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Program Highlights

MRSEC collaborations celebrate diversity and professional growth in materials research

UD CHARM and Princeton’s PCCM coordinated with the Chicago MRSEC to host three virtual events (Soft Matter for All, Rising Stars, and a Professional Development Workshop) to highlight early career, high-impact research and ignite discussion for graduate students and postdocs pursuing academic and non-academic career paths.

Spin-to-charge conversion in ferromagnet/ topological insulator bilayers at GHz and THz frequencies

Experimental studies combined with theoretical calculations of spin dynamics across a wide frequency range from ~10 GHz to several THz in a novel amorphous ferromagnet (FM)/3D topological insulator (TI) (FeGaB/BiSb) system that is scalable and provides a promising platform for spin-electronic devices.

Deformation and Orientational Order of Chiral membranes with Free Edges

Producing self-assembled structures of prescribed limited size and shape is a major challenge in nanoscience. A major achievement of the MRSEC was to elucidate a new chirality-based mechanism that leads to self-limiting assembly of colloidal rafts.

Confinement Controls the Bend Instability of Three-Dimensional Active Liquid Crystals

Here, three IRG2 PP developed a combination of experiments with 3D active fluids confined in microfluidic channels and a minimal hydrodynamic model to show that size of the channel determines the emergent lengthscale of the growing deformations. These findings will advance our understanding of active nemato-hydrodynamics and the pathways to 3D active turbulence at low Reynolds number.

Fibrous Networks in Liver Fibrosis

Animal tissues are composed of cells attached to either the surface of a fibrous network called a basement membrane or embedded within a 3D extracellular or interstitial matrix. As the disease liver fibrosis progresses, the extracellular fibrous networks become denser and more aligned. These physical changes lead to different mechanical properties and structures to which cells are exquisitely sensitive. To better understand the pathological effects of these changes during fibrosis on cells, we have engineered material platforms that mimic the extracellular matrix in tissue health and disease. As an example, we have fabricated fibrous materials that have varied mechanical properties and fiber densities when mechanically loaded due to the chemical adhesion between fibers, similar to natural extracellular matrix (see Figure).

Effects of extracellular matrix viscoelasticity on cellular behavior

Linearly elastic elastomers coated with matrix proteins are widely used to assess the role of stiffness. Such experiments are often assumed to reproduce the effect of the mechanical environment experienced by cells in vivo. However, tissues and the extracellular matrix (ECM) are not linearly elastic materials. They exhibit far more complex mechanical behaviors. These behaviors include viscoelasticity, as well as mechanical plasticity, and nonlinear elasticity. Our theoretical and experimental work has revealed that matrix viscoelasticity regulates fundamental cell processes and can promote behaviors – such as proliferation, motility and spreading – that are not observed with elastic hydrogels in both two- and three-dimensional culture microenvironments.

The Perpetual Fragility of Creeping Hillslopes

Soil is a highly disordered granular material. Slow soil deformation (creep) controls the shape of hills in the natural landscape, and is a precursor of catastrophic landsliding. Our work demonstrates a surprising observation: an apparently static sandpile, sitting on a table, is actually alive with motion. We study a 3D granular heap, confined by walls and prepared by pouring. Via Diffusive Wave Spectroscopy (DWS), we observe the existence of spatially-heterogeneous micro-deformations that decay in size and frequency as time progresses but persist up to 11 days after the preparation of the system; the heap relaxes. We find that this relaxation can be enhanced  (overaged) or reversed (rejuvenated) by tuning the types of disturbances applied to system.

Surface Modification of Black Phosphorus with Group 13 Lewis Acids for Ambient Protection and Electronic Tuning

We have developed a solution-phase protocol to modify the Lewis basic surface of few-layer black phosphorus (bP) using commercially available Lewis acids, and demonstrated its effectiveness at providing outstanding ambient stability and tuning of electronic properties.

Tunable Correlated and Topological States in Twisted Graphene Multilayers

Stacking various atomically-thin crystals on top of one another can strongly modify their overall properties. When two materials are stacked with a twist angle, a geometric interference pattern (a moiré pattern) emerges. At special twist angles, the moiré pattern can result in new electronic states dominated by strong correlations between electrons.

Holiday Lecture 2020: A Materials Wonderland

PCCM celebrated its annual Holiday Lecture 2020: A Materials Wonderland: A Celebration of How Materials Science Make Our Holidays Fun with PCCM faculty, research members and others providing (virtual) materials science presentations. The audience helped with experiments and demonstrations from their homes. 426 families registered, some with multiple children (tuning from all over the world), resulting in ~1,000 attendees!