MSE Department Seminar

Thin films used in microelectronic and other microsystems are metastable.  If heated at sufficiently high temperatures they will agglomerate or dewet to form islands while remaining in the solid state.  The temperature at which solid state dewetting occurs decreases as the thickness of a film is decreased and dewetting can occur well below a material’s melting temperature.  The dewetting temperature also decreases as other dimensions are decreased, as in the case of the diameters of nanowires.  Scaling of feature sizes in microelectronic systems has led to increasing pro

2D material-based devices have received a great deal of attention as they can be easily stacked to obtain multifunctionality. With their ultrathin thicknesses, such multifunctioning devices become so flexible and conformal that they can be placed onto any 3D featured surfaces. However, 2D heterostructures are typically demonstrated as stacked flakes where single or few devices can be fabricated due to lack of strategies for layer-by-layer stacking of 2D materials at the wafer scale.

Polymers solvated by imidazolium salts exhibit better thermal stability and lower glass-transition temperature. Understanding the interactions and solvation between polymer and ionic liquid is important for designing soft and mechanically strong membranes with high ionic conductivity and thermal stability for their applications in electrochemical devices. In this talk, I will present our recent results about the structural and dynamic relations of poly(methyl methacrylate) (PMMA)-grafted nanoparticles in imidazolium-based ionic liquids.

Solid-state batteries (SSBs) are being considered as one of the most promising technologies for safer, high-energy, and long-term energy storage. However, key materials issues remain unsolved and serious barriers must be overcome for the full-scale commercialization of SSBs. In this presentation I will discuss some of our approaches to understand the key challenges in solid electrolyte materials.

The nano- to macro-scale physical and chemical properties of the environment that surrounds a cell play an important role in cell function and fate.

Sustaining local electric fields in confined microscopic environments as polarizing agents for catalyzing reactions is important. It is argued that many enzymes operate based on this principle and lessons learned from them can be extended to other catalytic systems. We use Stark shift spectroscopy to measure electric fields in electrochemical interfaces for understanding solvation, interfacial polarization, molecular structure, steric hindrance, and frustrated bond formation. We will present experimental results on fields at the junction of electrolytes and biased metal electrodes.

Silk fibroins are a class of proteins produced by a variety of insects and arachnids that can surpass man-made materials in specific strength and toughness. From a macromolecular perspective, silk fibroins have a linear architecture predominantly consisting of regularly alternating -sheet forming peptide segments and flexible peptide segments, resulting in a supramolecular network structure with stiff crystalline domains reinforcing an amorphous matrix.

Soft electronic devices that can acquire vital signs from the human body represent an important trend for healthcare. Combined strategies of materials design and advanced microfabrication allow the integration of a variety of components and devices on a stretchable platform, resulting in functional systems with minimal constraints on the human body. In this presentation, I will demonstrate a wearable multichannel patch that can sense a collection of signals from the human skin in a wireless mode.

Polymorphism is the phenomena of solid compounds forming different crystal structures. Polymorphism is important in a myriad of practical applications of solid compounds such as pharmaceutical solids. However, the origin of the polymorphic behavior of solid compounds is still not well understood. We investigated the fluid-to-solid and solid-to-solid phase transitions of close-packed structures of strongly-segregated polymeric block copolymer micelles, model colloidal spheres.

I will present several examples in which materials informatics can be used to elucidate and quantify complex correlations linking structure, properties and processing of materials. In the first example, I consider the case of high-entropy (HE) (or multi-principal element) alloys, typically comprising five or more elements. The study of these alloys is a relatively new area of materials research that has attracted intense interest in recent years as, in many cases, these systems possess unexpected and superior mechanical (and other) properties relative to those of conventional alloys.