Highlights

An atomic force microscope probe (top) is used to measure the shape of a nanoparticle packing before (left) and after an indentation experiment is performed. After the experiment, performed in the boxed region, only one particle (right) is seen to be perturbed.

J. A. Lefever, T. D. B. Jacobs, Q. Tam, J. L. Hor, Y.-R. Huang, D. Lee (Chemical and Biomolecular Engineering), R. W. Carpick (Mechanical Engineering and Applied Mechanics)

At the smallest length scales, disordered systems such as nanoparticle packings and glass resemble the grains of sand on a beach. Lacking a structure, it is very difficult to understand how they deform and flow. We use a technique called atomic force microscopy, in which a sharp probe “feels” and pokes at a sample to measure its shape and mechanical properties. We are able to investigate at the length scale of a single particle.

Illustration of the assembly of hybrid vesicles from artificial dendrimersome and natural E. Coli components.

May 24, 2017

University of Pennsylvania

Hybrid Cell-Like Vesicular Assemblies from Bacterial Membranes and Synthetic Components

D. A. Hammer (Chemical Engineering), M. L. Klein (Temple, Chemistry), M. Goulian (Physics), V. Percec (Chemistry) Summer students, undergraduates, and high school students who contributed to the project

Hybrid cell-like vesicles were prepared by coassembling (glyco)dendrimersomes with bacterial membrane vesicles (BMVs) derived from E. Coli. These assemblies incorporated transmembrane proteins such as the small fusion protein MgrB tagged with a red fluorescent protein, and glycoconjugates such as lipopolysaccharides and glycoproteins from E. Coli. In future work, coassembly of (glyco)dendrimersomes with mammalian including human cell membranes will be a focus with the goal of developing new systems for biomedical application. Broader Impact

Optical microscopy images of example strips of bilayer films with thin parylene-C film deposited on the topographically patterned side of the PDMS. Scale bars: 300 mm. (a) Top-view of two dry bilayer strips with ridges at different angles. (Inset) Cross-sectional view of strip showing topographic pattern. (b, c) Swollen bilayer strips made from bilayer strips in (a) after immersion in hexadecane. The strip on the left in (a) transforms into a “tube roll” (b) after swelling. The strip on the right in (a) transforms into a “helical tube” (c) after swelling. Red shading is to guide the eye about representative ridges on the strip.

May 24, 2017

University of Pennsylvania

Three-dimensional Objects from Swollen, Topographically-Patterned Bilayer Films

R. D. Kamien (Physics), S. Yang (Materials Science & Engineering) and A. G. Yodh (Physics) Topography-guided buckling of swollen polymer bilayer films into three-dimensional helices. Based on physical constraints, simple surface topography can guide buckling of flat bilayer films to form objects such as half-pipes, helical tubules, and ribbons.

Building complex three-dimensional (3D) materials from pre-programmed two-dimensional films presents exciting challenges and opportunities. To achieve this goal, researchers inspired by the paper folding techniques of origami and kirigami have successfully utilized the mechanical instabilities of thin films, such as buckling.

*S. Ulstrup et al. “Spatially Resolved Electronic Properties of Single-Layer WS2 on Transition Metal Oxides.” ACS Nano, 10, 11 (2016).
J. Katoch et al. “Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures.” arXiv:1705.04866. — *S. Ulstrup et al. “Spatially Resolved Electronic Properties of Single-Layer WS2 on Transition Metal Oxides.” ACS Nano, 10, 11 (2016). J. Katoch et al. “Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures.” arXiv:1705.04866.

May 16, 2017

Ohio State University

Control of Spin-Orbit Splitting in 2D Semiconductors

R. Kawakami, J. Goldberger, W. Windl The Ohio State University

Probing and manipulating electronic band structures of 2D materials.

Elemental mapping image of Ni-Pt nanoparticles obtained by a scanning transmission electron microscope

May 16, 2017

Ohio State University

Translating Spin Seebeck Effect Physics into Practice

S. R. Boona, K. Vandaele, I. N. Boona, D. W. McComb, and J. P. Heremans, "Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites," Nature Communications 7, 13714 (2016). *supported by the Center for Emergent Materials, an NSF MRSEC (DMR1420451) and by MURI (W911NF-14-1-0016)

Study reveals thin film physics also manifests in random nanocomposite geometry.

(Foreground) Mirror image materials created by stacking single-atom-thick films. (Background) Artist’s rendering of (top) right-handed and (bottom) left-handed films at the atomic scale.

Mar 21, 2017

Cornell University

Through the Atomic Scale Looking Glass

In Through the Looking Glass, Alice steps through a mirror into a world in which everything is its mirror image. Realizing that writing in books is reversed, Alice wonders what has happened on the atomic scale.

Programming molecular self-assembly of intrinsically disordered proteins

Mar 20, 2017

Duke University

Programming molecular self-assembly of intrinsically disordered proteins

Gabriel López, University of New Mexico Ashutosh Chilkoti, Duke University Michael Rubinstein, University of North Carolina at Chapel Hill Nick Carroll, Duke University Joseph Simon, Duke University

New model systems of liquid protein assemblies offer insights into naturally-occurring counterparts.

Mar 20, 2017

Colorado School of Mines

The materials genome gets hot!

V. Stevanovic, R. O’Hayre, A. Zakutayev REMRSEC, NSF DMR-0820518

The goal of this seed project is to bring first-principles theory closer to experimental reality.

The motion of charge carriers in ruthenates is imaged using a technique known as Angle Resolved Photoemission Spectroscopy (ARPES).

Mar 19, 2017

Cornell University

Simple stretch “flips” the sign of charge carriers

Electricity is the flow of charged particles through a material, such as a wire — a process that resembles a river of water molecules flowing through a canyon. But are the charged particles positive or negative?

Down the rabbit hole: Sinking electrons in a Weyl sea

Oct 27, 2016

Princeton University

Down the rabbit hole: Sinking electrons in a Weyl sea

H. Inoue, Princeton University A. Gyenis, Princeton University Z. Wang, Princeton University J. Li, Princeton University S. Oh, Princeton University S. Jiang, Princeton University N. Ni, Princeton University B. A. Bernevig, Princeton University A. Yazdani, Princeton University Inoue, et al., Science 351, 1184 (2016)

Weyl semimetals are newly discovered topological electronic materials in which surface electrons (Fermi arcs) are topologically connected with those of the bulk. Princeton researchers have found experimental evidence that electrons can transverse the bulk through the special momentum states, called Weyl points, moving between opposing surfaces.