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Ph.D. Dissertation Jinsheng Fan SoET

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THE EFFECTS OF ADDITIVE MANUFACTURING AND ELECTRIC POLING TECHNIQUES ON POLY(VINYLIDENE FLUORIDE) MATERIALS: TOWARDS FULLY THREE-DIMENSIONAL PRINTED FUNCTIONAL MATERIALS

thesis
posted on 2023-08-03, 13:07 authored by Jinsheng FanJinsheng Fan

    An all-additive manufacturing technique was developed to print piezoelectrically active polymeric materials, primarily poly(vinylidene fluoride) (PVdF), for use in pressure sensors in soft robotics. The research proceeded in three stages. The initial stage used Fused Deposition Modeling (FDM) and electric poling independently to create piezoelectric PVdF pressure sensors. The second stage merged FDM and electric poling processes. The third stage introduced electrospinning to create flexible, high-output piezoelectric PVdF materials, which were combined with three-dimensional (3D) printed soft structures for stretchable pressure sensors.

    The main achievement of the research was the development of the Electric Poling-assisted Additive Manufacturing (EPAM) technique, combining electric poling and FDM 3D printing to print piezoelectric materials with custom structures at lower costs. β-phase in semicrystalline PVdF materials is mainly responsible for piezoelectricity. A higher β-phase content results in superior sensor performance. This technique was evaluated by measuring the piezoelectric output voltage of the printed PVdF films, and β-phase content was quantified using Fourier-transform Infrared spectroscopy (FTIR). The developed EPAM technique was combined with Direct Ink Writing (DIW), becoming a hybrid 3D printing technique. This is the first demonstration of applying a hybrid printing technique to print piezoelectric PVdF-based sensors directly. The sensor was constructed using FDM printed PVdF film as the dielectric sandwiched between two parallel DIW printed silver electrodes. The PVdF sensors have both piezoelectric pressure sensing and capacitive temperature sensing functionalities. The application of the capacitive temperature sensor was demonstrated by applying heating-and-cooling cycles while measuring the capacitance as a function of temperature at a constant frequency, showing improved sensitivities at higher frequencies (i.e., 105 Hz) after dielectric polarization.

    The third stage of research was motivated by the need for soft piezoelectric pressure sensors for soft robotics. Challenges were twofold: requiring soft piezoelectric materials with high coefficients for excellent sensors and fabrication techniques to incorporate soft materials into designed structures. Inspired by the EPAM technique, a method combining electrospinning and DIW was used to create soft piezoelectric PVdF/thermal plastic polyurethane (TPU) blend microfiber-based pressure sensors. The soft sensor was integrated with an FDM printed soft structure for a stretchable pressure sensor with both piezoelectric sensing and capacitive sensing mechanisms.

Funding

NSF grant CNS-1726865

NSF grant CNS-1439717

Ross Fellowship

Bilsland Dissertation Fellowship

History

Degree Type

  • Doctor of Philosophy

Department

  • Engineering Technology

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Robert A. Nawrocki

Additional Committee Member 2

Brittany Newell

Additional Committee Member 3

Jose Garcia

Additional Committee Member 4

Chelsea Davis