Alkaline vents recreated in two dimensions to study pH gradients, precipitation morphology and molecule accumulation

TL;DR

This study introduces a quasi-2D microfluidic model of alkaline vents that visualizes mineral precipitation and pH gradients, shedding light on early life emergence conditions.

Contribution

It presents a novel microfluidic setup enabling in situ visualization of mineral precipitation and pH gradients in alkaline vent analogs.

Findings

Finger-like precipitates maintain microscale pH gradients

Precipitation morphology depends on flow rate and ion concentration

Model demonstrates potential for early life compartmentalization

Abstract

Alkaline vents (AV) are hypothesized to have been a setting for the emergence of life, by creating strong gradients across inorganic membranes within chimney structures. In the past, 3-dimensional chimney structures were formed under laboratory conditions, however, no in situ visualisation or testing of the gradients was possible. We develop a quasi-2-dimensional microfluidic model of alkaline vents that allows spatio-temporal visualisation of mineral precipitation in low volume experiments. Upon injection of an alkaline fluid into an acidic, iron-rich solution, we observe a diverse set of precipitation morphologies, mainly controlled by flow-rate and ion-concentration. Using microscope imaging and pH dependent dyes, we show that finger-like precipitates can facilitate formation and maintenance of microscale pH gradients and accumulation of dispersed particles in confined geometries. Our findings establish a model to investigate the potential of gradients across a semi-permeable boundary for early compartmentalisation, accumulation and chemical reactions at the origins of life.