Purpose-This paper aims to summarize the latest developments both in terms of theoretical understanding and experimental techniques related to inkjet fluids. The purpose is to provide practitioners a self-contained review of how the performance of inkjet and inkjet-based three-dimensional (3D) printing is fundamentally influenced by the properties of inkjet fluids. Design/methodology/approach-This paper is written for practitioners who may not be familiar with the underlying physics of inkjet printing. The paper thus begins with a brief review of basic concepts in inkjet fluid characterization and the relevant dimensionless groups. Then, how drop impact and contact angle affect the footprint and resolution of inkjet printing is reviewed, especially onto powder and fabrics that are relevant to 3D printing and flexible electronics applications. A future outlook is given at the end of this review paper. Findings-The jettability of Newtonian fluids is well-studied and has been generalized using a dimensionless Ohnesorge number. However, the inclusion of various functional materials may modify the ink fluid properties, leading to non-Newtonian behavior, such as shear thinning and elasticity. This paper discusses the current understanding of common inkjet fluids, such as particle suspensions, shear-thinning fluids and viscoelastic fluids. Originality/value-A number of excellent review papers on the applications of inkjet and inkjet-based 3D printing already exist. This paper focuses on highlighting the current scientific understanding and possible future directions.
The ability to control the properties of bio-inspired liquid-infused surfaces is of interest in a wide range of applications. Liquid layers created using oil-infused polydimethylsiloxane elastomers offer a potentially simple way of accomplishing this goal through the adjustment of parameters such as curing agent ratio and oil viscosity. In this work, the effect of tuning these compositional parameters on the properties of the infused polymer are investigated, including infusion dynamics, stiffness, longevity in the face of continuous liquid overlayer removal, and resistance to bacterial adhesion. It is found that that curing agent concentration appears to have the greatest impact on the functionality of the system, with a lower base-to-curing agent ratio resulting in both increased longevity and improved resistance to adhesion by Escherichia coli. A demonstration of how these findings may be implemented to introduce patterned wettability to the surface of the infused polymers is presented by controlling the spatial arrangement of bacteria. These results demonstrate a new degree of control over immobilized liquid layers and will facilitate their use in future applications.
This article reports 3D printing of carbon nanotube‐polylactic acid (CNT‐PLA) composites using an extrusion‐based Fused Deposition Modeling (FDM) method. CNTs with an average diameter of 128 nm and an average length of 2.5 μm were first compounded with PLA and extruded into feedstock filaments at 0.5%, 2.5%, and 5% (w/w) CNT loadings. CNT aggregates were observed, but no clogging occurred during printing with a 500‐μm print nozzle. The rheology of the CNT‐PLA samples was characterized to understand the printing‐induced alignment of CNTs along the road axis. Additionally, the effect of printing flow rate was explored for a fixed printing gap and nozzle diameter. Higher flow rates reduced the void fraction in the FDM parts, but unexpectedly resulted in less degree of CNT alignment, which is attributed to radial flow and fusion between adjacent roads. The mechanical properties of the CNT‐PLA tensile test coupons were characterized. Inclusion of CNTs increased the Young's modulus by 30% at 5% CNT loading, but reduced the tensile strength and overall toughness of the FDM parts. Experimental data were compared against the Rule of Mixtures (RoM) model, the Halpin‐Tsai model, and the modified RoM model and were further explained by the void fraction and CNT orientation. POLYM. COMPOS., 39:E1060–E1071, 2018. © 2017 Society of Plastics Engineers
This article reports the surface pressure and microstructure of two different types of carbon nanotubes (CNTs) at an air-water interface; namely, as-produced CNTs (nf-CNTs) and CNTs functionalized with carboxyl groups (f-CNTs). Both types of CNTs formed 3D aggregates upon compression using a Langmuir-Pockels trough. However, f-CNTs showed a lower degree of aggregation compared with that of nf-CNTs. This is attributed to the deprotonation of the carboxyl groups within the water subphase, leading to additional electrostatic repulsion between f-CNTs. For the same initial amount of CNTs spread onto the interface, the actual coverage of f-CNTs was higher than that of nf-CNTs at a given trough area. At high compression, f-CNTs formed aligned CNT domains at the interface. These 2D domains resembled 3D liquid-crystalline structures formed by excluded volume interactions. The denser packing and orientational ordering of f-CNTs also contributed to a compressional modulus higher than that of nf-CNTs, as calculated from the surface pressure isotherms. A Volmer equation of state was applied to model the measured surface pressure containing both thermodynamic and mechanical contributions. The Volmer model, however, did not consider the loss of CNTs from the interface due to 3D aggregation and consequently overestimated the surface pressure at high compression. The actual coverage of CNT during compression was back calculated from the model and was in agreement with the value obtained independently from optical micrographs. The findings of this work may have a broader impact on understanding the assembly and collective behavior of rod-like particles with a high aspect ratio at an air-water interface.
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