I-FMD's Material and Devices
Thursdays at 12 pm
Zoom Link: https://lehigh.zoom.us/j/99482961733
To view recordings, click on the title. You will need to log in with your Lehigh University credentials.
Thursday, July 2: Holiday Break
Thursday, July 9
Charge-regulation during bacterial adhesion: Can we design of surfaces to manipulate bioenergetics, chemical bioavailability, and surface sensing?
Derick Brown, Civil & Environmental Engineering
Since the first reported observations by Zobell in 1943, it has been recognized that the metabolic activity of adhered bacteria can differ from that of their planktonic counterparts. Activity may be enhanced, promoting bacterial colonization, or decreased, resulting in inhibited colonization and cell death. While the overwhelming evidence is that the process of adhesion results in changes in bacterial metabolic activity, the mechanism that results in these observations has remained elusive. In this talk, I will present results demonstrating how the physiochemical charge-regulation process – which alters interfacial pH, charge, and electrostatic potential as two surfaces approach each other in aqueous systems (e.g., a bacterium and an adhering surface) – can directly impact bacterial metabolic activity, quantified through cellular bioenergetics and ATP. I will also show how the charge-regulation effect provides a means for adhered bacteria to alter the bioavailability of sorbed and solid substrates. Throughout the talk, we’ll discuss how engineered surfaces can be designed to take advantage of the charge-regulation effect for applications such as controlling bacterial surface recognition and gene expression, enhancing or inhibiting surface growth, and targeting drug and substrate delivery to adhered cells. And I’ll even hint at how the charge-regulation effect might have played a role in the evolution of life itself.
Derick Brown is a Professor of Environmental Engineering and the Associate Chair of Civil and Environmental Engineering at Lehigh University. He earned his B.S. in Aerospace Engineering from Boston University and then worked at McDonnell Douglas Space Systems Company in Huntington Beach, CA, for eight years, during which time he earned a M.S. in Mechanical Engineering from UC Irvine. After taking several environmental engineering courses at UC Irvine, Dr. Brown left McDonnell Douglas to pursue his Ph.D. in Environmental Engineering at Princeton University. Dr. Brown joined Lehigh University in 2001. Dr. Brown’s research focuses on environmental biotechnology and the relationships between microbial and physiochemical processes, and his research has a strong interconnection between experimentation and numerical modeling.
In larger organic molecules, the first electronic excited state can have a significantly lower energy in a triplet configuration than in the photoexcited singlet configuration. In molecular crystals where the triplet exciton energy is less than half the singlet exciton energy, photon absorption results in a singlet exciton that can quickly undergo a "fission" process into two triplet excitons. The pair of triplet excitons generated in this way is entangled, with total spin of zero. The excitons that are part of this pair then diffuse in a complicated way in the crystal matrix (while their spin remains entangled) which is an interesting process by itself. Also, the triplet excitons transport energy over large distances (“large” meaning several micrometers). One reason this is interesting is that this method for energy transport could conceivably be used in future photovoltaics systems. Even more interesting things happen when the energy of a triplet exciton is just about half that of a singlet exciton. This is the case in a molecular crystal called rubrene. The consequence of this balance of energies is that it becomes possible for two triplet excitons that by chance meet each other to undergo a "fusion" process back into a singlet exciton. And this can then result in photon emission (radiative recombination), which has the effect that a “gas” of triplet excitons in the crystal can emit light, a trick that we used to observe triplet excitons and measure their diffusion length. In addition, even more interesting things can be seen when doing time-resolved experiments. Think again about that lone pair of triplet excitons that have been born from fission and then start wondering in the crystal like two drunkards after they leave their favorite pub. We can use the photons that they can emit after fusion as a probe of their probability of meeting again. And despite the fact that the probability of meeting again is low (especially for 3D diffusion), and that the probability that this results in photon emission is also low, we can use the sensitivity of single photon detection to harvest those fusion photons and explore how that probability of a re-encounter evolves over multiple time-decads. These photons then serve as a probe to study the behavior of the entangled triplet exciton pair and how its two members wander around in the crystal. We are looking at these things right now, so lot of things are still a bit uncertain, but I believe that we can say intelligent things about the dimensionality of the diffusion process (1D? 2D? 3D?) just by looking at the time-dynamics of the stream of photons generated when the triplet excitons meet again. And last by not least, did I already mention that the two triplet excitons are entangled? They are a solid-state equivalent of the entangled photons used for quantum encryption, or of any other of those spooky quantum systems. In rubrene, the entanglement of the spins of the two triplet excitons can be measured by detecting the interference effect of their wavefunctions when they meet again and fuse, which gives rise to regular oscillations of the emitted fluorescence, a.k.a. quantum beats. We have found that entanglement in this statement can last the relatively long time of several tens of nanoseconds (at room temperature!), so maybe these things can even be used for building qbits for quantum computing, but obviously I really have no idea. The talk will discuss the various processes involved in the exciton dynamics in rubrene, highlighting several strange things and open questions.
As a prehistory, Dr. Biaggio got his PhD from the Swiss Federal Institute of Technology (ETH) in Zürich, with a dissertation about some strange effects connected to photoexcitation and space-charge fields in a ferroelectric perovskite. He then went to the University of Southern California to work with Prof. Hellwarth on large polarons, nonlinear optical effects in atomic vapors, and on building an "atomic correlator". After a second postdoctoral stay at Orsay, near Paris, he went back to ETH, where he led a team that worked on vapor deposition of organic light emitting diodes and transistors while also doing research on nonlinear optics, charge-carrier photoexcitation, charge carrier mobility anisotropy, and four-wave mixing. During this second stint at ETH, he also got his “venia legend”, and became what is called a “Privatdozent:, before then leaving to come to Lehigh in 2002, which brings us to more modern times. At Lehigh, Ivan has established a research program dedicated to light-matter interaction, condensed matter physics, nonlinear optics, and materials for photonics, with a focus on interesting physical effects in organic materials, and the use of some of them to create some kind of optical transistor, or for optoelectronics. Recently, his research group has worked on uncovering some exciting properties of singlet and triplet excitons in a particularly nice organic molecular crystal, something that nowadays is also often called an “organic semiconductor”. Ivan holds the Joseph A. Waldschmitt Chair in Physics and he is a fellow of the optical society of America.
Transfer of thermal energy within the earth drives mantle convection dynamics that include the lithosphere as a thermal boundary layer, deformation within that lithosphere (complicated by strongly temperature-dependent rheology), and development of topography that can interact with the climate system and drive erosion and other surface processes. All of this activity leaves behind a clear signature as it modifies temperatures. We can use noble-gas geochronology to record a wide range of time-temperature histories and obtain the timing, rate, and magnitude of phenomena like erosion, deformation, and fluid flow. This is done by measuring the net balance in mineral grains between accumulation of daughter product from radioactive decay and its loss by temperature-activated diffusion. Together with knowledge about argon and helium diffusion kinetics in common minerals, inverse models of this production-diffusion balance allow thermal histories to be determined. This approach, thermochronology, is now a mainstream method in studies of geodynamics and Earth evolution. I will review how mainstream thermochronometers work, show some examples of how these have been applied to better understand mountain landscapes past and present, and conclude with a brief look at some current work we are doing to better understand how crystal imperfections of different types impact diffusion systematics.
Peter Zeitler is a professor of earth and environmental sciences at Lehigh University. He earned his Ph.D. from Dartmouth College in 1983, after also completing B.A. and M.S. degrees there. Before coming to Lehigh in 1988, he spent five years as a research fellow in isotope geochemistry at the Research School of Earth Sciences at the Australian National University.
Dr. Zeitler’s research interests include development and application of techniques in geochronology, with the focus of his laboratory at Lehigh being on noble-gas methods. Zeitler is also interested in crustal geodynamics, the nature and origin of mountains, and the geologic evolution of Asia, where he has worked for 35 years in the Himalaya and Tibet (mostly in Pakistan and China), and currently, in Mongolia. Research highlights include development of U-Th/He thermochronology, which can date low-temperature geologic events, and development of the “tectonic aneurysm” model, which posits that in geologically active mountain belts, feedbacks can develop between climate-mediated erosion and deformation of the crust.
Author or co-author of over 90 research papers, Zeitler is currently on the editorial advisory boards of the journal Earth and Planetary Science Letters and the preprint server ESSOAr, and serves as an editor of the journal AGU Advances. In 2013 Zeitler was named a Fellow of the America Geophysical Union, in 2014 he became chair of the International Standing Committee on Thermochronology, in 2016 he was awarded the Dodson Prize in thermochronology, and in 2019 he received Lehigh’s Libsch research award. Zeitler has served as EES department chair and inaugural director of South Mountain College, and is currently a member of the Lehigh Faculty Senate.
Thursday, July 30
Harnessing the Donnan membrane Principle in Developing Smart Materials and Processes in Water Space
Arup SenGupta, Chemical & Biomolecular Engineering / Civil & Environmental Engineering
The Donnan Membrane Principle is an extension of the second law of thermodynamics and it deals exclusively with completely ionized electrolytes. The conditions leading to the Donnan membrane equilibrium arise from the inability of ions to diffuse out from one phase to another in a heterogeneous system. In reality, the outcomes of the Donnan membrane principle can be somewhat counter-intuitive, such as the transport of ions from a lower to a higher concentration even in the absence of an electric potential gradient or achieving osmosis without the physical existence of a semi-permeable membrane. In our research, we have used the underlying “physical chemistry” of the Donnan membrane principle to develop new materials and processes. As with all of our work, we combine theory and experiments to examine the underlying mechanisms that underpin our nascent understanding in this area.
In this lecture, I will primarily emphasize on the two following applications:
First, Waste acid neutralization is thermodynamically very favorable and the most widely practiced pollution control process globally. Through intelligent application of the Donnan membrane principle, it is possible to achieve and harness mechanical/electrical energy from the acid-base neutralization reactions.
Second, there are nearly fifty countries around the world including the USA that are faced with the crisis of natural arsenic and fluoride contamination of groundwater, posing health risk to nearly 500 million people around the world. The Donnan principle based arsenic-selective nanosorbent is the first reusable polymer-based material currently in use in over 500 installations in half a dozen countries including the USA.
Arup SenGupta has been a faculty member in the college of engineering and applied science at Lehigh University for 35 years. He received his BS in chemical engineering from Jadavpur University in India; then worked for seven years as a process development engineer; and then proceeded to graduate school receiving his PhD in environmental engineering from the University of Houston before joining Lehigh University in 1985. SenGupta’s research during the last three decades spanned nearly every facet of water science and technology, from decontamination to desalination to sustainable materials and processes. In 2017, SenGupta’s single-authored book ‘Ion Exchange in Environmental Processes’ was published by Wiley & Sons. SenGupta sincerely hopes that the book will outlast him by many decades. Two of SenGupta’s US patents were recognized by the USPTO as ‘patents for humanity’ for their impacts in improving the quality of life of people and creating employment around the world.
SenGupta served as the CEE Department Chair from 1998 to 2005. He received Lehigh University’s Libsch Research Award in 1995, Hilman Graduate Advisor Award in 2007 and Hilman Faculty Award in 2013. He is a fellow of ASCE, AIChE and NAI.