Design of Compact Micro-Labyrinths for Low-Cost Drip Irrigation

There is an urgent need for sustainable agricultural intensification. Drip irrigation can save up to 50% more water than traditional irrigation technologies by supplying water using a network of pressurized tubing with flow metering devices called emitters bonded to them. Emitters operate using a turbulent labyrinth passage with staggered teeth-like structures (L ~ 0.01-0.1 mm) that promote energy dissipation. Despite its sophistication and water-saving ability, the adoption and retention of drip irrigation are limited by the high material cost of drip emitters. Designing compact, affordable emitter labyrinths (<1 inch long compared to typical 2 inches) is challenging due to the operating physics of emitters and their vast design space. We use manufacturing constraints and geometric relationships to identify two key parameters in the labyrinth – tooth tip gap and depth - that could be tuned to create high-resistance, compact labyrinths. Subsequent sensitivity analysis sheds light on 3 distinct fluid dynamical operating regimes in the labyrinth which yield design guidelines for the creation of low-cost emitters that can be up to 40% more compact than comparable commercial products. The sensitivity analysis could also be used to guide the hydraulic design of similar microfluidic devices for applications such as microreactors, particle separators, mixing-enhancing devices, etc.