Control of magnetotactic bacterium in a micro-fabricated maze

We demonstrate the closed-loop control of a magnetotactic bacterium (MTB), i.e., Magnetospirillum magnetotacticum, within a micro-fabricated maze using a magneticbased manipulation system. The effect of the channel wall on the motion of the MTB is experimentally analyzed. This analysis is done by comparing the characteristics of the transient- and steady-states of the controlled MTB inside and outside a microfabricated maze. In this analysis, the magnetic dipole moment of our MTB is characterized using a motile technique (the u-turn technique), then used in the realization of a closed-loop control system. This control system allows the MTB to reach reference positions within a micro-fabricated maze with a channel width of 10 μm, at a velocity of 8 μm/s. Further, the control system positions the MTB within a region-of-convergence of 10 μm in diameter. Due to the effect of the channel wall, we observe that the velocity and the positioning accuracy of the MTB are decreased and increased by 71% and 44%, respectively

Fast FIB-milled Electron-transparent Microchips for in situ TEM Investigations

In this work we present a fast approach to 50 nm resolution structures defined in a generic TEM-chip template in few minutes. While creating complex electrical and NEMS circuits for a specific insitu TEM experiment can be a cumbersome process, microchips with 100 nm thin flakes of single crystalline silicon and silicon nitride membrane templates suspended from the edge, can be patterned in less than 15 minutes using focused ion beam milling. This approach allows a FIB-SEM user to create free-form NEMS structures for nanoresonators, actuators, heaters, resistors or other structures for insitu TEM devices or materials research using the same template. We demonstrate insitu environmental TEM analysis of Au film migration on silicon during resistive heating of a microbridge, and show how the conductance of focused ion beam milled single crystalline silicon nanowires can be adjusted insitu over two decades using a high current to recrystallise the structure

Microassembly using a cluster of paramagnetic microparticles

We use a cluster of paramagnetic microparticles to carry out a wireless two-dimensional microassembly operation. A magnetic-based manipulation system is used to control the motion of the cluster under the influence of the applied magnetic fields. Wireless motion control of the cluster is implemented at an average velocity and maximum position tracking error of 144 μm/s and 50 μm, respectively. This control is used to achieve point-to-point positioning of the cluster, manipulation of microobjects, and assembly of microobjects into a microstructure. The control system achieves stable positioning of the cluster, while simultaneously compensating for the planar drag forces on the cluster and the microobject. The presented magneticbased microassembly technique allows for the selective pushing and pulling of microobjects with specific geometries towards their destinations inside a microstructure in an execution time of 18 s, within a workspace of 1.8 mm × 2.4 mm