Materials Science & Biophysics Research Seminar Series

FALL 2020 Seminar Series

Interactions of glass with the living world: impact of nanoheterogeneity

Himanshu Jain, PhD
T.L. Diamond Distinguished Chair in Engineering and Applied Science
Professor of Materials Science and Engineering and Director of Institute for Functional Materials and Devices (I-FMD)
Lehigh University, Bethlehem, Pennsylvania

Friday, September 25, 2020
1:00 - 2:00 p.m.
Virtual seminar - Join on MS Teams

Glass has been used in human body since late 16th century as ocular prosthesis. At present, bioactive glasses are the most promising candidates for enabling the regeneration of bones and dental tissue. Bioscaffolds for these applications should degrade at the rate of tissue regeneration, which is opposite to most other uses that rely on the long durability of glass. This challenge has been overcome through novel simultaneous, multiscale phase separations on macro (100s of mm) and nano (10s of nm) scales. The resulting tailored amorphous multiparous (TAMP) structures have shown to not only biodegrade at the desired rate, but also perform better under in vitro as well as in vivo tests on animals and humans. These studies have revealed, very unexpectedly, that the nanostructure of bioactive glass significantly impacts the behavior of more than ten thousand times larger cells. For example, preosteoblasts respond differently on TAMP calcium silicate scaffolds that differ only in the size of nanopores, say 4 nm vs. 18 nm. Thus, it becomes crucial to develop glass fabrication processes for a given chemical composition, which will yield desired nanostructure of the ultimate product. In this presentation we will review and discuss these specific processes, which are broadly based on the conventional melt-quench and sol-gel methods of glass making. The fundamental nature of the interaction between living cells and nanoscale structure of TAMP samples will also be presented.

Fluidity, jamming and glassy behavior in biological tissues

Dapeng Bi, PhD
Assistant Professor of Physics
Northeastern University, Boston, Massachusetts

Friday, October 16, 2020
1:00 - 2:00 p.m.
Virtual seminar - Join on MS Teams

Cells must move through tissues in many important biological processes, including embryonic development, cancer metastasis, and wound healing. Often these tissues are dense and a cell's motion is strongly constrained by its neighbors, leading to glassy dynamics. Although there is a density-driven glass transition in particle-based models for active matter, these cannot explain liquid-to-solid transitions in confluent tissues, where there are no gaps between cells and the packing fraction remains fixed and equal to unity. I will demonstrate the existence of a new type of rigidity transition that occurs in confluent tissue monolayers at constant density. The onset of rigidity is governed by a model parameter that encodes single-cell properties such as cell-cell adhesion and cortical tension. I will also introduce a new model that simultaneously captures polarized cell motility and multicellular interactions in a confluent tissue and identify a glassy transition line that originates at the critical point of the rigidity transition. This work suggests an experimentally accessible structural order parameter that specifies the entire transition surface separating fluid tissues and solid tissues. Finally, I will discuss recent work using a culture of human lung epithelial tissue to compare a newly discovered mode of fluidization of jammed cells ñ the unjamming transition (UJT) ñ with the canonical epithelial-to-mesenchymal transition (EMT).

Drop Generation in Electro-Coflows

Josefa Guerrero-Millan, PhD
Assistant Professor of Physics
Department of Chemistry and Physics
Augusta University, Augusta

Friday, October 30, 2020
1:00 - 2:00 p.m.
Virtual seminar - Join on MS Teams

Controlled generation of micron and sub-micron sized drops continues to be of strong interest for the scientific community due to the variety of applications in many different fields. Microfluidics allows the precision manipulation of small volume of fluids and it is used in areas like microanalysis, point-of-care detection and diagnostics, in vitro disease and tissue modeling, and organic synthesis, among others. In our experiments, we use glass-based microfluidics, where 3D flows travel in coaxially aligned glass capillaries producing emulsion drops. In addition to the hydrodynamic stresses, we use electrical stresses to force the drop formation. The presence of charge in the interface of the liquids adds another control parameter in the drop production process. In this talk, we present a qualitative study of jet structure and droplet formation in the different electrohydrodynamic spraying regimes when the hosting media is a flowing dielectric liquid.