Fabricating Robust Constructs with Internal Phase Nanostructures via Liquid‐in‐Liquid 3D Printing

Abstract

The ability to print soft materials into predefined architectures with programmable nanostructures and mechanical properties is a necessary requirement for creating synthetic biomaterials that mimic living tissues. However, the low viscosity of common materials and lack of required mechanical properties in the final product present an obstacle to the use of traditional additive manufacturing approaches. Here, a new liquid-in-liquid 3D printing approach is used to successfully fabricate constructs with internal nanostructures using in situ self-assembly during the extrusion of an aqueous solution containing surfactant and photocurable polymer into a stabilizing polar oil bath. Subsequent photopolymerization preserves the nanostructures created due to surfactant self-assembly at the immiscible liquid-liquid interface, which is confirmed by small-angle X-ray scattering. Mechanical properties of the photopolymerized prints are shown to be tunable based on constituent components of the aqueous solution. The reported 3D printing approach expands the range of low-viscosity materials that can be used in 3D printing, and enables robust constructs production with internal nanostructures and spatially defined features. The reported approach has broad applications in regenerative medicine by providing a platform to print self-assembling biomaterials into complex tissue mimics where internal supramolecular structures and their functionality control biological processes, similar to natural extracellular matrices.

Investigating the morphological transitions in an associative surfactant ternary system

“…The DPD method in this study validated by experiments can be an effective supplement for experimental setups and provides otherwise inaccessible mesoscopic information at the molecular level for a ternary phase of surfactant-polar oil-water. Apart from the scientific interest of such studies, the outcome highly affects the practical applications of surfactant systems such as liquid-inliquid 3D printing, 28,29 for instance, determining how rapidly and what kind of mesophase forms. The established ternary phase diagram along with the DPD model can be used to predict and control the formation of structures like lamellar or vesicles, which can be used as simple model systems for biological membranes in life sciences applications.…”

“…24 The interesting systems of surfactant-fatty acid-water have opened up new routes for applications in biotechnology, 25,26 proton conductors, 24,27 and liquid-in-liquid 3D printing. 28,29 Particularly, for the printing application, although the resulting nanoscale phases are known to exist and have enabled the printing of such materials, 28 the phase behavior of the used associative surfactant system is not well understood. In addition, fatty acids and their derivatives as green surface-active molecules have received increased attention due to their natural abundance, low toxicity, and biocompatibility.…”

Spongy all-in-liquid materials by in-situ formation of emulsions at oil-water interfaces

“…The presence of particles results in the arrest of the mixture in a transition zone of bicontinuous structures during the phase separation 30 . Recently, internal structures inside the all-in-liquid printed materials were achieved with photocurable polymers 31 . Oil-water interfaces can be stabilized by the interactions of surfactant assemblies, i.e., micelles, with fatty acids, where micelle morphology is changed from spherical to lamella and a gel phase is formed 31 , 32 .…”

“…Recently, internal structures inside the all-in-liquid printed materials were achieved with photocurable polymers 31 . Oil-water interfaces can be stabilized by the interactions of surfactant assemblies, i.e., micelles, with fatty acids, where micelle morphology is changed from spherical to lamella and a gel phase is formed 31 , 32 . In the presence of photocurable polymers inside the internal phase, submicrometer regions are formed after photopolymerization 31 .…”

“…Oil-water interfaces can be stabilized by the interactions of surfactant assemblies, i.e., micelles, with fatty acids, where micelle morphology is changed from spherical to lamella and a gel phase is formed 31 , 32 . In the presence of photocurable polymers inside the internal phase, submicrometer regions are formed after photopolymerization 31 . The STRIPS approach is limited to the use of a ternary mixture and the photopolymerization method eliminates the fluidity of the printed material.…”