(6lt) High Performance Materials for Wearable Electronics and Sensors

I am currently a 6^th year PhD candidate in the Department of Chemical and Biomolecular Engineering at Rice University under Matteo Pasquali. Individual carbon nanotubes (CNTs) have outstanding mechanical strength, electrical conductivity, and thermal conductivity. However, obtaining these excellent single molecular properties on the macroscale has proven difficult. My PhD work focuses on the dissolution of CNTs into chlorosulfonic acid and the processing of these solutions into high-performance CNT fibers. I have studied how the rheology and phase behavior of the solutions affect the spinning process and the electrical and mechanical properties of the resulting fibers. I demonstrated that lowering the concentration of CNTs in the spinning solution results in fibers with improved mechanical properties (higher tensile strength, Young’s modulus, and toughness) but similar electrical properties. Through wide-angle X-ray scattering (WAXS), polarized Raman spectroscopy, and nano-computed tomography, I determined that there was no significant change in alignment or porosity of the fibers. However, mechanical testing showed that the stronger fibers also had a larger elongation at break. Therefore, I concluded the lower concentration solutions are able to assemble into larger CNT bundles within the fiber structure. These bundles then slide past each other and are the driving mechanism for the tensile strength. The larger bundle size does not affect conductivity as the resistance in the fiber is dominated by the tube-tube junctions and material impurities. Additionally, I have been studying the mechanical behavior of CNT fibers under various strain rates and temperatures. Consistent with other polymeric materials, the tensile strength of CNT fibers decreases with increasing temperature and increases with increasing strain rate. I am currently studying the effects of CNT fiber purity and aspect ratio on these trends to better understand the frictional forces between the bundles of CNTs within the fiber. Finally, I have also studied the application of CNT fibers for use as wearable electrocardiogram (EKG) sensors for continuous heart monitoring. I plied CNT fibers together to make a CNT thread that can be sewn with a standard sewing machine. The material is soft and can be washed in washing machine without any signal degradation making it an ideal wearable sensor. Additionally, because it is carbon based, it can easily interface with skin which allows it to obtain similar quality EKG signals to that of commercial wet electrodes.

Research Interests:

My postdoctoral research interests include developing wearable sensors and flexible electronics for wearable devices. Wearable sensors have gained significant interest in recent years because they can seamlessly monitor and relay information about an individual’s wellbeing; this is demonstrated through the popularity of the Apple Watch and the Fitbit. Although these devices are sufficient for recreational use, they are limited in the sensors available (typically heart rate and step count) and they require an additional rigid device. There are applications for individuals such as military personal and first responders that could vastly benefit from lightweight sensors for physiological stressors, environmental hazards, and physical location. Furthermore, wearable sensors would make tracking training regiments easy for athletes and would make monitoring for individuals with chronic illness such as heart conditions or diabetes easier and less invasive. I feel that my background with colloidal processing and carbon nanotubes could help develop devices that are made using scalable techniques and are robust. I have background in this area due to my work on sewable EKG sensors, but I am interested in pursuing this line of research further and expanding my knowledge of the field.

Teaching Interests:

I am the most interested in teaching the Introduction to Chemical Engineering course. As students enter the chemical engineering curriculum for the first time, many students can feel anxious or hindered in their studies due to stereotype threat. I aim to develop and promote an inclusive curriculum with a growth mindset that guides a larger proportion of students towards success in the field. I plan to accomplish this by providing a highly structured course. The course would be composed of quizzes and small projects leading up to the exam so students can continuously gauge their understanding of the material. Furthermore, I would promote transparency by elucidating course expectations and learning goals at the start of the course. I would also like incorporate continuous feedback throughout the course by using anonymous surveys. These short surveys would ask students about the pace of the course and their current understanding of the material. Finally, I feel that it is crucial to also act as mentor for more than just the coursework. The adjustment to college life can be difficult and having a support system can make this transition much easier by helping students overcome financial and personal barriers.