In a recent study, published in Nanotechnology, scientists in Sweden have investigated a totally new printable approach to manufacturing nanoelectromechanical systems (NEMS). The devices are based on nanometre-sized, high aspect ratio, tuneable grating structures (interdigitated pairs of walls). Because the structures are fixed along their length at the bottom, in contrast to free cantilevers, the device can be fabricated directly by nanoimprint lithography in a photoresist or a plastic material.
Following a metallization step, the structures are ready for use. Almost any kind of substrate could be used, even no substrate at all. Some of the functioning devices were printed directly into plastic foil. A DC voltage applied to the metal layer on top of the structures gives rise to an electrostatic force between the walls whereupon the upper parts of the fingers bend towards each other. Adding an AC voltage causes an oscillatory motion, which allows for frequency response measurements in which the resonance frequency is recorded. This property was also used in the main application: a gas sensor. Airborne molecules may be caught on the sensor surface and by adding their mass to the oscillating walls they reduce the resonance frequency. It's hard to believe, but the plastic structures oscillate at frequencies of a few hundred megahertz, which together with the light material makes the device's responsitivity exceptionally high (0.1 Hz/zeptogram).
The same technique may also be used for other applications such as optical and sub-wavelength gratings, accelerometers and radio frequency devices. The plastic NEMS show that micromechanics may follow the examples of both microelectronics and photonics by also moving into the world of polymers.
Source: nanotechweb.orgAdded: 7 May 2009