Fig. 16.

Spatially controlled chemistry with droplet microfluidics. (a) A schematic of three different approaches, namely co-flow, T-junction and flow focusing, conventionally used for droplet generation. (Reprinted from ref. 183 with permission from The Royal Society of Chemistry). (b–d) Types of droplets/particles created in microfluidic devices. The devices are capable of creating disc-shaped Janus droplets which can be polymerized with UV into Janus particles, ternary droplets as well as emulsions with a hierarchy of droplets confined within one another (i.e. multiple emulsions). (Reprinted with permission from ref. 187, 190, 188. Copyright (2006), (2007) by The American Chemical Society and (2006) by John Wiley and Sons). (e) Sequential fusion of droplets in a microfluidic device. The laser (at the position indicated with the white arrow) is used to position the droplets while the electrodes (the black line at the bottom of the figure shows one of the electrodes, the top electrode is not shown) are used to induce coalescence of the droplets. The Roman numerals below the figure indicate different stages of the fusion process. (Reprinted from ref. 191 with permission from the Royal Society of Chemistry). (f) Chemical reaction product formation as a function of time for a reaction proceeding inside droplets as observed in a microfluidic device. The experimental setup allows for millisecond resolution of the reaction progress. (Reprinted with permission from ref. 194. Copyright (2003) by The American Chemical Society). (g) Small group of bacteria confined to a picoliter droplet. The white arrow points to one of the bacteria. (Reprinted with permission from ref. 196. Copyright (2009) by John Wiley and Sons). (h) An alginate bead encapsulating mammalian cells. The cells have been stained with trypan blue to differentiate the living cells from the dead ones. (Reprinted with permission from ref. 195. Copyright (2007) by John Wiley and Sons).