Fabrication of a NCD microelectrode array for amperometric detection with micrometer spatial resolution

Abstract

We report on the fabrication of a boron-doped nanocrystalline diamond (NCD) 3 × 3 high-density microelectrode array (MEA) for amperometric measurements, with a single electrode area of 3 × 5 μm 2 and a separation in the μm scale. The NCD microelectrodes were grown by hot filament chemical vapor deposition (HFCVD) on a double-side polished sapphire wafer in order to preserve the diamond transparency. Bias enhanced nucleation (BEN) was performed to ensure a covalent adhesion of the films to the substrate. A current background noise of less than 5 pA peak to peak over a 1 kHz bandwidth resulted from an electrochemical investigation of the new device, using 100 mM KCl solutions and ferrocyanide red-ox couples. Cyclic voltammetry measurements in physiological buffer solution and in the presence of oxidizable biomolecules strengthened its suitability for bio-sensing. When compared to a 2 × 2 NCD microelectrode array prototype, already used for in vitro cell measurements, the signal to noise ratio of the amperometric response of the new 3 × 3 device proved twice as good. In addition, the optical transmittance of the boron-doped thin layers exceeded 40% in the visible wavelength range. The excellent electrochemical properties of NCD electrodes and the transparency in combination with the high spatial resolution make the new 3 × 3 NCD MEA a promising tool for electrochemical sensing in a variety of applications, ranging from medical to industrial, in neutral or harsh environments.

Heterogeneous distribution of exocytotic microdomains in adrenal chromaffin cells resolved by high‐density diamond ultra‐microelectrode arrays

“…As previously reported, the main advantages of using boron-doped NCD-UMEAs to record amperometric signals are: the electrochemical stability, the large hydrolysis window, robustness, the transparency from the far infrared to UV, and the possibility of using CVD, photolithography and dry-etching techniques to construct microarrays of defined geometries Colombo et al 2011). With respect to our previous NCD prototypes Pasquarelli et al 2011) here we provide an advanced array geometry to spatially identify microdomains of neurosecretion in single chromaffin cells.…”

“…The 9‐Ch NCD‐UMEA is constructed by growing the nanocrystalline diamond (NCD) thin film on a double‐sided polished sapphire wafer (Epistone, Longgang, Shenzhen, China, 2 inch DSP wafers), after an initial bias‐enhanced nucleation process, which ensures strong covalent adhesion of the NCD film on the substrate (Colombo et al . ). A 200 nm NCD intrinsic layer is grown by means of hot filament chemical vapour deposition (HFCVD).…”

“…Given the importance of resolving the molecular events controlling the exocytotic machinery at higher‐spatial resolution, we recently fabricated a high‐density diamond ultra‐microelectrode array with nine recording channels (9‐Ch NCD‐UMEA), whose overall area fits the size of a bovine chromaffin cell (Colombo et al . ). The microchip relies on the outstanding properties of boron‐doped nanocrystalline diamond (Carabelli et al .…”

Electrochemical Sensors and Biosensors

“…The modification of these microelectrode arrays could potentially make this a powerful detection method for a number of different analytes. Colombo et al 102 used a microelectrode array of boron-doped nanocrystalline diamond to perform amperometric measurements with micrometer spatial resolution. The excellent electrochemical properties of the electrodes coupled with the transparency and high spatial resolution of the array makes this sensor attractive for numerous applications.…”

Progress in transparent diamond microelectrode arrays

“…Lately a 9‐channels (9‐Ch) ultra‐micro electrode array (uMEA) showed a signal to noise ratio of amperometric responses twice as good, compared to the 4‐Ch MEA and the ability to spatially resolve microdomains of cell secretory activity .…”