Sid Pathak: Analyzing grazing animal enamel for the engineering of novel materials

Title

Lattices promote a remarkable combination of fracture and wear resistance in grazing mammal dentitions 66,500 08/01/19

Mentor

Sid Pathak

Department

Chemical and Materials Engineering

Biosketch

I plan to integrate education and research to provide a multitude of enrichment opportunities for the undergraduate students to gain exposure to advanced research in the areas of experimental materials science and mechanics. Students participating in this project will be trained in research methods structural and chemical analysis (X Ray Diffraction, Scanning Electron Microscopy, and Transmission Electron Microscopy), synthesis, and nano-mechanical testing. Select students will also have the opportunity to present their work at international conferences, as well as publishing their work in peer-reviewed journals, depending on the quality of work performed.

I have mentored multiple undergraduates at UNR, both from programs such as the McNair Scholars Program, underrepresented students (3 female and one Hispanic), as well as regular undergraduates. Undergraduate students in my lab have gone on to receive a number of fellowships and scholarships, including the 2018-19 Nevada NASA Space Grant Consortium Undergraduate scholarship, 2018 TMS Structural Materials Division (SMD) Undergraduate Scholarship, 2017 Nevada Undergraduate Research Award and the Nevada National Science Foundation's Experimental Program to Stimulate Competitive Research (NSF EPSCoR) 2016 Academic Year Undergraduate Research Opportunity Program (UROP) fellowship. 

Check out our webpage at wolfweb.unr.edu/homepage/spathak

Project Overview

Fracture and wear are ubiquitous issues in engineering - to the extent that the terms "worn", "fractured" and "broken" as they pertain to devices are synonymous with the end-of-utility. In many cases, traditional materials fail to meet the simultaneous and rigorous performance demands (i.e. damage tolerant, wear resistant, low density, environmentally robust, tough, etc.) for next generation engineering systems. The enamel of grazing animals represents one of Nature's most remarkable biological materials - a ceramic-like composite showing exceptional strength, toughness, wear-resistance and controlled-crack propagation. The proposed work will study these multi-functional, damage-tolerant biomaterial composites that preserve and ensure life-long reliability for survival (feeding). The goal of this interdisciplinary research is to specifically understand the biomechanical form, function and performance of enamel lattices, known as Modified Radial Enamel (MRE) in the grinding teeth of large herbivorous mammals, including horses, bovids (e.g. bison and cattle) and suids (e.g. warthogs). Results and methods from this research will be of considerable interest to investigators in many disciplines including engineering, materials science, tribology, evolutionary biology, ecology, comparative anatomy, mammalogy and paleontology. The research will also have considerable broader impacts including the engineering of novel sustainable materials with wear and fracture applications.

Our research study will specifically focus on how these animal's teeth endure tens to hundreds of millions of high stress contact loading cycles and impacts while comminuting tough and abrasive plant matter such as grasses whose roots are laden with hard fracture-promoting sediment inclusions. Our cardinal hypothesis is that MRE is an evolutionarily optimized compromise for: 1) incredible fracture resistance due to prism arrangements that localize damage and strategically control crack direction; 2) unexpected strength and toughness made possible by compliant proteinaceous prism sheaths that circumvent hydroxyapatite's inherent brittleness; and 3) wear resistance conveyed through hard, hyper-mineralized, oriented enamel prisms. The team will: i) Identify the ancestral enamel fabric character states to MRE (that independently evolved in horses, bovids and warthogs) through an evolutionary biology approach. From these we will readily identify the specific evolutionary modifications to the enamel fabrics that enabled grinding and identify living species for making comparative biomechanical contrasts; and ii) Ascertain enamel fabric structure-property relationships across multiple length scales by comprehensively characterizing the material properties using micro-and nano-mechanical tools, spectroscopy and advanced electron microscopy. Teeth of grinding species with MRE will be compared with close relatives that retain the ancestral enamel fabrics, thereby revealing the salient anatomical changes that enabled the extreme biomechanical properties. We anticipate the results will transformatively introduce a new, more effective (evolutionary) approach for exploring Nature for biomimetics; and in the long term, inspire the design of new hard materials and structures to resist or strategically control fracture/wear.