Optofluidic crystallization of colloids tethered at interfaces
Prof. Erika Eiser (University of Cambridge, United Kingdom)
Optical tweezers have been established as indispensable tool for the manipulation of micro- and nano-sized objects. We show that colloids anchored to a water-oil interface via DNA-tethers will crystallize when only one of the particles is trapped with optical tweezers [1,2]. These DNA-anchored colloids are fully immersed in the water phase, thus they do not disturbe the oil-water interface, but allow the tethered colloids to diffuse freely along the oil-droplet surface in the absence of a tweezing laser [3,4]. Our combined experimental and theoretical analyses show that local temperature gradients induced by optical tweezers cause a thermophoretic force pushing the trapped particle towards the colder oil phase, causing an attractive long-ranged hydrodynamic flow towards the laser focus that promotes the observed out-of equilibrium crystallization of the DNA tethered colloids around the trapped particle. The crystallization is further enhanced by scattering forces known as optical binding.
 A. Caciagli, R. Singh, D. Joshi, R. Adhikari, E. Eiser, PRL accepted (2020)
 A. Caciagli, D. Joshi, J. Kotar & E. Eiser, arXiv 1703.08210 (2017)
 D. Joshi, D. Bargteil, A. Caciagli, J. Burelbach, J. Xing, A. Nunes, D. Pinto, N. Araujo, J. Bruijc & E. Eiser, Science Advances, 2 : e1600881 (2016)
 A. Caciagli, M. Zupkauskas, A. Levin, T.P.J. Knowles, C. Mugemana, N. Bruns, T. O’Neill, W. J. Frith & E. Eiser, Langmuir 34, 10073 (2018)