Previous Group Members: Tom Fennerty

Photo of Tom Fennerty

Bain Group History

Masters Student, Durham University, 2005–2006

Project Title

Optical Trapping through Evanescence

Research – Outline

I am currently in my fourth year at Durham University, and am just starting my masters project on OPTICAL TRAPPING. An evanescent field is formed when light is reflected off an interface at an angle greater than the critical angle so that total internal reflection occurs. This field is able to interact with colloidal particles. In this project I hope to explore the formation of arrays of colloidal particles in the evanescent field of two counter propagating laser beams at the silica prism–water interface.

Research – A Closer Look

Initially I will be building on previous work by Chris Mellor, characterising the size and polarisation dependence of arrays of polystyrene spheres with diameters ranging from 600–400 nm, whilst becoming competent at optically bound array generation and manipulation. After attaining the expertise to investigate optically bound arrays, I aim to generate multilayers by increasing the penetration depth of the evanescent field, which I will achieve through variation of the angle of incidence at which the laser beam will be totally internally reflected on the silica–water interface. I also aim to determine the packing of these multilayers, and to determine the effect of varying the Debye lengths on the arrays formed, through variation of salt concentrations, thus inferring information about the binding potential from this relationship. Time permitting; I also hope to explore the behaviour of arrays formed by a variety of colloidal particles with different refractive indices and shapes, such as TiO2 and gold.


C. D. Mellor, T. A. Fennerty, C. D. Bain "Polarization Effects in Optically Bound Particle Arrays" Optics Express 2006, 14, 10079-10088 (DOI).


I am a keen footballer, playing in midfield for my college and in a five-aside team in a university league. I enjoy my indie/alternative music and am a big fan of Belle and Sebastian, Massive Attack and Portishead.