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Material extrusion (MEX) of soft, multifunctional composites consisting of liquid metal (LM) droplets can enable highly tailored properties for a range of applications from soft robotics to stretchable electronics. However, an understanding of how LM ink rheology and print process parameters can reconfigure LM droplet shape during MEX processing for in-situ control of properties and function is currently limited. Herein, the material (ink viscosity, and LM droplet size) and process (nozzle velocity, height from print bed, and extrusion rate) parameters are determined which control LM microstructure during MEX of these composites. The interplay and interdependence of these parameters is evaluated and nearly spherical LM droplets are transformed into highly elongated ellipsoidal shapes with an average aspect ratio of 12.4 by systematically tuning each individual parameter. Material and process relationships are established for the LM ink which show that an ink viscosity threshold should be fulfilled to program the LM microstructure from spherical to an ellipsoidal shape during MEX. Additionally, the thin oxide layer on the LM droplets is found to play a unique and critical role in the reconfiguration and retention of droplet shape. Finally, two quantitative design maps based on material and process parameters are presented to guide MEX additive manufacturing strategies for tuning liquid droplet architecture in LM-polymer inks. The insights gained from this study enable informed design of materials and manufacturing to control microstructure of emerging multifunctional soft composites.
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Understanding inks for porous-electrode formation
Scalable manufacturing of high-aspect-ratio multi-material electrodes are important for advanced energy storage and conversion systems. Such technologies often rely on solution-based processing methods where the active material is dispersed in a colloidal ink. To date, ink formulation has primarily focused on macro-scale process-specific optimization ( i.e. viscosity and surface/interfacial tension), and been optimized mainly empirically. Thus, there is a further need to understand nano- and mesoscale interactions and how they can be engineered for controlled macroscale properties and structures related to performance, durability, and material utilization in electrochemical systems.
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- Award ID(s):
- 1727863
- PAR ID:
- 10047193
- Date Published:
- Journal Name:
- J. Mater. Chem. A
- Volume:
- 5
- Issue:
- 39
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 20527 to 20533
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C7TA07255D
