Fig. 3.

Optical and microfluidic negative refraction. (A) Refraction of light at the interface between materials having same refractive index for both identical (blue, normal refraction) or opposite (red, negative refraction) signs. (B) Two birefringent microfluidic elements are connected in series form a prismatic metamaterial. The compound element is made by joining a +α array (upstream) to a −α array (downstream). (C) Top-view SEM of the interface between the two subelements. (D) False color, epifluorescent time exposure of a supercritical, 2.7-μm-diameter fluorescent particle (top trace, red) moving from the left to the right and refracting the boundary, and a subcritical, 1.0-μm particle (bottom trace, green) following the characteristic zigzag path across the interface (see Movie S2).