Abstract: A fluid delivery device is configured to create a pressure differential across a compartment in which a liquid resides, causing the liquid to flow through the compartment. After a period of time, the fluid delivery device is configured to eliminate the pressure differential and thereby equilibrate the pressure across the compartment, with the use of a pressure equilibration channel that is separate from the compartment. The compartment may contain a packed bed of solid phase particles such as beads. In such case, the pressure differential causes the liquid to flow through the packed bed. The liquid may include chemical reagents or precursors that participate in chemical reactions on or at the solid phase particles. The reactions may relate to chemical synthesis, for example the synthesis of bio-chemicals such as nucleotides.