Emerging semiconductors such as tin-based oxides have enormous application potential in devices, as they are transparent, support highly mobile electrons, and have wide “energy gaps”. Unlike better developed semiconductors, however, these materials are prone to harboring defects, which can limit essential properties such as electron mobility.

This highlight illustrates a key characterization advance realized at the Center for Dynamics and Control of Materials – temporally resolved light-induced microwave impedance microscopy. 

Our team designed a protein-based RGG material capable of self-assembly into micron size condensates that can be genetically encoded and expressed to form membranelles organelles in living cells. RGG is an intrinsically disordered peptide that coacervates to form a dynamic protein phase through weak, multivalent interactions. We leveraged this principle to designed RGG variants whose assembly could be enzymatically regulated through protease-mediated control of valency and solubility.

Based on the hypothesis that blending LAM- and CYL-forming block oligomers may yield stable network phases, molecular dynamics simulations are used to study binary blend self-assembly of AB-type diblock (n-tridecan-1,2,3,4-tetraol) and AB2-type miktoarm (5-octyl-tridecan-1,2,3,4-tetraol)  amphiphiles. The AB2-rich and AB-rich blends form double gyroid (DG) networks and perforated lamellae (PL), respectively.

This highlight demonstrates the gelation assembly of colloidal nanocrystals using uniquely developed ligands that can form a metal coordination linkage. Metal ions that are paired with ligand functional groups were used to control the assembly of nanocrystals from a stable dispersion to full spanning gel networks. The metal coordination linkage was reversed using temperature as an external trigger and enabled thermally switchable nanocrystal gel networks.

We studied graphene double layers separated by an atomically thin insulator. Under applied magnetic field, electrons and holes couple across the barrier to form bound magneto-excitons. Using temperature-dependent Coulomb drag and counterflow current measurements, we were able to tune the magneto-exciton condensate through the entire phase diagram from weak to strong coupling.

Since 2003 we have successfully partnered with universities in Southern Africa, specifically the National University of Lesotho and the University of Pretoria, to bring faculty members to the LRSM every summer to participate in collaborative research projects with our faculty. Often the students of faculty members are invited to join as well to gain research experience. This was the case with Mopeli Fabiane (top picture), who originally came as a lecturer, then a graduate student, and now continues to visit as a researcher with his Ph.D. The program started with 2-3 faculty/students visiting each summer and now this summer, 2019, will support 7 visitors (6 faculty and 1 student).

The self-assembly of biological molecules into large, but finite-size, superstructures is fundamental to life. A grand challenge for colloidal self-assembly is to produce colloidal monomers with valence-limited interactions, that have arbitrary angles and strengths, to produce structures with the precision, complexity and functionality of biological assemblies.

The resarch focus of this effort involved computationally designing a homotetrameric helical bundle to have a variety of net charges. The charged bundle variants showcase how charge state can be controlled for a common peptide structure, as well as the properties of the fibril nanomaterials constructed by the peptide building blocks.

In collaboration with the newly established NSF BioPacific MIP, the MRL X-ray facility team spearheaded the development of an SAXS-WAXS (small and wide angle x-ray scattering) laboratory beamline with unparalleled beam brightness for high throughput characterization of biopolymers and nanostructures.