Simulating three dimensional self-assembly of shape modified particles using magnetic dipolar forces

The feasibility of 3D self-assembly of milli-magnetic particles that interact via magnetic dipolar forces is investigated. Typically magnetic particles, such as isotropic spheres, self-organize in stable 2D configurations. By modifying the shape of the particles, 3D self-assembly may be enabled. The design of the particles and the experimental setup are presented. The magnetic configurations of simple particle arrangements are obtained via energy minimization in simulations. The simulations show that a 3D configuration can become energetically favourable over 2D configurations, if the shape of the particle is modified

Elastocapillary folding of three dimensional micro-structures using water pumped through the wafer via a silicon nitride tube

In this paper we present the first investigation of a batch method for folding of threedimensional micrometer-sized silicon nitride structures by capillary forces. Silicon nitride tubes have been designed and fabricated using DRIE at the center of the planar origami patterns of the structures. Water is brought to the structures by pumping the liquid through the wafer via those tubes. Isolated micro-structures were successfully folded using this method. The potential of this technique for batch self-assembly is discussed

Magnetic Response of Magnetospirillum Gryphiswaldense

In this study we modelled and measured the U-turn trajectories of individual magnetotactic bacteria under the application of rotating magnetic fields, ranging in ampitude from 1 to 12 mT. The model is based on the balance between rotational drag and magnetic torque. For accurate verification of this model, bacteria were observed inside 5 m tall microfluidic channels, so that they remained in focus during the entire trajectory. From the analysis of hundreds of trajectories and accurate measurements of bacteria and magnetosome chain dimensions, we confirmed that the model is correct within measurement error. The resulting average rate of rotation of Magnetospirillum Gryphiswaldense is 0.74 +- 0.03 rad/mTs.Comment: 17 pages, 12 figure

Trajectory Deflection of Spinning Magnetic Microparticles, the Magnus Effect at the Microscale

The deflection due to the Magnus force of magnetic particles with a diameter of 80 micrometer dropping through fluids and rotating in a magnetic field was measured. With Reynolds number for this experiment around 1, we found trajectory deflections of the order of 1 degree, in agreement within measurement error with theory. This method holds promise for the sorting and analysis of the distribution in magnetic moment and particle diameter of suspensions of microparticles, such as applied in catalysis, or objects loaded with magnetic particles.Comment: 12 pages, 3 figures. Appendix with 6 figure

Young's modulus and residual stress of GeSbTe phase-change thin films

The mechanical properties of phase change materials alter when the phase is transformed. In this paper, we report on experiments that determine the change in crucial parameters such as Young's modulus and residual stress for two of the most widely employed compositions of phase change films, Ge1Sb2Te4 and Ge2Sb2Te5, using an accurate microcantilever methodology. The results support understanding of the exact mechanisms that account for the phase transition, especially with regard to stress, which leads to drift in non-volatile data storage. Moreover, detailed information on the change in mechanical properties will enable the design of novel low-power nonvolatile MEMS

Capillary origami of micro-machined micro-objects: Bi-layer conductive hinges

Recently, we demonstrated controllable 3D self-folding by means of capillary forces of silicon-nitride micro-objects made of rigid plates connected to each other by flexible hinges [1]. In this paper, we introduce platinum electrodes running from the substrate to the plates over these bendable hinges. The fabrication yield is as high as (77 +/- 2) % for hinges with a length less than 75 {\mu}m. The yield reduces to (18 +/- 2) % when the length increases above 100 {\mu}m. Most of the failures in conductivity are due to degradation of the platinum/chromium layer stack during the final plasma cleaning step. The bi-layer hinges survive the capillary folding process, even for extremely small bending radii of 5 {\mu}m, nor does the bending have any impact on the conductivity. Stress in the different layers deforms the hinges, which does not affect the conductivity. Once assembled, the conductive hinges can withstand a current density of (1.6 +/- 0.4) $10^6$ A/cm$^2$ . This introduction of conductive electrodes to elastocapillary self-folded silicon-based micro-objects extends the range of their possible applications by allowing an electronic functionality of the folded parts.Comment: Currently on a peer review process. 13 page

Elastocapillary folding using stop-programmable hinges fabricated by 3D micro-machining

We show elasto-capillary folding of silicon nitride objects with accurate folding angles between flaps of 70.6$\pm$0.1{\deg} and demonstrate the feasibility of such accurate micro-assembly with a final folding angle of 90{\deg}. The folding angle is defined by stop-programmable hinges that are fabricated starting from silicon molds employing accurate three-dimensional corner lithography. This nano-patterning method exploits the conformal deposition and the subsequent timed isotropic etching of a thin film in a 3D shaped silicon template. The technique leaves a residue of the thin film in sharp concave corners which can be used as an inversion mask in subsequent steps. Hinges designed to stop the folding at 70.6{\deg} were fabricated batchwise by machining the V-grooves obtained by KOH etching in (110) silicon wafers; 90{\deg} stop-programmable hinges were obtained starting from silicon molds obtained by dry etching on (100) wafers. The presented technique is applicable to any folding angle and opens a new route towards creating structures with increased complexity, which will ultimately lead to a novel method for device fabrication.Comment: Submitted to a peer reviewed journa

Force modulation for enhanced nanoscale electrical sensing

Scanning probe microscopy employing conductive probes is a powerful tool for the investigation and modification of electrical properties at the nanoscale. Application areas include semiconductor metrology, probe-based data storage and materials research. Conductive probes can also be used to emulate nanoscale electrical contacts. However, unreliable electrical contact and tip wear have severely hampered the widespread usage of conductive probes for these applications. In this paper we introduce a force modulation technique for enhanced nanoscale electrical sensing using conductive probes. This technique results in lower friction, reduced tip wear and enhanced electrical contact quality. Experimental results using phase-change material stacks and platinum silicide conductive probes clearly demonstrate the efficacy of the proposed technique. Furthermore, conductive-mode imaging experiments on specially prepared platinum/carbon samples are presented to demonstrate the widespread applicability of this technique

Late Quaternary Distribution of the Cycladophora davisiana Radiolarian Species: Reflection of Possible Ventilation of the North Pacific Intermediate Water during the Last Glacial Maximum

A comparison of micropaleontological data on the distribution of the Cycladophora davisiana radiolarian species in the surface sediment layer and the Late Quaternary sediments from the Subarctic Pacific and Far East marginal seas allowed conclusions concerning the possible conditions and occurrence of intermediate waters during the last glacial maximum. We used the modern data on the C. davisiana species, which is a micropaleontological indicator of the cold oxygen-rich upper intermediate water mass, which is now forming only in the Sea of Okhotsk. The high amount of C. davisiana in sediments of the last glacial maximum may point to the possible formation and expansion of the ventilated intermediate water in the most part of the Subarctic paleo-Pacific: the Bering Sea, the Sea of Okhotsk, within the NW Gyre, and in the Gulf of Alaska

A model for mark size dependence on field emission voltage in heat-assisted magnetic probe recording on CoNi/Pt multilayers

A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2-7 V with a duration of 500 ns were applied to a CoNi/Pt multilayered film. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm when the pulse voltage is above a threshold voltage. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. The emission area of our tip-sample system derived from an analytic expression for field emission current is approximately equal to the mark size, and is largely independent of pulse voltage. This emission area is large compared to lateral heat diffusion in the film. Thus higher applied voltages lead to higher peak temperatures in the model of the write process, but the mark diameter remains relatively unchanged