Oscillatory Growth of Silica Tubes in Chemical Gardens

Abstract

We report distinct growth regimes of hollow silica fibers formed by hydrodynamic injection of cupric sulfate into silicate solution. The tubes grow either steadily along a continuous jet of buoyant solution or through relaxation oscillations that are governed by chemo-mechanical processes. The dependence of the oscillation period on flow rate and copper concentration is explained in the framework of a simple model. Tailored flow patterns allow the directional control of the tubes and their use as miniature connectors. Our findings are applicable to the understanding of chemical gardens, promise a wealth of nonlinear phenomena, and offer possible applications in microfluidics.

The fertile physics of chemical gardens

“…5 Such injection delivery is typically performed in the upward direction, at constant rates, using a needle or small tube. Downward-directed injection is also possible if the seed solution is denser than the reservoir solution; so is horizontal injection if buoyancy is excluded.…”

Genericity of confined chemical garden patterns with regard to changes in the reactants

“…Depending on the concentration of the injected solution, different growth regimes, such as popping, jetting, budding and ocean-ridge-like dynamics, have been observed. [25][26][27] Injection reduces the role played by osmosis during the growth and leads to the formation of regular tubes provided the concentration of metallic salt is not too large. Beyond some limit, wide bulging tubes are formed.…”

“…Beyond some limit, wide bulging tubes are formed. 25 Buoyant gas bubbles can also be used to stabilize the tubular growth and select the tube radius. 28 In order to have more control over the emerging patterns and to gain insight into their growth properties, chemical gardens have recently been grown by injection of solutions in a horizontal Hele-Shaw cell to confine the dynamics to a quasi-2D geometry and to reduce the influence of buoyancy and osmosis.…”

Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics

“…Numerous chemical modifications have been reported including tube-forming reactions involving polyoxometalates (22) and organic reactants (23). The seed particle may be replaced by injected salt solutions (24). Furthermore, one can reduce the dimensionality of the system by the injection of salt solutions from a point-like source into a thin, horizontal layer of silicate solution contained within a Hele-Shaw cell (25)(26)(27).…”