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Highlights

Highlights

Fig. 1. A. Sequence of disordered RGG domain of Laf-1. B. Coarse-grain simulations identifies hydrophobic motif 21-28 that self-associates for condensation. C. Re-design of charge partitioning tunes phase behavior. D-F. Photocleavable RGG construct undergoes soluble to condensed transition upon 405 nm illum. G-H. Expression and optically induced condensation construct (D) in a model single cell system.
Fig. 1. A. Sequence of disordered RGG domain of Laf-1. B. Coarse-grain simulations identifies hydrophobic motif 21-28 that self-associates for condensation. C. Re-design of charge partitioning tunes phase behavior. D-F. Photocleavable RGG construct undergoes soluble to condensed transition upon 405 nm illum. G-H. Expression and optically induced condensation construct (D) in a model single cell system.
May 27, 2020
University of Pennsylvania

Membraneless Organelles Built from Engineered Assemblies of Intrinsically Disordered Proteins

Matthew C. Good, Daniel A. Hammer and Elizabeth Rhoades, University of Pennsylvania. Jeetain Mittal, Lehigh University
The SuperSeed labs of Hammer and Good designed a disordered protein material called ‘SPLIT’ capable of self-assembly into micron size protein condensates when illuminated with brief pulses of 405 nm laser light [1]. The saturation concentration of these photo-regulated coacervates were characterized biochemically in vitro, and imaging confirmed optically-induced condensation from genetically encoded components in living cells.
Figure 1: showing the structure of Xe encapsulated in a tetra cobalt cage and the temperature-dependent xenon-129 MR signal. Figure 2: showing xenon atoms encapsulated in the crystal lattice of tetra cobalt cages with xenon-xenon and inter-cage distances equal to 1.57 nanometer and 3.23 angstrom, respectively.
Figure 1: showing the structure of Xe encapsulated in a tetra cobalt cage and the temperature-dependent xenon-129 MR signal. Figure 2: showing xenon atoms encapsulated in the crystal lattice of tetra cobalt cages with xenon-xenon and inter-cage distances equal to 1.57 nanometer and 3.23 angstrom, respectively.
May 27, 2020
University of Pennsylvania

Paramagnetic Organocobalt Capsule Reveals Xe Host-Guest Chemistry

Kang Du, Serge D. Zemerov, Sebastian Hurtado Parra, James M. Kikkawa, Ivan J. Dmochowski, University of Pennsylvania
This collaboration between Dmochowski (Seed) and Kikkawa (IRG-3) addresses a  major challenge for molecular imaging with conventional MRI: the probes typically have low sensitivity and lack of responsiveness to local environment. The team developed a Co4 129Xe MRI sensor, which takes advantage of the high sensitivity of hyperpolarized 129Xe (~104 times greater signal than conventional MRI), and also has a very temperature-responsive 129Xe chemical shift.
Figure illustrating reconfigurable nematic liquid crystal drops filled with polydisperse nematic liquid crystal oligomers (NLCOs)
Figure illustrating reconfigurable nematic liquid crystal drops filled with polydisperse nematic liquid crystal oligomers (NLCOs)
May 27, 2020
University of Pennsylvania

Molecular Heterogeneity Drives Reconfigurable Nematic Liquid Crystal Drops

W. S. Wei, Y. Xia, S. Ettinger, Shu Yang and A.G. Yodh, University of Pennsylvania
With few exceptions, polydispersity or molecular heterogeneity in matter tends to impede assembly Shape transformations of liquid droplets, for example, are readily understood on the basis of homogeneous material responses. Here, Yodh and Yang in IRG-3 studied drops filled with polydisperse nematic liquid crystal oligomers (NLCOs). They discovered that chain-length heterogeneity in the drops promotes reversible shape transitions to a rich variety of non-spherical morphologies with unique internal structure.
Figure top left: multiaxial response of soft tissues, figure bottom left: predicted response of the network model from the Shenoy group, figure top right: Polymer networks that soften in compression but stiffen in extension can be converted to materials that stiffen in compression but not in extension by including within the network either cells or inert particles to restrict the relaxation modes of the fibrous networks that surround them, figure bottom right: predicted response of the network model from the Shenoy group
Figure top left: multiaxial response of soft tissues, figure bottom left: predicted response of the network model from the Shenoy group, figure top right: Polymer networks that soften in compression but stiffen in extension can be converted to materials that stiffen in compression but not in extension by including within the network either cells or inert particles to restrict the relaxation modes of the fibrous networks that surround them, figure bottom right: predicted response of the network model from the Shenoy group
May 27, 2020
University of Pennsylvania

Emergence of Tissue-like Mechanics from Fibrous Networks Confined by Close-packed Cells

Anne van Oosten, Xingyu Chen, Vivek Shenoy, Paul Janmey, University of Pennsylvania
The Janmey and Shenoy groups in IRG-2 studied multiaxial response of soft tissues (top left image). Measurements (Janmey) and a theoretical model (Shenoy) show that the tissue rheology emerges from an interplay between strain-stiffening polymer networks and the volume-conserving cells within them.
Figure Top: capillary-rise infiltration (CaRI) method in which polymer (polystyrene) is infiltrated into a nanoparticle film to form highly confined states. Figure Bottom: Experiments show that both the characteristic time of degradation and the activation energy for degradation increase, with values that correlate with increased Tg in these systems
Figure Top: capillary-rise infiltration (CaRI) method in which polymer (polystyrene) is infiltrated into a nanoparticle film to form highly confined states. Figure Bottom: Experiments show that both the characteristic time of degradation and the activation energy for degradation increase, with values that correlate with increased Tg in these systems
May 27, 2020
University of Pennsylvania

Thermal Degradation of Polymers under Extreme Nanoconfinement

H. Wang, Y. Qiang, A. A. Shamsabadi, P. Mazumder, K. T. Turner, D. Lee, Z. Fakhraai, University of Pennsylvania
A collaboration between members of IRG-1 (Fakhraai, Lee, Turner) explored the properties of disordered packings in different environments. Specifically, they investigated the effects of extreme confinement on the thermal properties of polymer-infiltrated nanoparticle films. The films are formed using capillary-rise infiltration (CaRI) method in which polymer (polystyrene [PS]) is infiltrated into a nanoparticle film to form highly confined disordered solids (top panel).
Figure top: Evaporation of a bidisperse suspension, figure bottom: monodisperse aggregates are weaker than polydisperse ones, highlighting the effects of particle size dispersivity. Interestingly, particles segregate by size during the evaporation process due to capillary forces to form remarkable self-similar, fractal structures
Figure top: Evaporation of a bidisperse suspension, figure bottom: monodisperse aggregates are weaker than polydisperse ones, highlighting the effects of particle size dispersivity. Interestingly, particles segregate by size during the evaporation process due to capillary forces to form remarkable self-similar, fractal structures
May 27, 2020
University of Pennsylvania

Formation of Stable and Hierarchical Particle Aggregates by “Solid Bridging”

A. Seiphoori, X-G Ma, P.E. Arratia, D. Jerolmack, University of Pennsylvania
This IRG-1 collaboration, is focused on the mechanics of disordered solid granular matter and is led by Arratia, Ma (post-doc, Yodh lab) and Jerolmack (MRSEC collaborator). This work[1] discovered that stable particle aggregates can be formed by a continuous wetting and evaporation process via formation of solid bridges: particle strands that connect larger aggregates. These strands can increase the strength (bonding) of particle aggregates by an order of magnitude or more.
Atomic Force Microscopy (AFM) image of an Nb4C3Tx MXene flake covering an 820 nm microwell in a Si/SiO2 substrate. The color map reflects AFM measured height on the sample. The blue spot indicates an AFM-indented area of the flake atop of the microwell.
Atomic Force Microscopy (AFM) image of an Nb4C3Tx MXene flake covering an 820 nm microwell in a Si/SiO2 substrate. The color map reflects AFM measured height on the sample. The blue spot indicates an AFM-indented area of the flake atop of the microwell.
May 25, 2020
University of Nebraska - Lincoln

Nanoscale Properties of MXene Membranes

A. Sinitskii and A. Gruverman (University of Nebraska-Lincoln) and Y. Gogotsi (Drexel University)
MXenes are two-dimensional (2D) ceramics made of transition metal carbides and nitrides. Unlike other 2D ceramics, MXenes have inherently good conductivity and thus are promising for various applications. Probing the local physical properties of MXenes monolayers is important for the understanding of their functional performance. Nebraska MRSEC researchers in collaboration with their colleagues at Drexel University have developed an improved method for synthesis of monolayer membranes of Nb4C3Tx MXene.
Schematic showing a ferroelectric tunnel junction (FTJ) with a composite barrier consisting of a ferroelectric layer (red) and a polar lanthanum aluminate (LaAlO3) layer (brown). The LaAlO3 layer creates a positive ionic charge at the interface which pins ferroelectric polarization (P) away from it. This property makes one state having a uniform polarization (top panel) and the other state having a head-to-head polarization (bottom panel). As a result the resistance of the FTJ corresponding to the two polarization states differs significantly, resulting in the enhanced TER effect.
Schematic showing a ferroelectric tunnel junction (FTJ) with a composite barrier consisting of a ferroelectric layer (red) and a polar lanthanum aluminate (LaAlO3) layer (brown). The LaAlO3 layer creates a positive ionic charge at the interface which pins ferroelectric polarization (P) away from it. This property makes one state having a uniform polarization (top panel) and the other state having a head-to-head polarization (bottom panel). As a result the resistance of the FTJ corresponding to the two polarization states differs significantly, resulting in the enhanced TER effect.
May 25, 2020
University of Nebraska - Lincoln

Ferroelectric Tunnel Junctions Enhanced by a Polar Oxide Barrier Layer

Qiong Yang, Lingling Tao, Evgeny Tsymbal, and Vitali Alexandrov (University of Nebraska-Lincoln)
Nebraska MRSEC researchers have proposed a new concept to design high-performance ferroelectric tunnel junctions with enhanced tunneling electroresistance (TER). This design exploits property of a polar oxide material to create an ionic charge at the interface.
Northwestern University Center for Atom Probe Tomography
Northwestern University Center for Atom Probe Tomography
May 22, 2020
Northwestern University

Northwestern University Center for Atom Probe Tomography

Northwestern University MRSEC Shared Facilities play a central role in education and outreach programs. For example, the Northwestern University Center for Atom Probe Tomography recently hosted a two-day workshop to offer hands-on user training in the  latest methods in atom probe tomography including materials analysis and visualization tools.
Facilitating Technology Transfer and Commercialization
Facilitating Technology Transfer and Commercialization
May 22, 2020
Northwestern University

Facilitating Technology Transfer and Commercialization

In partnership with the Northwestern University Kellogg School of Management, McCormick School of Engineering, Pritzker School of Law, and Innovation and New Ventures Office, the Northwestern University MRSEC fosters a comprehensive innovation ecosystem that allows fundamental research to be transferred to the market via startup companies.

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