8 Aug 2014
Adam Eales was awarded a Rideal Travel Bursary in April 2014. He participated in the 88th ACS Colloids & Surface Science Symposium. Here he tells us a little about this background and reports on his attendance at the Symposium.
My undergraduate studies were in Chemical Engineering at the University of Cambridge. Following that, I embarked on a PhD programme at the BP Institute for Multiphase Flow, University of Cambridge under the supervision of Dr Alex Routh and Dr Nick Dartnell, from our industrial collaborators, Cambridge Display Technology Ltd. I'm currently completing the 3rd year of my PhD.
My research aims to understand the physical behaviour driving coffee-ring formation and to propose mechanisms by which it can be mitigated. Everybody will have experienced the coffee-ring effect at some point. Following evaporation of the volatile liquid from a droplet containing a non-volatile component (e.g. coffee, polymer etc.), the non-volatile material will be deposited at the periphery of the droplet, provided the contact-line is pinned. This phenomena is frustrating for scientists and engineers in many fields, for example DNA microarrays & disease diagnostics, distribution of pesticides on leaves and inkjet printing applications such as polymer-organic light emitting diode (P-OLED) displays. A uniform film profile is desirable, for operational reasons.
The 20 minute oral presentation that I gave at the ACS Colloids & Surface Science Symposium was entitled 'Achieving a flatter film profile for applications in P-OLED displays: mixed solvent inks and their influence on film shape'. It has previously been shown, experimentally, that the coffee-ring effect can be suppressed by using a binary liquid system. There has been no consensus of opinion, on the mechanism for the improvement in film shape. Through a combination of mathematical modelling and experimentation, we have elucidated the important parameters controlling the behaviour of the systems. These include the relative evaporation rates, surface tensions and the initial mixing ratio of the two liquid components. The experiments use an industrial inkjet printer, to jet droplets onto an indium tin oxide (ITO) substrate. The film shape is measured using white light interferometry.
My talk was very well received; I had a number of stimulating questions and very interesting discussions. This has enabled me to adapt my model and to steer the future direction of my research. I would like to thank the ACS Colloids & Surface Science Symposium organisers John Crocker, Kate Stebe and Arjun Yodh for giving me the opportunity to speak. The conference was an excellent platform for me to disseminate my findings, with approximately 700 delegates and 14 parallel sessions, ranging from biocolloids and colloid and surface forces, to microfluidics, and rheology and dynamics. There were some excellent talks, plenary lectures and a total of 48 keynote speakers. The breadth of research on display was astonishing. It has provided me with a broader understanding of the field. Giving an oral presentation at a conference of this stature, has given me the experience and extended my confidence, to communicate my viewpoint to a large audience, with diverse scientific backgrounds and research interests.
The funding received from the SCI/RSC Rideal Travel Award has enabled me to attend this meeting. I am immensely grateful for this financial assistance; the conference was inspirational, a huge success and provided me with the opportunity to develop many skills that will benefit me in my future career.
Adam Eales
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