Biogenic nanoporous shells derived from marine diatoms Coscinodiscus wailesii were used for nanoparticle translocation experiments, and the observed ionic current was compared with results of analytical calculation and finite-element simulation. The lateral size (250 μm) of the shells enabled positioning and immobilization on micromachined silicon substrates. Since these shells have a hierarchical structure with the smallest aperture diameter of 40 nm and length of 50 nm as obtained from scanning electron microscopy, the ionic current reduction of 28.69 ± 4.12 pA could be measured during the translocation of 27-nm diameter polystyrene spheres. Note, this average current of 10 events, measured for 120 s, was comparable with the results of: 1) finite-element simulation as a function of the position of the polystyrene sphere using a simplified geometry of the smallest aperture and 2) analytical calculation from the Coulter Counter theory. The current reduction obtained from the simulation and theory was 28.36 and 29.95 pA, respectively. In addition, a mobility of 1.11 × 10-8 m2 s-1 V-1 for the 27-nm polystyrene spheres was used to convert the simulated current from spatial dependence to time dependence in order to match the average experimental translocation time of 155 μs.

Lifetime and stability of lipid bilayer membranes are essential parameters in ion channel reconstitution experiments. Reports on nano-BLMs across porous silicon nitride and alumina membranes with nanometer-sized apertures show a dramatically enhanced bilayer lifetime. In addition, the particular porous structure of the membranes enables the formation of a nano-BLM array, where failure of one membrane will not affect the membranes suspended across the other nanopores. However, a tradeoff between membrane thickness and mechanical stability is necessary when manufacturing these devices, with a three-dimensional multi-layer structure, substantially raising the cost of top-down device fabrication. In our study, the use of biogenic nanopores as substrates to host nano-BLMs was explored. Diatoms are unicellular marine algae in porous silica shells, called frustules. These shells have a tiered structure, with pores of minimum diameter 40 nm. The hierarchical porous structure of these shells makes them exceptionally mechanically stable. Frustules obtained from the marine algae Coscinodiscus wailesii were supported on a silicon platform with a micron-sized through-wafer aperture that allows fluidic access to either side of the frustule. Nano-BLMs were formed across the frustule pores using bubble-collapse method and were monitored by measuring the seal resistance and capacitance. Untreated frustules are hydrophilic, preventing the organic solvent from wetting the surface, resulting in a low BLM formation probability. Our studies indicate a formation probability of 1 out of 10 attempts. To render the surface hydrophobic, frustules were functionalized usingsilane chemistry, significantly improving bilayer formation probability. To study the effect of pore size on the incorporation probability and functionality of membrane proteins, the self-insertion of outer membrane protein OmpF of E.Coli in the nano-BLMs was investigated using single channel recordings. Blocking of the channel in the presence of the antibiotic ampicillin indicates the full functionality of the channel protein.

Marine diatoms provide an alternative to machined silica nanopores, avoiding costly and slow throughput fabrication steps, while being able to achieve pore structures with diameters on the order of 40 nm. The hierarchical pore architecture makes these biogenic nanomembranes exceptionally mechanically stable, while maintaining a short pore length and a high porosity. The most prominent issue when replacing machined silica nanopore membranes with biogenic membranes is the initial random placement of the membranes on the solid substrate. This is also problematic when trying to accomplish a permanent fluidic seal around the membrane. In our study, we demonstrate the ability to localize and immobilize a 200μm-diameter biomineralized nanopore membrane structure from marine algae, Coscinodiscus wailesii, on pre-defined positions on micro-machined silicon substrates. The substrates feature micron-sized through-wafer channels that allow easy access to the nanopore membrane. Localization of the membrane structure is accomplished using patterning of 8 μm thick hydrophobic resin. The addition of poly-L-lysine to the surface before solution-depositing the nanopore membranes results in a strong electrostatic binding force between the oxidized silicon platform and the diatom membranes. Lift-off of the photoresist in acetone removes randomly placed nanopore membranes on the resist-coated area, not affecting diatoms adhering to the silicon surface. While poly-L-lysine provides an initial fluidic seal, permanent immobilization is accomplished by using UV-curable photoresist SU-8 and proximity photo lithography. Scanning electron micrographs after processing show intact diatoms without the presence of stress cracks. While initial electrochemical measurements indicate that some of the nanopores are clogged by residual epoxy resist after development, subsequent sulfuric-peroxide mixture (SPM) treatment removes the residual resist. Successful translocation experiments using polystyrene beads shows presence of unclogged pores, also indicating that the pore size of the biogenic silica nanomembranes can be modified by chemical treatment.

Nanopore membranes are extremely valuable for applications such as molecular filtration, nanoparticle counting, and sizing studies. However, the fabrication of nanopore membranes using top-down silicon microfabrication technology requires using slow serial patterning processes, making it unsuitable for large-scale manufacturing. Marine diatoms on the other hand feature biomineralized silica shells with the smallest pore diameters on the order of 40 nm. Their hierarchical pore architecture makes these nanomembranes exceptionally mechanically stable, while maintaining a short pore length and a high porosity. In our study, we immobilized the biogenic silica nanomembranes on micromachined silicon substrates. These substrates feature micron-sized, through-wafer channels, enabling free fluidic access to the nanopore membrane. The diatom shells were mounted on top of the silicon microstructure using either poly-L-lysine or UV-polymerizable low-stress epoxy. The resulting microsystem allowed easy handling and mounting in a fluidic platform for nanoparticle transport studies. Using fluorescent nanoparticles we were able to verify that particles with a diameter larger than that of the nanopores were completely retained, while smaller particles, such as polystyrene beads or gold nanoparticles did permeate through the membrane. No evidence for leakage around the diatom was observed, indicating a successful seal around the perimeter of the membrane. When the particles passed through the membrane, the temporary blockage resulted in a reduction in ionic current corresponding to the ratio between the bead and pore size. The characteristic electrophoretic mobility of the beads allowed a characterization of nanoparticles of different origin. The large number of nanopores available for particle translocation (>200) makes them ideal size-selective filters with a low probability of clogging. The combination of biomineralized and microfabricated structures shows a pathway for integrating low-cost nanostructures with BioMEMS devices.

The oxygen-deficient orthorhombic oxide YBa2Cu3O7-δ has been the center of intense recent interest because of its high Tc superconducting proper-ties[l-3]. Recently, the structurally related La3Ba3Cu3O15-δ, has received increasing attention[4–9]. The pure Y analog[10,11] cannot be synthesized by usual solid state reaction routes probably because of its metastability near 880°C. Here we report on the successful synthesis of pure tetragonal Y3,Ba3CU6O15-δ (referred to as Y 3–3–6), via the firing of an atomically mixed citrate precursor at a relatively low temperature. X-ray diffraction data characterize Y 3–3–6 to be isostructural with the corresponding La compound[4]. The unit cell composition can then be written as: Y(Ba2−x Yx) CU3O7+δ with the parent compound at x = 0.50. Specimens of Y 3–3–6 at × = 0.50 and 0.375 annealed at 650°C under 1 atmosphere of O2 are non-superconducting. Higher pressure O2 annealing and fluorine-doping leads to a 1–5% superconducting volume fraction with onset at 85K. Annealing near 880°C creates a 10% superconducting fraction which shows near-zero resistivity at 62K and a reproducible, small resistive transition near 260K.

In this talk we will discuss the use of high resolution transmission electron microscopy (HRTEM) in the study of high Tc superconducting oxides. HRTEM has played an important part in the characterization of microstructure in YBa2Cu3O7−x, and in structure refinement of mixed phase Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O compounds. It is unlikely that HRTEM will contribute to any great extent to the understanding of why these materials are superconductors. But HRTEM will continue to make vital contributions to the studying and understanding of defect structures (such as grain boundaries and planar defects) which interfere with the flow of supercurrents.

Nanopore membranes exhibit tremendous potential for applications such as molecular filtration and DNA sequencng studies. However, the large-scale manufacturing of these nanopore membranes using MEMS technology is challenging, requiring slow serial electron or ion-beam patterning. Marine diatoms on the other hand feature biomineralized silica shells with the smallest pore diameters being 40 nm. Their hierarchical pore architecture makes these nanomembranes exceptionally mechanically stable. Moreover, the nanopores are homogeneous in size and have a low aspect ratio, enabling fast diffusion-driven transport. The drawback of the biomineralized structures is that they are single entities, which have to be combined with a support structure to integrate them into a microsystem. Our solution consists of immobilizing the biomineralized structures on silicon substrates. With the diatom shells growing up to 200 μm in diameter, they are easy to manipulate on the oxidized silicon surface. Through-wafer via holes with diameters between 5 μm and 30 μm were etched using a dry etching technique to allow free access to the bottom of the immobilized diatom shell. Two pathways towards immobilization of the diatom shells were used, one being a chemical linkage approach using poly-L-lysine and the other involving UV-polymerizable epoxy. Controlled etching of the silica structure has been employed to manipulate both the dimensions of the nanopores as well as the pore hierarchy. Studies of transport phenomena were carried out after mounting the silicon chip in a fluidic chamber with reservoirs for aqueous solution on either side of the chip. Electrical contact was made via Ag/AgCl electrodes and the transmembrane current was measured by a transimpedance amplifier. Results on our transport studies based on size and chemical considerations will be presented for ions, such as potassium and sodium, present in physiologically relevant isotonic buffers, polystyrene nanobeads and gold nanoparticles.

The goal of our research is to demonstrate the feasibility of employing biogenic nanoporous silica as a key component in developing a biosensor platform for rapid label-free electrochemical detection of cardiovascular biomarkers from pure and commercial human serum samples with high sensitivity and selectivity. The biosensor platform consists of a silicon chip with an array of gold electrodes forming multiple sensor sites and works on the principle of electrochemical impedance spectroscopy. Each sensor site is overlaid with a biogenic nanoporous silica membrane that forms a high density of nanowells on top of each electrode. When specific protein biomarkers: C-reactive protein (CRP) and myeloperoxidase (MPO) from a test sample bind to antibodies conjugated to the surface of the gold surface at the base of each nanowell, a perturbation of electrical double layer occurs resulting in a change in the impedance. The performance of the biogenic silica membrane biosensor was tested in comparison with nanoporous alumina membrane-based biosensor and plain metallic thin film biosensor. Significant enhancement in the sensitivity and selectivity was achieved with the biogenic silica biosensor, in comparison to the other two, for detecting the two protein biomarkers from both pure and commercial human serum samples. The sensitivity of the biogenic silica biosensor is approximately 1 pg/ml and the linear dose response is observed over a large dynamic range from 1 pg/ml to 1 microg/ml. Based on its performance metrics, the biogenic silica biosensor has excellent potential for development as a point of care handheld electronic biosensor device for detection of protein biomarkers from clinical samples.

We report a photonic approach for selective inactivation of viruses with a near-infrared subpicosecond laser. We demonstrate that this method can selectively inactivate viral particles ranging from nonpathogenic viruses such as the M13 bacteriophage and the tobacco mosaic virus to pathogenic viruses such as the human papillomavirus and the human immunodeficiency virus (HIV). At the same time, sensitive materials such as human Jurkat T cells, human red blood cells, and mouse dendritic cells remain unharmed. The laser technology targets the global mechanical properties of the viral protein shell, making it relatively insensitive to the local genetic mutation in the target viruses. As a result, the approach can inactivate both the wild and mutated strains of viruses. This intriguing advantage is particularly important in the treatment of diseases involving rapidly mutating viral species such as HIV. Our photonic approach could be used for the disinfection of viral pathogens in blood products and for the treatment of blood-borne viral diseases in the clinic.

The title compound, tetrabutylammonium bis(1,2-dimercaptoethene-1,2-dicarbonirtilato-S,S′)-nickel (III) [henceforth (NBu4)Ni(mnt)2] undergoes a hysteretic phase transition that occurs at 172 K upon cooling. Crystallographic studies show that the phase transition is an order–disorder type involving one arm of the NBu4+ cation. Both phases are monoclinic, space group C2/c with a=30.860(3), b=13.804(2), c=15.678(2) Å and β=115.642(3)° with V=6020.8(11) Å3 at room temperature and with a=31.073(3), b=13.928(1), c=14.414(1) Å and β=115.073(2)° and V=5652.1(9) Å3 at 84 K. In both phases, the anions form non-uniform stacks parallel to the crystallographic c direction. In the high temperature phase, the Ni–S distances between anions are accidentally equal, and the stacks behave as nearly uniform antiferromagnetic chains with nearly equal exchange constants. At the phase transition, a non-uniform compression of the stacks occurs and the magnetic moment drops rapidly, indicating a magnetic dimerization of the stacks. Susceptibility and Cp measurements show an approximate 7 °C thermal hysteresis.

Because of the current and future importance of the Atomic Force Microscope (AFM) in education and research, our team has been working on transferring this technology to the college classroom. In this paper we present the initial findings of a case study in which two years of cutting-edge AFM research was transferred to the college classroom in the form of a one-semester course. The course was developed before the research was completed and published in final form. While, the course centered on the re-creation and explanation of the most recent advances in building high-throughput AFMs, it also implemented and assessed the use of two online AFMs. Student response to the initial course offering, its content, and the tools used, was very positive. The students rated the course above the department average on 14 of the 15 survey metrics and claimed that the teaching method would help them remember more than other classes (average 8 on a ten-point scale. N=24). As a result of the course, several students have shown interest in pursuing work and research in this field. These results indicate that the course has successfully broadened the horizons of undergraduate and graduate students at the University of Nevada Reno, which had no microtechnology or AFM course offering prior to this work. It has also demonstrated the potential of using the AFM as the center focus of a MEMS/Nano-technology course. Finally, this case study may serve as a model for future technology transfer to the classroom by Ph.D. candidates who have not fully completed their technical research

Abstract: Tele-microscopy has become a very active area of research and development in the 1990s where there was a desire to give researchers better access to expensive and specialized microscopes, breaking geographical and time barriers. Rapid advances in telecommunication, computers, and microscopy technologies make possible the establishment of the World Wide Web and the realization of the goal of developing a “laboratory without walls”. This provides unprecedented opportunities for researchers and educators alike to gain access to shared instrumental and educational resources. In this presentation, a description of the Interactive Nano-Visualization for Science and Engineering Education (IN-VSEE) project will be given. The primary goals of IN-VSEE are to (i) convey the excitement of nanoscience and nanotechnology to promote studentmotivated learning and pursuit of science and engineering careers, (ii) teach fundamental interdisciplinary concepts in science and engineering using a visual format to help students learn and integrate information more effectively, (iii) provide students with the capability to routinely explore materials in three dimensions with resolutions at the nanoscale and even down to the atomic scale, and (iv) demonstrate the feasibility of remote operation of research-grade laboratory instrumentation for development into a powerful educational and collaborative tool.

Transmission electron microscopy (TEM) reveals exsolution lamellae in a cryptoperthite; their spacing results in a greenish-yellow iridescent color. High-resolution TEM images show that the boundaries between Ab-rich and Or-rich lamellae are semi-coherent along the b axis.Scanning force microscopy (SFM) of a (001) cleavage surface reveals exsolution lamellae, wavelike (001) surfaces of the Ab-rich lamellae, and surface steps with heights of similar to 6.6 and similar to 3 Angstrom. The wave-like (001) surfaces of albite twin lamellae may result from surface relaxation. Surface height differences between Ab- and Or-rich lamellae in some areas indicate a semi-coherent boundary along the c axis.