Two-dimensional dielectrophoretic particle trapping in a hybrid crystal/PDMS-system

Abstract

Dielectrophoretic forces originating from highly modulated electric fields can be used to trap particles on surfaces. An all-optical way to induce such fields is the use of a photorefractive material, where the fields that modulate the refractive index are present at the surface. We present a method for two-dimensional particle alignment on an optically structured photorefractive lithium niobate crystal. The structuring is done using an amplitude-modulating spatial light modulator and laser illumination. We demonstrate trapping of uncharged graphite particles in periodic and arbitrary patterns and provide a discussion of the limitations and the necessary boundary conditions for maximum trapping efficiency. The photorefractive crystal is utilized as bottom part of a PDMS channel in order to demonstrate two-dimensional dielectrophoretic trapping in a microfluidic system.

Efficient photo-induced dielectrophoretic particle trapping on Fe:LiNbO_3 for arbitrary two dimensional patterning

“…In the last years a new technique for particle manipulation, the so called photovoltaic tweezers (or photorefractive tweezers), has been proposed [4][5][6]. The basis of this technique is the bulk photovoltaic (PV) effect [7,8] that generates high light-induced electric fields in some ferroelectric crystals.…”

“…However, although the method works very well for ID particle structuring, 2D patterning has a limited quality [6,13] because particle alignment in directions parallel to the polar axis of the PV material is not possible. Moreover, the particle pattern does not reproduce the light distribution but presents a contouring effect more pronounced in directions normal to the polar axis.…”

Optoelectronic tweezers under arbitrary illumination patterns: theoretical simulations and comparison to experiment

“…An emergent methodology of this type [4][5][6][7] uses light-induced space charge fields generated in photorefractive materials by inhomogeneous illumination [8]. The space charge fields responsible for particle trapping are particularly large in PR crystals exhibiting a large photovoltaic effect such as Fe:LiNb03.…”

“…The procedure does not require electrodes and it is usually called photovoltaic or, more generally, optoelectronic tweezers. The number of experimental works showing the capabilities of optoelectronic tweezers has been rapidly increasing in the last few years [4][5][6][7][9][10][11][12]. Different dielectric and metallic nanoparticles, neutral or charged, have been used to generate the particle patterns showing the universality of the method.…”

Diffractive optical devices produced by light-assisted trapping of nanoparticles

“…A method for massive parallel trapping and patterning of nanoparticles has been recently developed [1][2][3]. It is based on the high bulk photovoltaic (PV) effect of certain ferroelectric materials [4].…”