Nanofluidics in hollow nanowires.

We present a novel scheme for producing nanotube membranes using free-standing hollow nanowires, with easily controllable dimensions. GaAs-AlInP core-shell nanowires were grown by metal-organic vapor phase epitaxy and were partially embedded in a polymer film. The GaAs core and substrate were etched selectively, leaving tubes with open access to both sides of the membrane. Electrophoretic transport of T4-phage DNA through the hollow nanowires was demonstrated using epifluorescence microscopy.

Fifteen-piconewton force detection from neural growth cones using nanowire arrays.

We used epitaxially grown monodisperse nanowire arrays to measure cellular forces with a spatial resolution of 1 mum. Nerve cells were cultured on the array and cellular forces were calculated from the displacement of the nanowire tips. The measurements were done in situ on live cells using confocal microscopy. Forces down to 15 pN were measured on neural growth cones, showing that this method can be used to study the fine details of growth-cone dynamics.

Rectifying and sorting of regenerating axons by free-standing nanowire patterns: a highway for nerve fibers.

We present an EBL-defined nanowire pattern that can sort axons coming from different directions on a substrate. The pattern defines tracks for left-bound traffic and right-bound traffic, which opens up new possibilities for designing neural networks on a chip.

Axonal guidance on patterned free-standing nanowire surfaces.

We demonstrate high-fidelity guidance of axons using rows of nanowires. The axons are prevented from crossing the rows, making it possible to guide and sort a large number of axons as opposed to when chemical patterns are used. Focal adhesion forms at the nanowires establishing a possible site of information transfer between the surface and the cells. Rows of gallium phosphide (GaP) nanowires were epitaxially grown on GaP(111) substrates in patterns defined by electron beam lithography.

Gallium phosphide nanowires as a substrate for cultured neurons.

Dissociated sensory neurons were cultured on epitaxial gallium phosphide (GaP) nanowires grown vertically from a gallium phosphide surface. Substrates covered by 2.5 microm long, 50 nm wide nanowires supported cell adhesion and axonal outgrowth. Cell survival was better on nanowire substrates than on planar control substrates. The cells interacted closely with the nanostructures, and cells penetrated by hundreds of wires were observed as well as wire bending due to forces exerted by the cells.