Tag: John & Virginia Towers Lecture Series

Design and Application of Bioadhesives Inspired by Marine Mussels

Friday, March 4, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Bruce P. Lee
Director of New Technology
Nerites Corporation, Madison, WI

Abstract

Bioadhesives have a wide range of important applications in the biomedical field.  Tissueadhesives simplify complex surgical procedures to achieve effective wound closure and surgicalrepair. Despite these important functions, currently available adhesives seldom meet the basicrequirements for in vivo applications because of possible disease transmission, poor adhesivequality, or toxicity concerns. Thus, there is an ongoing need for the development of tissueadhesives with improved characteristics. Nature provides many outstanding examples ofadhesive strategies from which chemists and materials scientists can draw inspiration in theirpursuit of new biomaterials. Of particular interest is the mussel adhesive protein (MAP) secretedby marine mussels. MAP is initially secreted as a proteinaceous fluid, and then subsequentlyharden in situ to form an adhesive plaque, which allow mussels to bind tenaciously to varioustypes of surfaces underwater. One of the unique structural features of MAP is the presence of L-3,4-dihydroxyphenylalanine (DOPA), an amino acid post-translationally modified from tyrosine,which is believed to fulfill the dual role as the adhesive moiety and the crosslinking precursor.Our research focuses on the incorporation of DOPA and its derivatives in creating syntheticmimics of MAPs for various medical applications. In this seminar, I will discuss the design andapplication of these biomimetic adhesive materials.

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Hybrid Nanomaterials and New Designs for Energy Conversion and Storage Applications

Friday, February 25, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Leela Mohana Reddy Arava
Postdoctoral Research Fellow, Department of Mechanical Engineering and Materials Science
Rice University

Abstract

In response to the needs of modern society and emerging ecological concerns, it is nowessential to provide efficient, low-cost, and environmentally friendly electrochemicalenergy conversion and storage devices. These electrochemical devices are expected tohave pronounced technological impact on the society – especially for powering anincreasingly diverse range of portable electronic and vehicular applications.Rechargeable Lithium-ion batteries and Fuel cells are amongst the most promisingcandidates in terms of their wide spread applicability, owing to their high energy andpower densities. The performance of these devices depends intimately on the propertiesof materials used to build them. This talk will focus on the new designs and performanceof the next generation of energy and power delivery devices by the use of tailorednanostructured materials and by nanoscale engineering. Some of the current challengespertaining to the energy storage technology and the effective utilization of new electrodematerials such as graphene and carbon nanotubes will be discussed. Furthermore, thetalk will also evaluate approaches for optimization of the Li-ion battery performance withnovel designs, leading to prototype nanoscale 3D battery architectures offeringimprovements in energy and power density with respect to the geometrical foot print ofdevices.

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Bottom-Up Novel Hybrid Nanostructures for Solar Energy Harvesting

Monday, February 21, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Shenqiang Ren
Department of Materials Science and Engineering
Massachusetts Institute of Technology

Abstract

Nanostructured materials – including atomic clusters, quantum dots, nanowires or nanotubes –have dimensions in the range of 1 to 100 nm, the length scale that offers unique and sizetunable properties. They provide solutions to some of the current challenges in science andengineering, and would potentially lead to discoveries of new phenomena and novelapplications that are impossible to realize with their bulk counterparts. A challenging task in thisarea is to manipulate nanostructured materials and assemble them into desired structural forms– one, two or three-dimensional structures – so that their unique physical properties can beharvested. Among the bottom-up strategies, self-assembly of nanostructured materials andorganic conjugated polymers provides a promising route to the build-up of complex systems withimmense flexibility in terms of nanoscale building blocks and resulting novel physical properties.Current research is focused mainly on nanostructured hybrid solar cells that combine thebenefits of inorganic materials (thermal and chemical stability, high charge transport, solutionprocessing) and organic materials (strongly absorbing, mechanical flexibility, low-cost).

In this talk, I will discuss my research on rational design of self-assembling nanostructuredphotovoltaic systems on scales from molecular through macroscopic, to the development of“synthetic” strategies. Specifically, I will focus on three main topics: (a) bridging quantum dotsand conjugated polymer nanowires for efficient (>4%) hybrid solar cells; the data provides aunique new insight into the operation of hybrid bulk heterojunction devices and providesdirections to further improvements; (b) drying mediated self-assembly of inorganic nanowirehybrid solar cell; prospects for further enhancement will be discussed; (c) self-assembly of allconjugated block copolymers combined with metal oxide. The key aim of this study is to developa better understanding of the parameters that control such interfacial charge transfer processes.Another critical aim of this work is to develop quantitative structure-function relationships thatcan be used to guide the design and development of efficient nanostructured organic-inorganichybrid solar cells

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Infrared Photodetectors for Conformal Substrates

Friday, February 18, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Jeramy D. Zimmerman
Department of Electrical Engineering and Computer Science
University of Michigan

Abstract

Simple lens systems generally suffer from Petzval field curvature aberrations and focus on a curvedsurface; therefore, complicated lens systems are needed to create the flat focal surface required byconventional semiconductor fabrication techniques. To simplify the optics systems, we are designingimagers with curved imaging surfaces, which reduces other optical aberrations as well as system weight.The adoption of curved focal planes requires the development of new processing techniques and newmaterials for conformal surfaces. This talk will focus on two infrared-sensitive organic semiconductorphotodetector systems developed at the University of Michigan for use on conformal substrates.

Organic photodetectors are efficient (20-80% quantum efficient) in the visible region of the spectrum, butvery few organic materials exist with useful photoresponse beyond λ ≈ 1000 nm. Carbon nanotubes(CNTs) have band gaps that absorb in the λ ≈ 1000 to 2000 nm region, motivating our development of aprocedure to use single-wall CNTs wrapped with conjugated polymers as a photoactive component inphotodetectors. We have demonstrated that excitons on CNTs can be dissociated at CNTC60 interfaces, and have created the first photovoltaic detectors fabricated from bulk CNT films. Detectorspecific detectivities above D*=1010 cm-Hz½/W were demonstrated from λ ≈ 400 to 1400 nm, with peakexternal quantum efficiencies of approximately EQE=2% at λ ≈ 1155 and 1300 nm.[1]

More recently, we demonstrated a new porphyrin tape-based organic semiconductor materials systemwith the highest quantum efficiencies demonstrated to date at peak wavelengths greater than λ ≈ 1000nm. The porphyrin tapes consist of two porphyrin units triply linked to form a rigid tape with variousfunctional groups at the terminus of the tape, notably a pyrene group bonded in either one or twolocations. We have demonstrated quantum efficiencies of up to EQE=4% (D*=9×1011 cm-Hz½/W) at λ ≈1080 nm for a singlybonded pyrene end group and EQE=13% (D*=8×1010 cm-Hz½/W) at λ ≈ 1400 nm fora doubly-bonded pyrene end group.[2]

The presentation will discuss fabrication and analysis of devices and materials and conclude with afuture outlook and other applications for these materials.

  1. M. S. Arnold, J. D. Zimmerman, C. K. Renshaw, X. Xu, R. R. Lunt, C. M. Austin and S. R. Forrest, Nano Lett.9 (9), 3354-3358 (2009).
  2. J. D. Zimmerman, V. V. Diev, K. Hanson, R. R. Lunt, E. K. Yu, M. E. Thompson and S. R. Forrest, Adv. Mater.22 (25), 2780-2783 (2010).

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Microstructural Engineering for Solar Photovoltaic Devices

Monday, February 14, 2011 2:00 pm – 3:00 pm
Room G06, Rekhi Hall

Dr. Joshua M. Pearce
Department of Mechanical and Materials Engineering
Queen’s University, Canada

Abstract

Although, solar photovoltaic (PV) electrical production is technologically feasible, growing rapidlyand a environmentally-benign solution to society’s energy requirements, its costs must declinefor deployment at the necessary TW scale. This presentation will review two fundamentalapproaches to reach this goal using microstructural engineering of PV devices. The firstapproach uses relatively inefficient, but proven hydrogenated amorphous silicon (a-Si:H)-basedsolar cells. Thin film cells from a-Si:H are currently the least expensive PV and possess anexcellent ecological balance sheet.  Utilizing AFM, TEM, and real time spectroscopicellipsometry to track the phase of Si:H, the evolutionary nature (protocrystallinity) and substratedependence of its growth were established. This enabled the contributions of the carrierrecombination from the p/i interface regions and the bulk to the dark and light current-voltage (IV) characteristics of a-Si:H p-i-n and n-i-p solar cells to be separated and identified. By applyingthis knowledge of both microstructure and recombination a-Si:H solar cell performance can beimproved to improve efficiency and the cost of electricity provided. The second approach usespotentially ultra-high efficiency indium gallium nitride (InGaN) PV. InGaN shows such incrediblepromise as a PV material due to the ability to modify its band gap by adjusting the ratio ofindium and gallium in the film. A multi-layered cell of InGaN can be made with band gapsranging from 0.7eV (InN) to 3.4eV (GaN), which nearly covers the entire range of the solarspectrum. InGaN has been grown by plasma enhanced evaporation in nanocolumn crystals,which provide optical enhancement and reduce strain during growth and defects. Thus, a welldesigned InGaN solar cell could absorb and convert a much higher fraction of solar energy intoelectricity. The presentation reports on the first stage of research on the characterization andmicrostructural engineering of InGaN nanocolumns. Conclusions are drawn from theexperimental evidence and a path is outlined for future research using both of these approachesto assist society move towards a sustainable energy system using solar photovoltaic devices.

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Effect of Electric Field on Hydrogen Storage over Carbonaceous Sorbents at Ambient Temperature

Friday, February 4, 2011 3:00 pm – 4:00 pm
Room 610, M&M Building

Zheng Zhang
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

Storage and transportation of hydrogen in large quantities at small volume iscurrently a big obstacle on the way of hydrogen application. The primaryissue for hydrogen adsorption is weak interactions between hydrogen andthe surface of solid materials, which results in negligible sorption capacity atroom temperature. To solve this problem, electric field was introduced to theprocess of hydrogen adsorption at ambient temperature. For a certaincommercial activated carbon (NAC) with surface area of 1836m2/g, 12.5%and 18.5% enhancements were obtained at 80 bar under 1500V and 2000V.The enhancements were considered to be brought by strong orbitalinteractions between electrically charged sorbent and hydrogen. Moreover,dielectric phase, TiO2, was added to activated carbon to hold electricalcharges around carbon particles without distributing onto the body surface.Employing 2000V electric potential to the samples showed up to 100%enhancement.

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Development of an Empirical Model of Rehydration/Rehydroxylation Kinetics for Archaeological Ceramics

Friday, January 21, 2011 3:00 pm – 4:00 pm (1 of 2 speakers)
Room 610, M&M Building

Patrick Bowen
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

Fired-clay ceramic rehydroxylation dating has recently been proposed as a newchronometric dating tool for use on archaeological ceramics.  The technique reliesupon the well-known characteristic of fired clay objects to take up water in a slowmanner, which has been shown to follow a (time)1/4 power law.  Experiments wereconducted in which the mass measurements taken from XIX-century ceramicartifacts revealed a deviation from the (time)1/4 power law over a wide range oftemperatures.  These findings have led to the formation of a general empiricalequation which describes the observed rehydration/rehydroxylation behavior.  This presentation will describe the development of an empirical model describingrehydration/rehydroxylation of ceramic artifacts.  It will also briefly discuss theapproach that can be used to date artifacts using this method, as well as issues ofprecision

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A Systematic Investigation of Decomposition of Nano Zn4O(C8H4O4)3 Metal-Organic Framework

Friday, January 21, 2011 3:00 pm – 4:00 pm (1 of 2 speakers)
Room 610, M&M Building

Lei Zhang
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

Metal-Organic Framework (MOF) is a network in the appropriate topology via thecombination of inorganic and organic linker moieties from a wide range ofmultidentate ligands and metals or metal clusters secondary building units. Herein,the systematic investigation of thermal decomposition of the metal-organicframework Zn4O(BDC)4 (MOF-5) was carried out. It was found that thedecomposition of MOF-5, which could take place at 400 °C or above, was due tothe breaking of carboxylic bridges between benzene rings and Zn4O clusters. Thedecomposition produced CO2, benzene, and amorphous carbon besides crystalZnO. Furthermore, the ZnO was covered by amorphous carbon, resulting in theC/ZnO nanoparticles of about 10 nm. The removal of ZnO from the C/ZnOnanoparticles could generate mesoporous carbon with a large surface area of1844 m2/g.Metal-Organic Framework (MOF) is a network in the appropriate topology via thecombination of inorganic and organic linker moieties from a wide range ofmultidentate ligands and metals or metal clusters secondary building units. Herein,the systematic investigation of thermal decomposition of the metal-organicframework Zn4O(BDC)4 (MOF-5) was carried out. It was found that thedecomposition of MOF-5, which could take place at 400 °C or above, was due tothe breaking of carboxylic bridges between benzene rings and Zn4O clusters. Thedecomposition produced CO2, benzene, and amorphous carbon besides crystalZnO. Furthermore, the ZnO was covered by amorphous carbon, resulting in theC/ZnO nanoparticles of about 10 nm. The removal of ZnO from the C/ZnOnanoparticles could generate mesoporous carbon with a large surface area of1844 m2/g.

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Crystallographic Domain Engineering of Ferroelectric Single Crystals

Friday, November 19, 2010 3:00 pm – 4:00 pm (1 of 2 speakers)
Room 610, M&M Building

Jie Zhou
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

Phase field modeling and computer simulation is performed to study the mechanisms ofcrystallographic domain engineering technique for ferroelectrics. It is found that both domainconfigurations and domain sizes in ferroelectric single crystals can be controlled throughsophisticated thermal and electrical conditions imposed on the materials during ferroelectricphase transformations. The simulations reveal that minimal domain sizes and highest domainwall densities are obtained with intermediate magnitude of electric field applied along non-polaraxis of ferroelectric crystals, while lower and higher fields produce coarser domains and lowerdomain wall densities. It is found that temperature also plays an important role in domain sizecontrol. The simulations show that selection of polar domain variants by external electric fieldduring nucleation stage of ferroelectric phase transition significantly affects subsequent domaingrowth and evolution kinetics and controls the formation and sizes of twin-related lamellardomains. It is also found that the long-range electrostatic and elastostatic interactions generateinsurmountable energy barrier to isolated ferroelectric nucleation, and independent nucleation offerroelectric phase in the context of classical nucleation theory is impossible. In order tocircumvent such an energy barrier, ferroelectric nucleation exhibits strong spatial correlation andself-organization behaviors, and ferroelectric phase transformation proceeds via spatial andtemporal evolution of self-accommodating domains that provide a low-energy kinetic pathwaythroughout the entire phase transformation process.

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Particles at Fluid Interfaces and Effects on Coarsening Kinetics

Friday, November 19, 2010 3:00 pm – 4:00 pm (1 of 2 speakers)
Room 610, M&M Building

Tianle Cheng
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

A newly developed diffuse interface field approach (DIFA) is employed to perform simulationstudy of particles assembly at fluid interfaces. The model employs diffuse interface fields todescribe arbitrary particle shapes as well as multi-phase fluid. It takes into account capillaryforces associated with fluid interfaces, inter-particle short-range repulsions due to mechanicalcontact and/or steric force, hydrostatic force, and Brownian motion force. The model is appliedto simulate particle self-assembly in fluid that undergoes spinodal decomposition. It is shownthat particles stabilize the two-phase fluid morphology by slowing down the coarsening kinetics,and the fluid interfaces are finally arrested by particles closely packed at the interfaces. Inparticular, the effects of particles on the curvature of the fluid interfaces are discussed. It isfound that capillary force and pressure both play important roles in equilibrium of particles atfluid interfaces as well as the interface curvature. The latter is essential for coarsening kineticsof spinodal decomposition.

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