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Three-Dimensional, Flexible Nanoscale Field-Effect Transistors as Localized Bioprobes

Science  13 Aug 2010:
Vol. 329, Issue 5993, pp. 830-834
DOI: 10.1126/science.1192033

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Nanoprobes of Cell Potential

Direct electrical measurements of cell potentials usually face design compromises. Microelectrodes probe within the cytosol of cells but have a minimum size (hundreds of nanometers in width) for obtaining useful signals. Nanoscale field effect transistors (FETs) can have an active probe size of only tens of nanometers but generally allow only the outer cell potential to be measured. Tian et al. (p. 830) fabricated nanowires in which kinks could be introduced to create a sharp probe tip pointing away from the fabrication substrate. Coating the tip with a phospholipid bilayer allowed the probe to be inserted through the membranes of beating cardiac cells, where it could be used to follow temporal changes in cell potential.

Abstract

Nanoelectronic devices offer substantial potential for interrogating biological systems, although nearly all work has focused on planar device designs. We have overcome this limitation through synthetic integration of a nanoscale field-effect transistor (nanoFET) device at the tip of an acute-angle kinked silicon nanowire, where nanoscale connections are made by the arms of the kinked nanostructure, and remote multilayer interconnects allow three-dimensional (3D) probe presentation. The acute-angle probe geometry was designed and synthesized by controlling cis versus trans crystal conformations between adjacent kinks, and the nanoFET was localized through modulation doping. 3D nanoFET probes exhibited conductance and sensitivity in aqueous solution, independent of large mechanical deflections, and demonstrated high pH sensitivity. Additionally, 3D nanoprobes modified with phospholipid bilayers can enter single cells to allow robust recording of intracellular potentials.

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