Microfluidic sorting in an optical lattice

Abstract

The response of a microscopic dielectric object to an applied light field can profoundly affect its kinetic motion. A classic example of this is an optical trap, which can hold a particle in a tightly focused light beam. Optical fields can also be used to arrange, guide or deflect particles in appropriate light-field geometries. Here we demonstrate an optical sorter for microscopic particles that exploits the interaction of particles-biological or otherwise-with an extended, interlinked, dynamically reconfigurable, three-dimensional optical lattice. The strength of this interaction with the lattice sites depends on the optical polarizability of the particles, giving tunable selection criteria. We demonstrate both sorting by size (of protein microcapsule drug delivery agents) and sorting by refractive index (of other colloidal particle streams). The sorting efficiency of this method approaches 100%, with values of 96% or more observed even for concentrated solutions with throughputs exceeding those reported for fluorescence-activated cell sorting. This powerful, non-invasive technique is suited to sorting and fractionation within integrated ('lab-on-a-chip') microfluidic systems, and can be applied in colloidal, molecular and biological research.

An optical toolbox for total control of droplet microfluidics

“…Our approach to controlling microfluidic droplets relies on all-optical techniques which have been greatly developed in recent years in connection with microfluidic devices [21,22,23,24,25]. Indeed, optical trapping has become a standard tool in biophysics [26] and holographic [22] and generalized phase contrast [25] methods now allow a single laser to be divided into many spots which can be independently manipulated.…”

Size-Based Separation of Particles and Cells Utilizing Viscoelastic Effects in Straight Microchannels

“…[4][5][6] Microfluidic systems have been proven to be promising tools for particle/cell manipulation with higher sensitivity and accuracy than their macroscale counterparts. The last decade has seen extensive development of microfluidic approaches for particle/cell manipulation that resort to immunocapture, 7 externally applied physical fields, [8][9][10][11][12][13][14][15][16][17][18] microfiltration, 19,20 gravitational sedimentation, 21 or deterministic lateral migration. 22,23 More recently, cross-streamline migration induced by the hydrodynamic effects of carrier media, such as inertia 24,25 and viscoelasticity, 26,27 has shown its promise for effective particle/cell manipulation without need of labeling and external force fields.…”

Rigorous diffraction theory applied to the analysis of the optical force on elliptical nano- and micro-cylinders

“…For example it is still problematic to fabricate particles with a controlled axis ratio, while statistical approaches such as irradiation with pulsed laser beams to deform particles yield a mixture of particles with different shapes. In this situation, the application of a sorting mechanism with optical tweezers could be a promising technique to obtain particles with a well controlled shape [38].…”