New Graduate Student Orientation

August 18, 2010

Dr. Phillip R. White

www.eng.utoledo.edu/~pwhite

Solid Mechanics Focus Group• Dr. Lesley Berhan Assoc. Professor Lesley.Berhan@utoledo.edu

NI 4025 419 530 8220• Dr. Mohammad Elahinia Assoc. Professor Mohammad.Elahinia@utoledo.edu

NI 4045 419 520 8224• Dr. Ali Fatemi Professor Ali.Fatemi@utoledo.edu

NI 4029 419 520 8213• Dr. Yong Gan Assist. Professor Yong.Gan@utoledo.edu

NI 4024 419 520 6007• Dr. Mohamed Samir Hefzy Professor Mohamed.Hefzy@utoledo.edu

NI 1016 419 520 6086• Dr. Ahalapitiya Jayatissa Assoc. Professor Aayati@utnet.utoledo.edu

NI 4049 419 520 8245• Dr. Efstratios Nikolaidis Professor Efstratios.Nikolaidis@utoledo.edu

NI 4035 419 520 8216• Dr. Mehdi Pourazady Assoc. Professor Mehdi.Pourazady@utoledo.edu

NI 4036 419 520 8221• Dr. Phillip White * Professor Phillip.White@utoledo.edu

NI 4065 419 520 4241* = not adding new students at this time.

Dr. Lesley BerhanResearch Interests:

• Negative Poisson’s ratio materials

• Nanocomposites

• Composites

• Heterogeneous materials

• Fibrous networks

• Structural mechanics

• Finite element analysis

Interested in hiring one or two graduate students

Modeling electrical percolation onset in polymer nanocompositesComposite and Fibrous Materials Laboratory | University of Toledo

Dr. Lesley Berhan

Conventional modeling approach•Reinforcement (e.g. graphene platelets, nanotubes, nanoparticles, etc.) modeled as fully penetrable objects•Relationship between excluded volume and percolation threshold used obtain percolation threshold

Hard-core modeling approach•Reinforcement modeled as impenetrable objects (hard core) embedded within a soft (i.e. penetrable) shell•Excluded volume of objects found numerically•Relationship between percolation threshold and excluded volume found using Monte Carlo simulations•Analytical solution will be derived and compared with experimental results

Percolation in nanocomposites is of high interest because of the potential to create electrically and/or thermally conductive systems with an extremely low mass of particles. At relatively low concentrations of nanofillers the electrical conductivity of polymer nanocomposites dramatically increases.

The study of percolation is relevant to many areas of research including thermal management, EMI shielding, and lightning strike protection

Dr. Mohammad Elahinia

• I am looking for one Ph.D. student. The area of the research is biomedical applications of shape memory materials.

• Please see next slide.

Dynamic and Smart Systems Laboratory

North Engineering Room 2045

Phone: (419) 530-8130

Fax: (419) 530-8126

http://smartsys.eng.utoledo.edu/

Background (I) Bio-inspired Shape Memory Alloy Pedicle Screw to Compensate for

Bone Degradation in Osteoporosis Patients

(II) Bio-inspired Shape Memory Alloy Esophagus Positioner

for Minimally Invasive Surgeries

Conclusions

Allows a material to return to its original shape within a strain of up to 8% by increasing the temperature.

Shape memory alloy (SMA) technology offers new capacities to medical devices, negotiating the obstacles in:

Spinal instrumentation of osteoporotic bone and

Esophageal fistula during Radiofrequency ablation (RFA).

References1. H. Fischer, B. Vogel, and A. Welle. “Applications of shape memory alloys in medical instruments”. Minimally

invasive therapy and allied technologies, Volume 13, Issue 4 August 2004, pages 248-253.2. H. A. Yuehuei. Internal fixation in osteoporotic bone. Edited by H. A. Yuehuei. Thieme Medical Publishers, INC.

2002.3. D Sanchez-Quintana et al. Anatomic Relations between the Esophagus and Left Atrium and Relevance for

Ablation of Atrial Fibrillation. Circulation, v. 112 issue 10, 2005.

Initially, this SMA scaffold is pre-compressed in its martensitic state. As the scaffold is heated, due to the body temperature, tends to recover its original shape, to maintain the inner diameter of a blood vessel or any tubular passage.

Shape Memory Alloys, such as equiatomic Nickel Titanium (NiTi or Nitinol), undergo a phase transformation in their crystal structure when cooled from the stronger, high temperature form (Austenite) to the weaker, low temperature form (Martensite). This inherent phase transformation is the basis for the unique properties of :

Allows the formation of an elastic behavior with significant recoverable strain (up to10%)

NiTi is also biocompatible , biomechanically compatible, MR compatible, fatigue resistant, etc which constitute excellent medical characteristics.

Self-expanding stents Orthopedic staples

The SMA staple, in its opened shape, is placed at the fractured bone site. Through heating by an external device, this staple tends to close, compressing the separated parts of bone to accelerate the healing process of bone fractures.

Pedicle Screw: a particular type of bone screw designed for implantation into vertebral pedicle.

Can be used in instrumentation procedures for fixating rods and plates to the spine with the purpose of:

Dynamic stabilization of the spine Immobilization for Spinal Fusion Spinal Deformity correction, …

Osteoporosis is a systemic skeletal disease characterized by low bone mass, micro architectural deterioration of bone tissue, and a consequent increase in bone fragility and susceptibility to fracture.

It is a major drawback in spinal instrumentation due to hardware loosening or pulling-out both intra and post operation.

Osteoporosis and spinal instrumentation

The screw assembly before placement The screw assembly after placement

Anchoring system with expandable thread inserts

NiTi insert. Initial low-temperature (at insertion). and closed high temperature form (at withdrawal).

Final form when reached to body temperature. A portion of the insert from both ends expands.

Atrial fibrillation: an abnormal heart rhythm (cardiac arrhythmia).

Involves the two upper chambers (atria) of the heart.

Patients with AF are believed to have a significantly higher risk of stroke

Radiofrequency ablation (RFA): catheter based treatment method

For patients who do not respond to other methods. Low voltage alternating electricity at high frequencies to

create controlled thermal injury in a group of cells near the pulmonary veins.

RFA could cause thermal injury to the esophagus (fistula). The esophagus and posterior left atrium (LA) wall are in close contact over a

large area that may often lie within the atrial fibrillation ablation zone The RF could burn the esophagus tissues, causing esophageal perforation

leading to mediastinal infection, stroke, and death.

SMA esophagus positioner

SMA wires, if heated, will deflect the esophagus away from the ablation site.

Biomedical Applications of NiTi Shape Memory Alloys:(I) Smart pedicle screw (II) Esophagus positioner

Majid Tabesh, Amin Mohaghegh, and Mohammad ElahiniaDynamic and Smart Systems Laboratory, MIME Department, University of Toledo

Dr. Ali Fatemi

• Primary areas of interest: Fatigue, Fracture Mechanics, Failure Analysis, Materials Mechanical Behavior, Fatigue of  Elastomers, Composite Materials, Nano-Fiber Reinforced Plastics, Damage Mechanics, Solid Mechanics, Mechanical Design, Experimental Mechanics.

Dr. Yong Gan

• See next slides for research areas

• He is interested in working with Ph.D. students and is seeking funding.

Outline

• Thermal Evaporated Thin Films and Their Temperature Sensitive Electric Property

• Silicate Glass-Based Silver Composites for High Temperature Thermoelectric Energy Conversions

• Preparation of Photovoltaic (PV)/Thermoelectric (TE) Nanofiber Arrays on Conductive Substrates

• Biophotofuel Cell Electrode Research

Introduction Morphology of CdS Film

I-V Curve at Different Temperatures

1. CdS film coated on glass with thermally-evaporating method.

2. Experiment setup includes: Multimeter with Thermocouple, Heater, Electrochemical Analyzer, and Computer with analysis software.

1. When temperature increases the current increasers significant ly. Such a heat sensitive behavior reveals the thermoelectricity within the CdS thin film.

2. Future research: X-ray analyze the components of the film.

References

Cadmium sulfide (CdS) is a semiconductor material [1]. The polycrystalline CdS layer is n-type doped (as CdS invariably is) [2], and therefore provides one half of the p-n junction. It has the optical band gap of 2.42 eV or 514.5 nm (in wavelength units) [3], which is sensitive to visible light. Thin films of CdS have found applications as detectors of light and window materials for solar cells.

There is little work on the thermoelectricity of CdS. Recently, we have demonstrated that CdS thin films are very sensitive to heat. The change of surface temperature of this material results in significant increase in electrical conductivity.

In this study, we focus on the heat sensitivity of CdS thin films. CdS thin film in the thickness of about 5~10 nm was prepared by thermal evaporation at 3000C. A three-electrode system was used for linear sweep voltammetry measurement. The three electrodes are connected with a CHI 400A electrochemical quartz microbalance to conduct data acquisition. The three electrodes are the reference electrode, the work electrode (cathode), and the counter electrode (anode). The width of the specimens is 25 mm, and the distance between the counter electrode and the work electrode is also 25 mm. The potentials were changed in a triangle waveform.

Experimental

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-6

-5

-4

-3

-2

-1

0

1x 10

-8 CdS I-V curve under different temperature

Potential (V)

Cur

rent

(A

)

T=70FT=90F

T=100F

T=120F

T=140F

T=170FT=220F

[1] J.F. Shackelford, Introduction to Materials Science for Engineers, 6th Edition, Pearson Prentice Hall, Upper Saddle River, new Jersey, (2005), pp.13-14.[2] Junichi Nishino, Sunao Chatani, Yukifumi Uotani, Yoshio Nosaka, Journal of Electroanalytical Chemistry 473 (1999) 217–222.[3] J. Britt, C. Ferekides, Appl. Phys. Lett. 62 (1993) 285.

Summary

Thermal Evaporated CdS Thin Film on Glass and the Temperature Sensitive Electric Property

Conductive and Oxidation Resistant Silicates-Silver

Research Objective

To develop glass-based electrode materials for high temperature thermoelectric energy conversions that exhibit the following properties: high conductivity, high oxidation resistance and good bonding to TE legs.

G.J. Snyder, et al., Nat. Mater. Vol.7, 105, 2008.

Significance and BackgroundThermoelectric (TE) materials generate electricity from thermal gradient. The electrode connecting TE elements is critical for effective power generation. Due to the high temperature reactions and intra-diffusion between Si and metals, the electrical conductive behavior of most metallic electrodes degrades. Judicious selection of electrode materials was under-taken to develop interconnects for high temperature TE materials. Solution : Glass-Based Composite

Materials• Silver Solder alloys• Glass-Based Adhesive

Electrically and Thermally Conductive Oxidation Resistant

Preparation of PV/TE Nanofiber Arrays on Conductive Glass

Liquid Solution Method: TiO2 and CoO made

Preparation of PV/TE Nanofiber Arrays on Conductive Glass

Biophotofuel Cell Electrode (anode)

CdS + hν (sunlight) → CdS + e- (CdS is n-type semiconductor with band gap of 2.45 eV)TiO2 + hν (sunlight or UV light) → TiO2 (h

+) + TiO2 (e-)

O=C(NH2)2 (in biowastes) + 6h+ + H2O → CO2↑ + N2 + 6H+

2NH3 (released from biowastes) + 6h+ → N2↑ + 6H+

Dr. Ahalapitiya Jayatissa

• Please see next slide

Nanotechnology and MEMS Laboratory, MIME Department

Current Research Projects: 1. Graphene based multiplexed Sensors: The main thrust of this research is to improve the sensing properties of carbon nanotube and graphene based gas sensors by understanding the mechanism underpinning the selectivity and sensing properties.

PhD: 1 student, MS: 1 student

2. Novel Material System based on Zinc-Oxy-Nitride: The determination of the properties of the thin films so grown by a variety of experimental techniques, leading to a cross-correlation between the growth parameters, the resulting film structure and its physical properties.

PhD: 2 students

3. Laser Processing of Thin Films: The objective of this research project is to investigate the fundamental phenomena of laser irradiation on metal oxide-based thin films relevant to gas sensor performance by employing experimental as well as computational approaches.

PhD: 2 students

Contact: Professor A. H. Jayatissa Tel: 419-530-8245

Room #: 4049 NIE-mail: ajayati@utnet.utoledo.edu

All projects involve Experimental activities and Modeling/Simulations.(Synthesis, coating and fabrication of thin films, MEMS, and Sensors; Modeling/Simulation based on finite element analysis)

Dr. Efstratios Nikolaidis

• Research interest: Efficient Re-Analysis Methodology for Sound and Vibration of Large-Scale Structures

• Please see next slide

Vibratory displacement and sound

Excitation

Uncertainty Propagation

Monte Carlo Simulation (10,000 replications) Statistics of

displacement and SPL

Design Optimization: Several MCS (e.g. 100)

Definition and Significance

It is expensive to optimize vehicle body design by using detailed FEM for sound and vibration

Dr. Mehdi Pourazady

• Areas of interest: Applications of Finite Element Methods in modeling and numerical solution of problems in two areas of Biomechanics and Nano Engineering.

• He would like to have one MS and One PhD student.