Hamdy Abdelhamid

Adipose Stem Cells Display Higher Regenerative Capacities and More Adaptable Electro-Kinetic Properties Compared to Bone Marrow-Derived Mesenchymal Stromal Cells.

Adipose stem cells (ASCs) have recently emerged as a more viable source for clinical applications, compared to bone-marrow mesenchymal stromal cells (BM-MSCs) because of their abundance and easy access. In this study we evaluated the regenerative potency of ASCs compared to BM-MSCs. Furthermore, we compared the dielectric and electro-kinetic properties of both types of cells using a novel Dielectrophoresis (DEP) microfluidic platform based on a printed circuit board (PCB) technology. Our data show that ASCs were more effective than BM-MSCs in promoting neovascularization in an animal model of hind-limb ischemia. When compared to BM-MSCs, ASCs displayed higher resistance to hypoxia-induced apoptosis, and to oxidative stress-induced senescence, and showed more potent proangiogenic activity. mRNA expression analysis showed that ASCs had a higher expression of Oct4 and VEGF than BM-MSCs. Furthermore, ASCs showed a remarkably higher telomerase activity. Analysis of the electro-kinetic properties showed that ASCs displayed different traveling wave velocity and rotational speed compared to BM-MSCs. Interestingly, ASCs seem to develop an adaptive response when exposed to repeated electric field stimulation. These data provide new insights into the physiology of ASCs, and evidence to their potential superior potency compared to marrow MSCs as a source of stem cells.

Performance evaluation of FinFET-based FPGA cluster under threshold voltage variation

The performance of FinFET-based FPGA cluster is evaluated with technology scaling for channel length from 20nm down to 7nm showing the scaling trends of basic performance metrics. The impact of threshold voltage variation, considering die-to-die variations, on the delay, power, and power-delay product is reported after the simulation of a 2-bit adder benchmark. Simulation results show an increasing trend of the average power and power-delay product variations with threshold voltage as we go down with technology node. On the contrary, the delay is showing the least percentage of variations with threshold voltage at the most advanced node of 7nm.

A 2D model of different electrode shapes for traveling wave dielectrophoresis

The movement of uncharged polarizable particles towards the location of extreme field strength in a non-uniform electric field is known as Dielectrophoresis phenomena. A traveling wave dielectrophoresis (twDEP) is an effective technique for particle manipulation and separation of biological particles. The twDEP is an electro-kinetic method resultant of the interaction between a non-uniform electric field and polarizable particles. The proposed twDEP is used to manipulate microbeads. The model of twDEP platform and polarizable particles (microbeads) in addition to the twDEP force which is a resultant of the interaction of a non-uniform electric field and polarizable particles were simulated using COMSOL Multiphysics ®. In this work, a 2D model of different shapes of traveling wave microelectrodes array based on printed circuit board (PCB) technology is presented and discussed to reach the efficient design of twDEP microelectrodes.

The impact of FinFET technology scaling on critical path performance under process variations

Comparisons of FinFET based ring oscillator (RO) metrics are evaluated with technology scaling from 20nm to 7nm technology. Simulations are based on predictive technology models (PTM) developed by Arizona state university. The impact of process and temperature variations on frequency, power, and power delay product is reported. Performance and power of the RO are improved with technology scaling, however performance is degraded after 14nm technology.

A comparative evaluation of single-walled carbon nanotubes and copper in interconnects and Through-Silicon Vias

In this paper we compare Single-walled Carbon nanotubes (SWCNT) and copper as fillers for Through-Silicon Vias (TSVs) in 3D chips and as materials for on chip interconnects. It is shown that vias and interconnects made from SWCNTs handle crosstalk better than those made from copper. The choice of SWCNT is based on their higher resilience to electromigration due to the strong sp2 bonding between the carbon atoms, which enables SWCNT wires to carry more current than a copper wire of the same dimensions.

Technology Scaling Roadmap for FinFET-Based FPGA Clusters Under Process Variations

The technology scaling impact on FinFET-based Field-Programmable Gate Array (FPGA) components (Flip-Flops and Multiplexers) and cluster metrics is evaluated for technology nodes starting from 20nm down to 7nm. Power consumption, delay and energy (Power Delay Product, or PDP) trends are reported with FinFET technology scaling. Cluster metrics are then evaluated based on three benchmarking circuits: 2-bit adder, 4-bit NAND and cascaded flip-flops chain. The study shows that power, delay and PDP of the FPGA cluster are improved as we scale down the technology. An example for improvement is that for 7nm 2-bit adder, circuit speed is 15% higher than its value at 20nm and PDP at 7nm is reduced by 43% compared to its value at 20nm. The impacts of temperature and threshold voltage variations on FPGA cluster performance are also reported after evaluating a 2-bit adder circuit as a benchmark which is then used to calculate the design constraints to meet 99.9% yield percentage.

An improved planar electrode for dielectric parameters extraction

Detection dielectric properties of a biological cell as a function of frequency sweeping is very important, this response can be used to define different information like a chemical, physical or kinetic properties. We analyzed the cell by its conductance and capacitance. This paper presents a numerical study for the capacitance and the conductance based on asymmetric electrodes (AE) configuration compared with a 2D planar electrode are presented. We found the AE configuration improves the sensitivity of the measured capacitance and conductance. Also, a comparison with different cell shapes is simulated using the proposed AE. The simulation shows that there is a difference in a both capacitance and conductance based on the cell shape.

Dielectric analysis of changes in electric properties of leukemic cells through travelling and negative dielectrophoresis with 2-D electrodes

Dielectrophoretic force has been used to manipulate biological microparticles, such as red blood cells, white blood cells, cancer cells, etc… This technique has been used for trapping, sorting and separating biological particles suspended in a buffer medium. The strength of dielectrophoretic force depends strongly on the particles electrical properties, the geometry of the microfluidic device, dielectric properties of the medium, particle shape and size and the frequency of the electric field. Therefore, to design an effective microfluidic separation platform, it is important to understand the effect and the role of the aforementioned parameters on the particles motion. In this paper, the dielectrophoretic separation in a microfluidic device based on 2D electrodes is studied. Also, a comparison between the velocity of B and T leukemia K365 cells due to the drag force is conducted and presented. Moreover, the conductance of the leukemia K365 cells before and after dragging is presented and discussed.

A Model of Electrokinetic Platform for Separation of Different Sizes of Biological Particles

The dielectrophoresis (DEP) phenomena is a motion of uncharged polarizable particles in the direction of most field strength site within a non-uniform electric field. Unlike various techniques, the DEP is an effective technique for particles manipulation and separation of biological particles. The manipulation and separation of biological cells are necessary to various biomedical applications such as cell biology analysis, diagnostics, and therapeutics. The traveling-wave dielectrophoresis (twDEP) and levitation are major subcategories of electro-kinetic motions that are generated as a result of the interaction between a non-uniform electric field and polarizable particles. This article presents a model of an electrokinetic platform that has a working principle of dielectrophoresis phenomena and Printed Circuit Board (PCB) technology for separation of different sizes of biological particles such as microbeads (simulated biological cells) and the blood formed elements (platelets and red blood cells (RBCs)) using two configurations of microelectrodes (traveling and levitation).

A 3D model of quadrupole dielectrophoresis levitation

The Dielectrophoresis (DEP) is a phenomenon in which a force exists on a particle due to a non-uniform electric field. A DEP levitation is widely used technique for particle trapping and levitation, where it is used mainly with biological particles. In this work, a 3D and 2D model of quadrupole levitation system of printed circuit board (PCB) based technology is presented and discussed. The levitation DEP is an electro-kinetic technique resulting from the interaction of a non-uniform electric field and polarizable particles. The electric field and the interaction of a non-uniform electric field and polarizable particles were simulated using COMSOL Multiphysics®. The proposed levitation DEP is used to trap and levitate microbeads (Carboxyl Polystyrene particles). In the scope of paper, a levitation quadrupole electrodes based on PCB technology is designed to trap and levitate the microbeads to be viewed and fixed for measurement of dielectric properties by another techniques using COMSOL Multiphysics®.