Our paper on measuring the optical binding interaction between microparticles in an evanescent wave surface trap has been published as Xiang Han and P. H. Jones, Evanescent wave optical binding forces on spherical microparticles Optics Letters 40 4042-4045 (2015).
From the abstract: In this Letter, we demonstrate stable optical binding of spherical
microparticles in counter-propagating evanescent optical fields formed
by total reflection at a dielectric interface. The microspheres are
observed to form one-dimensional chains oriented parallel to the
direction of propagation of the beams. We characterize the strength of
the optical binding interaction by measuring the extent of Brownian
position fluctuations of the optically bound microspheres and relating
this to a binding spring constant acting between adjacent particles. A
stronger binding interaction is observed for particles near the middle
of the chain, and the dependence of the binding strength on incident
laser power and number of particles in the chain is determined.