Cho named NASA Space Technology Research Fellow
Chullhee (Chace) Cho, a PhD candidate in MechSE, has been selected as a 2017 NASA Space Technology Research Fellow (NSTRF). Cho conducts research on two-dimensional materials in Assistant Professor SungWoo Nam’s lab.
The competitive fellowships, which sponsor U.S. citizen and permanent resident graduate students who show significant potential to contribute to NASA’s goal of creating innovative new space technologies for our Nation’s science, exploration and economic future, are made in the form of grants to U.S. universities, with the student’s faculty advisor serving as the principal investigator. The fellowship will enable Cho to collaborate with top researchers at NASA’s Langley Research Center and perform his research at various facilities.
Cho’s proposal, “Frequency Tunable Piezoelectric Energy Harvester based on Crumpled MoS2 and Graphene,” will focus on a new type of energy harvester based on crumpled structures of two-dimensional materials and ensuring mechanical flexibility, frequency-tunability, lightweight and radiation-tolerant features.
Most space missions are long-term, and some are conducted entirely remotely, making issues in power generation crucial, particularly given the constraints on sources like fuel or energy harvesting systems on spacecraft. Conventionally used batteries are bulky, pose a danger of explosion, are inconvenient to recharge, and suffer from limited lifetime. As a result, the development of lightweight energy generation devices with high power outputs and low cost is essential.
According to Cho, harvesting ambient energy is a possible solution to extend the limit of power production in space. Many researchers, including those at NASA, have been working on energy harvesters to convert vibration energy into usable electric energy based on piezoelectric materials. Cho proposes converting energy from vibration sources to electrical energy that astronauts can use in their daily activities in space.
Compared to previously fabricated nanogenerators, a single layer of an MoS2 based nanogenerator has the advantage of withstanding enormous strains, while also being lightweight and with a high stiffness and high surface area-to-volume ratio. These present some of the biggest challenges NASA faces for future space missions as well as energy problems—and if resolved, could increase the life and scope of space missions.
Space exploration missions require devices capable of stable operation in harsh environments such as damage from cosmic rays. Improving the frequency-tunability could affect power output, resulting in a better response range to the surrounding environment. Combining graphene with MoS2 can provide radiation-tolerant structure to the whole system. Harmful radiation can be mitigated by taking advantage of the inherent radiation tolerance and electrical conductivity of graphene.
Additionally, said Cho, “The dimension we are dealing with here is in the atomic scale. In other words, we can enhance the performance by stacking up the layers of device while still in nano- or micro- scales.”
Cho earned his bachelor’s and master’s degrees in 2011 and 2013. He worked as a research engineer for Korea Institute of Industrial technology until 2016, when he joined MechSE for his PhD degree.