题目:Transparent nanoelectrode array with pA background current in diamond technology
Microelectrode arrays (MEAs) are commonly used to analyse electrical activity of cells and membranes. They have been realized on many substrate materials with individal dimensions in the range of typically 10 to 25 ?m to take advantage of 3D spherical diffusion characteristics. Here we report on an MEA on sapphire with electrodes realized by highly boron doped nanocrystalline diamond films. This configuration will allow using the unique electrochemical properties of diamond (e.g. high electrochemical activity without fouling, large potential window of water dissociation enabling oxidizing most organic molecules, high corrosion resistance). Used here is the layout of a quadropole configuration, where the total electrode area exposed to the liquid is approx. that of the cell investigated (approx. 15 ?m diameter). Early experiments on this macroscopic configuration have been published recently . In this work we downscale the individual electrodes to a diameter of 500 nm. Common microelectrodes may have a nm-size patterned surface, mostly using metallic nanoclusters, thus cannot be addressed individually. The array technology is in most cases still immature. Here planar nanospot electrodes have been implemented into a planar diamond MEA technology. The nanospot electrodes can be biased individually, allowing individual analysis by cyclic voltammetry and impedance spectroscopy. The transparent sapphire substrate allows simultaneous fluorescence analysis. Challenging features have been to reach a background current in the lower pA-range and the extraction of redox reactions which are also in the pA-range for this electrode dimension.
The goal is to bring the array in contact with a cell membrane and measure individual channel activities. Usually, many channels are activated in parallel not allowing to see the response of an individual channel. The diameter of such channel is below 50 nm, and thus still by a factor of at least 10 smaller than that of the electrode diameter at present. Further downscaling will not only be in geometry but also reduction in electrode leakage, capacitive loading and current measurement resolution. However, extrapolation of the present data suggests already that electrodes in the 100 nm range diameter seem possible.
 Z.Gao et.al. J. Micro-Nano Mech. (2011) 6:33-37
 Z.Gao et.al. 22nd European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes, and Nitrides, Oral contribution, 2011