YINQE Seminars

Unless otherwise noted, all YINQE seminars meet on Fridays, 12:00-1:00 pm in the J. Robert Mann, Jr. Student Center, Dunham Lab 107. 

 Prof. Sigworth arrives at seminar            Prof. Dufresne presents results

Spring 2008

May 9
The Development of “Smart” Magnetic Solders

Ainissa G. Ramirez, Mechanical Engineering
Magnetic solders are a new class of magnetorheological materials or “smart fluids.” The suspension of micron-sized magnetic particles in tin-silver solders enables them to respond to magnetic fields. This ability to manipulate solder has several potential microfabrication applications: specifically, the filling of vertical paths and other hard-to-reach regions. Self-healing structures based on these materials could potentially be repaired in service by the application of heat and a magnetic field. The inclusion of magnetic particles has also been found to drastically increase the solder’s strength. In addition to these practical issues, these magnetically-responsive solders are a compelling tool for microfabricating adaptable and complex 3D geometries. This talk will describe the synthesis, mechanical behavior, and applications of these new materials.

Targeting the foreign body response via biomaterial-based drug
and gene delivery
Themis Kyriakides, Pathology
The implantation of biomaterials into soft tissues leads to the development of the foreign body response (FBR) that can interfere with the function of the implant and eventually lead to implant failure. In general, due to the FBR a largely avascular and dense collagenous capsule forms around biomaterials and scaffolds. A hallmark of the FBR is the formation and persistence of foreign body giant cells (FBGC) on the surface of the implant, a process that is indicative of a chronic inflammatory response. In addition, FBGC have been shown to cause extensive surface damage to a variety of biomaterials and cause the release of microparticles that can have toxic effects. Furthermore, a role for FBGC in promoting biomaterial encapsulation has been proposed. Thus, unlike a wound healing response that is self-limiting, the FBR can last for the duration of the implantation period. Despite the prominence of FBGC at implantation sites, little is known about their formation in vivo.

Through our work, we have identified several intracellular and extracellular modifiers of various aspects of the FBR including FBGC formation. Furthermore, we have developed localized drug and gene delivery strategies to target molecules that are essential for the development of the FBR. These include the angiogenesis inhibitor thrombospondin-2, a matrix-degrading enzyme (MMP-9), a chemokine (MCP-1), and a small GTPase (Rac1). Modulation of the expression or activity of these molecules suggests that a shift towards a wound healing-like response is possible and can lead to enhanced biocompatibility by preventing damage and extending the lifespan of implants.

May 2
Transmission Electron Microscopy with High Spatial, Temporal
and Spectroscopic Resolution

Nigel D. Browning, Professor of Materials Science, Department of Chemical Engineering and Materials Science, University of California-Davis
The last few years have seen a paradigm change in (scanning) transmission electron microscopy with unprecedented improvements in spatial, spectroscopic and temporal resolution being realized by aberration correctors, monochromators and pulsed photoemission sources. Spatial resolution now extends to the sub-angstrom level, spectroscopic resolution into the sub-100meV regime, and temporal resolution to the nanosecond scale. However, while these instrumentation developments have brought notable successes in materials analysis, they have also challenged the established experimental protocols and our fundamental understanding of both imaging and spectroscopy in the (S)TEM. In this presentation, examples of where the new instrumentation has successfully been used to address materials issues in nanoscale systems will be described. Additionally, the challenges associated with the routine use of the new (S)TEMs for reliable quantitative imaging and spectroscopy will be discussed. Finally, a personal perspective on the upcoming technology that will shape (S)TEM experimental capabilities in the next few years will be presented.

April 25
DNA-Guided Nanoassembly: Synthetic Biology Using an Orthogonal Genetic Code Where DNA-Makes-Protein

Paul M. Lizardi, Pathology
Abstract TBA

Did Life Grind to a Start? A Brief History of the Origins of Homochirality
J. Michael McBride, Chemistry
Ever since Pasteur discovered the handedness of natural molecules 160 years ago, there has been a nagging question: How was symmetry broken so that life on Earth came to use D-sugars and L-amino acids and not their mirror images? After surveying approaches to this question by chemists, physicists, biologists, statisticians, and geologists at 50-year intervals, this talk concludes with evidence published in February showing that grinding a slurry of mirror-image crystals converts their molecules to a single hand. John Tully and I advocate an amplification mechanism that depends on saving subcritical, chiral clusters from dissolution by means of their intact incorporation into larger crystals of the same hand.

April 11
Nanomechanical Devices Riding Optical Forces

Hong Tang, Mechanical and Electrical Engineering
Optical forces are generally thought to be too weak for practical use. This picture changes when applied to lightweight nanoscale devices. In this talk, we demonstrate that significant optical force can be produced by a single pass of light in a silicon photonic circuit. This optical force, originated from lateral photon confinement rather than from momentum transfer, is applied in a planar geometry and offers high scalability. Control and harnessing optical force will allow solid state devices to operate under new physical principle, and open doors to non-charge based classical and quantum devices. Practical application enabled by this strong mechanics-photonics interaction, such as all-optical logic, reconfigurable photonics, mechanical nonlinear optics, ultrasensitive transducers, will be discussed.

Designed Synthesis of Uniform Property Single-Walled Nanotubes of Carbon, Boron and GaN for Biomedical, Superconductivity and Solar Harvesting Applications
Lisa Pfefferle, Chemical Engineering
The ability to produce a selected structure carbon nanotube by design during synthesis is an important goal to enable applications. For example, electronic properties are a strong function of diameter and structure ((n,m) identity) with approximately 2/3 of SWNT formed in most processes being semi conducting and 1/3 metallic. Small diameter nanotubes are particularly interesting as their strong radius of curvature leads to increased reactivity. Since, cleaning/separation can introduce defects and change properties, selective synthesis is crucial. Achieving selectivity for (n,m) synthesis of SWNT is one of the holy grails for nanotube research. I will show how the diameter and structure of a carbon nanotube can be controlled through designed synthesis and how understanding carbon nanotube growth led to our synthesis of the first pure boron and GaN single-walled nanotubes. Applications we have demonstrated for each system will be discussed along with the remaining challenges in the synthesis to optimize the performance of these applications.

March 28
Chemical dynamics at metal and nanoparticle surfaces
John Tully, Chemistry
The adiabatic (Born-Oppenheimer) approximation underlies most of our understanding of molecular dynamics. It is becoming clear, however, that this approximation is often inadequate to describe atomic motions at metal surfaces and metal nanostructures; nonadiabatic behavior is the rule rather than the exception. Electron-hole pair transitions, charge transfer and hot-electron-induced motion can be dominant pathways for energy flow and can drastically alter the pathways of atomic motion. This talk will present progress toward a unified picture of nonadiabatic dynamics at metal surfaces. Initial applications to multi-quantum vibrational-to-electronic energy transfer in scattering of nitric oxide from gold and creation of excited electrons in the CO oxidation reaction on a platinum nanodiode will be presented.

Strain engineering of SiGe for photovoltaics, nanoelectronics, and nanostructured thermoelectric materials
Minjoo Larry Lee, Electrical Engineering
SiGe alloys were first studied in the 1960s for use in radioisotope thermoelectric power generators in deep-space satellites. Since then, SiGe has become prevalent in CMOS manufacturing due to its use in high-speed strained Si technology. In this talk, I will introduce three aspects of strain engineering in SiGe: engineering of the strain relaxation process, MOSFET channel engineering using strained Si, SiGe, and Ge, and the use of strain-driven Stranski-Krastanov nanodots for reduction of thermal conductivity. I will also discuss examples of how strain-engineered SiGe can be applied to a broad range of electrical and optoelectronic devices, including high-efficiency photovoltaics, high-speed MOSFETs, and next-generation thermoelectric materials.

March 14
Student Poster Session

February 29
Biotitanification
Ann Valentine, Chemistry
Many organisms produce or employ inorganic minerals for mechanical support or protection, for metal storage or detoxification, or as instruments, weapons, or sensor components. Although titanium minerals are prevalent in the environment, titanium is not usually considered a bioactive element, and instances of its association in mineral form with organisms are very few. One example is that titanium occurs at up to 1254 ppm in the acid-resistant siliceous frustules of diatoms. We wondered whether the biomolecules that induce nanostructured silica formation, also called biosilicification, might also produce titanium minerals, whether this process could be used to make materials of controlled morphology, and whether proteins could be immobilized in the materials. Naturally occurring polyamines spermidine and spermine are analogs of the species-specific polyamines found in diatoms. These molecules, as well as poly(allylamine) (a mimic of longer biopolyamines) and the R5 peptide (a repeat unit of a silaffin protein isolated from a diatom) induce the formation of mineralized nanostructured titanium from soluble titanium(IV) precursors.

Trapping Protons and Electrons on Little Chunks of Water: Using Size-Selected Cluster Ions to Capture Molecular Level Aspects of Water at Work
Mark Johnson, Chemistry
When an elementary electric charge is forced onto a collection of water molecules, only a select few molecules do the heavy lifting in accommodating the excess charge.  The ability of an excess charge to compromise the molecular integrity of a single water molecule is quite different for protons and electrons.  These differences are manifest as distinct shapes in the emerging water "crystal" upon addition of the first few hydration shells, where the size of the cluster indeed changes the local charge accommodation motif.  We use size-selected vibrational spectroscopy to understand the structural consequences of charge accommodation, where we combine laser spectroscopy with free-jet ion sources and mass spectrometry.  Unexpected (but welcome!) practical implications of these molecular-level measurements for understanding charge transport in biological processes (trans-membrane proton pumps) and solar energy conversion (proton exchange membranes) are discussed.

February 15
Title TBA
Robert Schoelkopf, Applied Physics
Abstract TBA

MEMS Electrosprays for Versatile Nanoparticle Synthesis
Alessandro Gomez, Mechanical Engineering
The generation of nanoparticles with narrow size distributions at flow rates adequate for a variety of applications is the ultimate goal of all synthesis approaches. Our research focuses on the use of the electrospray in the so-called cone-jet mode for a variety of applications requiring nanoparticle synthesis and coatings. This technology has the unique capability of producing monodisperse droplets/particles over a wide size range, from a few nanometers to several micrometers, depending on liquid flow rate, applied voltage and liquid electric conductivity. With appropriate selection of the liquid formulation, the droplets after evaporation and/or chemical reaction ultimately yield either nanoparticles residues of controlled and narrow size distribution or uniform deposits. The electrospray had a dramatic technological impact in the field of analytical chemistry, leading to the awarding of the 2002 Chemistry Nobel Prize to John B. Fenn, for his pioneering work at Yale. Its widespread application to other fields has been hampered by two drawbacks: first and foremost, low flow rates, and, to a lesser extent, restrictions on the physical properties of the liquids that can be electrosprayed. I will discuss key aspects of the research in our group that is aimed at: i) increasing by orders of magnitude the liquid flow rate to be dispersed, without compromising the quasi-monodispersity of the generated droplets; ii) extending the technique to a broad range of liquids by using a twin fluid approach, in which one fluid that is well suited to being electrosprayed “drags” the second fluid, that is compatible with a given applications but could not be otherwise electrosprayed; and iii) using this technique in a variety of high-value-added applications.

February 1
Computational and Experimental Study of Diffusion Flames
Mitchell Smooke, Mechanical Engineering
Our research has centered on an investigation of the effects of complex chemistry and
detailed transport on the structure and extinction of hydrocarbon flames in coflowing
axisymmetric configurations. We have pursued both computational and experimental
aspects of the research in parallel. The computational work has focused on the application of accurate and efficient numerical methods for the solution of the boundary value problems describing the various reacting systems. Detailed experimental measurements have been performed using two-dimensional imaging techniques. Spontaneous Raman scattering and laser-induced fluorescence have been used to measure the temperature, major and minor species profiles and Laser-induced incandescence has been used to measure soot volume fractions. Our goal has been to obtain a more fundamental understanding of the important fluid dynamic and chemical interactions in these flames so that this information can be used effectively in combustion modeling. In this talk we will discuss the development and application of the model and diagnostics to both sooting and nonsooting diffusion flames at atmospheric pressure. We will discuss issues related to flame lift-off, soot distribution, and NOx formation.


Active Photonic Nanomaterials
Hui Cao, Applied Physics
Active photonic nanomaterials, which have high gain or large nonlinearity, are essential to the development of nanophotonic devices and circuits. In this talk, I will provide a review of our recent research activities related to the fabrication of active photonic nanomaterials and the development of photonic devices based on such materials. In particular, we focus on a wide bandgap semiconductor zinc oxide and fabricate a broad range of structures, from disordered to periodic, with various nanofabrication techniques. Lasing in the near-ultraviolet frequency has been realized in both periodic and random structures at room temperature under optical pumping.

January 18
Ab Initio Theory of Micro and Nanolasers
A. Douglas Stone, Applied Physics
Progress in the fabrication of micro and nanostructured lasers has led to a number of novel and complex laser designs. Among these are circular and deformed microdisk lasers, photonic crystal defect lasers and random semiconducting nanolasers. These complex laser designs have highlighted the shortcomings of conventional laser theory, which is based on relatively simple one-dimensional laser cavities, and assumes the lasing modes are resonances of the passive cavity (without gain). Recently we have developed a time-independent theory which can treat quantitatively and predictively lasers with arbitrarily complex cavity design and any degree of outcoupling. We sketch the main ideas of the theory and show results from application to edge-emitting, disk and deformed disk lasers, and to random lasers.

Polar Molecules as Quantum Tools
David DeMille, Physics
Our group has devised a set of ideas for using the internal quantum states of simple molecules as the building block for obtaining complete control over a complex quantum system. A wide set of many-body quantum states can in principle be engineered from the bottom up, by manipulating the dipolar couplings between polar molecules. In order to implement these ideas, it is necessary to control not only the internal (rotational, vibrational) states of molecules, but also their motion. We are developing techniques for cooling molecules to extremely low temperatures (~10 microKelvin or lower), trapping them, and then manipulating their internal states. This talk will describe some of the basic ideas for quantum engineering using polar molecules, as well as our currents experimental progress.

Fall 2007

September 14
Erin Lavik, Biomedical Engineering
(Abstract TBA)

Folded Proteins Devoid of Alpha Amino Acids
Alanna Schepartz, Chemistry & Molecular Cellular and Developmental Biology
Non-natural polymers have the capacity to recapitulate both the well-folded structures and resultant functionalities of biological polymers.  Peptides composed of ß³-amino acids, which have one additional backbone methylene unit compared to natural a-amino acids, can adopt stable helices in water and interact with cellular proteins and membranes.  This lecture will describe the x-ray structures and solution phase kinetic and thermodynamic properties of a series of ß-peptides that self-assemble spontaneously in aqueous solution into highly thermostable ß-peptide bundles.


September 28
Magnetic Liquids for Lab-on-a-Chip and Rapid Diagnostics Applications
Hür Köser, Electrical Engineering
Ferrofluids are stable colloidal suspensions of nanosize ferromagnetic particles in either aqueous or oil-based media.  They have found their way into a variety of applications, such as sealing, damping and blood separation; in dilute, functionalized forms, they have also been used as drug delivery and MRI contrast agents.  These complex liquids offer attractive alternatives to moving mechanical components in miniaturized cooling, pumping and integrated micro-total-analysis-systems for chip-scale chemistry and biology.  Water-based ferrofluids can also be made bio-compatible, rendering them useful in novel cell manipulation and sorting schemes.  We have recently proposed, modeled and experimentally confirmed that ferrofluids can be actuated and pumped in closed-loop geometrics, even within geometries of micro-scale devices.  The pumping dynamics depend on the average nanoparticle size within the ferrofluid.  If particles are functionalized with a receptor molecule, the entire volume of the ferrofluid becomes a pathogen sensor that can detect minute quantities of target antigens efficiently and effectively.  We are working on creating portable, disposable, cheap and miniaturized sensor and diagnostic devices based on this dynamic effect.  We also briefly report on the development of a novel, ferrofluid-based cellular manipulation platform and a new assay to study a large quantity of ligand-receptor interactions quickly and simultaneously, without the need for any wash cycles.

Polyelectrolyte Nanofilm Biomaterials
Paul Van Tassel, Chemical Engineering
Emerging biomedical therapies and devices demand cell-contacting biomaterials meeting increasingly stringent criteria.  Candidate materials must exhibit precisely controlled bulk properties (structure, mechanical moduli, degredation rate, etc.), while also presenting a surface capable of promoting a favorable cellular response.  Designing materials to meet both bulk and surface requirements presents an enormous challenge.  Nanofilm biomaterials are attractive in this regard as they potentially allow for the decoupling of bulk and surface properties.  The idea is to place a thin film (ca. 10-100 nm), chosen for its cell-contacting properties, onto the surface of a biomaterial, chosen for its bulk properties.  We discuss here the formation of nanofilm biomaterials through layer-by-layer assembly, various strategies toward controlling their cell-contacting properties, and examples showing their potential as tissue engineering substrates.  We also introduce a new method of nanofilm formation, based on deposition under an applied electric potential, enabling single component films of arbitrary thickness to be grown in a single step.


October 12
Heteropolymer Dynamics and Random Walks on a Lattice: Course-Grained Computer Simulations of Protein Folding and Unfolding
Corey O'Hern, Mechanical Engineering & Physics
We perform computer simulations of simple polymer models to elucidate important questions concerning the structure of native and denatured proteins and the dynamics of protein folding.  We will focus on two key open questions.  First, what is the structure of the denatured state of proteins?  A. L. Cortajarena and Lynne Regan (Yale MB&B) and coworkers have performed experiments on modular repeat proteins and find that denatured proteins can be significantly more compact than that expected for structureless linear polymers.  Simulations of simple polymer lattice models confirm this result and suggest that attractions are necessary to give rise to the amount of compaction seen in experiments.  The second question is focused on the connection between the protein's amino acid sequence and the folding pathway of the protein.  Can we predict whether a given protein undergoes a quick, one-step folding process, passes through one or several intermediate states before reaching the native state, or becomes trapped in one of many glassy states that have nearly identical energies.  We will use a combination of molecular dynamics simulations and single-molecule experiments (Elizabeth Rhoades, MB&B) on short peptides to understand the link between amino acid sequence and folding pathways.

Nanotubes by Example: Carbon, Gallium Nitride, and Boron
Sohrab Ismail-Beigi, Applied Physics & Physics
Carbon nanotubes are probably one of the best known examples of nano-materials, although atomically-thin nanotubes of other elements are now fabricated.  Theoretically, nanotubes are constructed by rolling up a two-dimensional sheet-like material into tubular form.  Hence, they provide ideal cases for studying nanoscopic effects:  e.g., geometric and quantum confinement of electrons, enhanced Coulomb interactions, curvature effects, and novel bonding schemes in two dimensions.  We provide some examples based on our recent theoretical work on carbon, gallium nitride, and boron nanotubes.

October 26
Probing Transient Photoconductivity in Nanostructured Materials using Time-Resolved Terahertz Spectroscopy
Charles A. Scmuttenmaer, Chemistry
The microscopic details of carrier transport in nanocrystalline colloidal thin films is required for complete understanding of a variety of photochemical and photoelectrochemical cells utilizing interpenetrating networks.  Measuring the photoconductivity and charge transport properties in these materials, however, is a challenging problem because of the inherent difficulty of attaching wires to nanometer-sized objects.  Furthermore, picosecond (ps) carrier dynamics play an important role in efficient charge separation and transport, but the low temporal resolution of traditional methods used to determine the photoconductivity precludes their use in studying sub-ps to ps dynamics.  Time-resolved THz spectroscopy (TRTS), on the other hand, is a non-contact electrical probe capable of measuring the photoconductivity on a sub-ps to nanosecond (ns) timescale.  In this talk, TRTS is employed to determine the transient photoconductivity of ZnO nanowires, polycrystalline, and nanoparticle films, as well as dye-sensitized nanocrystalline colloidal TiO₂ films.  Electron injection occurs on sub-ps time scales.  Decay kinetics (on hundreds of ps to ns time scales) indicate that surfaces and interfaces are the dominant sources of recombination.  The photoconductivity deviates strongly from Drude behavior and is explained by disorder-induced carrier localization and/or backscattering of the photogenerated carriers.  Trends as a function of material and morphology will be discussed.

Interaction of Bacteria with Carbon Nanotubes
Menachem Elimelech, Chemical Engineering
Recent and ongoing work in our lab on the interaction of well characterized single-walled and multi-walled carbon nanotubes with bacterial (E. coli) cells will be presented.  Direct contact of bacterial cells with the carbon nanotubes results in significant cell damage and loss of viability, as verified by several independent techniques.  Single-walled carbon nanotubes exhibit a much stronger antibacterial activity than multi-walled carbon nanotubes.  Possible mechanisms for the inactivation of the bacterial cells upon contact with the carbon nanotubes are discussed.  The results point out to the potential biotoxicity of carbon nanotubes in aquatic environments.  The finding may also be useful in the application of carbon nanotubes as building blocks for antimicrobial materials.


November 9
III-Nitride Nanowires: Heterostructures, Epitaxial Alignment, and Applications
Jung Han, Electrical Engineering
Most of NWs are prepared by catalytic VLS method on amorphous or polycrystalline substrates.  The as-grown, hay-stack like NWs are dispersed randomly onto target wafers where electrical contacting and/or characterizations are performed.  The purpose of this paper is to demonstrate a hybrid approach toward the construction of GaN NW arrays and networks through the use of (optical) lithographically-defined selective-area growth (SAG) and bottom-up VLS synthesis.  Spatially ordered and flexibly patterned NW networks are prepared, in which the stochastic nature in contemporary process of NW synthesis and fabrication is greatly mitigated.  Beyond the obvious application in nanoelectronics, the availability of aligned, horizontal nanowires opens up new possibility in nano-electromechanical system (NEMS) application as nanoscale resonators in gravimetric detection with ultrahigh sensitivity.  The combination of SAG with nanowire synthesis is expected to provide a new paradigm for nanoscale electronics, photonic, and nano-electromechanical devices.

Characterizing the Shape and Size of Nanoparticles in the Gas Phase
Juan Fernandez de la Mora, Mechanical Engineering
Size, density, and shape are important characteristics of nanoparticles enabling simple indirect tests of their functionality.  When the particles are charged and suspended in the gas phase, such tests can be made very fast via electrical mobility (drag) measurements combined with mass spectrometry (or other schemes such as inertial impaction), allowing on-line monitoring during a process of synthesis.  In cases where the liquid solvent can be electrosprayed, the same can be done for nanoparticle syntheses proceeding in the liquid phase.  The potential of these techniques will be illustrated in various applications from several laboratories.  These include for instance the observation of phase changes in individual metal clusters; or the study of loss of stability of the spherical shape in charged polymer particles (or proteins) once their charge exceeds a critical (mass dependent) value; or the determination of the size and density distribution of lipoproteins.  One of the features limiting on-line monitoring in aerosol reactors is the low efficiency with which nanoparticles can be charged.  This problem arises also in the analysis of vapor species (for instance, low vapor pressure explosives), and can be addressed by high pressure variants of conventional confinement techniques based on RF fields.  Size selection in the gas phase at high resolution is a possibility that has not been sufficiently explored, but is theoretically possible under certain circumstances that will also be discussed.


November 30
Molecular Recognition In Catalysis
Robert H. Crabtree, Chemistry
In a biomimetic application based on the way enzymes carry out selective chemistry hydrogen bonding molecular recognition groups appended to terpyridine ligands give manganese based catalysts capable of completely selective conversion of C-H bonds into C-O-H groups at otherwise unactivated remote positions.

Atomic Scale Mechanisms of Surface Phenomena Through Direct Observation
Eric Altman, Chemical Engineering
The development of scanning probe microscopies has made it possible to follow the motions of individual atoms and molecules on surfaces.  In my lab, we have built several ultra-high vacuum, variable temperature scanning tunneling microscopes capable of recording movies of surfaces at high resolution at temperatures as high as 900 K.  In this talk, I will show how we have been using these instruments to characterize growth mechanisms on semiconductor surfaces, the oxidation and reduction of metal surfaces, and the structure and reactivity of transition metal oxide surfaces.  New collaborative directions in chemically sensitive imaging in which tips are functionalized to identify different types of atoms on the surface and to probe the chemical reactivity of different surface atoms will also be discussed.


December 14
Biotitanification
Ann Valentine
Many organisms produce or employ inorganic minerals for mechanical support or protection, for metal storage or detoxification, or as instruments, weapons, or sensor components.  Although titanium materials are prevalent in the environment, titanium is not usually considered a bioactive element, and instances of its association in mineral form with organisms are very few.  One example is that titanium occurs at up to 1254 ppm in the acid-resistant siliceous frustules of diatoms.  We wondered whether the biomolecules that induce nanostructured silica formation, also called biosilicification, might also produce titanium minerals, whether this process could be used to make materials of controlled morphology, and whether proteins could be immobilized in the materials.  Naturally occurring polyamines spermidine and spermine are analogs of the species-specific polyamines found in diatoms.  These molecules, as well as poly(allylamine) (a mimic of longer biopolyamines) and the R5 peptide (a repeat unit of a silaffin protein isolated from a diatom) induce the formation of mineralized titanium from soluble titanium(IV) precursors.

David DeMille
(Abstract TBA)

Summer 2007

August 17
Nanosystems for Engineering and Detection of Immunity
Tarek Fahmy, Biomedical Engineering
The immune system is made up of a complex network of molecules and cells that can screen its own components, protect itself, and attack invaders, such as bacteria and viruses.  Immune system malfunction can result in the genesis of many common chronic, autoimmune, and alloimmune diseases.  Failure of this system to recognize pathogens or ever cancer cells can lead to progressive debilitating disease states.  The immune system therefore offers a wealth of targets and strategies that need to be understood and modulated.  Engineered nanoscale biomaterials may facilitate detection and modulation of immunity.  In this discussion, we will focus on the engineering, fabrication and application of nanobiomaterials for applications in understanding, detection and modulation of the immune response.

Parametric Amplification of Quantum Signals with Superconducting Circuits
Michel Devoret, Applied Physics & Physics
Quantum Mechanics puts a limit on how small the degradation of information passing through an amplifier can be.  It is known theoretically that the minimum noise added by the amplifier to the signal amounts at least to half a photon at the signal frequency.  Is it possible to construct a practical amplifier working at microwave frequencies that would reach this quantum limit?  We will present recent work by our group aiming at answering this question, which is of practical importance for the readout of solid state qubits, and, more generally, for the measurement of very weak signals in various areas of science.

July 18
June 15

Spring 2007

May 18  

Superconducting Nanodetectors for Studies in Spectoscopy; Astrophysics and Nanotubes

Daniel Prober, Applied Physics

The production of nanoscale superconducting detectors can be accomplished in most major laboratories in the US.  This area has been a leading interest at Yale, and has now produced a number of new detectors that are being used in other scientific fields.  We explain the operation of these devices and their potential.  We also show how the separate concepts can be used to study electromagnetic waves propagating on a single carbon nanotube, in order to explore a regime that cannot be access with other methods.

Proteins: The Ultimate Nanomachines

Lynne Regan, Molecular Biophysics & Biochemistry

Proteins perform a myriad of different functions within all living organisms. They mediate muscle contraction, chromatin condensation, gene expression, hormone-receptor interactions, enzymatic catalysis, and much, much more.  In spite of their amazing diversity of function, proteins are all made of linear combinations of the same 20 amino acids, or a subset thereof. The grand challenges are to be able to predict the structure, function and properties of a protein from its amino acid sequence, and to be able to exploit our knowledge of the construction and properties of natural proteins to engineer novel proteins to perform the functions we specify. I will present a snapshot of the current efforts of my group towards meeting these challenges.

April 20       

Looking at Ion Channels and Measuring their Currents

Frederick J. Sigworth, Physiology

Ion channels are cell-membrane proteins that control the electrical activity of neurons and many other cell types.  Their function can be studied by sensitive electrical measurements using the "patch clamp" technique. Understanding how they respond to stimuli such as transmitter molecules, mechanical stretch and voltage requires the analysis of their structure in their various functional states.  First I will describe our efforts toward making the patch clamp technique into a high-throughput screening tool. Second I will describe our efforts to obtain structures of ion-channel proteins, in their "open" and "closed" states, using new methods in high-resolution electron microscopy.

Nanophotonic Probes of Soft and Biological Matter

Eric R. Dufresne, Mechanical Engineering

We exploit surprising properties of light near -- and even below -- the diffraction limit to study and control materials. Optical forces, negligible at the macroscale, can dominate the dynamics of materials at the scale of hundreds of nanometers. I will describe how we harness these effects to measure tiny forces, sort materials, assemble microscale structures and probe the biochemical pathways of live cells. In addition, I will briefly outline our recent efforts to characterize material properties and dynamics below the diffraction limit ­ with applications to plasmonics and single molecule biophysics.

April 6         

Moore’s Law and CMOS

T.P. Ma, Electrical Engineering

Since the invention of the transistor more than 5 decades ago, the tremendous progress of the electronics industry has been riding on the exponential growth of the IC technology, as characterized by the “Moore’s Law”, which basically says that the information storage capacity of a silicon chip, as well as its information processing power, doubles every 18 months.  This talk will give an overview of the silicon chip technology and how we got to where we are, with a preview of what’s to come in the future. The various challenges in continued scaling of CMOS devices will be highlighted, and research opportunities will be discussed.

Sizing Up Cellular Magnetic Resonance Imaging

Eric Shapiro, Diagnostic Radiology

Cell tracking using magnetic resonance imaging is rapidly moving towards in vivo single cell detection. This has largely been facilitated by improved efficiency of contrast agent uptake, as well as optimized pulse sequences. Micron sized iron oxide particles (MPIOs) are emerging as a robust contrast agent for cell tracking. In contrast to the more commonly used nano-sized dextran coated particles, MPIOs have very high amounts of iron, as high as 90% iron and from 0.1 to 10 pg iron per particle, and are non-biodegradable, which extends the observable temporal window. Indeed, single MPIOs are detectable by MRI in cells in culture and in mouse embryos. This talk will present recent data on two projects. The first is in vivo detection of single cells in mouse livers.  Primary mouse hepatocytes were labeled in culture with MPIOs and transplanted into the spleen of recipient mice. The labeled cells migrated to the liver and engrafted as single cells, which were visible by MRI. The second project is the use of MPIOs to directly label adult rat neural stem cells, in situ, and monitor the migration of the daughter neuroblasts to the olfactory bulb

March 23    

Finding Fufillment in the Filling of Fullerenes

R. James Cross, Jr., Chemistry

We have devised several techniques for putting atoms and small molecules inside fullerenes. There is no chemical bond between the trapped atom and the carbon cage, yet they cannot escape without breaking several C-C bonds. So far, we have put He, Ne, Ar, Kr, Xe, CO, N2, N, and T inside C60 and higher fullerenes. NMR spectroscopy of trapped 3He and 129Xe gives a measure of the electronic structure of the carbon cage and can be used to follow chemical reactions. The trapped atom can affect the chemistry of the fullerene.

Designing Biomimetic Nanoscale Ion Transport Systems

David A. LaVan, Mechanical Engineering

The National Center for the Design of Biomimetic Nanoconductors (NCDBN) was founded to develop new technologies based on natural and synthetic ion transport devices.  One project within this center is to create a synthetic in vivo power source based on the ion transport mechanism of the electric eel.  The electric eel generates electricity by converting chemical energy stored in ion concentration gradients which are produced through the ATP cycle.  A numerical model of electrogenic cells has been created which allows for accurate extraction of channel parameters, clarification of the mechanism of energy transduction and enables the design of electrogenic artificial cells.  Using optimization methods, an artificial cell has been designed that achieved higher energy density and higher energy conversion efficiency than the natural cells.  These findings are the starting point for additional studies of energy conversion in polarized cells as well as the foundation for system level design of artificial cells.

March 9      

Nanoparticle Phase Transitions

Simon Mochrie, Physics

The collective behavior of nanopartlcles provides the opportunity to explore a host of key scientific questions. For example,the glass transition and protein folding remain grand challenges to both condensed matter and to nanoscience. This talk will describe recent x-ray measurements which reveal the existence of two distinct glass phases in concentrated suspensions of nanoparticles in a binary fluid. We characterize the remarkable transition from one to the other via a nanoparticle liquid phase. We will also describe recent efforts to characterize the order-disorder and mechanical behavior of a family of smart, biological nanoparticles, namely TPR repeat proteins.

Peptide-Based Catalysts for Organic Synthesis: Biomimetic Designs and Discovery Platforms

Scott J. Miller, Chemistry

Modern organic synthesis depends heavily on the use of catalysts for selective transformations. We have discovered a class of synthetic peptides that catalyze a number of selective reactions.  The biomimetic design principles that led to our initial discoveries will be described.  Combinatorial technique development based on the synthesis polymeric supports as vehicles for catalyst discovery will be presented.  The connection between these techniques and complex, biologically active compound synthesis will be illustrated.

February 23        

Nanoparticles for Drug Delivery

W. Mark Saltzman, Biomedical Engineering

Drug-loaded nanoparticles, particularly those formed from degradable polymers, have several properties that will make them useful vehicles for drug delivery including high drug loading, efficient entry into cells, and capability for selective targeting.  This presentation reviews these properties, and engineering methods for achieving them with PLGA materials.  The application of nanoparticles for cancer treatment, drug delivery to the brain, and delivery through epithelial cells will be reviewed.

High-Resolution Atomic Force Microscopy

Udo Schwarz, Mechanical Engineering

The world's most sensitive noncontact atomic force microscopes allow high-resolution imaging for both hard and soft materials as well as both conducting and insulating materials. They can be used to image short-range interatomic forces, resulting in “atomic resolution” images featuring single atomic defects, as well as long-range electrostatic and magnetic forces, leading to high-resolution maps of charge distributions or magnetic domains. This talk will give a short overview on the activities at Yale designed to push the resolution to its limits.