A computer-controlled laser cutter (Trotec Speedy 100) cut the channel design into 60-μm-thick Scotch tape. This was stuck to a Petri dish, which was used as a master for making a polydimethylsiloxane (PDMS) replica of the design. The PDMS master was used to fabricate the device in “microfluidic stickers” [Norland Optical Adhesive 81 (NOA81); Norland Adhesive] (53). A glass cover slide was used to seal the device, with holes drilled to provide access for inlet and outlet tubing. A PDMS inlet was ozone bonded to the cover slide to provide support for pins and tubings. The device was then baked at 80°C for at least 4 hours to strengthen the bonding. For the triggered release experiments, the microfluidic device had same dimensions as the one used in our previous work (30). For the multibeacon experiments, a two-inlet, single-outlet microfluidic device was used, where the two inlets enabled the simultaneous flow of two different liquid streams side by side. The two inlets were 500 μm wide, while the center channel where the inlets merge had a width of 4000 μm.