College of Arts and Sciences

Capillary pressure can destabilize a thin stream of water and break it up into a succession of small droplets. The addition of a minute quantity (some part per million) of a long, flexible and water-soluble polymer is enough to modify the growth and morphology of this instability and leads, close to breakup, to the development of Beads-on-a-string structures (BOAS) where droplets are connected by thin threads. The BOAS phenomenon is also observed after stretching a bridge of a viscoelastic liquid.

Experiments on jets and stretched bridges of viscoelastic polymeric solutions were conducted to gain more insight into the formation and time evolution of the BOAS in both configurations.

Continue reading… The Break-up of Viscoelastic Jets and Filaments: The Beads-on-a-string Structure – Marie-Charlotte Renoult

Carbon nanotubes combine low density with exceptional mechanical, electrical and optical properties. Unfortunately, these nanoscale properties have not been retained in bulk structures. I will describe surface modification assisted self‐assembly of single wall carbon nanotube into macroscopic nanotube networks  ‐  hydrogels and aerogels. The nanotube networks are ultra‐ lightweight, electrically conducting and thermally insulating. The shapes and sizes of these nanotube networks are readily tunable and is a tremendous strength of our fabrication method. The interesting properties and structure of these nanotube networks make them suitable for diverse applications. For example, we have used these networks as scaffolds to enhance elastic modulus of polymers by 40,000%.

Continue reading… Soft Materials Approaches to Carbon Nanotubes: from Gels to Composites – Mohammed F. Islam

A fundamental transformation of the transportation sector in the United States is underway. In parallel with advances in renewable energy resources for power generation, the rising use of electric and hybrid vehicles is reshaping the future of public transportation. Similar efforts are moving forward for more-electric ships, aircraft, and other military technologies. Due to their prevalence, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, and conversion. However, significant challenges exist for magnetic materials especially when used for transportation technologies, where enhanced reliability, power density, and overall energy capacity are increasingly important.

Continue reading… Soft Magnetic Materials for Energy Applications in Extreme Environments – Matthew A. Willard

The development of complex oxides over the past fifteen years has raised the prospect for new classes of electronic devices. In particular, it has been discovered that a high-mobility two-dimensional electron gas (2DEG) can be formed at the interface between two high-k insulators: LaAlO3 and SrTiO3. More interestingly, in samples with 3-unit-cell LaAlO3 (LAO) film grown on SrTiO3 (STO) substrate, a biased conducting atomic force microscope probe can locally and reversibly control the interfacial metal-insulator transition. This method is capable of patterning arbitrary conducting structures at LAO/STO interfaces with a spatial resolution of only a few nanometers. Based on such technique,

Continue reading… On Demand 2D Electron Gas at LaAlO3/SrTiO3 Interfaces – Cheng Cen

The proton is a bound state of quarks and gluons, described by the low-energy limit of quantum chromodynamics. Recent measurements using muonic hydrogen have, however, called our understanding of proton physics into question. In this first lecture, I will describe the significant discrepancy that exists between the recent muonic hydrogen measurements and previous measurements on protons — this is the // proton radius puzzle //. In the absence of any feasible theoretical solutions, new experiments might provide the best clues. I shall describe some of the experiments that are attempting to shed light on this puzzle, including our ongoing efforts to measure the proton radius via the Lamb shift in hydrogen atoms.

Continue reading… “How Big is the Proton Anyway?” – Amar Vutha

Semiconductor quantum wells, inter-metallic interfaces, layered oxides, and monolayer materials are all promising platforms for the observation of spincharge conversion due to strong spin-orbit interaction in the quasi two dimensional electron liquid they host. In this talk I focus on two closely related effects that can occur in these materials, namely the conversion of charge current to spin current (spin Hall effect) and the generation of spin polarization from an electric current (Edelstein effect). Together with their inverses (in the sense of Onsager reciprocity relations), these effects constitute a useful set of tools for spintronic applications. The theoretical challenge is to provide a unified treatment of the different mechanisms at work,

Continue reading… Spin-charge Conversion in Interfacial Electron Liquids – Giovanni Vignale