bluuebunny/crossref_metadata_2025 huggingface dataset:
New Technique for Testing Performance of Thermoelectric Quantum Well Materials
Authors: Jovanovic Velimir , Ghamaty Saeid , Elsner Norbert B. , Krommenhoek Daniel , Morris John
Published: January 2011

A new test technique and apparatus have been developed for measuring the thermoelectric (TE) performance of the quantum well (QW) thin films. Innovative, nanotechnology Si/SiGe QW TE thin film materials have been developed that appear to demonstrate significantly higher Seebeck coefficients and lower electrical resistivities that show the power factor, Seebeck coefficient squared divided by resistivity, to be many times higher than for the state-of-the-art TE materials such as Bi2Te3, PbTe, TAGS or SiGe bulk materials. The power factor values were derived from QW films deposited on very electrically resistive Si substrates. Since the electrical resistance of the Si substrate is so high (> 100 times the QW film sample resistance) it acts like an insulator and the Seebeck and resistivity values that are measured are essentially those of the QW films. The measurement of thermal conductivity of QW films to obtain efficiency and the Figure of Merit, ZT, is much more difficult to measure and spurred this new experimental approach. This test was designed to determine if the QW materials are significantly better in ZT and efficiency than state-of-the-art TE materials such as Bi2Te3. As with the Seebeck and resistivity measurements, the presence of the Si substrate complicates the performance analysis. This test setup was designed to minimize the influence of the substrate. The technique developed allows the N or P sample to be measured as a thermoelectric couple with a copper wire as the other leg. During the test, the electrical output of the test sample and the imposed temperature difference are recorded simultaneously. The measured temperature difference, along with measured electrical properties at the steady-state conditions, is used to calculate the conversion efficiency by two different methods. Three separate QW samples were tested in the new test apparatus. A bulk Bi2Te3 sample was also tested to compare the QW performance with a state-of-the-art bulk TE material. From the experimental data, it was found that the QW samples exhibited conversion efficiencies which were approximately three times higher than the efficiency of the bulk Bi2Te3 material. Also, the experimentally measured properties of the Bi2Te3 sample were in good agreement with the published properties of the material, thus providing additional confirmation of this new test technique. Another confirmation of a higher ZT is that maximum efficiency and maximum power peaks exist at considerably different loads, whereas these peaks both occur near matched loads for Bi2Te3 alloys. The new test apparatus has been used effectively to measure the power factor of the QW thin films deposited on silicon substrates, and this power factor is significantly higher than for the state-of-the-art bulk TE materials.
Quantum Simulation of Nanocrystalline Composite Thermoelectric Properties
Authors: Musho T. D. , Walker D. G.
Published: January 2011

For the past few years, nanoscale structures have been proposed and investigated experimentally for their enhanced thermoelectric properties over bulk materials. These structures offer several advantages: 1) increased local density of states, which can improve the Seebeck coefficient and 2) reduced thermal transport due to phonon confinement and increased scattering. Recently, nanocrystalline composites (NCC) have been examined for their ability to outperform the alloy limit in terms of reduced thermal conductivity. However, the electrical performance has not been examined from a quantum point of view. This work provides quantum simulations of a two-dimensional composite system meant to model certain geometric features of NCC’s. While the results cannot be quantitatively compared to actual measurements, they show how their electrical behavior differs from well-known superlattice devices. This work will aid in the design of the next generation of NCC devices for thermoelectric performance.
Flat Tree Networks
Authors: Khanduri P. , Wood A. , Cohen D. , Birkeli I. , Sem-Jacobsen F.
Published: January 2011

Hierarchical switching networks connecting hundreds to thousands of servers are common in most large corporations. The state-of-the-art switches used in those networks are usually implemented by interconnecting a set of line cards that connect to hosts with a set of fabric cards that connect to other switches. This paper presents a new approach to implementing those switches using innovative packaging techniques that permit the 3-dimensional line/fabric card structure to be flattened into a 2-dimensional array of switch chips packaged on a PCB. The result of this flattening is a non-hierarchical network topology that we call a “flat tree”. This new approach reduces cost and complexity while improving performance and signal integrity.
Integrating Novel Packaging Technologies for Large Scale Computer Systems
Authors: Mitchell James , Cunningham John , Krishnamoorthy Ashok V. , Drost Robert , Ho Ron
Published: January 2011

Proximity Communication (PxC) enables VLSI chips placed face-to-face to communicate using close-field capacitive coupling. In a 90 nm standard CMOS technology, using the packaging techniques described in this paper, PxC provides chip-to-chip latency of 2.5 ns at 4 Gb/s per channel with less than 2.5 mW/Gb/s, an areal bandwidth density of 0.83 Tb/s/mm2, and a BER less than 10−15. At a system level, the benefits of PxC scale directly with the number of chips that can be packaged together, because PxC enables designers to aggregate multiple chips that perform as a single large piece of silicon. The chips can also be heterogeneous to provide an optimized mix of process technology and functionality, such as integrating DRAM chips, NAND flash memory, and CMOS processor chips. In this paper we describe packaging advances and technology prototypes that enable PxC and provide its system-level benefits.
A Sophisticated Method for Static Testing of TIM
Authors: Sze´kely V. , Somlay G. , Szabo´ P. , Kolla´r E. , Rencz M.
Published: January 2011

Measuring the thermal resistance of thermal interface materials is an increasingly difficult task. The values to be measured are becoming smaller and smaller as a result of the huge efforts in material science to develop better thermal interface material in order to cope with the growing challenges of thermal management. In this paper we present the concept and some first results of a new TIM tester. The tester is using steady state measurement principle. With the help of dedicated test dies that are used to measure temperature, heat flux and parallelism at the same time, Rth values in the range of as low as 0.01 K/W can be measured with better than 5% accuracy.
Optimal Pellet Geometries for Thermoelectric Refrigeration Under Robin Boundary Conditions
Authors: Hodes Marc
Published: January 2011

Thermoelectric refrigeration offers advantages (e.g., lack of any moving parts) over other refrigeration technologies. However, because maximum performance (i.e., head load for a specified temperature drop below ambient temperature) and efficiency (i.e., coefficient of performance) are relatively low, it is important to realize them to the extent possible. Here it is shown that although the cross-sectional area of the semiconductor pellets in a thermoelectric module (TEM) does not affect performance or efficiency, it may be sized to tune TEM operating current and voltage. Then, a procedure is provided to determine the (unique) height of the semiconductor pellets and corresponding current flux through them which maximize performance. Next, it is shown that a range of pellet heights accommodates a specified performance below the maximum one and a procedure is provided to compute that corresponding to maximum efficiency. A Robin (thermal resistance) boundary condition is applied between the interface where Peltier cooling in a TEM occurs and the control point where a TEM maintains the temperature of a component or medium below ambient temperature. Robin boundary conditions are also applied between the control point and its local ambient and the interface in a TEM where Peltier heating occurs and its local ambient. The analysis is generalized by using flux based quantities where applicable and the electrical contact resistance at the interconnects in a TEM is accounted for. Flow of heat and charge are considered one-dimensional.
Joint Development of a Package-Level Thermal Interface Material Test System
Authors: Chen Yanshu Susan , Pecavar Stanley , Gektin Vadim
Published: January 2011

As the microelectronics industry continues to trend towards smaller, lighter, and higher power devices, thermal management is becoming more important than ever. Thermal interface materials (TIMs) play a crucial role in removing heat from both bare die and lidded packages. A serious challenge the industry has been facing is the lack of an agreed upon test standard that is specifically tailored for TIM thermal performance measurements between TIM suppliers and OEM customers. ASTM D 5470 is not necessarily the best gauge for TIMs in-application performance. Data generated by the OEM often differ from TIM supplier’s results, and thus can not be used confidently in thermal design. An OEM’s material selection can also prove to be unreliable when comparing data from different TIM suppliers. This paper presents a successful model that an OEM customer (Sun Microsystems) and a TIM supplier (LORD Corporation) have established for characterization of TIMs, and illustrates a package-level thermal test vehicle (TTV) setup for junction-to-sink thermal resistance measurements. Also presented are test results for several TIMs and repeatability of the test method. The effects of a few influencing factors, such as pressure load and TIM staging time, on the test results are also discussed.
A Novel Approach to Optimizing Solder Reflow Process in Assembling PQFN Packages
Authors: Yu Youmin , Su Y. Q. , Yao S. A. , Jiang Y. W. , Wang Sonder
Published: January 2011

Solder void is a common defect during assembling Power Quad Flat No-lead (PQFN) packages. It is detrimental to the packages’ feature of good power management and reliability performance and needs to be controlled within certain specification. Reflow process is well considered as critical to the solder void formation for a given solder paste. The transport index of reflow oven, which determines how solder paste are reflowed through solder reflowing process within the reflow oven, has therefore been optimized by a novel approach in this study. The underlying principle of the optimization is to find such a transport index that solder paste have a best possibility to experience homogeneous heat transfer during reflow phase of the whole reflow process. Different from the traditionally experimental trial and error, the present approach first predicts the optimal transport index by calculating the relative locations of lead frame (solder paste are dispensed on it) to the heating blocks of the reflow oven and the amount of heat input at different locations on the lead frame during the reflow phase. Then only necessary experiments are conducted to validate the prediction. As the theoretic calculations already screen out part of experiments that have to be conducted in the traditional trial and error, the present approach saves time and cost in practice.
Multiscale Modeling of Blood Flow in Cerebral Malaria
Authors: Fedosov Dmitry A. , Caswell Bruce , Karniadakis George Em
Published: January 2011

Healthy red blood cells (RBCs) have relatively soft membranes that allow them to pass through narrow capillaries of the diameter as small as 3 μm. Recent experiments [1] showed that malaria-parasitized RBCs are characterized by a considerable stiffening of their membranes compared to healthy RBCs. This results in an increased blood flow resistance in the capillary bed, and may lead to an obstruction of small capillaries and significant blood-flow reduction. In addition, malaria-infected cells are able to adhere to each other and endothelium in arterioles and venules leading to more severe blood-flow reduction or blockage. Blood flow in cerebral malaria is extremely complex due to the mentioned effects, and requires multiscale modeling of RBCs and adhesive interactions. We developed a coarse-grained RBC model which is able to accurately reproduce RBCs mechanics and dynamics for different malaria stages: ring-trophozoite-schizont from the earliest to the latest. RBC adhesion is simulated based on the stochastic bond formation/dissociation model, which is able to capture complex adhesive dynamics.
Micropattern Effect on Breast Cancer Cells Behavior on Isotropically Etched Silicon Microenvironments
Authors: Nikkhah Mehdi , Strobl Jeannine S. , Peddi Bhanu , Omotosho Adedamola , Agah Masoud
Published: January 2011

In this paper we are investigating three dimensional (3-D) silicon-based microenvironments as potential platforms for breast cancer diagnostics. We have developed isotropically etched microstructures with a wide range of geometrical patterns for this purpose. Our results indicate that with the etched surface ratio of ∼65%, it is possible to capture 80–90% of the cancer cells within each silicon chip. After treatment of the cells with mitomycin C (to block the cell growth) more number of the cells are trapped inside the etched features for longer cultures times (72 h) suggesting that there is a directed motility and attraction of the cells toward the etched cavities and by optimally designing the etched features, the proposed platforms can be potentially used for diagnostics purposes.
Material Study for Electrowetting-Based Multi-Microfluidics Array Printing of High Resolution Tissue Construct With Embedded Cells and Growth Factors
Authors: Geisler Chris G. , Wootton David M. , Lelkes Peter I. , Fair Richard , Zhou Jack G.
Published: January 2011

Tissue engineering (TE) is evolving as a potential solution for repair and reconstruction of diseased or damaged tissues. TE faces major manufacturing challenges: manufacturing techniques are needed to mimic tissue and extra cellular matrix (ECM) architecture, with high resolution (less than 10 μm) for tissues such as myocardium (heart muscle), blood vessels, bone or nerves; innovative methods are needed for delivery of cells and growth factors into scaffolds; and manufacturing techniques are needed to create vascular structure in tissue construct; lack of nutrient transport currently limits the size and cellular content of implants.
Characterization of Biosensor Detection Process at Ultra-Low Concentration Through a Stochastic Particle Model
Authors: Shah Samar , Liu Yaling , Hu Walter
Published: January 2011

Biosensor detection process involves binding between biomolecules in a solution and a functionalized sensor surface. These sensors are time and cost efficient, sensitive, and enable new applications in medicine, drug design, and environmental monitoring. In literatures, various biosensor designs have been proposed, such as planar electrodes, nanowire, and nanospheres for different applications. However, to fully realize the potentials of these biosensors for biomarker/nanoparticle detection, several challenges must be addressed. In particular, ultra-sensitive biosensors are needed for detection of ultra-low concentration biomarkers such as cancer markers for early disease detection. The goal of this paper is to understand the diffusion process of biomarkers in a liquid solution and the binding with nanosensor surface through a stochastic particle model.
Nano-Structure of Collagen Fibrils in Human Intervertebral Discs and Its Correlation With the Tissue Mechanics
Authors: Aladin Darwesh M. K. , Cheung Kenneth M. C. , Ngan Alfonso H. W. , Chan Danny , Leung Victor Y. L. , Lim Chwee Teck , Luk Keith D. K. , Lu William W.
Published: January 2011

The intervertebral disc (IVD) consists of three major components: the gelatinous nucleus pulposus (NP) at the centre, surrounded by concentric layers of annulus fibrosus (AF), and the superior and inferior endplates sandwiching the AF and NP. Collagen fibrils are the main structural components in all three parts of the disc. The dry mass of collagen in the IVD is about 70% [1]. The outer AF is predominantly collagen I with minor traces of collagen II. A gradual replacement in the collagen I by collagen II occurs in the inner regions [2]. Lumbar disc degenerative disease or early-onset disc degeneration is a primary cause for sciatica and low back pain in young individuals. The most significant biochemical change that occurs in disc degeneration is the loss of proteoglycans in the nucleus pulposus [3]. The mechanical inability of collagen fibrils to withstand the load may be one of the factors causing the loss of proteoglycans. The reason why collagen degrades may be environmental or genetic [4,5]. Researchers are working on developing tissue engineered disc replacements, stem cell therapy etc. to treat disc degeneration. Understanding the disc environment at the nano level is essential in order for these techniques to be clinically successful, as it is well known that the environment in the extracellular matrix plays an important role in determining the stem cells’ fate [6]. Therefore, in order to gain a better understanding on the role played by these matrix proteins, this study aimed at evaluating the correlation between the nano scale properties of the disc collagens with the disc tissue’s macro mechanics.
Ethical Challenges Posed by Nanotechnology
Authors: Saha Subrata , Florczyk Stephen J.
Published: January 2011

Nanotechnology Developments and Ethical Challenges: The hype surrounding nanotechnology includes the transformation of the world for the better, with the elimination of poverty and hunger and human life being extended. Medicine would be revolutionized by new treatments developed and “nanobots” circulating throughout the human body that would repair damage and prevent disease and aging.
Multiscale Elastic Network Model for Macromolecular Machines
Authors: Kim Moon K. , Lim Byeongsoo , Liu Wing Kam
Published: January 2011

In the early year of this century the human genome sequencing project was successfully completed so that we can understand all the human genes and their corresponding protein sequences. Now our interests have naturally moved from genetics to proteomics in which we challenge to elucidate the relationship between functions and structures of proteins. In particular, understanding large conformational changes occurring at molecular machinery systems or protein assemblies have received great attentions. However, it has been rarely studied both experimentally and theoretically because of limitation of experimental setup for capturing real time protein dynamics and computing power, respectively.
Transition Pathway for the Minus-End Directed Movement of Kinesin-14 NCD
Authors: Lakkaraju Sirish Kaushik , Hwang Wonmuk
Published: January 2011

Using Targeted Molecular Dynamics (TMD), we trace the transition pathway of the minus-end directed movement of the Ncd stalk. TMD reveals a number of substeps involved in the rotation of the stalk towards the minus end of microtubules (MT). Our results show that the stalk motion does not possess any directional bias (neither towards the plus or minus end of MT). The minus-end directed movement could thus be due to thermal diffusion between the series of substeps, rather than a rigid body rotation driven by a power stroke. Further tests are necessary to characterize substeps and the relative role played by thermal fluctuation and deterministic motion.
Innovative Magnetic Nanoparticles Approaches for Bone and Osteochondral Tissue Engineering
Authors: Russo A. , Panseri S. , Casino D. , Shelyakova T. , Tampieri A. , Bock N. , Goranov V. , Landi E. , Dionigi C. , Riminucci A. , Dediu V. , Marcacci M.
Published: January 2011

The necessity of new clinical approaches regarding musculoskeletal system regeneration is evident. Nowadays different strategies such as autografts, allografts also used in synergy with cell therapy are already used in clinical treatments for moderate defects, but they face significant limitations due to limited supply, and risk of immune rejection. Currently, the treatments of extended osteochondral and bone defects involve invasive permanent metallic prosthesis, challenging reconstructive procedures and long rehabilitation period. Despite that, the gold standard seems to be far to obtain.
Preparation of Interconnected Microporous Poly(glycolic-co-lactic acid) With High Hydroxyapatite Loading
Authors: Zhang Wei , Yao Donggang , Zhang Qingwei , Zhou Jack G. , Lelkes Peter I.
Published: January 2011

Hydroxyapatite (HA) is known to promote osteogenicity and enhance mechanical strength of biopolymers. However, incorporating a large amount of HA into aporous biopolymer still remains a challenge. In this study, a new method was investigated to incorporate high HA loading into interconnected microporous poly(glycolic-co-lactic acid) (PLGA). Specifically, a tertiary blend comprising PLGA/PS/HA (40/40/20 wt%), prepared by melt blending under conditions for formation of a co-continuous structure, was annealed under small-strain oscillation between parallel plates. The results from different characterizations suggested that the applied small-strain oscillation substantially accelerated the migration of HA nanoparticles during annealing from the PS phase to the PLGA phase; nearly all HA particles were uniformly presented in the PLGA phase after a short period of annealing. After dissolution of the PS phase, a PLGA material with interconnected microporous structure was successfully produced, with a high HA loading above 30 wt%.
A Microfluidic Chip for Studying Intercellular Communication via Gap Junction Channels
Authors: Bathany Ce´dric , Suchyna Thomas , Hua Susan Z.
Published: January 2011

Cells in tissues and organs coordinate their activities with each other, and this communication is mainly mediated by specialized channels, called Gap Junctions. To date, our understanding of specificity of reagents and extracellular stimuli to gap junctions is very limited. Existing techniques for gap junctions assay are tedious and not convenient. We have developed a microfluidic chip that is capable of detecting chemical diffusion across gap junctions, as well as screening reagents for specific gap junction channels.
Ultra Sensitive Detection of Eneterovirus 71 by Modified Electrochemical Impedance Spectroscopy
Authors: Tseng Shin-Hua , Tseng Dion T. , Lee Tzu-Cheng , Cheng Tsai-Mu , Yang Jyh-Yuan , Hsieh Ruo-Yu , Tsai Chuan-Mei , Chang Chia-Ching
Published: January 2011

The enterovirus 71 (EV71) has threatened Taiwan for more than ten years. Since traditional diagnostic methods are complicated, time consuming, and high-qualified personnel required. Therefore, a new detection process is highly desired. In this study, a high sensitive PC-based electrochemical analyzing system with a functionalized nano-gold modified immunological electrode are developed to detect EV71. Immobilizing specific EV71 polyclone antibodies, which is developed by center for disease control (CDC) Taiwan, onto nano gold of sensing electrode, the affinity interaction of the immobilized antibody with the specific antigen is identified quickly by electrochemical impedance spectrum (EIS) within 20 minutes. The detection limit of this EIS analysis was as low as 50 copy per ml (∼sub-atto molar). In summary, a biosensor and analyzing system based on EIS has been developed to identify EV71 with efficiency, high sensitivity and specificity.
Atomistic to Continuum Modeling of DNA Molecules
Authors: Lee C. H. , Teng H. , Chen J. S.
Published: January 2011

The mechanical properties of DNA has very important biological implication. For example, the bending and twisting rigidities of DNA affect how it wraps around histones to form chromosomes, bends upon interactions with proteins, supercoils during replication process, and packs into the confined space within a virus. Many biologically important processes involving DNA are accompanied by the deformations of double helical structure of DNA.
Modeling the Effect of Hemodynamics on Cardiac Growth During Embryonic Development
Authors: Rugonyi Sandra , Thornburg Kent
Published: January 2011

Congenital heart disease (CHD) affects about 1% of newborn babies in the US, and is the leading cause of non-infectious death in children. Abnormal blood flow dynamics during early development can lead to CHD. Although the effect of hemodynamic conditions on cardiac development — even under normal conditions — has been widely accepted, the mechanisms by which blood flow influences cardiac cell responses are only starting to emerge. Mathematical models of cardiac growth could then help elucidate key aspects of cardiac development.
Nanofluidic Devices for Rapid Analysis of DNA and Proteins
Authors: Fu Jianping
Published: January 2011

A new class of nanofluidic filter array devices were designed and fabricated to perform rapid separation (both analytical and preparative) of DNA and proteins covering very broad biological size scales. By virtue of its separation efficiency, gel-free operation, ease of sample recovery and high throughput, these nanofluidic filter array devices hold great promise for an integrated biomolecule sample preparation and analysis system.
Mechanical Regulation of Stem Cell Differentiation on Geometrically Modulated Elastomeric Substrates
Authors: Fu Jianping
Published: January 2011

We report the use of micromolded elastomeric micropost arrays to modulate substrate rigidity independently of effects on adhesive and other material surface properties. We demonstrate that micropost rigidity impacts cell morphology, focal adhesions, cytoskeletal contractility, and stem cell differentiation. Furthermore, these micropost arrays reveal that changes in cytoskeletal contractility can precede stem cell differentiation and be utilized as a non-destructive predictor for fate decisions at the single cell level.
Electrokinetic Transport of Molecules Through Nanochanneled Membranes
Authors: Grattoni Alessandro , Liu Xuewu , Wang Zongxing , Gill Jaskaran , Ziemys Arturas , Ferrari Mauro
Published: January 2011

Our research group was the first one to microfabricate and demonstrate nano-channels in silicon membranes (1, 2). We employed nano-channeled chips to provide immuno-isolation for cell transplantation towards the treatment of diabetes (3), for biomolecular separation (4), and for the controlled passive and active release of drug molecules from implanted capsules (5). We showed that the constraints placed upon molecular agitation in nano-channels affected their concentration-driven transport kinetics (6, 7). A zero-order passive release of biological molecules was achieved, by the rational tailoring of nano-channels dimensions. This achievement allowed releasing of a constant amount of drugs over a long period of time. However, the development and optimization of many drug therapies require long-term drug delivery with controlled but variable dosage using miniaturized systems (8). Moreover, application such as drug release from implanted devices requires tight operational control, of regulatory agency caliber. We have engaged in the development and characterization of elecroosmotic nano-channels membranes, and present our results in this communication. These include the influence of the drug release rate on nanochannel size, membrane configuration, and applied voltage.
Nonlinear Parametric Resonance for NEMS and MEMS Biosensor Applications
Authors: Caruntu Dumitru I. , Knecht Martin W.
Published: January 2011

This paper deals with electrostatically actuated resonator micro- and nano-sensor for mass detection for applications in medicine and biology. Nonlinear parametric resonance of the sensor when the electrostatic actuation frequency is near natural frequency of the system is investigated. Mass deposition is included and its effect on the nonlinear behavior of the resonator is predicted.
Regulating Motion of Magnetic Capsules in Microfluidic Systems
Authors: Masoud Hassan , Kilimnik Alexander , Alexeev Alexander
Published: January 2011

Magnetic microcapsules are often used as vesicles in targeted drug delivery systems, where focused magnetic field propels the capsules to highly specific locations in tissue. To fully realize this potential it is important to understand the dynamics of magnetically-responsive micrometer sized particles in viscous fluids and the effect of boundaries on particle motion. Furthermore, for practical biomedical applications, it could be useful to create synthetic micrometer-sized vesicles able to perform controlled self-propelled motion. Herein, using computer simulations, we examine the motion of magnetically-responsive synthetic microcapsules that able to crawl along walls in microchannels filled with a viscous fluid. The compliant fluid-filled capsules considered in this study encompass superparamagnetic nanoparticles in their solid shells and, therefore, can be manipulated by alternating magnetic forces.
Numerical Simulation of Arbitrarily Shaped Particle Transport in an Incompressible Flow
Authors: de Tullio M. D. , Adriani G. , De Palma P. , Pascazio G. , Decuzzi P.
Published: January 2011

Passive delivery of arbitrarily shaped particles is one of the main concern for several biomedical applications. Properly designed particles, once administrated at the systemic level and transported by the blood flow along the circulatory system, are expected to improve the efficiency of molecule-based therapy and imaging by increasing the mass fraction of therapeutic molecules and tracers that are able to reach their targets. To this purpose different kinds of particle have been presented in the literature, with different composition and chemico-physical properties. The prediction of the transport dynamics of one or more particles (bolus) in a blood vessel becomes of primary importance, the main parameters involved in the phenomenon being: (a) dimension and shape of the particle; (b) Reynolds number based on the flow rate and diameter of the vessel; (c) density of the particle; (d) number of particles in the bolus. The development of suitable computational techniques able to predict such a complex dynamics could help and speed-up the design process, shedding some light onto the basic mechanism of the phenomena of interest.
Molecular Dynamics Study of Nanobio Membranes
Authors: Maftouni Negin , Amininasab M. , Kowsari Farshad
Published: January 2011

Molecular models of lipid bilayers have ignored the interface of two monolayers of nanobiomembranes in detail by now, however in this paper a new physical model is proposed based on variation of surface tension in the interface of two monolayers of membrane. Experimental results have shown that some peptides and proteins like antimicrobial peptides and cytotoxins are able to change the shape of — or in some cases to destroy — the bilayer membrane during insertion to external monolayer. All interfaces in nanobiomembrane are liquid-liquid type. In this paper appropriate ensembles to simulate liquid/liquid interfaces are presented with special focus on proper ones for surface tension analysis.
Platelet Nano-Forces are Similar on Fibronectin and Fibrinogen Ligands
Authors: Liang Xin M. , Sniadecki Nathan J.
Published: January 2011

We present a new biomechanical approach to measure nanoscale platelet contractile forces, which play an important role in the regulation of hemostasis and thrombosis. Previous studies have indicated that platelets generate contractile forces through actin-myosin interactions that lead to clot retraction and stability. If platelets are unable to generate forces, then the clots they form are loosely-bound and may detach to cause an embolism. Likewise, a higher propensity toward contractility by platelets may cause excessive clot formation in arteries and block blood flow.
Nanochannels Fabrication, Filling and DNA Manipulation
Authors: Mokkapati V. R. S. S. , Di Virgilio V. , Mollinger J. , Bastemeijer J. , Bossche A.
Published: January 2011

Fabrication of nanochannels is drawing considerable interest due to its broad applications in nanobiotechnology (e.g. biomolecular sensing and single DNA manipulation). Nanochannels offer distinct advantages in allowing a slower translocation and multiple sensing spots along the channel both of which improve the read-out resolution. However, implementing electrodes inside nanochannel has rarely been demonstrated to our knowledge. Therefore, we are highly motivated to do this research. The device described in this work is a Si-Glass anodically bonded Lab-on-a-Chip (LOC) device of a few millimeters in size using femtoliters in volume capable of performing DNA manipulation. The LOC structure is based on two mainstream microchannels interconnected by nanochannels. Organic samples as DNA will be released in the microfluidic mainstream and then, once confined in the nanochannels, are observed, manipulated and analyzed. We expect the general folded shape of DNA evolves to the unfolded linear shape due to the confinement in narrow channels. This shape is especially suitable for advanced manipulation and analysis.
The Effect of Nano Hydroxyapatite Particles on Morphology and Mechanical Properties of Microcellular Injection Molded Polylactide/Hydroxyapatite Tissue Scaffold
Authors: Kramschuster Adam , Turng Lih-Sheng , Li Wan-Ju , Peng Yiyan , Peng Jun
Published: January 2011

The current large demands for transplant organs and tissues has led to extensive research on material synthesis and fabrication methods for biodegradable polymeric scaffolds, which are required to have high porosity, well interconnected pore structure, and good mechanical properties. However, the majority of current scaffold fabrication techniques are either for batch processes or use organic solvents, which can be detrimental to cell survival and tissue growth. The ability to mass produce solvent-free, highly porous, highly interconnected scaffolds with complex geometries is essential to provide off-the-shelf availability [1]. Injection molding has long been used for mass production of complex 3D plastic parts. The low-cost manufacturing, repeatability, and design flexibility inherent in the injection molding process make it an ideal manufacturing process to create 3D scaffolds, as long as high porosity and interconnectivity can be imparted into the finished product.
Shadow Edge Lithography and Application to Nanofluidics
Authors: Yeo Woon-Hong , Lee Dong Won , Lee Kyong-Hoon , Chung Jae-Hyun
Published: January 2011

Many upcoming applications, such as nanoelectronic circuitry, single-molecule based chips, nanofluidics, chemical sensors, and fuel cells, require large arrays of nanochannels and nanowires. To commercialize such nanostructured devices, a high resolution and high throughput patterning method is essential. For this purpose, we developed the shadow edge lithography (SEL) as a wafer-scale, high-throughput nanomanufacturing method [1]. In the proposed method, the shadow effect in the high-vacuum evaporation was theoretically analyzed to predict the geometric distribution of the nanoscale patterns [2]. In experiment, nanoscale patterns were created by the shadow of aluminum (Al) edges that were prepatterned using a conventional microfabrication method.
A Theoretical Analysis for the Effect of Substrate Elasticity on Cellular Adhesion
Authors: Sarvestani Alireza
Published: January 2011

Cell behavior is mediated by variety of physiochemical properties of extracellular matrix (ECM). Material composition, surface chemistry, roughness, and distribution pattern of cell adhesive proteins are among the ECM properties which are known to modulate various cellular physiological functions. Mechanical stiffness of ECM in particular is found to be a major regulator for multiple aspects of cellular function. Experiments show that cells in general, exhibit an apparent adhesion preference for stiffer substrates with a larger projected spread area with increasing the substrate stiffness. In addition, it seems that the effect of substrates elasticity is strongly coupled with adhesivity of the substrate; on relatively stiff substrates the spread area of the cells exhibits strong biphasic dependence to the changes in ligand density, whereas on soft substrates their limited spreading is much less sensitive to the density of surface ligands. This study aims to propose a theoretical basis for the interplay between substrate elasticity and cellular adhesion, using an equilibrium thermodynamic model. Within this framework, the equilibrium contact area is assumed to ensure minimization of the free energy contributed by interfacial adhesive and repulsive interactions between the membrane and substrate as well as the deformation of cell and substrate. Hence, this thermodynamic model overlooks the contribution of intracellular signaling or actively regulated cytoskeleton and assumes that cell adhesion is solely a result of the balance between the membrane-substrate repulsive potentials, stored elastic energy, binding enthalpy, and mixing entropy of mobile receptors. The predictions of this purely mechanistic model for cell adhesion qualitatively follow the experimental results featuring the variation of cell spread area on compliant bio-adhesive substrates. This suggests that the mechanistic pathways inherent to membrane-substrate interactions may be equally important as intracellular signaling pathways to mediate the cellular adhesion.
Nanofabricated Sensing Electrodes in a Batteryless Endoluminal Sensing Telemeter for Diagnosis of Gastroesophageal Reflux Disease (GERD)
Authors: Hsu Lun-Chen , Huang Wen-Ding , Tang Shou-Jiang , Spechler Stuart , Tibbals H. F. , Chiao J.-C.
Published: January 2011

Gastroesophageal reflux disease (GERD) is recognized the primary risk factor associated with esophageal cancers. Therefore, monitoring GERD symptoms accurately is important for early diagnosis of such cancers. In this work, interdigitated impedance sensing electrodes and nanofabricated IrOx-based pH sensing electrodes were made on the flexible substrates that can be easily embedded into an implantable device. The dual sensor electrodes were integrated into a batteryless wireless capsule packaged with biocompatible material for implant applications. The proposed sensing system has been tested with stimulated solutions of different pH values recording modulated sensor data in terms of frequency shifts to verify its performance. The experimental results showed that the impedance electrodes responded to ion content variations and the pH electrodes identified the pH values of various pH solutions. Our sensing system has demonstrated the ability to detect gastroesophageal reflux activities more accurately, which could help doctors to provide precise treatment methods, consequentially lowering the risks of esophageal cancer development.
Development of a Microfluidic Injection and Perfusion Device for Single Cell Study
Authors: Chen Hsiu-hung Simon , Shu Zhiquan , Cheng Lei , Gao Dayong
Published: January 2011

The cell membrane, composed primarily of proteins and lipids, is a selectively permeable lipid bilayer in the scale of 10 nm or so. Molecules permeating through cell membranes play critical roles in the applications of drug delivery, cell therapy, and cryopreservation. Cryopreservation and banking of cells, such as umbilical cord bloods, female eggs, etc., are critical to facilitate practical and effective in vitro fertilization (IVF). The determination of molecule transport properties of cells, such as water and cryoprotectants (CPAs), is indispensable for developing optimal conditions for cryopreserving them. On the other hand, injection of material of interests, such as sperms and DNA segments, to female eggs or blastocysts, so-called intracytoplasmic sperm injection (ICSI) technique, are playing important roles on IVF and advanced gene knock-out. In this study, a novel micro-nano-fluidic system that allows perfusion and injection in nano-liter scale has been developed and fabricated by soft lithographic methods. A single cell in the microfluidic system is able to be trapped on site and then either be perfused by various solutions or injected with plain solutions or solutions with genetic materials. Our ongoing study will demonstrate that the micro-nano-fluidic system allows us to: 1) confine cells in a channel; 2) deliver drugs by perfusing the cell; 3) monitor osmotic behaviors of the cell by replacing its extracellular environment; and 4) perform ICSI with sperms or genetic materials.
Kinetics of Membrane Spreading on Compliant Bio-Adhesive Substrates
Authors: Sarvestani Alireza
Published: January 2011

The contact formation between cell membrane and a bio-adhesive substrate is driven by binding between transmembrane mobile receptors (e.g., integrin) and complementary ligand molecules on the substrate (fibronectin, collagen, etc.) This short range specific adhesion is alleviated by a phalanx of interfacial non-specific forces. In addition to cell-substrate interfacial interactions, cell adhesion can be mediated by a wide range of substrate physiochemical properties. In particular, mechanical stiffness of the substrate has been recognized as one of the major regulators for bio-adhesion. Cells in general, exhibit an apparent adhesion preference for stiffer substrates and switch from a round to spread morphology as the substrate stiffness increases. Understanding the mechano-chemical pathways mediating the interplay between the substrate properties and cell behavior could be critical for effective performance of synthetic biomaterials in tissue engineering applications. In this study, we consider the effect of substrate elasticity on the dynamics of membrane spreading and growth of focal adhesion zone. The formation and growth of the focal adhesion points during the early stage of adhesion process is a result of spontaneous spreading of membrane on the substrate. This can be considered as a non-equilibrium kinetic process which is controlled by the diffusibility of receptor molecules. In order to study the effect of substrate elasticity on the kinetics of membrane-substrate association, receptors are assumed as ideal solute particles laterally diffusing within the plane of the membrane until they are stabilized through association with their complementary ligands which are immobilized on the surface of a compliant substrate. Considering different mechanical stiffness for the substrates, the displacement and speed of spreading at the edge of adhesion zone are predicted as a function of time. Results show that decreasing the stiffness of bio-adhesive substrates reduces the rate of membrane spreading, due to a weaker thermodynamic force which drives the membrane-substrate association. This mechanism restrains the growth of focal adhesion zones on compliant substrates and can be considered as a reason for smaller spread area of the cells after stabilization of adhesion.
A Self-Contained Microfluidic Cassette for the Detection of Nucleic Acids at the Point-of-Care
Authors: Chen Dafeng , Qiu Xianbo , Mauk Michael , Bau Haim H.
Published: January 2011

In recent years, there has been a growing interest in developing integrated, self-contained, disposable, inexpensive microfluidic devices for point-of-care diagnostics [1–3]. These devices are required to identify pathogens rapidly, facilitate use by minimally trained personnel, and be able to operate in regions where sophisticated laboratories are lacking.
Microtechnologies for Neurobiology
Authors: Zeringue Henry C.
Published: January 2011

Oscillatory activity in cortical networks is thought to provide the foundation for many high-level processes including working memory and attention. It has been shown that spatial information propagation delay and connectivity density can determine the innate properties of local network activity. The initial formation of neuronal networks in the central nervous system occurs due to the interaction of the genetic programming of the cells and the presentation of external molecular cues. The activity-driven refinement that occurs later, giving rise to the highly complex networks within the brain, are dependent on the initial anatomical formation and structural connectivity which occurs without external activity cues. We describe technologies used to (1) modulate the genetic programming of neurons and (2) precisely control temporal and spatial presentation of environmental cues in vitro. We are exploring the ability to define simple oscillatory networks using these experimental techniques.
Microstructure-Based Modeling of Ti-6Al-4V Lattice Structures and Trabecular Bone
Authors: Yao Hang , Tong Wei
Published: January 2011

Knowledge of mechanical properties of bones is important for the designing of bone replacements and implants as well as the research of bone diseases such as osteoporosis. However, bone, especially trabecular bone, is a highly anisotropic and heterogeneous living tissue. Micro-computed-tomography (micro-CT) and three-dimensional ultrasound imaging techniques are valuable tools for nondestructive investigation of three-dimensional trabecular bone architecture. From a reconstruction of trabecular bone, a numerical model such as finite element (FE) model can be generated. Using this FE model to simulate compression test, and comparing the simulation results to the results from real mechanical test of the same specimen, the relationship between the observed mechanical behaviors and the microstructure can be established.
Analysis of Red Blood Cell Deformation in a Microfluidic Device
Authors: Tomaiuolo Giovanna , Guido Stefano , Cassinese Antonio
Published: January 2011

In this work, a microfluidics system to investigate the flow behaviour of red blood cells (RBCs) in a microcirculation-mimicking network of PDMS microchannels with thickness comparable to cell size is presented.
Metals, Semiconductors, and Alloy Nanowires on DNA Scaffolds: Synthesis and Device Applications
Authors: Kundu Subrata , Liang Hong
Published: January 2011

In this presentation, we will demonstrate fast and electroless UV-photo activation techniques to synthesize electrically conductive metals (Pd), semiconductors (CdS), and alloy (Au-Ag) nanowires of diameter ∼10–180 nm on DNA. The electrical characterization showed that DNA nanowires are either exhibiting Ohmic or semiconducting behavior having low contact resistance with the electrodes. The nanowires are about 1–10 micrometers long and the length depends on the molecular weight of DNA. Highly selective deposition on DNA is obtained by specific complexation between the metal ions and DNA, followed by the growth of nanoclusters in DNA chain to form the corresponding nanowires. The eventual diameter of the nanowires obtained in our experiments is over 10 nm that is significantly larger than the ∼1–2 nm diameter of the double helix DNA. The DNA nanowires orchestrated with semiconducting Si nanowires, carbon nanotubes, or co-deposited with metal nanoparticles can potentially lead to avenues for making complex single electron devices and Schottky nanodevices.
Nanomedical Applications of Optofluidics
Authors: Erickson David
Published: January 2011

In this talk I will discuss some of the nanomedical applications of optofluidic systems. As will be demonstrated such devices hold significant promise for improving on the state of the art in detection sensitivity as well as enable entirely new modalities for molecular analysis. Two example platforms will be discussed. The first of these will be our Nanoscale Optofluidic Sensor Arrays which comprise of a series of 1D evanescently coupled linear optical resonators. In addition to demonstrating both nucleic acid (Dengue virus) and immunological detection (Interleukins), I will show how optical forces can be used to increase the functionality of these devices including single molecule analysis. The second platform described is a method for performing surface enhanced raman spectroscopy (SERS) on a chip. A unique ligase detection reaction based assay will be demonstrated to show the unique advantages of the approach.