Figure 16.3 — Microfluidic sorting in a speckle pattern Figure 16.3 — Microfluidic sorting in a speckle pattern. Optical sieving using a static speckle field. Time-lapse snapshots of the flow (flow speed 3.01 ± 0.12 μm/s in the direction of the arrow) of two types of particles with similar radii, a ≈ 1 μm, but different refractive indices, in a speckle field: the brighter particles are made of silica, np = 1.42, whereas the darker ones are made of melamine, np = 1.68. The speckle landscape traps the particles with higher refractive index while letting the ones with lower refractive index flow away.Reprinted from Volpe et al., Opt. Express 22, 18159–66. Copyright (2014) The Optical Society.