Optical manipulation – Dielectrophoretic particle manipulation
An alternative approach for the manipulation of several micro/nano particles consist of using dielectrophoretic forces. Dielectrophoresis is an electronic effect that can be neglected in homogeneous or weakly inhomogeneous electric fields (Figure (a)), but becomes dominant if the field is strongly modulated. In this case, the field acts upon locally induced dipoles in the object to be controlled (Figure (b)). This results in a net force, either attracting or repulsing matter from regions of high field intensity, depending on the electric properties of the object and the surrounding medium. Conventional dielectrophoretic setups consist of fixed electrodes on a substrate, which typically require a laborious manufacturing process including lithography. In contrast, we use light for the creation of the electrodes: Nonlinear optics can store a field structure inside a photorefractive material, which can then exert dielectrophoretic forces upon matter. By means of this, it is possible to realize a precise assembly of macroscopic structures made of a huge number of individual units of micro/nano particles as e.g. graphite, glassy carbon spheres or zeolite L nanocontainers (Figure (c)). In this context, and in analogy to the optical tweezers, this approach is referred as optoelectronic tweezers.
Two-dimensional dielectrophoretic particle trapping in a hybrid PDMS/crystal system, M. Esseling, F. Holtmann, M. Woerdemann, and C. Denz, Optics Express 18, 17404 - 17411 (2012)
Opto-electric particle manipulation on a bismuth silicon oxide crystal, M. Esseling, S. Glaesener, F. Volonteri, and C. Denz, Applied Physics Letters 100, 161903 (2012)
Multiplexing and switching of virtual electrodes in optoelectronic tweezers based on lithium niobate, S. Glaesener, M. Esseling, and C. Denz, Optics Letters 37, 3744 - 3746 (2012)
Highly reduced iron-doped lithium niobate for optoelectronic tweezers, M. Esseling, A. Zaltron, N. Argiolas, G. Nava, J. Imbrock, I. Cristiani, C. Sada, and C. Denz, Applied Physics B 113, 191 - 197 (2013)
Charge sensor and particle trap based on z-cut lithium niobate, M. Esseling, A. Zaltron, C. Sada, and C. Denz, Applied Physics Letters 103, 061115 (2013)