ABSTRACT: In my presentation, I will first briefly introduce research projects in my group and focus on two studies about how we can harness coupling between materials and geometry by design, fabrication, and testing of architected materials for adaptive energy absorption and self-adaptable bioimplant devices. An architected material (or metamaterial) is a class of materials that provide new properties that are not observed in natural materials and/or from a bulk material that the “material” is made of. I will present two examples of architected materials that we can have desired mechanical behaviors by harnessing coupling between material and geometry.

First, I will present adaptive energy-absorbing “materials” with extreme energy dissipation and improved energy absorption with increasing strain rate. We utilize energy dissipation mechanisms across different length scales to maximize energy dissipation by utilizing architected liquid crystalline elastomers (LCEs). As a result, our energy-absorbing material shows about order of magnitude higher specific energy dissipation at quasistatic condition compared with the previous reports and even higher energy dissipation at faster strain rates with power-law relation, whose exponent can be tuned by controlling the mesoscale alignment of molecules using a simple strain control-based approach. The findings from our study can contribute to realizing extremely lightweight and high energy dissipating materials, which will be beneficial for various applications including aerospace, automotive, and personal protection.

Second, I will present self-adaptive cardiovascular implant devices that can accommodate the growth of pediatric patients. Right ventricle–to–pulmonary artery (RV-PA) conduits are used as a surgical palliative treatment for various congenital heart diseases. Due to the growth of the infant or child, these conduits require replacement as they cannot grow, which involves several major open-heart surgeries. To address this issue, we have investigated self-adaptable RV-PA conduits that “grow” via tailored self-unfolding mechanisms triggered by flow and pressure change associated with growth so that fewer surgeries are required from infancy to adulthood. I will present our numerical simulation results for design of self-adaptable implants, followed by experimental results of testing 3D printed implant devices using an in-vitro testing set-up. The results showed that our self-adaptable implants can match the required shape changes to accommodate the growth of children. We anticipate that our approaches and findings can contribute to improving patient welfare by customized designs with growth potential based on patient anatomy, which can minimize the number of required surgeries and associated danger, trauma, and expenses.

BIOSKETCH: Sung Hoon Kang is an Assistant Professor in the Department of Mechanical Engineering since January 2015 and is an associate faculty of Hopkins Extreme Materials Institute and Institute for NanoBioTechnology. He earned a Ph.D. degree in Applied Physics at Harvard University and M.S. and B.S. degrees in Materials Science and Engineering from MIT and Seoul National University, respectively. Sung Hoon has been investigating bioinspired solutions to address current challenge in synthetic materials and mechanical systems with applications including healthcare, safety, and energy. Throughout his career, Sung Hoon has co-authored 36 peer-reviewed papers, has given over 80 presentations (including ~50 invited talks), and has two patents and three pending patents. His honors include FY 2018 Air Force Office of Scientific Research Young Investigator Program Award, Alumnus of 2016 National Academy of Engineering US Frontiers of Engineering Symposium, and 2011 Materials Research Society Graduate Students Gold Award. He served as an editorial board member of Scientific Reports (Nov. 2014 – Oct. 2017) and a guest editor of February 2016 issue of Materials Research Society Bulletin. He has been co-organizing ~20 symposia on bioinspired materials, 3D printing, and mechanical metamaterials at international conferences. He is a member of American Society of Mechanical Engineers (ASME), American Physical Society (APS), Society of Engineering Science (SES), and Materials Research Society (MRS). He serves as the Vice Chair of ASME Technical Committee on Mechanics of Soft Materials and will serve as Chair in 2020.