Microfluidically produced microcapsules with amphiphilic polymer conetwork shells

Microcapsules with an aqueous core can be conveniently prepared by water-in-oil-in-water double emulsion microfluidics. However, conventional shell materials are based on hydrophobic polymers or colloidal particles. Thus, these microcapsules feature a hydrophobic shell impermeable to water-soluble compounds. Capsules with semipermeable hydrogel shells have been demonstrated but may exhibit poor mechanical properties. Here, amphiphilic polymer conetworks (APCNs) based on poly(2-hydroxyethyl acrylate)-linked by-polydimethylsiloxane (PHEA-l-PDMS) are introduced as a new class of wall materials in double emulsion microcapsules. These APCNs are mechanically robust silicone hydrogels that are swellable and permeable to water and are soft and elastic when dry or swollen. Therefore, the microcapsules can be dried and rehydrated multiple times or shrunken in sodium chloride salt solutions without getting damaged. Moreover, the APCNs are permeable for hydrophilic organic compounds and impermeable for macromolecules. Thus, they can be loaded with macromolecules or nanoparticles during microfluidic formation and with organic molecules after capsule synthesis. The microcapsules serve as microreactors for catalytically active platinum nanoparticles that decompose hydrogen peroxide. Finally, the surface of the APCN microcapsules can be selectively functionalized with a cholesterol-based linker. Concluding, APCN microcapsules could find applications for the controlled delivery of drugs, as microreactors for synthesis, or as scaffolds for synthetic cells

Hierarchical porous materials made by stereolithographic printing of photo-curable emulsions

Porous materials are relevant for a broad range of technologies from catalysis and filtration, to tissue engineering and lightweight structures. Controlling the porosity of these materials over multiple length scales often leads to enticing new functionalities and higher efficiency but has been limited by manufacturing challenges and the poor understanding of the properties of hierarchical structures. Here, we report an experimental platform for the design and manufacturing of hierarchical porous materials via the stereolithographic printing of stable photo-curable Pickering emulsions. In the printing process, the micron-sized droplets of the emulsified resins work as soft templates for the incorporation of microscale porosity within sequentially photo-polymerized layers. The light patterns used to polymerize each layer on the building stage further generate controlled pores with bespoke three-dimensional geometries at the millimetre scale. Using this combined fabrication approach, we create architectured lattices with mechanical properties tuneable over several orders of magnitude and large complex-shaped inorganic objects with unprecedented porous designs.ISSN:2045-232

3D printing of sacrificial templates into hierarchical porous materials

Hierarchical porous materials are widespread in nature and find an increasing number of applications as catalytic supports, biological scaffolds and lightweight structures. Recent advances in additive manufacturing and 3D printing technologies have enabled the digital fabrication of porous materials in the form of lattices, cellular structures and foams across multiple length scales. However, current approaches do not allow for the fast manufacturing of bulk porous materials featuring pore sizes that span broadly from macroscopic dimensions down to the nanoscale. Here, ink formulations are designed and investigated to enable 3D printing of hierarchical materials displaying porosity at the nano-, micro- and macroscales. Pores are generated upon removal of nanodroplets and microscale templates present in the initial ink. Using particles to stabilize the droplet templates is key to obtain Pickering nanoemulsions that can be 3D printed through direct ink writing. The combination of such self-assembled templates with the spatial control offered by the printing process allows for the digital manufacturing of hierarchical materials exhibiting thus far inaccessible multiscale porosity and complex geometries.ISSN:2045-232

Microfluidically produced microcapsules with amphiphilic polymer conetwork shells

Microcapsules with aqueous core can be conveniently prepared by water-in-oil-in-water double emulsion microfluidics. However, conventional shell materials are either based on polymers or monomers that are soluble in the oil phase, or based on hydrophobic colloidal particles. As a result, microcapsules derived from double emulsions usually feature a hydrophobic shell that is not semipermeable for water-soluble compounds. While capsules with semipermeable hydrogel shells have been demonstrated, these may exhibit poor mechanical properties and lack the robustness required in many applications. In this study, amphiphilic polymer conetworks (APCNs) based on poly(2-hydroxyethyl acrylate)-linked by-polydimethylsiloxane (PHEA-l-PDMS) are introduced as a new class of wall materials in double emulsion microcapsules. These APCNs are mechanically robust silicone hydrogels that are swellable and permeable to water, and are soft and elastic in the dry and swollen states. Thus, the microcapsules can be dried and rehydrated multiple times or shrunken in sodium chloride salt solutions without getting damaged. Moreover, the APCNs are semipermeable for hydrophilic organic compounds, while being impermeable for macromolecules and colloids. Thus, they can be loaded with macromolecules or nanoparticles during microfluidic formation, and with organic molecules after capsule synthesis. Uptake into and release from the capsules were studied with the model compounds fluorescein and fluorescently labelled dextran. Moreover, the microcapsules served as microreactors for catalytically active platinum nanoparticles that decomposed hydrogen peroxide. Finally, the surface of APCN microcapsules can be selectively functionalized with a cholesterol-based linker that non-covalently binds to the hydrophobic domains of the APCN. Thus, APCN microcapsules represent versatile and broadly applicable capsules that could find application for the controlled delivery of drugs, as microreactors for synthesis, or even as scaffolds for synthetic cells