We report the development of useful chemical sensors from chemically converted graphene dispersions using spin coating to create single-layer films on interdigitated electrode arrays. Dispersions of graphene in anhydrous hydrazine are formed from graphite oxide. Preliminary results are presented on the detection of NO 2 , NH 3 , and 2,4-dinitrotoluene using this simple and scalable fabrication method for practical devices. Current versus voltage curves are linear and ohmic in all cases, studied independent of metal electrode or presence of analytes. The sensor response is consistent with a charge transfer mechanism between the analyte and graphene with a limited role of the electrical contacts. A micro hot plate sensor substrate is also used to monitor the temperature dependence of the response to nitrogen dioxide. The results are discussed in light of recent literature on carbon nanotube and graphene sensors.

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Graphene's single atomic layer of sp(2) carbon has recently garnered much attention for its potential use in electronic applications. Here, we report a memory application for graphene, which we call graphene flash memory (GFM). GFM has the potential to exceed the performance of current flash memory technology by utilizing the intrinsic properties of graphene, such as high density of states, high work function, and low dimensionality. To this end, we have grown large-area graphene sheets by chemical vapor deposition and integrated them into a floating gate structure. GFM displays a wide memory window of ∼6 V at significantly low program/erase voltages of ±7 V. GFM also shows a long retention time of more than 10 years at room temperature. Additionally, simulations suggest that GFM suffers very little from cell-to-cell interference, potentially enabling scaling down far beyond current state-of-the-art flash memory devices.

Electrowetting and dielectrophoretic actuation are potentially important microfluidic mechanisms for the transport, dispensing, and manipulation of liquid using simple electrode structures patterned on a substrate. These two mechanisms are, respectively, the low- and high-frequency limits of the electromechanical response of an aqueous liquid to an electric field. The Maxwell stress tensor and an RC circuit model are used to develop a simple predictive model for these electromechanics. The model is tested by measuring electric-field-induced pressure changes within an aqueous droplet trapped between two parallel, disk-shaped electrodes immersed in a bath of immiscible, insulating oil. The experiment is an adaptation of Quincke's original bubble method for measuring the dielectric constant of a liquid. For AC voltages lower than ∼100 V-rms, the pressure data largely conform to the square-law predictions of the model. At higher voltages, this square-law behavior is no longer evident, a result consistent with the well-known contact angle saturation effect. Pressure data obtained with DC electric fields are not consistent with either the lowest frequency data (10 Hz) or with the model.