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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.

The 6th annual Philadelphia Materials Day was held on Saturday, February 6, 2016 at the Bossone Research Center at Drexel University. This joint venture between Penn and Drexel Universities was attended by over 1100 students and parents. Each year faculty and their students present demos on materials-related themes of interest to K-12 students. The themes this year were: Communications, Earth, Environment, Energy, and Sports.

A dendrimer is a synthetically made branched molecule. In this work, a family of amphiphilic Janus dendrimers bearing precise carbohydrate residues arranged in a defined sequence – glycodendrimers – were used to make vesicles that could be agglutinated by naturally occurring lectins that binds to carbohydrates. The lectins, called galectins, are human adhesion and growth regulatory lectins. Very small differences in the chemistry of different galectin were detected through differences in agglutination with different Janus glycodendrimers.

Shape morphing systems may find potential application in smart textiles, autonomous robotics, biomedical devices, drug delivery and tissue engineering. Lewis and Mahadevan at the Harvard MRSEC have developed 4-D printing by creating a hydrogel-cellulose fibril ink that could be printed to induce a programmable shape change as recently reported in Nature Materials.

Optimum function of plasmonic nanocrystal in assembly requires precision control of separation. Often, larger separations are desired while still maintaining order. With our COMPASS collaborators, Hough and Donnio, IRG-4 has developed a new class of building blocks that incorporate dendrimer ligands. Dendrimer-nanocrystal building blocks have diameters controlled by dendrimer “generation.” This work was published in  J. Am. Chem. Soc. 137, 10728–10734 (2015).

The NSF has awarded additional funds to support helium conservation in the Property Measurement Shared Experimental Facility (SEF). The SEF hosts over a dozen low temperature measurement capabilities requiring liquid helium.