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Designing materials nature never intended

A NSF MRSEC innovation comes back home to reveal the atomic structure of new materials

Since 2011, the Wisconsin MRSEC has created over 40 unique research-inspired education resources. These resources are disseminated through educational kits, outreach activities, instructional videos and other online resources, all based on cutting-edge research going on in the Wisconsin MRSEC. These resources have impacted: >650,000 people in 194 countries. Over the last year:

Leveraged upgrades to Scanning Transmission Electron Microscope (S/TEM) and Focused Ion Beam System (FIB):

The resources of the Wisconsin MRSEC Shared Facilities impact researchers campus-wide and beyond. Over the past year >79,000 usage hours accounted for:

Synthetic methods produce colloidal nanocrystals that are metallic, semiconducting, and insulating. These nanocrystals have been typically used to form only a single component in devices. IRG-4 has exploited the library of colloidal nanocrystals and designed the materials, surfaces, and interfaces to construct all the components of field-effect transistors.The transistors are fabricated from solution over large areas and on flexible plastics and have excellent electrical performance.   This work was published in  Science, 352, 205-208 (2016).

Janus colloids are composed of two-faced particles with distinctive surfaces and/or compartments. Lee, Collings, & Yodh have created the first Janus particles with a liquid crystal (LC) compartment. The droplets were prepared by combining microfluidic and phase separation techniques, and the LC compartment morphologies can be easily controlled to realize unique confining geometries (Fig. 1).

Microcapsules that encapsulate and protect molecules and materials by forming isolated aqueous compartments inside hollow shells are widely used in a variety of applications in the food, pharmaceutical, cosmetics, and agriculture industries. One promising method that has emerged is layer by layer (LbL) assembly, but this method to make microcapsules has low encapsulation yield, is tedious, and is time consuming.

Topological insulators, which were first introduced at Penn, are new materials with novel features such as protected states that hold potential for quantum computing. We have identified a class of 3D crystals that feature a new kind of topological band phenomena: Dirac line nodes (DLN).   These are lines in momentum space where the conduction band and valence band touch, and their degeneracy is required by inversion symmetry even in the absence of spin orbit interactions.