Photorelease of caged Ca(2+) is a uniquely powerful tool to study the dynamics of Ca(2+)-triggered exocytosis from individual cells. Using photolithography and other microfabrication techniques, we have developed transparent microchip devices to enable photorelease of caged Ca(2+), together with electrochemical detection of quantal catecholamine secretion from individual cells or cell arrays as a step towards developing high-throughput experimental devices. A 100 nm thick transparent indium-tin-oxide (ITO) film was sputter-deposited onto glass coverslips, which were then patterned into 24 cell-sized working electrodes (approximately 20 microm by 20 microm). We loaded bovine chromaffin cells with acetoxymethyl (AM) ester derivatives of the Ca(2+) cage NP-EGTA and Ca(2+) indicator dye fura-4F, then transferred these cells onto the working ITO electrodes for amperometric recordings. Upon flash photorelease of caged Ca(2+), a uniform rise of [Ca(2+)](i) within the target cell leads to quantal release of oxidizable catecholamines measured amperometrically by the underlying ITO electrode. We observed a burst of amperometric spikes upon rapid elevation of [Ca(2+)](i) and a "priming" effect of sub-stimulatory [Ca(2+)](i) on the response of cells to subsequent [Ca(2+)](i) elevation, similar to previous reports using different techniques. We conclude that UV photolysis of caged Ca(2+) is a suitable stimulation technique for higher-throughput studies of Ca(2+)-dependent exocytosis on transparent electrochemical microelectrode arrays.

Here we describe a method to fabricate a multi-channel high-throughput microchip device for measurement of quantal transmitter release from individual cells. Instead of bringing carbon-fiber electrodes to cells, the device uses a surface chemistry approach to bring cells to an array of electrochemical microelectrodes. The microelectrodes are small and “cytophilic” in order to promote adhesion of a single cell whereas all other areas of the chip are covered with a thin “cytophobic” film to block cell attachement and facilitate movement of cells to electrodes. This cytophobic film also insulates unused areas of the conductive film, thus the alignment of cell docking sites to working electrodes is automatic. Amperometric spikes resulting from single-granule fusion events were recorded on the device and had amplitudes and kinetics similar to those measured using carbon-fiber microelectrodes. Use of this device will increase the pace of basic neuroscience research and may also find applications in drug discovery or validation.

Electrochemical measurement of transmitter or hormone release from individual cells on microchips has applications both in basic science and drug screening. High-resolution measurement of quantal exocytosis requires the working electrode to be small (cell-sized) and located in immediate proximity to the cell. We examined the ability of candidate electrode materials to promote the attachment of two hormone-secreting cell types as a mechanism for targeting cells for to recording electrodes with high precision. We found that nitrogen-doped diamond-like carbon (DLC:N) promoted cell attachment relative to other materials tested in the rank order of DLC:N > In2O3/SnO2 (ITO), Pt > Au. In addition, we found that treating candidate electrode materials with polylysine did not increase attachment of chromaffin cells to DLC:N, but promoted cell attachment to the other tested materials. We found that hormone-secreting cells did not attach readily to Teflon AF as a potential insulating material, and demonstrated that patterning of Teflon AF leads to selective cell targeting to DLC:N “docking sites”. These results will guide the design of the next generation of biochips for automated and high-throughput measurement of quantal exocytosis.

Abstract-The charge-storage characteristics of a metal-oxidesemiconductor (MOS) structure containing size-tunable sub-2 nm Pt nanoparticles (NPs) between Al 2 O 3 tunneling and capping oxide layers were studied. Significantly different amounts of memory window were obtained with the different sizes of Pt NP embedded MOS structures and reached a maximum of 4.3 V using a 1.14 nm Pt NP, which has the strongest charging capability caused by optimum size and the largest particle density obtained in our deposition method. Satisfactory long-term nonvolatility was attained in a low electric field due to the Coulomb blockade and quantum confinement effects in ∼1 nm Pt NP. These properties are very promising in view of device application.Index Terms-Nanoparticle (NP), nonvolatile memory (NVM), size-tunable platinum.

We present a wafer-level heterointegrated indium phosphide double heterobipolar transistor on silicon germanium bipolarcomplementary metal oxide semiconductor (InP DHBT on SiGe BiCMOS) process which relies on adhesive wafer bonding. Subcircuits are co-designed in both technologies, SiGe BiCMOS and InP DHBT, with more than 300 GHz bandwidth microstrip interconnects. The 250 nm SiGe HBTs offer cutoff frequencies around 200 GHz, the 800 nm InP DHBTs exceed 350 GHz. Heterointegrated signal sources are demonstrated including a 328 GHz quadrupling source with −12 dBm RF output power. A common design kit for full InP DHBT/SiGe BiCMOS co-design was set up. The technology is being opened to third-party customers through IHP's multi-purpose wafer foundry interface. Microphotograph of InP DHBT / SiGe BiCMOS wafer

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Crystallization of amorphous silicon ͑a-Si͒ thin film occurred by the self-propagation of copper oxide/aluminum thermite nanocomposites. Amorphous Si films were prepared on glass at a temperature of 250°C by plasma enhanced chemical vapor deposition. The platinum heater was patterned on the edge of the substrate and the CuO / Al nanoengineered thermite was spin coated on the substrate that connects the heater and the a-Si film. A voltage source was used to ignite the thermites followed by a piranha solution ͑4 Unlike most other techniques, laser induced crystallization does not require high temperatures ͑Ͼ180°C͒ and long processing times to produce good quality poly-Si films. The major disadvantage of laser crystallization is its low throughput due to small laser spot size, which is not suitable for large area such as solar cells. Thus, high temperature and long processing times for various crystallization methods, and small spot size of the laser are not suitable for producing poly-Si film on a large surface area of glass or flexible plastic substrates. Low cost plastic substrates such as polyethersulphone can be used for flexible electronics if the device is fabricated under 180°C. This study investigates the crystallization of a-Si layer achieved by the ignition of nanoengineered thermite materials such as CuO / Al. Explosives have been utilized previously to crystallize amorphous materials; 5,6 however, there is no information currently available on thin film crystallization using nanoengineered thermites. Our approach utilizes thermite reaction to induce crystallization of a-Si thin film; such energetic reactions are self-propagating exothermic reactions, which produce localized heating effects. We discovered that thermites, nanoengineered by the self-assembly approach, produced a self-propagating chemical reaction over a period of microseconds. 7,8 The exothermic reaction propagates at a rate of 1500-2000 m / s resulting in heat release. This heat can be used advantageously to crystallize a-Si. High quality poly-Si films can be prepared on large substrates utilizing this released heat. Nanoengineered thermites were prepared by sonicating a mixture of CuO nanorods ͑10 nm diameter and 70 nm long͒ and aluminum nanopowder ͑80 nm diameter͒. The details of the nanorod preparation and the characterization of the thermites are presented in Ref. 9. The thermites displayed the following chemical reaction:where ⌬H is the released heat. For CuO / Al exothermic reaction, the released heat is 604 kJ/ mol and the adiabatic reaction temperature is 3794 K. 10The a-Si samples were prepared by plasma enhanced chemical vapor deposition on glass substrates. The thickness of the a-Si layer was 300 nm. A thin layer of platinum ͑90 nm thick and 2.5 mm wide͒ was deposited on the edge of the substrates, which functioned as a heater for initiating the self-propagating reaction for the energetic materials. The substrates with a-Si and the platinum heater were spin coated with the thermites and dried at 105°C in an oven for 10 min. Th...

Carbon-based electrode materials have been widely used for many years for electrochemical charge storage, energy generation, and catalysis. We have developed an electrode material with high specific capacitance by entrapping graphite nanoparticles into a sol-gel network. Films from the resulting colloidal suspensions were highly porous due to the removal of the entrapped organic solvents from sol-gel matrix giving rise to high Brunauer-Emmett-Teller (BET) specific surface areas (654 m(2)/g) and a high capacitance density ( approximately 37 F/g). An exponential increase of capacitance was observed with decreasing scan rates in cyclic voltammetry studies on these films suggesting the presence of pores ranging from micro (< 2 nm) to mesopores. BET surface analysis and scanning electron microscope images of these films also confirmed the presence of the micropores as well as mesopores. A steep drop in the double layer capacitance with polar electrolytes was observed when the films were rendered hydrophilic upon exposure to a mild oxygen plasma. We propose a model whereby the microporous hydrophobic sol-gel matrix perturbs the hydration of ions which moves ions closer to the graphite nanoparticles and consequently increase the capacitance of the film.