Surface-acoustic-wave counterflow micropumps for on-chip liquid motion control in two-dimensional microchannel arrays

Fully controlled liquid injection and flow in hydrophobic polydimethylsiloxane (PDMS) two-dimensional microchannel arrays based on on-chip integrated, low-voltage-driven micropumps are demonstrated. Our architecture exploits the surface-acoustic-wave (SAW) induced counterflow mechanism and the effect of nebulization anisotropies at crossing areas owing to lateral propagating SAWs. We show that by selectively exciting single or multiple SAWs, fluids can be drawn from their reservoirs and moved towards selected positions of a microchannel grid. Splitting of the main liquid flow is also demonstrated by exploiting multiple SAW beams. As a demonstrator, we show simultaneous filling of two orthogonal microchannels. The present results show that SAW micropumps are good candidates for truly integrated on-chip fluidic networks allowing liquid control in arbitrarily shaped two-dimensional microchannel arrays.

Classification of organisms previously reported as the SP and Stewart-Letscher groups, with descriptions of Necropsobacter gen. nov. and of Necropsobacter rosorum sp. nov. for organisms of the SP group

To allow classification of bacteria previously reported as the SP group and the Stewart-Letscher group, 35 isolates from rodents (21), rabbits (eight), a dog and humans (five) were phenotypically and genotypically characterized. Comparison of partial rpoB sequences showed that 34 of the isolates were closely related, demonstrating at least 97.4 % similarity. 16S rRNA gene sequence comparison of 20 selected isolates confirmed the monophyly of the SP group and revealed 98.5 %-100 % similarity between isolates. A blast search using the 16S rRNA gene sequences showed that the highest similarity outside the SP group was 95.5 % to an unclassified rat isolate. The single strain, P625, representing the Stewart-Letscher group showed the highest 16S rRNA gene similarity (94.9-95.5 %) to members of the SP group. recN gene sequence analysis of 11 representative strains resulted in similarities of 97-100 % among the SP group strains, which showed 80 % sequence similarity to the Stewart-Letscher group strain. Sequence similarity values based on the recN gene, indicative for whole genome similarity, showed the SP group being clearly separated from established genera, whereas the Stewart-Letscher group strain was associated with the SP group. A new genus, Necropsobacter gen. nov., with only one species, Necropsobacter rosorum sp. nov., is proposed to include all members of the SP group. The new genus can be separated from existing genera of the family Pasteurellaceae by at least three phenotypic characters. The most characteristic properties of the new genus are that haemolysis is not observed on bovine blood agar, positive reactions are observed in the porphyrin test, acid is produced from (+)-L-arabinose, (+)-D-xylose, dulcitol, (+)-D-galactose, (+)-D-mannose, maltose and melibiose, and negative reactions are observed for symbiotic growth, urease, ornithine decarboxylase and indole. Previous publications have documented that both ubiquinones and demethylmenaquinone were produced by the proposed type strain of the new genus, Michel A/76(T), and that the major polyamine of representative strains (type strain not included) of the genus is 1,3-diaminopropane, spermidine is present in moderate amounts and putrescine and spermine are detectable only in minor amounts. The major fatty acids of strain Michel A/76(T) are C(14 : 0), C(16 : 0), C(16:1)omega7c and summed feature C(14 : 0) 3-OH/iso-C(16 : 1) I. This fatty acid profile is typical for members of the family Pasteurellaceae. The G+C content of DNA of strain Michel A/76(T) was estimated to be 52.5 mol% in a previous investigation. The type strain is P709(T) ( = Michel A/76(T) = CCUG 28028(T) = CIP 110147(T) = CCM 7802(T)).

Lung on Chip: In vitro HGF effects on injured alveolar A549 epithelial cells in microfluidic system

Microfluidic systems have become competitive tools in the invitro modelling of diseases and promising alternatives to animal studies. They allow obtaining more invivo like conditions for cellular assays. Research in idiopathic pulmonary fibrosis could benefit from this novel methodological approach to understand the pathophysiology of the disease & develop efficient therapies. The use of hepatocyte growth factor (HGF) for alveolar reepithelisation is a promising approach. In this study, we show a new microfluidic system to analyse the effects of HGF on injured alveolar epithelial cells. Microfluidic systems in polydimethylsiloxane were fabricated by soft lithography. The alveolar A549 epithelial cells (10,000 cells) were seeded and studied in these microfluidic systems with media perfusion (1μl/30min). Injury tests were made on the cells by the perfusion with media containing H2O2 or bleomycin. The degree of injury was then assessed by a metabolic and an apoptotic assays. Wound assays were also performed with a central laminar flow of trypsin. Monitoring of wound closure with HGF vs control media was assessed. The alveolar A549 epithelial cells grew and proliferated in the microfluidic system. In the wound closure assay, the degree of wound closure after 5 hours was (53.3±1.3%) with HGF compared to (9.8±2.4%) without HGF (P <0.001). We present a novel microfluidic model that allows culture, injury and wounding of A549 epithelial cells and represents the first step towards the development of an invitro reconstitution of the alveolar-capillary interface. We were also able to confirm that HGF increased alveolar epithelial repair in this system.

Lung on a chip: Co-culture of alveolar epithelial cells and bone marrow derived stromal stem cells in a microfluidic system

Background: Microfluidics system are novel tools to study cell-cell interactions in vitro. This project focuses on the development of a new microfluidic device to co-culture alveolar epithelial cells and mesenchymal stem cells to study cellular interactions involved in healing the injured alveolar epithelium. Methods: Microfluidic systems in polydimethylsiloxane were fabricated by soft lithography. The alveolar A549 epithelial cells were seeded and injury tests were made on the cells by perfusion with media containing H2O2 or bleomycin during 6 or 18hrs. Rat Bone marrow derived stromal cells (BMSC) were then introduced into the system and cell-cell interaction was studied over 24 hrs. Results: A successful co-culture of A549 alveolar epithelial cells and BMS was achieved in the microfluidic system. The seeded alveolar epithelial cells and BMSC adhered to the bottom surface of the microfluidic device and proliferated under constant perfusion. Epithelial injury to mimic mechanisms seen in idiopathic pulmonary fibrosis was induced in the microchannels by perfusing with H2O2 or bleomycin. Migration of BMSC towards the injured epithelium was observed as well as cell-cell interaction between the two cell types was also seen. Conclusion: We demonstrate a novel microfluidic device aimed at showing interactions between different cell types on the basis of a changing microenvironment. Also we were able to confirm interaction between injured alvolar epithelium and BMSC, and showed that BMSC try to heal the injured epitelium.

Stewart-Treves syndrome: MR imaging of a postmastectomy upper-limb chronic lymphedema with angiosarcoma

The rare occurrence of angiosarcoma in postmastectomy upper-limb lymphedema with magnetic resonance (MR) imaging is discussed. Unfamiliarity with this aggressive vascular tumor and its harmless appearance often leads to delayed diagnosis. Angiosarcoma complicating chronic lymphedema may be low in signal intensity on T2-weighting and short tau inversion recovery (STIR) imaging reflecting the densely cellular, fibrous stroma, and sparsely vascularized tumor histology. Additional administration of intravenous contrast medium revealed significant enhancement of the tumorous lesions. Awareness of angiosarcoma and its MR imaging appearance in patients with chronic lymphedema may be a key to early diagnosis or allow at least inclusion in the differential diagnosis.

On-chip non-invasive and label-free cell discrimination by impedance spectroscopy

OBJECTIVES: Many flow-cytometric cell characterization methods require costly markers and colour reagents. We present here a novel device for cell discrimination based on impedance measurement of electrical cell properties in a microfluidic chip, without the need of extensive sample preparation steps and the requirement of labelling dyes. MATERIALS AND METHODS, RESULTS: We demonstrate that in-flow single cell measurements in our microchip allow for discrimination of various cell line types, such as undifferentiated mouse fibroblasts 3T3-L1 and adipocytes on the one hand, or human monocytes and in vitro differentiated dendritic cells and macrophages on the other hand. In addition, viability and apoptosis analyses were carried out successfully for Jurkat cell models. Studies on several species, including bacteria or fungi, demonstrate not only the capability to enumerate these cells, but also show that even other microbiological life cycle phases can be visualized. CONCLUSIONS: These results underline the potential of impedance spectroscopy flow cytometry as a valuable complement to other known cytometers and cell detection systems.

On-chip Non-reciprocal Optical Devices Based on Quantum Inspired Photonic Lattices

We propose integrated optical structures that can be used as isolators and polarization splitters based on engineered photonic lattices. Starting from optical waveguide arrays that mimic Fock space (quantum state with a well-defined particle number) representation of a non-interacting two-site Bose Hubbard Hamiltonian, we show that introducing magneto-optic nonreciprocity to these structures leads to a superior optical isolation performance. In the forward propagation direction, an input TM polarized beam experiences a perfect state transfer between the input and output waveguide channels while surface Bloch oscillations block the backward transmission between the same ports. Our analysis indicates a large isolation ratio of 75 dB after a propagation distance of 8mm inside seven coupled waveguides. Moreover, we demonstrate that, a judicious choice of the nonreciprocity in this same geometry can lead to perfect polarization splitting.

A STUDY ON THE FEASIBILITY OF UNIVERSAL CHIP CONTROL IN MACHINING

A novel solution to the long standing issue of chip entanglement and breakage in metal cutting is presented in this dissertation. Through this work, an attempt is made to achieve universal chip control in machining by using chip guidance and subsequent breakage by backward bending (tensile loading of the chip's rough top surface) to effectively control long continuous chips into small segments. One big limitation of using chip breaker geometries in disposable carbide inserts is that the application range is limited to a narrow band depending on cutting conditions. Even within a recommended operating range, chip breakers do not function effectively as designed due to the inherent variations of the cutting process. Moreover, for a particular process, matching the chip breaker geometry with the right cutting conditions to achieve effective chip control is a very iterative process. The existence of a large variety of proprietary chip breaker designs further exacerbates the problem of easily implementing a robust and comprehensive chip control technique. To address the need for a robust and universal chip control technique, a new method is proposed in this work. By using a single tool top form geometry coupled with a tooling system for inducing chip breaking by backward bending, the proposed method achieves comprehensive chip control over a wide range of cutting conditions. A geometry based model is developed to predict a variable edge inclination angle that guides the chip flow to a predetermined target location. Chip kinematics for the new tool geometry is examined via photographic evidence from experimental cutting trials. Both qualitative and quantitative methods are used to characterize the chip kinematics. Results from the chip characterization studies indicate that the chip flow and final form show a remarkable consistency across multiple levels of workpiece and tool configurations as well as cutting conditions. A new tooling system is then designed to comprehensively break the chip by backward bending. Test results with the new tooling system prove that by utilizing the chip guidance and backward bending mechanism, long continuous chips can be more consistently broken into smaller segments that are generally deemed acceptable or good chips. It is found that the proposed tool can be applied effectively over a wider range of cutting conditions than present chip breakers thus taking possibly the first step towards achieving universal chip control in machining.

IN-SITU TEM PLASMA CHIP NANOFABRICATION AND CHARACTERIZATION

A silicon-based microcell was fabricated with the potential for use in in-situ transmission electron microscopy (TEM) of materials under plasma processing. The microcell consisted of 50 nm-thick film of silicon nitride observation window with 60μm distance between two electrodes. E-beam scattering Mont Carlo simulation showed that the silicon nitride thin film would have very low scattering effect on TEM primary electron beam accelerated at 200 keV. Only 4.7% of primary electrons were scattered by silicon nitride thin film and the Ar gas (60 μm thick at 1 atm pressure) filling the space between silicon nitride films. Theoretical calculation also showed low absorption of high-energy e-beam electrons. Because the plasma cell needs to survive the high vacuum TEM chamber while holding 1 atm internal pressure, a finite element analysis was performed to find the maximum stress the low-stress silicon nitride thin film experienced under pressure. Considering the maximum burst stress of low-stress silicon nitride thin film, the simulation results showed that the 50 nm silicon nitride thin film can be used in TEM under 1 atm pressure as the observation window. Ex-situ plasma generation experiment demonstrated that air plasma can be ignited at DC voltage of 570. A Scanning electron microscopy (SEM) analysis showed that etching and deposition occurred during the plasma process and larger dendrites formed on the positive electrode.