DNA and Gold Nanoparticles Form 3D Nanoscaffolds
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sensor arrays with tunable spectral response” and the dry polymer deposition process “is compatible with batch microfabrication processing.” STEVEN TROHALAKI
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DNA and Gold Nanoparticles Form 3D Nanoscaffolds
Figure 1. (a) Schematic illustration of a bimaterial cantilever bending with incident heat. (b) Side view of an optical image of a polymer–silicon microcantilever bending as the temperature increases 20–40°C. Reproduced with permission from Nano Letters 6 (4) (April 12, 2006) p. 730; DOI: 10.1021/nl0525305. © 2006 American Chemical Society.
sometry to be in the range of 20–200 nm. AFM revealed that the PS layer has a smooth, uniform surface morphology and an elastic modulus of nearly 2 GPa. In addition, the PS could not be dissolved in or swollen by organic solvents. Compressive residual stresses arising from PECVD of PS result in a bent and stressed bimorph beam (see Figure 1), whose initial parameters can be controlled by deposition conditions. The researchers showed that deflections of their microcantilever as a function of temperature within either a narrow temperature range (30–31ºC) or a broader range (20–45ºC) are many times higher than those of a reference microcantilever composed of silicon with a 60-nm gold layer, which is the common materials platform for uncooled IR bimaterial microsensors. The thermal sensitivity of 1–2 nm/mK is much higher than that displayed by the gold–silicon reference (0.056 nm/mK) or the value achieved by the best uncooled microcantilever IR detectors (0.12 nm/mK) currently on the market. Using a mathematical analysis, the researchers concluded that the intrinsic stress within the PS layer reverses sign and becomes tensile at the elevated temperature at which their microcantilevers attain planarity. In a temperature range of 20–45ºC, the overall variability between the first and 100th cycle was
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