Long-time data storage: relevant time scales

Dynamic processes relevant for long-time storage of information about human kind are discussed, ranging from biological and geological processes to the lifecycle of stars and the expansion of the universe. Major results are that life will end ultimately and the remaining time that the earth is habitable for complex life is about half a billion years. A system retrieved within the next million years will be read by beings very closely related to Homo sapiens. During this time the surface of the earth will change making it risky to place a small number of large memory systems on earth; the option to place it on the moon might be more favorable. For much longer timescales both options do not seem feasible because of geological processes on the earth and the flux of small meteorites to the moon.\u

Silicon active microvalves using buckled membranes for actuation

Design considerations and experiments have been made for obtaining a new type of active microvalves using silicon buckled membranes. The properties of the buckled membranes permitting to obtain high deflections and to actuate them more convenient are demonstrated. A thermal actuation using an aluminium ring layer heated with a polysilicon resistor is analysed. The polysilicon and the aluminium ring layers have been deposited in the region of the membrane having the minimum internal stress. The fabrication process consist of photolithography, LPCVD depositions, diffusion, AI sputtering. isotropic, anisotropic etching and anodic bonding. The design and experiments show a convenient low temperature range necessary to actuate the microvalve.\ud \u

High resolution powder blast micromachining

Powder blasting, or Abrasive Jet Machining (AJM), is a technique in which a particle jet is directed towards a target for mechanical material removal. It is a fast, cheap and accurate directional etch technique for brittle materials like glass, silicon and ceramics. By introducing electroplated copper as a new mask material, the feature size of this process was decreased. It was found that blasting with 9 µm particles (compared with 30 µm particles) result in a higher slope of the channel sidewall. The aspect ratio of powder blasted channels was increased by using the high resistance of the copper mask in combination with the use of 9 µm particles. Furthermore, our measurements show how the blast lag (small channels etch slower compared to wider channels) is decreased by using smaller particles

Beyond the Linearity of Current-Voltage Characteristics in Multiwalled Carbon Nanotubes

We present local and non-local electron transport measurements on individual multi-wall nanotubes for bias voltage between 0 and about 4 V. Local current-voltage characteristics are quite linear. In contrast, non-local measurements are highly non-linear; the differential non-local conductance can even become negative in the high-bias regime. We discuss the relationship between these results and transport parameters such as the elastic length, the number of current carrying shells, and the number of conducting modes.Comment: 5 pages, 5 figure

Optimization of a Thermal Flow Sensor for Acoustic Particle Velocity Measurements

In this paper, a thermal flow sensor consisting of two or three heated wires, the Microflown, is treated for application to acoustic measurements. It is sensitive to flow ("particle velocity"), contrary to conventional microphones that measure acoustic pressures. A numerical analysis, allowing for detailed parametric studies, is presented. The results are experimentally verified. Consequently, improved devices were fabricated, and also sensors with a new geometry consisting of three wires, instead of the usual two, of which the central wire is relatively most heated. These devices are the best performing Microflowns to date with a frequency range extending from 0 to over 5 kHz and a minimum detectable particle velocity level of about 70 nm/s at 2 to 5 kHz (i.e., 3 dB PVL or SPL, corresponding to a pressure of 3.1/spl middot/10/sup -5/ Pa at a free field specific acoustic impedance)

Micromachined capacitive displacement sensor for long-range nano-positioning

Integrated long-range position sensing with high accuracy will be of paramount importance for high-potential applications in a.o. future probe-based datastorage and microscopy applications [1], provided that nm position accuracy can be obtained over a range of tens of micrometers or more. This work presents the design, fabrication and measurements for an integrated incremental capacitive long-range position sensor for nano-positioning of microactuators. For compactness, economical viability and optimal performance, the aim has been to fully integrate sensor and actuator through micromachining technology, without additional micro-assembly. Two related concepts are presented and evaluated through analysis, 2D-Finite-Element Simulations and experimental assessment. The sensors consist of two periodic geometries (period ≈ 8-16μm) on resp. a slider, movable in x-direction, and sense-structures, movable in y-direction, at both sides of the slider, Fig. 1. In ICMM the displacement of the slider is measured by measuring the periodic change in capacitance ΔCs(x) with a charge-amplifier and synchronous detection technique [2]. Using sense-actuators, the gap-distance between sense-structures and slider is made smaller than is possible with standard available photo-lithography (< 2 μm), thus increasing the capacitance and the S-N Ratio

Micromachined capacitive long-range displacement sensor

First measurement results are presented for a surface-micromachined long-range (50– 100 μm) periodic capacitive position sensor. The sensor consists of two periodic geometries (period = 10 μm) sliding along each other with minimum spacing of about 1.5 μm. The relative displacement between the two, results in a periodic change in capacitance. An electrostatic comb-drive actuator is employed to generate displacements. Measured maximum capacitance change ΔC=0.72 fF corresponds to simulation results but needs better shielding from external noise sources. The results show this sensorconcept can potentially lead towards long-range nano-positioning control of microactuator systems

Determination of the Intershell Conductance in Multiwalled Carbon Nanotubes

We report on the intershell electron transport in multiwalled carbon nanotubes (MWNT). To do this, local and nonlocal four-point measurements are used to study the current path through the different shells of a MWNT. For short electrode separations $\lesssim$ 1 $\mu$m the current mainly flows through the two outer shells, described by a resistive transmission line with an intershell conductance per length of ~(10 k\Omega)^{-1}/$\mu$m. The intershell transport is tunnel-type and the transmission is consistent with the estimate based on the overlap between $\pi$-orbitals of neighboring shells.Comment: 5 pages, 4 figure

Optimized comb drive finger shape for shock-resistant actuation

This work presents the analytical solution, realization and measurement of a comb drive with finger shapes optimized for shock-resistant actuation. The available force for actuating an external load determines how large shock forces can be compensated for. An analytical expression is presented for the finger shape that provides a constant large available force over the actuation range. The finger shape is asymmetric, resulting in a 20% smaller unit cell width compared to a symmetric shape. This finger shape provides 4 times more available force than the standard straight finger shape