3D printing of concentrated emulsions into multiphase biocompatible soft materials

Abstract

3D printing via direct ink writing (DIW) is a versatile additive manufacturing approach applicable to a variety of materials ranging from ceramics over composites to hydrogels. Due to the mild processing conditions compared to other additive manufacturing methods, DIW enables the incorporation of sensitive compounds such as proteins or drugs into the printed structure. Although emulsified oil-in-water systems are commonly used vehicles for such compounds in biomedical, pharmaceutical, and cosmetic applications, printing of such emulsions into architectured soft materials has not been fully exploited and would open new possibilities for the controlled delivery of sensitive compounds. Here, we 3D print concentrated emulsions into soft materials, whose multiphase architecture allows for site-specific incorporation of both hydrophobic and hydrophilic compounds into the same structure. As a model ink, concentrated emulsions stabilized by chitosan-modified silica nanoparticles are studied, because they are sufficiently stable against coalescence during the centrifugation step needed to create a bridging network of droplets. The resulting ink is ideal for 3D printing as it displays high yield stress, storage modulus and elastic recovery, through the formation of networks of droplets as well as of gelled silica nanoparticles in the presence of chitosan. To demonstrate possible architectures, we print biocompatible soft materials with tunable hierarchical porosity containing an encapsulated hydrophobic compound positioned in specific locations of the structure. The proposed emulsion-based ink system offers great flexibility in terms of 3D shaping and local compositional control, and can potentially help address current challenges involving the delivery of incompatible compounds in biomedical applications.

Forming Sticky Droplets from Slippery Polymer Zwitterions

“…The lower solubility of polymer 3 in low salt aqueous solutions is thought to confine the polymer to the oil–water interface, prevent coalescence, and promote interdroplet interactions. The stability of the adhesive 3 ‐stabilized emulsions to centrifugation suggests the suitability of these materials for direct ink writing processes, which we are currently exploring.…”

Printing Therapeutic Proteins in 3D using Nanoengineered Bioink to Control and Direct Cell Migration

“…Rotational time sweeps were executed at three different shear rates (s −1 ) in sequential order: 10 −2 (60 s), 3000 (5s), and 10 −2 (120s) to determine shear recovery of solutions . Time to 80% recovery was manually observed/calculated . Oscillatory shear stress sweeps between 10 −1 and 10 3 performed at 1 Hz and frequency sweeps between 10 0 and 10 2 performed at 10 Pa to further validate yield points and investigate dependence on frequency.…”

Two‐Phase Emulgels for Direct Ink Writing of Skin‐Bearing Architectures

“…However, this depends on the ability to engineer phase‐separation to achieve high fidelity without compromising the required balance between ink composition and printability . In line with this effort, we noted that the absence of a solid support in the aqueous phase of the emulsion prevented phase separation; otherwise, such phenomenon could be enhanced by the incorporation of a hydrophilic component that is miscible with the aqueous phase to solidify the emulsions prior to printing …”