Processable Composites with Extreme Material Capacities: Toward Designer High Internal Phase Emulsions and Foams

Abstract

High internal phase emulsions (HIPEs) and foams are ubiquitous in our daily lives. They are considered f luid composites with an extremely high-volume fraction of f luid fillers. As all other composite materials do, HIPEs and foams exhibit enhanced properties compared with the simple base fluids without liquid/gas fillers. They can disperse a huge amount of immiscible fluids in other fluids, and fluid fillers remarkably change their physicochemical properties, especially their rheological properties. Their unique structural and compositional features make this material special: A large amount of a dispersed phase is in a very small amount of a continuous phase, and they have an unusual flow behavior as soft glassy materials. Because their fluid nature allows many other materials (e.g., small molecules, polymers, colloids) to be easily dispersed inside, they have a huge potential to be transformed into functional materials that cannot easily be obtained with other hard materials. Here, we summarize the recent progress on HIPEs and foams, particularly in terms of four themes: (1) fabrication techniques, (2) stabilizers and their requirements, (3) flow behavior relating to rheological properties, and (4) porous materials templated from HIPEs and foams. We also discuss future directions and what needs to be done for each theme. Finally, although there have been numerous studies on HIPEs and foams, we present the general outlook for HIPEs and foams to better understand them so that they can be applied to new and unprecedented applications.

Jammed Emulsions with Adhesive Pea Protein Particles for Elastoplastic Edible 3D Printed Materials

“…The applications of 3D printing range from scaffolds for tissue cartilages and specialized functional foods. [3,[5][6][7] Currently food printing is mostly performed using carbohydrate polymer materials, with added cross-linking agents and other natural fillers such as vegetables or chocolates. [8,9] Besides 3D printing conventional foods with attractive designs, 3D printing is also widely studied to create specific food structures for specialized nutrition.…”

Considerations Using Additive Manufacture of Emulsion Inks to Produce Respiratory Protective Filters Against Viral Respiratory Tract Infections Such as the COVID-19 Virus

“…There are detailed reviews on emulsion templating applications[ 48 - 51 ] as well as the range of materials and uses of a porous foam manufactured using both liquid- and bubble-based templating[ 52 ]. Some specific reviews also detailed the porous materials and uses of HIPE-based emulsions and foam templating[ 53 ] as well as the potential of 3D printing as a method to produce tissue engineering scaffolds[ 54 ].…”

3D Printable and Sub‐Micrometer Porous Polymeric Monoliths with Shape Reconfiguration Ability by Miniemulsion Templating

“…For conventional HIPE, such an increase in viscosity usually occurs when the fraction of the internal phase exceeds 74 vol%. [39] The earlier work by Pal shows that the decrease of droplets size could significantly increase the G' and yield stress of HIPE. [45] In our MIPE ink, the ultrasonication process reduced the size of the droplets, so the jamming effect occurred even at 50 vol% of the internal phase.…”

“…Nevertheless, the proper jamming of the internal phase for DIW only occurs if the fraction of the internal phase is high. [39] In the field of emulsion polymerization for polymer latex, miniemulsion is a kinetically stable system that reduces the droplet size to a few hundred nanometers. [40,41] The introduction of costabilizers prevents the Ostwald ripening of the small droplets, and enhances the shelf-life of the emulsion.…”