Fig. 1.

(a) The goal is to create arbitrary sequences of sub-second chemical pulses to stimulate C. elegans animals and monitor neuronal activity. (b) A limitation of previous devices seeking to deliver multiple stimuli is the inability to switch from one chemical to another without cross-contamination. In previous configurations, alternating from blue to green is not possible without an intermediate step through yellow. (c) Our system integrates multiple flow selectors and uses pressure modulation of chemical inlets to create any sequence of four chemicals at sub-second speed.