Fariha Rubaiya
(Advisor: Dr. Meisha Shofner)
will propose a doctoral thesis entitled,
“Understanding Coupling of Auxeticity and Piezoelectricity in Cellulose
Structures”
On
Thursday, December 5th, 2024
1:00 PM
in-person
Price-Gilbert 4222
Or via
Join the meeting now
Meeting ID: 274 745 260 39
Passcode: TdvX4P
Committee Members:
Dr. Meisha Shofner, MSE
Dr. Lauren Garten, MSE
Dr. Kyriaki Kalaitzidou, ME, MSE
Dr. Vladimir Tsukruk, MSE
Dr. Christopher Luettgen, ChBE
Executive Summary: Cellulose is the most abundant organic compound on the planet and has the potential to enable more sustainable and emergent technologies because of its exceptional properties. This work explores two unique properties of cellulose that rarely coexist – auxeticity and piezoelectricity. Auxeticity, which occurs in materials with a negative Poisson’s ratio, has been found in crystalline cellulose Iβ. Moreover, cellulose based materials such as various papers, hand sheets and paperboards are known to show auxetic response at a macroscopic level. Cellulose Iβ forms in a non-centrosymmetric structure (space group P21) of ordered hydrogen-bond networks and permanent dipole moments which makes it piezoelectric. This current research will investigate the potential for auxeticity and piezoelectricity to occur simultaneously and interact constructively with cellulose structures of different length scales.
The key objective of this research is to understand the coupling between auxeticity and piezoelectricity in cellulose structures. I hypothesize that the auxetic response and piezoelectric effect occurs simultaneously in cellulose crystal structure and microscopic auxetic response can amplify piezoelectric response in cellulose films. This study employs cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and kraft pulp as the primary sources for film formation. The proposed work is structured into three specific aims. First, we will investigate the auxetic behavior of cellulose films, examining how fabrication techniques such as drop casting, vacuum filtration, and blade coating influence the out-of-plane auxetic responses. This aim includes characterizing the structure-property relationships within films, examining how factors like morphology and fiber-fiber interactions contribute to auxeticity. Auxetic behavior of the cellulose films will also be examined at the crystallographic level. Second, we will analyze the role of crystal alignment on the piezoelectric behavior of cellulose films, where the above-mentioned fabrication techniques will be used to understand the influence of processing on the crystal alignment and dielectric behavior. This aim is designed to identify correlations between film alignment and piezoelectric properties, enhancing the understanding of how crystallographic orientation affects electrical performance. Lastly, we will evaluate the combined auxetic and piezoelectric properties in cellulose films both at crystal and microscopic level. By integrating simultaneous measurements of auxetic and piezoelectric responses at multiple length scales, this aim will advance knowledge on electromechanical coupling effects in cellulose. Successful completion of these aims will provide a comprehensive understanding of how auxeticity can be tuned in cellulose materials to maximize piezoelectric output. This understanding could lead to the development of sustainable, cellulose-based sensors, actuators, and other electromechanical devices, promoting advancements in green technology and clean energy applications.