In this report, the fabrication of vertically aligned carbon nanotube nanoelectrode array (VACNT-NEA) by photolithography method is presented. Electrochemical impedance spectroscopy as well as cyclic voltammetry was performed to characterize the arrays with respect to different diffusion regimes. The fabricated array illustrated sigmoidal cyclic voltammogram with steady state current dominated by radial diffusion. The fabricated VACNT-NEA and high density VACNTs were employed as electrochemical glutamate biosensors. Glutamate dehydrogenase is covalently attached to the tip of CNTs. The voltammetric biosensor, based on high density VACNTs, exhibits a sensitivity of 0.976 mA mM(-1) cm(-2) in the range of 0.1-20 μM and 0.182 mA mM(-1) cm(-2) in the range of 20-300 μM glutamate with a low detection limit of 57 nM. Using the fabricated VACNT-NEA, the sensitivity increases approximately to a value of 2.2 Am M(-1) cm(-2) in the range of 0.01 to 20 μM and to 0.1 A mM(-1) cm(-2) in the range of 20-300 μM glutamate. Using this electrode, a record of low detection limit of 10 nM was achieved for glutamate. The results prove the efficacy of the fabricated NEA for low cost and highly sensitive enzymatic biosensor with high sensitivity well suited for voltammetric detection of a wide range of clinically important biomarkers.

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The authors report the realization of highly featured three-dimensional structures on silicon substrates with a single masking layer using a hydrogen-assisted deep reactive ion etching process. Oxygen, hydrogen, and SF6 are used in a sequential passivation and etching process to achieve high aspect ratio features. By controlling the flows of these gases and the power and timing of each subsequence, it is possible to achieve desired deep vertical etching, controlled underetching, and recovery, yielding three-dimensional features directly on silicon substrates. Etch rates up to 0.75 μm/min have been achieved with a low plasma power density of 1 W/cm2. In addition, features with a controllable underetching and recovery with more than 8 μm in sidewall recession have been achieved. Furthermore, values of aspect ratio higher than 40 can be obtained. The formation of three-dimensional features with nanowall structures is reported.

Silicon nanograss and nanostructures are realized using a modified deep reactive ion etching technique on both plane and vertical surfaces of a silicon substrate. The etching process is based on a sequential passivation and etching cycle, and it can be adjusted to achieve grassless high aspect ratio features as well as grass-full surfaces. The incorporation of nanostructures onto vertically placed parallel fingers of an interdigital capacitive accelerometer increases the total capacitance from 0.45 to 30 pF. Vertical structures with features below 100 nm have been realized.

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