Figure 1.

The Crystal Hotel microfluidic device. a) Photograph of a PDMS device bonded to a glass slide and filled with a solution of red dye. b) Chip design of a Crystal Hotel with 48 “rooms”. c) Crystallization in a single room (i). An aqueous solution (light blue) is introduced through inlet 2 to fill the channel and rooms (ii). Subsequently, air (white) is introduced through inlet 1 to push the solution out of the channel and isolate the solution contained in each room (iii). (NH₄)₂CO₃ vapor (green) is then pumped through inlet 1 (iv), and CaCO₃ precipitation is initiated by diffusion of CO₂ and NH₃ gas into the solution (v). Once crystals have formed, ethanol (yellow) is pumped through the device to terminate the reaction (vi).