Coaxial Ceramic Direct Ink Writing on Heterogenous and Rough Surfaces: Investigation of Core–Shell Interactions

Abstract

In this work, coaxial conductor–ceramic direct ink writing enables the printing of sensitive or encapsulated materials onto heterogeneous and rough substrates. While encasing the core fluid within a stiff ceramic shell, continuity may be maintained, even while printing onto conventionally challenging substrates. Here, we report the development of a coaxial ceramic direct ink writing suite and explore coflow interrelationships based on microfluidic principles. A coaxial nozzle is designed to facilitate the coextrusion of an alumina shell, whereas indium–tin-oxide inks constitute the core. In this manner, a core–shell ceramic element may be printed onto rough substrates for future high-temperature applications. Colloidal inks are engineered to provide the required rheological and sintering performance. Moreover, flow simulations in conjunction with microfluidic coflow principles are used to explore the coaxial printing processing space, thus controlling the core–shell architectures. Physical modeling is further used to analyze core deformations and eccentricity. Simulations are validated experimentally, and the analyses are used to deposit coaxial ceramic features onto heterogeneous, high-temperature ceramic substrates.

Multicore–Shell Direct Ink Writing of Coaxial Transmission Lines

“…The ratio of major and minor axes of the printed core structure displays 1.034 (Figure S5a), which is close to a perfect circle. This can be supported by the dimensionless quantity, Ξ: , normalΞ = τ normaly ρ g h + γ R − 1 where τ y and ρ are the dynamic yield stress and density of the Ag ink respectively, γ is the interfacial tension between the core Ag ink and shell epoxy ink, and R is the core radius. In our case, the calculated Ξ is ∼2.24 (details in Supporting Information), indicating that the dynamic yield stress of Ag ink is enough to resist the potential deformations caused by the gravitational pressure and capillary forces.…”

Additive Manufacturing of Multimaterial Composites for Radiation Shielding and Thermal Management

“…Material extrusion-based additive manufacturing enables the ability to selectively dispense multiple materials in three-dimensional space with custom chemistries and architectures. , Fused deposition modeling (FDM) has been demonstrated as a viable process to generate multimaterial radiation shields. − The integration of shields produced via FDM, however, requires separate assembly steps as the processing temperatures of extrusion and poor adhesion to microelectronics prevent the direct deposition of shielding onto devices. ,,, Conversely, direct ink writing (DIW) additive manufacturing enables the deposition of composite inks with high volumetric loading of additives. Depending on the binder chemistry, inks can be printed at room temperature and be conformally deposited on a wide range of substrates. , Furthermore, DIW enables architecture modification of filaments into core-shell, graded, and blended additive structures. − FDM printing has also demonstrated the ability to make core-shell architectures, although the requirements for fabrication limit the volumetric loading of inorganic particle additives. Furthermore, the processing conditions require 3D printing of preforms with two materials which are then thermally drawn into core-shell filaments or melt extrusion of two polymer feedstocks which prevent adhesion directly onto electronics. − Brounstein et al have shown that DIW can be used to produce shielding against neutron radiation that could also readily dissipate heat from the shielded device .…”

Multimode coaxial extrusion of segmented core-shell structures for soft metamechanics and biomimetic applications

“…Multi-material DIW based on fluidic strategy is executable. But due to complex extrusion control [5,[47][48][49][50], it presents limitations on producing functional filaments or products with complicated shapes.…”