Reflectivity spectra of magnetic porous Si microparticles surrounding aqueous droplets that contain fluorophore-conjugated oligonucleotides. (a) Reflectivity spectra obtained from the particles half-covering droplet 1 (D1), which contain Cy3-conjugated oligonucleotides, and the particles half-covering droplet 2 (D2), containing Cy5-conjugated oligonucleotides. The particles on D1 possess a spectral code consisting of one peak, while the particles on D2 carry a spectral code consisting of three peaks. The inset represents a schematic of the experimental setup used for manipulating the droplets. D1 is merged with D2, which is trapped a shallow well, using a magnet. (b) Reflectivity spectrum obtained after merging D1 and D2 shows the superposition of the two spectral codes from the two sets of particles. The inset represents a schematic of the experiment after merging D1 with D2.