Three-Dimensional Direct Ink Writing of Low Viscosity Inks in a Polyvinyl Alcohol Suspension

Three-dimensional printing of nanomaterial based composites makes it possible to directly construct high-resolution multi-functional parts with complex geometry and topological features, thus facilitates research and development of next generation soft electronics, biocompatible and biomaterial-based structures, and conductive 3D lattices. The work presents an attempt of developing an additive manufacturing method for low-viscosity nanomaterial inks composed of polyvinyl alcohol (PVA) as matrix and various nanomaterial fillers in forming 3D gel structures. This methodology can be extrapolated to other material systems without the requirement of supporting structure in maintain structural integrity. In this study we developed a physical based mathematical model to describe polymer-solvent molecule motion and phase transformation to better quantification the gel separation and formation process so that matrix gel microstructure and properties can be fine-tuned for ink suspension used in 3D printing. In current gel matrix system, the PVA chain motion was found to be dominated by translational motion mode under neutral conditions at atmospheric pressure and temperature, driven by a free energy differential leading to spinodal decomposition of the polymer-solvent mixture. For depressed temperatures and in highly crosslinked solutions, the polymer motion was found to be heavily constrained to rotational motion, limiting the phase separation rate of the mixture and increasing the stability of the matrix gel to the point that low viscosity inks can be suspended and immobilized. Based on our approach, construction of both 2D and 3D structures of low viscosity inks were demonstrated in polymer suspension. A water-based ink was printed in a 10% weight POVAL 56-98 grade PVA hydrogel mixed with a 50:50 volumetric mixture of DMSO and water, which was found to best support the ink while responding fluidly to the motion of the print head. A flat tipped needle in a perpendicular orientation was used for deposition and printing motion was limited to smooth curves to prevent any damage to prior depositions. A thin film of water was applied to the surface of the polymer suspension to prevent gelation from occurring on the print needle. Resolution improvements can be achieved using a thinner needle and a lower extrusion to reduce deposition amounts while maintaining the required extrusion pressure. Ink printability can also be improved by reducing surface tension and increasing viscosity to allow for smooth deposition at low extrusion rates. This method shows great potential for constructing biomaterial lattices for next generation drug and medical research and developing structured functional materials based on ink contents for flexible and wearable devices.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Materials Engineering

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Jenkinson, Jim William

Advisor dc:contributor.advisor

• Sun, Li

Committee members dc:contributor.committeemember

• Fan, Zheng
• Song, Gangbing
• Liu, Dong
• Chen, Zheng

• Additive Manufacturing, Polyvinyl Alcohol, PVA, 3D printing, nanomaterials

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/17691

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/17691