquid crystal laser gel is shown in Figure 3.
Figure 3. Stretchable cholesteric liquid crystalline gels
Figure 4. Stretchable cholesteric liquid crystalline gels