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In this study, high-aspect ratio silicon nanowire (SiNW) – modified atomic force microscopy (AFM) probes are fabricated using focused ion beam (FIB) microfabrication technology and vapor-solid-solid synthesis. Commercially available soft silicon nitride probes are used for localized nanowire growth yielding soft high-aspect ratio AFM probes. The SiNW-modified cantilevers are used here for imaging in PeakForce Tappingۛ (PFT) mode, which offers high force control along with valuable information about tip-sample adhesion. A platinum catalyst, deposited accurately at a truncated AFM tip by ion beam-induced deposition (IBID), was used for localized nanowire synthesis. It could be shown that the deposition of a thin silicon dioxide layer prior to the catalyst deposition resulted in controlled SiNW growth on silicon as well as silicon nitride probes. In addition, a FIB-based method for post-growth alignment of the fabricated SiNW tips is presented, which allows tilt-compensation specifically tailored to the specifications of the used AFM instrumentation. To demonstrate the capability of such soft, high-aspect ratio AFM probes, optical gratings fabricated in GaAs and silver halide fibers were imaged in PFT mode. Additionally, the mechanical stability of these high-aspect AFM probes was evaluated on a sapphire substrate. [ABSTRACT FROM AUTHOR]

Arrays composed of vertically aligned nanoscale electrodes are under discussion for various biological and analytical applications including extra- and intracellular measurements, intracellular drug delivery, and cellular interfacing. Based on their nanoscale morphology, conductive nanowires are a preferred electrode material but device fabrication remains a key challenge. In this article, we present a straightforward assembly strategy for directly connected and quasi-vertically aligned silicon nanowires (SiNWs) that could lead to well-defined electrode arrays in future. Our strategy exploits certain features of platinum-catalyzed SiNW growth and simultaneously interlinks the SiNW synthesis and the formation of the electrical contacts using a single metallization film. Our assembly strategy relies fully on conventional photolithography and can cope with various electrode designs and configurations considering single-nanowire electrode readouts. [ABSTRACT FROM AUTHOR]

In this paper, we derive a quantitative model for the manipulation of superparamagnetic particles by superposition of a homogeneous magnetic field and magnetic field gradients. Our results show that by this combination, the magnitude as well as the sign of the force on a magnetic particle can be controlled. By quantitatively modeling the magnetic force on a representative superparamagnetic particle, we find that for a common lab-on-chip scenario large repulsive forces can be achieved by adding a homogeneous field perpendicular to the plane of the chip. This offers new perspectives for the on-chip manipulation of magnetic particles. As a first example, in-plane positioning of particles with an accuracy of \(\sim 1 \mu \) m is experimentally demonstrated. [ABSTRACT FROM AUTHOR]