Relying on the local readout of minute electric currents within neurons and nerve cells, one way to improve electrophysiological human-machine interfaces, is to increase the resolution (both spatial and temporal) of the probes in use, moving from micrometer-sized devices to nanometre-sized probes.
Following this trend, a team of researchers from the University of Surrey and Harvard University have devised U-shaped nanowire field-effect transistor (U-NWFET) arrays, using a scalable production process whereby they could accurately tune the probes’ geometry. Because they could modulate the location, size and geometry of each probe (including the radii of curvature and the length of the FET sensing elements at the tips of the U-shaped nanowire probes), the researchers were able to systematically investigate how these parameters influenced intracellular electrophysiological recordings. Playing with various process parameters, they went on fabricating arrays of U-NWFET probes ranging from 15nm-diameter p-type Si nanowires with radii of curvature ranging from 0.75 to 2μm and active channel lengths from 50 to 2,000nm and then used them to probe cultured primary neurons and human cardiomyocytes.
The results published in a Nature Nanotechnology paper under the title “Scalable ultrasmall three-dimensional nanowire transistor probes for intracellular recording” revealed comparable recording signal-to-noise ratio and amplitude to those of patch clamp measurements, with the capability to record full amplitude intracellular action potentials from primary neurons and other electrogenic cells, while also offering the possibility to perform multiplexed recordings (with multiple wire tips of different curvatures).