Vertical Oxide Nanotubes Connected by Subsurface Microchannels

We describe the fabrication of arrays of oxide nanotubes using a combination of bottom up and top down nanofabrication. The nanotubes are made from epitaxially grown semiconductor nanowires that are covered with an oxide layer using atomic layer deposition. The tips of the oxide-covered nanowires are removed by argon sputtering and the exposed semiconductor core is then selectively etched, leaving a hollow oxide tube. We show that it is possible to create fluidic connections to the nanotubes by a combination of electron beam lithography to precisely define the nanotube positions and controlled wet under-etching. DNA transport is demonstrated in the microchannel. Cells were successfully cultured on the nanotube arrays, demonstrating compatibility with cell-biological applications. Our device opens up the possibility of injecting molecules into cells with both spatial and temporal control.