Een klok doet geen "pok"

Debakel, fiasco, mislukking. Het zijn dagelijkse bezigheden voor ons onderzoekers. Je kan er dus maar beter mee leren omgaan. Veel mensen hebben zich uitgesproken over hun tevredenheid met mislukkingen. Bijvoorbeeld Albert Einstein’s “Anyone who has never made a mistake has never tried anything new.‿ Robert Oppenheimer leert ons dat we er juist trots op moeten zijn, want “Any man whose errors take ten years to correct is quite a man.‿ Je kan het ook te bont maken, dus opgepast. “Only a fool learns from his own mistakes. The wise man learns from the mistakes of others,‿ aldus Otto von Bismarck. Het inzetten van studenten op kansarme idee¨en lijkt dus een goede oplossing

Shutdown Policies for MEMS-Based Storage Devices -- Analytical Models

MEMS-based storage devices should be energy ecient for deployment in mobile systems. Since MEMS-based storage devices have a moving me- dia sled, they should be shut down during periods of inactivity. However, shutdown costs energy, limiting the applicability of aggressive shutdown decisions. The media sled in MEMS-based storage devices is suspended by springs. We introduce a policy that exploits the spring structure to reduce the shut- down energy. As a result, the aggressiveness of the shutdown decisions can be increased, reducing the energy consumption. This report devises analytical models of the shutdown time and energy of this policy

Long-range elastic guidance mechanisms for electrostatic comb-drive actuators

The range of motion and output force of the often used electrostatic comb-drive with folded flexure straight guidance, as shown in Figure 1, is limited by sideways instability due to poor sideways stiffness of the folded flexure at relatively large deflections [1]

Thermally induced switching field distribution of individual single nanomagnets in a large assembly

The Anomalous Hall Effect (AHE) can be used to measure the magnetization reversal of individual nanomagnets, under varying field angle and wide temperature range [1]. By passing a current through the magnetic elements, and measuring the voltage generated perpendicular to the current direction, one can determine the component of magnetisation perpendicular to the film plane. This extremely sensitive method can be used to observe reversal of magnetic elements with diameters below 10 nm or individual elements inside large assemblies

A single-mask thermal displacement sensor in MEMS

Position sensing in MEMS is often based on the principle of varying capacitance [1]. Alternative position sensing principles include using integrated optical waveguides [2] or varying thermal conductance [3]. Lantz et al demonstrated a thermal displacement sensor achieving nanometre resolution on a 100mm range. However a multi-mask production process and manual assembly were needed to fabricate this displacement sensor. In this work we present a 1-DOF thermal displacement sensor integrated with an actuated stage, and its experimental characterization. The system was fabricated in the device layer of a silicon-on-\ud insulator (SOI) wafer using a single-mask process.\ud \u

A single-mask thermal displacement sensor in MEMS

This work presents a MEMS displacement sensor based on the conductive heat transfer of a resistively heated silicon structure towards an actuated stage parallel to the structure. This differential sensor can be easily incorporated into a silicon-on-insulator-based process, and fabricated within the same mask as electrostatic actuators and flexure-based stages. We discuss a lumped capacitance model to optimize the sensor sensitivity as a function of the doping concentration, the operating temperature, the heater length and width. We demonstrate various sensor designs. The typical sensor resolution is 2 nm within a bandwidth of 25 Hz at a full scale range of 110 μm

Optimization of comb-drive actuators : nanopositioners for probe-based data storage and musical MEMS

The era of infinite storage seems near. To reach it, data storage capabilities need\ud to grow, and new storage technologies must be developed.This thesis studies one\ud aspect of one of the emergent storage technologies: optimizing electrostatic combdrive\ud actuation for a parallel probe-based data storage system.\ud It is no longer possible to store all created information. New storage technologies\ud must be developed as current commercial technologies reach their fundamental\ud limits. One promising technology is parallel probe-based data storage, using a\ud nanometre-scale probe to write data on a moving platform. The working principle\ud is very similar to that of a record player applied in parallel on the nano scale. In\ud order to access all bits on the storage medium, a nano-positioner, or scanner, is\ud used to move the storage medium relative to the read-out probes.\ud Several nano-positioner designs for probe data storage are found in the literature.\ud It is not clear which actuator type (electromagnetic, electrostatic, or piezoelectric)\ud is most suited for probe data storage. We replaced the electrodynamic\ud actuators by comb-drives in the scanner prototype by IBM, to enable a direct comparison.\ud e comb-drive’s areal efficiency is low, due to a relatively low electrostatic\ud force. e comb-drive finger profile is optimized for probe data storage, for an\ud increased shock resistance.\ud e suitability of electromagnetic and electrostatic actuation is, among others, determined by their energy consumption.Three (partly) hypothetical scanner designs\ud using electrodynamic, electromagnetic and electrostatic comb-drive actuators\ud are described. Their performance is approximately equal, however electrostatic\ud comb-drive actuation requires an order of magnitude less energy. Equations are\ud presented for further investigations into the performance and energy consumption\ud of the different actuation types for different file-system use cases.\ud We succeeded in making music with MEMS structures, and named our microinstrument\ud ‘the micronium’. Due to fabrication inaccuracies, the instrument is outof-\ud tune and requires tuning. Besides teaching students about MEMS technology in\ud a fun way, the micronium succeeded in presenting MEMS technology to a broad\ud audience

Nanopositioner actuator energy cost and performance

We investigate the energy consumption and seek-time performance of different actuator types for nanopositioners, with emphasis on their use in a parallel-probe-based data-storage system. Analytical models are derived to calculate the energy consumption and performance of electrodynamic (coil and permanent magnet) and comb-drive actuators. The equations are used to simulate the operation of probe-storage devices with these actuator types under a realistic file system load. The electrostatic comb-drive actuators are more energy efficient than the electrodynamic actuators, by an order of magnitude for slow movements and a factor of 2.5 for high-acceleration movements. Overall in a probe-storage device, comb-drive actuation is a factor of 3.3 more energy efficient than electrodynamic actuation, at the same level of performance. The analytical model presented in this work can be used to direct the optimization of nanopositioners and their use, for example, in terms of the data layout on the medium and the ‘shutdown’ policy of probe-storage devices

Switching field distribution of arrays of Co-Pt Nanodots determined by anomalous hall effect measurements

Anomalous Hall Effect (AHE) measurements have previously been used to measure the magnetization of L10-FePt [1] and Co/Pt multilayer nanodots [2]. The high sensitivity allows us to measure the magnetization reversal behaviour of sub-100-nm dots. In this work, we investigate the magnetization reversal of 180 nm Co80Pt20 dots, with a focus on the switching field distribution (SFD) of individual dots in an array. Fig. 1 shows hysteresis curves of an array of Co80Pt20 dots measured by AHE. Several steps and plateaus, due to the independent reversal of individual dots, are clearly visible. By consecutively measuring several hysteresis curves, one can observe different switching field values for a single dot (inset Fig. 1). A mathematical model was derived to calculate the effect of thermal activation on this SFD, which depends mainly on the anisotropy, switching volume and the magnetization reversal mechanism of the dot. The SFD was determined from 1000 curves and coincides with the modelled distribution (Fig. 2). By investigating different dots in the array, we conclude that there is a difference in reversal mechanism between weak and strong dots in the array

Ultra-flat bismuth films for diamagnetic levitation by template-stripping

In this paper we present a method to deposit thin films of bismuth with sub-nanometer surface roughness for application to diamagnetic levitation. Evaporated films of bismuth have a high surface roughness with peak to peak values in excess of 100 nm and average values on the order of 20 nm. We expose the smooth backside of the films using a template stripping method, resulting in a great reduction of the average surface roughness, to 0.8 nm. Atomic force microscope and X-ray diffraction measurements show that the films have a polycrystalline texture with preferential c-axis orientation. On the back side of the film, fine grains are grouped into larger clusters. Cantilever resonance shift measurements indicate that the Young's modulus of the films is on the order of 20 GPa