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ILCS Picture of the Month

Published:

The International Liquid Crystal Society (ILCS) have chosen my image entitled ‘Trapped Transitions’ as their Liquid Crystal Picture of the Month! It will be featured on the ILCS homepage throughout June.

The Jury said: “I find it visually very attractive with the distribution of different spreading lines and the positioning of shapes of different colours. The connection to the microfluidics technology is of course technologically and scientifically very interesting and new to the field.”

You can see other beautiful liquid crystal related images in the ILCS Gallery.

Trapped Transitions

“A polymer channel laser-written in a pi-cell liquid crystal device, inspired by developments in microfluidics technology. The device is relaxing to a topologically discontinuous director state and the transition is confined and unable to penetrate through the topologically discontinuous polymer walls. Scale: the central channel is 45 µm in width.”

Paper published in Nature Communications

Published:

My latest paper “Electrically-tunable positioning of topological defects in liquid crystals” has been published in Nature Communications today!

I have written a “Behind The Paper” post explaining topological defects in liquid crystals to a general audience, which you can find here.

The Department of Engineering Science at Oxford have written a featured news item on the paper.

Defect confinement channel
Topological defect confinement channel created with direct laser writing

IET Award Evening

Published:

Today I received an award from the Institution of Engineering and Technology (IET) at a fantastic ceremony at Saville Place in London. The IET awards recognise postgraduate research students from around the world conducting research in engineering-related topics. You can read about the 2019 winners here.

John Sandford O'Neill

I was awarded the Leslie H. Paddle scholarship which was established in 1979 under a bequest from Leslie H. Paddle, the vice-president of the Institution of Electronic and Radio Engineers (IERE).

My family
Celebrating with my family

Many thanks to the IET for an excellent evening at Saville Place. It was great to see the global outlook and breadth of the IET awards and scholarships programme.

You can read more about my work and the award in this article hosted by the Department of Engineering Science at Oxford.

publications

Read on Demand Images in Laser-Written Polymerizable Liquid Crystal Devices

Published in Advanced Optical Materials, 2018

Two‐photon laser writing is a powerful technique for creating intricate, high resolution features in polymerizable materials. Here, using a single‐step process to microfabricate polymer inclusions, the ability to generate read‐on‐demand images and identification codes in a liquid crystal (LC) device is demonstrated.

Tartan, C. C., Sandford O’Neill, J. J., Salter, P. S., Aplinc, J., Booth, M. J., Ravnik, M., Morris, S. M., Elston, S. J., "Read on Demand Images in Laser-Written Polymerizable Liquid Crystal Devices." Advanced Optical Materials, 6, 1800515 (2018) http://dx.doi.org/10.1002/adom.201800515

Robust measurement of flexoelectro-optic switching with different surface alignments

Published in Journal of Applied Physics, 2019

The alignment of chiral nematic liquid crystals in the so-called uniform lying helix geometry allows for the observation and exploitation of the flexoelectro-optic effect. However, high-quality uniform lying helix alignment is difficult to achieve reliably, and this can potentially impact the accuracy of the measurements made on the flexoelectro-optic switching behaviour. Here, we show that, using an appropriate method, it is possible to make measurements of the flexo-electric coefficients that are not substantially influenced by the alignment quality.

Sandford O’Neill, J. J., Fells, J. A. J., Welch, C., Mehl, G., Yip, W. C., Wilkinson, T. D., Booth, M. J., Elston, S. J., Morris, S. M., "Robust measurement of flexoelectro-optic switching with different surface alignments." Journal of Applied Physics, 125, 093104 (2019) http://dx.doi.org/10.1063/1.5086241

Electrically-tunable positioning of topological defects in liquid crystals

Published in Nature Communications, 2020

Topological defects are a consequence of broken symmetry in ordered systems and are important for understanding a wide variety of phenomena in physics. In liquid crystals (LCs), defects exist as points of discontinuous order in the vector field that describes the average orientation of the molecules in space and are crucial for explaining the fundamental behaviour and properties of these mesophases. Recently, LC defects have also been explored from the perspective of technological applications including self-assembly of nanomaterials, optical-vortex generation and in tunable plasmonic metamaterials.

Here, we demonstrate the fabrication and stabilisation of electrically-tunable defects in an LC device using two-photon polymerisation and explore the dynamic behaviour of defects when confined by polymer structures laser-written in topologically discontinuous states. We anticipate that our defect fabrication technique will enable the realisation of tunable, 3D, reconfigurable LC templates towards nanoparticle self-assembly, tunable metamaterials and next-generation spatial light modulators for light-shaping.

Download paper here

I have written a “Behind The Paper” post explaining topological defects in liquid crystals, which you can find here.

Sandford O’Neill, J. J., Salter, P. S., Booth, M. J., Elston, S. J., Morris, S. M., "Electrically-tunable positioning of topological defects in liquid crystals." Nature Communications, 11, 2203 (2020) https://doi.org/10.1038/s41467-020-16059-1