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Self-Organization of Layered Inorganic Membranes in Microfluidic Devices
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posted on 2017-06-09, 00:00 authored by Qingpu Wang, Megan R. Bentley, Oliver SteinbockInorganic
precipitate membranes play an important role in chemobrionics
and origin of life research. They can involve a range of catalytic
materials, affect crystal habits, and show complex permeabilities.
We produce such membranes in a microfluidic device at the reactive
interface between laminar streams of hydroxide and Co(II) solutions.
The resulting linear membranes show striking color bands that, over
time, expand in the direction of the Co(II) solution. The cumulative
layer thicknesses (here up to 600 μm) obey square root laws,
indicating diffusion control. The effective diffusion coefficients
are proportional to the hydroxide concentration, but the membrane
growth slows down with increasing concentrations of Co(II). On the
basis of spatially resolved Raman spectra and other techniques, we
present chemical assignments of the involved materials. Electron microscopy
reveals that the important constituent β-Co(OH)2 crystallizes
as thin hexagonal microplatelets. Under drying, the membrane curls
into spirals, revealing mechanical differences between the layers.
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layer thicknessesmicrofluidic devicemembrane curlsMicrofluidic Devicesdiffusion coefficientschemical assignmentsmembrane growthsquare root lawscrystal habitsmaterialdiffusion controlRaman spectrareactive interfacelife researchlaminar streamsmembranes showCoelectron microscopysolutionhydroxide concentration600 μ mcolor bands
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