Center for Soft Matter and Biological Physics Seminars

Fall 2019

Organizer: Vinh Nguyen

These meetings occur on Mondays from 4:00pm to 5:00pm in Robeson 304.
Refreshments are served before the seminars (unless otherwise indicated)

August 2019
August 26

Monday 4:00pm
304 Robeson Hall
(poster)

"Fall Semester Classes Begin"

Host:

September 2019
September 2

Monday, 4:00pm
304 Robeson Hall
(poster)

"Labor Day" (No Classes)

Host:

September 9

Monday 4:00pm
304 Robeson Hall
(poster)

Dr. Carolina Tallon (Materials Science and Engineering, Virginia Tech)

“Rocket Science meets Colloidal Surface Science: Near-Net-Shaping of Dense and Porous Ultra High Temperature Ceramics for Extreme Applications”

Ultra High Temperature Ceramics and other non-oxide ceramics represent the best candidate materials for use in extreme applications, including components for hypersonic vehicles, personal armor devices and cathodes for aluminum smelting and lithium air batteries. However, most of these applications require either a very complex geometry or very high and intricate porosity which cannot be achieved or designed using the current state-of-the-art for these types of compounds. The colloidal powder processing approach seems the natural answer to this problem, since it allows the preparation of high and uniform green density bodies facilitating densification, to control the porosity and the preparation of near-net-shaped dense and porous components, while minimizing defects and flaws through the preparation of ceramic powder suspensions. In this presentation, two cases studies related to hypersonic applications are discussed: The first one comprises the preparation of dense ultra-high temperature ceramics for leading edges in hypersonic vehicles by using the combination of colloidal processing and pressure less sintering. The second case study focused on the preparation of multi-scale porous materials for ultra-high temperature insulation. Highly porous UHTC materials have been produced by four different processing routes. The exhaustive control of the forces between particles and understanding the interaction between additives and powder surfaces have been key in developing highly porous ZrB2 and TiB2. The relationship between microstructure and properties of these materials was elucidated by the 3D image reconstruction and predictive modelling via a combination of x-ray tomography and simulations, which are validated against experimental values at room temperature. These models can be used to simulate and predict the thermal and mechanical properties of the materials under relevant extreme environment conditions.

Host: Vinh Nguyen

September 16

Monday 4:00pm
304 Robeson Hall
(poster)

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Host:

September 23

Monday 4:00pm
304 Robeson Hall

(poster)

Vinh Ho (Physics, Virginia Tech)

“Fast and High Responsivity Graphene-based Photodetectors at Room-temperature by Engineering Dielectric Films”

The realization of low-cost photodetectors with high quantum efficiency, high sensitivity, and fast photo-response in the visible and infrared remains one of the challenges in optoelectronics. Ideally, these photodetectors should be based on Complementary Metal-Oxide-Semiconductor (CMOS) compatible platform for monolithic integration with read-out electronics to provide for high-density, high-throughput and low-cost manufacturing. Graphene is ideally suitable for optoelectronic photodetectors sensitive from visible to infrared frequencies, and have proved to fulfil those requirements. Here, we have engineered the interface between graphene and dielectric Ta2O5 and Ti2O3 thin-films by e-beam evaporation method to introduce quantum dots as absorption centers from visible to infrared region. Our graphene-based photodetectors have showed a high responsivity up to 2×105 A/W as well as a fast response time in the nano-second time scale at room temperature. These results address key challenges for broadband photodetectors from visible to infrared region, and are promising for the development of graphene-based optoelectronic applications.

Host: Vinh Nguyen

September 30

Monday, 4:00pm
304 Robeson Hall
(poster)

Prof. Rui Qiao (Mechanical Engineering, Virginia Tech)

"Modeling of Inter-facial and Transport Phenomena: Ionic Self-assembly, Active Colloids, and Beyond "

Interfacial and transport processes are at the core of many engineering and biological technologies. Experimental studies of these phenomena often have difficulties in fully resolving their underlying phenomena and pinpointing their physical mechanisms. These difficulties can often be addressed using numerical modeling. Our group specializes in molecular, mesoscopic and continuum simulations of interfacial and transport phenomena, especially those involving ions and non-equilibrium effects. In this talk, I will first introduce our molecular modeling of ionic liquids near electrified interfaces and in nanoscale confinement, with a focus on the self-assembly of ions, the transport of ions under far-from equilibrium conditions, and the effects of impurities. Next, I will introduce our continuum modeling of active colloids, with a focus on their hydrodynamic behavior in multiphase systems and in confinements. Ample time will be left for the discussion of possible collaborative work with the audience.

Host: Vinh Nguyen

October 2019
October 7

Monday 4:00pm
304 Robeson Hall

(poster)

Dr. Patrick Dennis (Air Force Research Lab, Wright-Patterson Air Force Base, Ohio)

"Protein Hydrogels from Marine Invertebrates: A Platform for Tunable Functionality”

Sclerotized, proteinaceous structures in marine invertebrates are used for predation by facilitating grappling, piercing and tearing of prey. These structures must have robust mechanical properties that are tailored to the size, shape and function of the specific predatory tool. Two such structures are the squid sucker ring teeth (SRT) assembly and jaws from the North Atlantic sandworm, Nereis virens. Both structures are not mineralized and are primarily comprised of proteins. Intriguingly, these sclerotized acellular structures are formed in a constitutive marine environment without the benefit of evaporation to aid in removal of bulk water. We have studied this phenomenon in hydrogels created from two proteins, suckerin and Nvjp-1, derived from the squid SRT assembly and sandworm jaw, respectively. Upon exposure of the protein-based hydrogels to aqueous salt solutions, a significant decrease in hydrogel size occurs where bulk water is driven out and a condensation of the protein hydrogel occurs. Interestingly, the contraction rate as well as the mechanical properties of the condensed hydrogels are greatly dependent on the type of cation and anion present in the salt, and the trends differ among the two proteins. The final size and mechanical properties of the condensed structures is dependent on both the initial concentration of the hydrogels as well as the ions used for condensation. Together, the results suggest that spatially controlled casting densities coupled with a selective exposure to ions can create features in the final condensed structure with tunable mechanical properties, similar to what is observed in the marine organisms.

Host: Vinh Nguyen

October 14

Monday, 4:00pm
304 Robeson Hall

(poster)

No Seminar Holiday (Columbus Day)

Host:

October 21

Monday 4:00pm
304 Robeson Hall

(poster)

Prof. Qi-Huo Wei (Kent State University)

“Printing Molecular Orientations as You Wish”

Liquid crystals consisting of rod-shaped molecules are a remarkable soft matter with extraordinary responsivity to external stimuli. Techniques to control molecular orientations are essential in both making and operating liquid crystal devices that have changed our daily lives completely. Traditional display devices are based on uniform alignments of molecules at substrate surfaces. In this talk, I will present a new photopatterning approach for aligning molecules into complex 2D and 3D orientations with sub-micron resolutions. This approach relies on so-called plasmonic metamasks to generate designer polarization direction patterns and photoalignments. I will present the basic principles behind this approach and a number of intriguing applications enabled by it, including micro-optical devices for laser beam shaping, commanding chaotic motions of bacteria, and creating topological defects with designer structures.

Host: Shengfeng Cheng

October 28

Monday 4:00pm
304 Robeson Hall

(poster)

Dr. Greg Quiroz (Johns Hopkins Applied Physics Lab)

“Deep Reinforcement Learning for Quantum Control: Learning to Optimally Navigate in Complex Noisy Environments”

Quantum control seeks to establish control over a quantum system in such a way so that logical operations are implemented while simultaneously mitigating unwanted interactions between the system and its environment. From the point of view of quantum computation, quantum control can potentially provide significant improvements in computational accuracy when quantum logic operations are tailored for the particular noise plaguing the hardware. Specifically tailoring each controlled operation can be quite demanding if one wishes to perform this task for every instantiation of a quantum algorithm. Here, we examine how one can leverage reinforcement learning to learn and predict quantum gates in the presence of noise; thus, providing a streamlined method for gate design for generic quantum algorithms.

Host: Sophia Economou

November 2019
November 4

Monday 4:00pm
304 Robeson Hall

(poster)

Host:

November 11

Monday 4:00pm
304 Robeson Hall


(poster)

Dr. Kin Chung Fong (Raytheon, BBN)

Host: Ed Barnes

November 18

Monday 4:00pm
304 Robeson Hall

(poster)

Dr. Vivek Amin (NIST)

Host: Satoru Emori

November 25

Monday 4:00pm
304 Robeson Hall

(poster)

Host:

December 2019
December 2

Monday 4:00pm
304 Robeson Hall
(poster)

Host:

December 9

Monday, 4:00pm
304 Robeson Hall
(poster)

Prof. Kwon Park (Korea Institute for Advanced Study)

Host: Vito Scarola

December 16

Monday, 4:00pm
304 Robeson Hall
(poster)


Host:
December 23

Monday, 4:00pm
304 Robeson Hall
(poster)


Host:
December 30

Monday, 4:00pm
304 Robeson Hall
(poster)


Host: