In my presentation, I will present our ongoing efforts to make self-adaptable materials and implant devices inspired by nature. Nature produces outstanding materials for structural applications such as bones and wood that can adapt to their surrounding environment. For instance, bone regulates mineral quantity proportional to the amount of stress. It becomes stronger in locations subjected to the higher mechanical loads. This leads to the formation of mechanically efficient structures for optimal biomechanical and energy-efficient performance. However, it is a challenge for synthetic materials to change and adapt their structures and properties to address the changes of loading conditions. To address the challenge, we are inspired by the findings that bones are formed by mineralization of ions from blood onto scaffolds. I will present a material system that triggers mineral synthesis from ionic solutions on organic scaffolds upon mechanical loadings and/or damages so that it can self-adapt to mechanical loadings and regenerate upon damages. For example, we observed ~30% increase in the modulus of the material upon periodic loadings for 3 days. We also observed that the material could self-repair damages generated by removing ~5 μm thick minerals from the matrix, in 7 days. We envision that our findings can open new strategies for making synthetic materials with self-adaptable mechanical properties and self-repair capability. Right ventricle–to–pulmonary artery (RV-PA) conduits are frequently used as a surgical palliative treatment for a variety of congenital heart diseases in infants and children. Due to the growth of the infant or child, these conduits require replacement as they cannot grow, which involves several major open-heart surgery before adulthood. To address this issue, we have investigated self-adaptable RV-PA conduits that “grow” via tailored self-unfolding mechanisms triggered by flow and time so that fewer complications as well as surgeries are required to maintain and develop normal pulmonary blood flow from infancy to adulthood. I will present our numerical simulation results for design of self-adaptable implants to control their shape changes as the flow rate increases with the growth of a child. I will also present our experimental results of testing 3D printed implant devices using an in-vitro set-up that can simulate pulsatile flow changes with the growth of a person to characterize the behaviors of implants for verification of our design. Both numerical and experimental data show that our self-adaptable implant devices can match the required shape changes to accommodate the growth of children by increasing the dimensions of the devices by self-unfolding mechanism. We anticipate that our self-adaptable RV-PA conduit will result in operation of the conduits over longer periods of infant and child growth into adulthood. The findings from our study can also contribute to other types of implant devices that require customized deformation/shape change mechanisms by the interplay between geometry and material.
About the Speaker
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 safety, healthcare, and energy. Throughout his career, Sung Hoon has co-authored 33 peer-reviewed papers, has given over 60 presentations (including over 30 invited talks), and has one patent and three pending patents. His honors include FY 2018 Air Force Office of Scientific Research Young Investigator Program Award, 2016 National Academy of Engineering’s US Frontiers of Engineering Symposium Invitee, 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. Currently, he serves as a reviewer for a number of journals including Science, Advanced Materials, ACS Materials & Interfaces, Nanoscale, Soft Matter, Applied Physics Letters, Composites Part A, Smart Materials and Structures, Bioinspiration & Biomimetics, Advanced Materials Technologies, and Science Advances. He is a member of American Society of Mechanical Engineers (ASME), Society of Engineering Science (SES), Materials Research Society (MRS), and American Physical Society (APS). He serves as the secretary of ASME Technical Committee on Mechanics of Soft Materials and will serve as Vice Chair (2019) and Chair (2020).
Host: Professor Sam Tawfick