Semester
Summer
Date of Graduation
2023
Document Type
Thesis
Degree Type
MS
College
Statler College of Engineering and Mineral Resources
Department
Mechanical and Aerospace Engineering
Committee Chair
Konstantinos Sierros
Committee Member
Edward Sabolsky
Committee Member
Jennifer Jones
Abstract
Direct ink writing (DIW) provides for an expansive material library and the ability to print multiple materials with tailored functionalities in a controllable and single-step process. Particularly beneficial is the net shape printing under ambient conditions of a wide range of materials normally incompatible with one another. Coaxial DIW is a 3D printing technique that allows for two dissimilar inks to be extruded simultaneously in a co-flow manner. In this work, custom-designed coaxial nozzles were 3D-printed using a stereolithography printer. Composite inks comprised of thermoplastic polyurethane and silver were developed and studied. The coaxial nozzles were then used to co-extrude the conductive ink cores within shells of silicone elastomers for the fabrication of embedded flexible sensors. The relationships between line width and cross-sectional geometry of printed coaxial fibers and a variety of printing parameters, such as height, flowrate, and print speed, were characterized. Individual fibers were electromechanically evaluated. Furthermore, stretchable strain sensors were developed by implementing coaxial fibers into rectangular silicone sensors and into soft robotic pneumatic actuators. Initial work was conducted to integrate the coaxial fibers into soft actuators or “PneuHinge”. The various sensors were evaluated for their electromechanical response due to induced strains from uniaxial tension, 3-point bending, and pneumatic actuation.
This work demonstrated the ability of coaxial DIW to expand the applicability of DIW, to control the spreading of fluids with low static yield-stresses, and to embed flexible sensors in a layer-by-layer process. The work supported the development of a multimaterial, single nozzle additive manufacturing process for a NASA project, “3D Printable Soft Actuators with embedded Smart Sensors for Extraterrestrial Applications.”
Recommended Citation
Burke, John Michael, "Multimaterial, Core-Shell Direct Ink Writing of Flexible Strain Sensors for Pneumatically-Actuated Soft Robotic Hinge Joints" (2023). Graduate Theses, Dissertations, and Problem Reports. 12145.
https://researchrepository.wvu.edu/etd/12145