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Urbana, IL, United States

Xiong F.,Micro and Nanotechnology Laboratory | Liao A.,Micro and Nanotechnology Laboratory | Bae M.-H.,Micro and Nanotechnology Laboratory | Estrada D.,Micro and Nanotechnology Laboratory | And 2 more authors.
2010 IEEE International Conference of Electron Devices and Solid-State Circuits, EDSSC 2010 | Year: 2010

Phase change memory (PCM) is a promising candidate for next-generation non-volatile data storage, though its high programming current has been a major concern. By utilizing carbon nanotubes (CNTs) and graphene as interconnects to induce phase change in ultra small regions (∼20 nm) of Ge2Sb 2Te5 (GST), we are able to build ultra-low power PCM devices. Normal memory operations are demonstrated with exceptionally low current (< 5 μA) and power consumption, nearly two orders of magnitude lower than state-of-the-art. Electrical characterization shows that switching voltages in PCM with both CNT and graphene electrodes are scalable to sub-1 V. Our experiments also pave the way to carbon nanoelectronics with integrated PCM data storage. © 2010 IEEE.

Zhou J.,University of Illinois at Urbana - Champaign | Wang F.,University of Illinois at Urbana - Champaign | Saif T.A.,Micro and Nanotechnology Laboratory
Biophysical Journal | Year: 2010

Cancer deaths are primarily caused by metastases, not by the parent tumor. During metastasis, malignant cells detach from the parent tumor, and spread through the circulatory system to invade new tissues and organs. The physical-chemical mechanisms and parameters within the cellular microenvironment that initiate the onset of metastasis, however, are not understood. Here we show that human colon carcinoma (HCT-8) cells can exhibit a dissociative, metastasis-like phenotype (MLP) in vitro when cultured on substrates with appropriate mechanical stiffness. This rather remarkable phenotype is observed when HCT-8 cells are cultured on gels with intermediate-stiffness (physiologically relevant 21-47 kPa), but not on very soft (1 kPa) and very stiff (3.6 GPa) substrates. The cell-cell adhesion molecule E-Cadherin, a metastasis hallmark, decreases 4.73 ± 1.43 times on cell membranes in concert with disassociation. Both specific and nonspecific cell adhesion decrease once the cells have disassociated. After reculturing the disassociated cells on fresh substrates, they retain the disassociated phenotype regardless of substrate stiffness. Inducing E-Cadherin overexpression in MLP cells only partially reverses theMLP phenotype in a minority population of the dissociated cells. This important experiment reveals that E-Cadherin does notplay a significant role in the upstream regulation of the mechanosensing cascade. Our results indicate, during culture on theappropriate mechanical microenvironment, HCT-8 cells undergo a stable cell-state transition with increased in vitro metastasis- like characteristics as compared to parent cells grown on standard, very stiff tissue culture dishes. Nuclear staining reveals that a large nuclear deformation (major/minor axis ratio, 2:5) occurs in HCT-8 cells when cells are cultured on polystyrene substrates, but it is markedly reduced (ratio, 1:3) in cells grown on 21 kPa substrates, suggesting the cells are experiencing different intracellular forces when grown on stiff as compared to soft substrates. Furthermore, MLP can be inhibited by blebbistatin,which inactivates myosin II activity and relaxes intracellular forces. This novel finding suggests that the onset of metastasis may, in part, be linked to the intracellular forces and the mechanical microenvironment of the tumor. © 2010 by the Biophysical Society.

Reddy R.,University of Illinois at Urbana - Champaign | Mayerich D.,University of Illinois at Urbana - Champaign | Walsh M.,University of Illinois at Urbana - Champaign | Schulmerich M.,University of Illinois at Urbana - Champaign | And 3 more authors.
Proceedings - International Symposium on Biomedical Imaging | Year: 2012

Fourier transform infrared (FT-IR) spectroscopic imaging provides spatially resolved chemical information. Recent developments have shown that this chemical information can be used to determine tissue cell types. Our goal is then to use the spatial distribution of tissue cell types to perform accurate diagnosis of cancer. However, this step is limited by the spatial resolution provided by current imaging systems. In this paper, we demonstrate that these instruments can be designed to provide better spatial resolution for tissue chemistry. We present an optical model for the propagation of light through an FT-IR spectroscopic imaging system. Using this model, we minimally modify an existing FT-IR spectroscopic imaging system to obtain significantly higher resolution and image quality. We demonstrate that it is possible to identify previously obscured tissue types by performing histological classification based on bio-chemically derived spectral features (metrics). © 2012 IEEE.

Neff A.L.,University of Illinois at Urbana - Champaign | Allain J.P.,University of Illinois at Urbana - Champaign | Allain J.P.,Micro and Nanotechnology Laboratory | Bedoya F.,University of Illinois at Urbana - Champaign | And 2 more authors.
Journal of Nuclear Materials | Year: 2015

Abstract Lithium wall conditioning on PFCs (Plasma Facing Components) on a variety of substrate platforms (e.g. graphite, Mo, etc.) has resulted in improved plasma performance on multiple magnetic fusion devices. On graphite, this improvement occurs through the control of retention and recycling of hydrogen at the plasma-material interface by the chemical bonding of Li, O, and D at the surface. Moderate fluence (1 × 1021 m-2) studies of Li on W, performed in PRIHSM (Particle Radiation in Soft and Hard Matter), demonstrated that H retention is similar to Li on ATJ graphite but He ions, when mixed in a D beam, can inhibit the retention. To expand these studies closer to reactor relevant regimes like inside ITER, irradiations were carried out in Magnum-PSI at DIFFER up to fluences of ∼1025 m-2 with D, He, and He-seeded D plasmas (He 5-10%). Results show that D is still retained at higher fluxes and fluences. © 2014 Elsevier B.V.

Park K.,Micro and Nanotechnology Laboratory | Millet L.J.,Micro and Nanotechnology Laboratory | Popescu G.,Micro and Nanotechnology Laboratory | Popescu G.,University of Illinois at Urbana - Champaign | And 4 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010

The characterization of physical properties of cells such as their mass and stiffness has been of great interest and can have profound implications in cell biology, tissue engineering, cancer, and disease research. For example, the direct dependence of cell growth rate on cell mass for individual adherent human cells can elucidate the mechanisms underlying cell cycle progression. Here we develop an array of micro-electro-mechanical systems (MEMS) resonant mass sensors that can be used to directly measure the biophysical properties, mass, and growth rate of single adherent cells. Unlike conventional cantilever mass sensors, our sensors retain a uniform mass sensitivity over the cell attachment surface. By measuring the frequency shift of the mass sensors with growing (soft) cells and fixed (stiff) cells, and through analytical modeling, we derive the Young's modulus of the unfixed cell and unravel the dependence of the cell mass measurement on cell stiffness. Finally, we grew individual cells on the mass sensors and measured their mass for 50+ hours. Our results demonstrate that adherent human colon epithelial cells have increased growth rates with a larger cell mass, and the average growth rate increases linearly with the cell mass, at 3.25%/hr. Our sensitive mass sensors with a position-independent mass sensitivity can be coupled with microscopy for simultaneous monitoring of cell growth and status, and provide an ideal method to study cell growth, cell cycle progression, differentiation, and apoptosis.

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