Materials by Design: Three Dimensional (3D) Nano-Architected Meta-Materials
Creation of extremely strong and simultaneously ultra lightweight materials can be achieved by incorporating architecture into material design. In our research, we design and fabricate three-dimensional (3D) nano-architected materials that can exhibit superior and often tunable thermal, photonic, electrochemical, biochemical, and mechanical properties at extremely low mass densities (lighter than aerogels), which renders them useful, and often enabling, in many technological applications. Dominant properties of such meta-materials are driven by their multi-scale nature: from characteristic material microstructure (atoms) to individual constituents (nanometers) to structural components (microns) to overall architectures (millimeters and above).
Our research is focused on fabrication and synthesis of nano- and micro-architected materials using 3D lithography, nanofabrication, and additive manufacturing (AM) techniques, as well as on investigating their mechanical, biochemical, electrochemical, electromechanical, and thermal properties as a function of architecture, constituent materials, and microstructural detail. The focus of this talk is on additive manufacturing via function-containing chemical synthesis to create 3D nano- and micro-architected metals, ceramics, multifunctional metal oxides (nano-photonics, photocatalytic, piezoelectric, etc.), shape memory polymers, etc., as well as demonstrate their potential in some real-use biomedical, protective, and sensing applications. I will describe how the choice of architecture, material, and external stimulus can elicit stimulus-responsive, reconfigurable, and multifunctional
response. Host: Nanetta Pon, firstname.lastname@example.org, Persons who may need assistance please contact Brenda Thomas at email@example.com.
October 26, 2021
GCIS W301 and Zoom | Tuesday, 4:00 pm
Tissue confinement governs cell size regulation in epithelial tissue
While populations of single-celled organisms increase exponentially, animal cell growth must be coupled to organism growth for tissues to maintain their structure. These spatial constraints lead to a different regime of growth and division regulation known as contact inhibition of proliferation. We still lack a general framework to describe contact inhibition across different biological systems. Here we use model epithelial monolayers with varying spatial constraints to explore how contact inhibition affects cell growth and division. We introduce a concept of tissue confinement which describes the extent to which spatial constraints suppress cell growth in different tissues. Interestingly, confinement has no effect on cell division leading to a decoupling between rates of cell growth and division. In confined tissues cell division outpaces growth causing cell size to decrease. However, when cell size decreases below a specific value cell division becomes arrested. This final cell size is near a physical limit set by the amount of space occupied by DNA in the cell. By perturbing cell division regulation, it is possible to push cells closer to this limit, however, this leads to DNA damage suggesting loss of size regulation could play a role in the development of cancer.
Feet look quite different from fins but face the same structural demand to be sufficiently stiff in order to withstand the forces of propulsion. In this talk, I will show that curvature-induced stiffness is the common principle underlying the stiffness of both primate feet and rayed fish fins. The principle is evident in a drooping currency note or slice of pizza that significantly stiffens upon slightly curling it along the width. We use mathematical analysis, physical mimics, and biological experiments to derive the relationship between curvature and stiffness, and apply this understanding to track the evolution of foot curvature among hominins (human lineage). I will also show how the same principle manifests in fish fins despite their different morphology, with implications for the 380 million year old water-to-land evolutionary transition among vertebrates.