Lithography-Free Technology for the Preparation of Digital Microfluidic (DMF) Lab-Chips with Droplet Actuation by Optoelectrowetting (OEW)

Figure 5

Frames from a video showing the droplet movement and mixing of sodium hydroxide (NaOH) and phenolphthalein (C₂₀H₁₄O₄) with the help of laser beam-based OEW. The beam is perpendicularly incident from below the chip. A spot of scattered light can be observed, since the photoconductive a-Si : H layer is thin enough (780 nm) to transmit some of the OEW control light at 520 nm wavelength. The NaOH droplet is moved to the C₂₀H₁₄O₄ droplet and both merged. The new droplet changes the color from colorless to purple. Transmission spectra of the single droplets and the resulting droplet are measured.