Honeycomb has fascinated humans for millennia. It is a naturally engineered structure that serves as storage for the bees, a place for the queen to lay eggs, rear their brood, among a multitude of additional functions. Even though honeycomb construction has been studied, results have been limited to two-dimensional and surface-level observations. X-ray microscopy is a very powerful tool to characterize structures in three-dimensions non-destructively. When a time element is added, one can obtain valuable data in four-dimensions (4D). In this study, through 4D X-ray microscopy, many fundamental questions related to how bees build hexagonal cells were answered. Hexagonal cells were seen to grow additively, directly based on a preformed hexagonal pattern formed on the central spine of the comb. Further, several seminal but previously unreported features were observed such as the formation of a corrugated spine of the comb. Furthermore, we observed that the coping, which serves as the location where new wax material is added, is compacted and densified. Porosity in the comb was also studied, particularly at alternating junctions of the spine and on the coping which arises due to the geometrical arrangement of the cells and the construction methodology of the bees, respectively. The evolution of these microstructural features and their deformation response will be described and discussed.
Nikhilesh Chawla is Ransburg Professor of Materials Engineering and Associate Head for Graduate Studies in the School of Materials Engineering at Purdue University. He joined Purdue in 2020, after previously serving as Founding Director of the Center for 4D Materials Science and Fulton Professor of Materials Science and Engineering at Arizona State University. Prof. Chawla received his Ph.D. in Materials Science and Engineering from the University of Michigan in 1997. He was a postdoctoral fellow jointly at Ford Motor Company and the University of Michigan, and a senior development engineer at Hoeganaes Corporation. In 2023 he served as Acting Head of the School of Materials Engineering at Purdue.
Prof. Chawla’s research is in the area Four-Dimensional (4D) materials science with a particular emphasis on the deformation behavior of advanced materials at bulk and small length scales. He has co-authored close to 300 refereed journal publications (Web of Science h-index of 54; Google Scholar h-index of 66) and over 500 presentations in these areas. He has over 15,700 citations to his work. He is the author of the textbook Metal Matrix Composites (co-authored with K.K. Chawla), published by Springer. The 2nd edition of this book was published in 2013.
Prof. Chawla is a fellow of ASM International and past member of The Minerals, Metals, and Materials Society (TMS) Board of Directors. He is the recipient of the Sigma Xi Distinguished Lecturer Award (2022-2023), University of Michigan Department of Materials Science and Engineering Distinguished Alumnus Award for 2018, Acta Materialia Silver Medal for 2017, and New Mexico Tech Distinguished Alumnus Award for 2016. In addition, he was named 2016 Structural Materials Division Distinguished Scientist/Engineering Award, as well as the 2016 Functional Materials Division Distinguished Scientist/Engineering Award, both from TMS; 2013 Brimacombe Medalist Award from TMS; 2011 Distinguished Lectureship given by Tsinghua University, China; 2004 Bradley Stoughton Award for Young Teachers, given by ASM International; and the 2006 TMS Young Leaders Tutorial Lecture. He’s also won the National Science Foundation Early Career Development Award and the Office of Naval Research Young Investigator Award.
Prof. Chawla is editor of Materials Science and Engineering A published by Elsevier (2022 Impact Factor of 6.4). He also serves on the Editorial Boards of Materials Characterization and Materials Chemistry and Physics. He has served or is serving on several external advisory boards, including that of Naval Research Laboratory, the Advanced Photon Source at Argonne National Laboratory, and New Mexico Tech.