A microfluidic labyrinth self-assembled by a chemical garden Testón Martínez, Sergio Huertas-Roldán, Teresa Knoll, Pamela Sainz Díaz, Claro Ignacio Cartwright, Julyan H. E. L. M. B. was supported by JPL Topical Research & Technology Development and a NASA PECASE award; L. M. B's research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). S. T. and T. H. thank the CSIC and Spanish Andalusian ‘Garantía Juvenil’ project AND21_IACT_M2_058. The authors would like to acknowledge the contributions of the European COST Action CA17120 supported by the EU Framework Programme Horizon 2020. Chemical gardens, self-assembling precipitates that spontaneously form when a metal salt is added to a solution of another precipitating anion, are of interest for various applications including producing reactive materials in controlled structures. Here, we report on two chemical garden reaction systems (CuCl2 and Cu(NO3)2 seed crystals submerged in sodium silicate) that produced self-assembled microfluidic labyrinths in a vertical 2D Hele-Shaw reactor. The formation of labyrinths as well as the specific growth modes of the precipitate were dependent on the silicate concentration: CuCl2 labyrinths formed only at 3 and 4 M silicate and Cu(NO3)2 labyrinths formed only at 4 and 5 M silicate. The labyrinth structures contained silicate on the exterior and crystalline material interpreted as hydrated minerals from the metal salt in their interiors. The bubble-guided tubes that form labyrinths can be controlled by changing the angle of the 2D reaction cell; this suggests that future experiments of this type could form self-organizing structures with controlled composition and orientation for use in microfluidics and various materials science applications. 2023-11-21T13:10:00Z 2023-11-21T13:10:00Z 2023-11-01 journal article Testón Martínez, S. et al. A microfluidic labyrinth self-assembled by a chemical garden. Phys. Chem. Chem. Phys., 2023, 25, 30469. [DOI: 10.1039/d3cp02929h] https://hdl.handle.net/10481/85815 10.1039/d3cp02929h eng http://creativecommons.org/licenses/by-nc/4.0/ open access Atribución-NoComercial 4.0 Internacional Royal Society of Chemistry