Hollow Microtubes and Shells from Reactant‐Loaded Polymer Beads

Makki, Rabih; Al-Humiari, Mohammed; Dutta, Subashisa; Steinbock, Oliver

doi:10.1002/ange.200903292

Cited by 22 publications

(27 citation statements)

References 30 publications

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“…Moreover, they share common properties with structures ranging from nanoscale tubes in cement [3], corrosion filaments [4] to larger-scale brinicles [5] or chimneys at hydrothermal vents [6]. This explains their success as prototypes to grow complex compartmentalized or layered self-organized materials, as chemical motors, as fuel cells, in microfluidics, as catalysts, and to study the origin of life [7,8,9,10,11,12,13,14,15,16,17,18]. However, despite numerous experimental studies, understanding the properties of the wide variety of possible spatial structures and developing theoretical models of their growth remains a challenge.…”

mentioning

confidence: 99%

Spiral precipitation patterns in confined chemical gardens

Haudin

Cartwright

Brau

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

121

163

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Chemical gardens are mineral aggregates that grow in three dimensions with plant-like forms and share properties with selfassembled structures like nanoscale tubes, brinicles, or chimneys at hydrothermal vents. The analysis of their shapes remains a challenge, as their growth is influenced by osmosis, buoyancy, and reaction-diffusion processes. Here we show that chemical gardens grown by injection of one reactant into the other in confined conditions feature a wealth of new patterns including spirals, flowers, and filaments. The confinement decreases the influence of buoyancy, reduces the spatial degrees of freedom, and allows analysis of the patterns by tools classically used to analyze 2D patterns. Injection moreover allows the study in controlled conditions of the effects of variable concentrations on the selected morphology. We illustrate these innovative aspects by characterizing quantitatively, with a simple geometrical model, a new class of self-similar logarithmic spirals observed in a large zone of the parameter space.C hemical gardens, discovered more than three centuries ago (1), are attracting nowadays increasing interest in disciplines as varied as chemistry, physics, nonlinear dynamics, and materials science. Indeed, they exhibit rich chemical, magnetic, and electrical properties due to the steep pH and electrochemical gradients established across their walls during their growth process (2). Moreover, they share common properties with structures ranging from nanoscale tubes in cement (3), corrosion filaments (4) to larger-scale brinicles (5), or chimneys at hydrothermal vents (6). This explains their success as prototypes to grow complex compartmentalized or layered self-organized materials, as chemical motors, as fuel cells, in microfluidics, as catalysts, and to study the origin of life (7-18). However, despite numerous experimental studies, understanding the properties of the wide variety of possible spatial structures and developing theoretical models of their growth remains a challenge.In 3D systems, only a qualitative basic picture for the formation of these structures is known. Precipitates are typically produced when a solid metal salt seed dissolves in a solution containing anions such as silicate. Initially, a semipermeable membrane forms, across which water is pumped by osmosis from the outer solution into the metal salt solution, further dissolving the salt. Above some internal pressure, the membrane breaks, and a buoyant jet of the generally less dense inner solution then rises and further precipitates in the outer solution, producing a collection of mineral shapes that resembles a garden. The growth of chemical gardens is thus driven in 3D by a complex coupling between osmotic, buoyancy, and reaction-diffusion processes (19,20).Studies have attempted to generate reproducible micro-and nanotubes by reducing the erratic nature of the 3D growth of chemical gardens (10,11,13,15,21). They have for instance been studied in microgravity to suppress buoyancy (22, 23), or by injecting aqueous ...

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mentioning

confidence: 99%

Spiral precipitation patterns in confined chemical gardens

Haudin

Cartwright

Brau

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

121

163

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“…Herein we report the use of local convective flow fields to direct the bottom-up growth of self-assembling nanometersized inorganic building blocks into micrometer-sized tubes, [10][11][12] by injecting solutions of polyoxometalate clusters into a bulk solution containing a large organic cation. [13][14][15][16][17] The resulting millimeter-sized network materials can be structured from the top down, by using polyoxometalate clusters assembled from the bottom up ( Figure 1).…”

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confidence: 99%

“…The self-assembly of these cluster anions into a membrane by a "chemical garden" [11] like mechanism is the first step towards constructing a network. Ion exchange and aggregation occurs at the interface between a solution of POM and a solution containing large cations (such as the dye solution used here), forming a membrane that is impermeable to the Schematic showing the assembly of the nanometer-sized polyoxometalate (POM) clusters (a) to form a membrane when they come into contact with cationic dye molecules (b).…”

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confidence: 99%

Directed Assembly of Inorganic Polyoxometalate‐based Micrometer‐Scale Tubular Architectures by Using Optical Control

et al. 2012

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The self-assembly of supramolecular architectures to produce functional systems and devices is a key goal where molecular design, self-assembly, and materials design need to be combined together. [1][2][3] In polyoxometalate chemistry we have taken the challenge to understand the assembly of clusters from the molecular to the nanoscale, by using a range of approaches including control of the available species and the use of macroscale flow systems. [3] This type of control is vital, especially if the link from the nanoscale to the mesoscale (and beyond) is to be made. [4] Nature can solve this problem by constructing a scaffold to direct the assembly processes. [5] By using this strategy, scaffolding allows complex structures to be assembled and self-correction ensures the formation of precise, highly complex architectures. However, even these systems displace the problem to the design of the scaffold that must be replaced in synthetic systems. Routes to accomplish this from the bottom up are limited because controlling the structures formed on longer length scales is extremely demanding. [6,7] The associated dynamic range currently requires specialist equipment for fabrication, and reliable new material and device architectures are difficult and time consuming to fabricate. [8,9] As such, the discovery of a strategy for the controllable and reliable fabrication of materials that bridges the gap between bottom-up self-assembly and topdown control would revolutionize the design and fabrication of mesoscopic materials.

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“…This precipitate reaction typically involves the formation of microscopically small colloid particles and their aggregation or addition to the membrane. This phenomenon is related to so-called "chemical gardens" which consist of thin cylindrical precipitate membranes separating a metal salt solution from silicate or hydroxide solutions [28,41].…”

Section: Introductionmentioning

confidence: 99%

Multiphase modelling of precipitation-induced membrane formation

et al. 2020

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We formulate a model for the dynamic growth of a membrane developing in a flow as the result of a precipitation reaction, a situation inspired by recent microfluidic experiments. The precipitating solid introduces additional forces on the fluid and eventually forms a membrane that is fixed in the flow due to adhesion with a substrate. A key challenge is that the location of the immobile membrane is unknown a priori. To model this situation, we use a multiphase framework with fluid and membrane phases; the aqueous chemicals exist as scalar fields that react within the fluid to induce phase change. To verify that the model exhibits desired fluid-structure behaviors, we make a few simplifying assumptions to obtain a reduced form of the equations that is amenable to exact solution. This analysis demonstrates no-slip behavior on the developing membrane without a priori assumptions on its location. The model has applications towards precipitate reactions where the precipitate greatly affects the surrounding flow, a situation appearing in many laboratory and geophysical contexts including the hydrothermal vent theory for the origin of life. More generally, this model can be used to address fluid-structure interaction problems that feature the dynamic generation of structures.dynamically according to equations governing the chemistry. We choose to model the fluid-structure combination as a single multiphase material: one component fluid or solvent and one component structure or precipitate membrane. Such multiphase models have proven useful in a variety of complex-fluid applications, such as bacterial biofilms [13,14], tumor-growth [9,21,37,44], and biological membranes [27]; their formulation is based on averaging momentum and stresses in separated, multi-component fluids [17,18].The multiphase framework developed here builds on previous ones [13,25,52], but with some keys differences that are guided by a combination of physical principles, model simplicity, and the micro-fluidic experiments mentioned above. First, our formulation conserves the total mass of the components solvent, dissolved species, and precipitate membrane throughout evolution. In particular, the model accounts for changes in solute concentrations that result from the formation of new membrane and the associated exclusion of solvent volume. This effect is neglected in previous models that treat reaction chemicals as scalar fields distinct from the multiphase material, but is essential for overall mass conservation. The treatment of reaction chemicals as additional components of a multiphase material has been successfully modeled by many [35, 51, see] but greatly complicates the analysis, interpretation, and simulation of the governing equations. Second, by making certain choices in the averaging procedure for the multicomponent stress, our formulation becomes equivalent to an incompressible Brinkman system with variable permeability. This equivalence is important for a few reasons. First, it guarantees that the model reduces to the Stokes equations in...

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Hollow Microtubes and Shells from Reactant‐Loaded Polymer Beads

Cited by 22 publications

References 30 publications

Spiral precipitation patterns in confined chemical gardens

Spiral precipitation patterns in confined chemical gardens

Directed Assembly of Inorganic Polyoxometalate‐based Micrometer‐Scale Tubular Architectures by Using Optical Control

Multiphase modelling of precipitation-induced membrane formation

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