September 05, 2009

NanoPen: Low-Power, and Light-Actuated Patterning of Nanoparticles

Nanoletters Journal: NanoPen: Dynamic, Low-Power, and Light-Actuated Patterning of Nanoparticles (H/t Brett Coalson)

We introduce NanoPen, a novel technique for low optical power intensity, flexible, real-time reconfigurable, and large-scale light-actuated patterning of single or multiple nanoparticles, such as metallic spherical nanocrystals, and one-dimensional nanostructures, such as carbon nanotubes. NanoPen is capable of dynamically patterning nanoparticles over an area of thousands of square micrometers with light intensities <10 W/cm2 (using a commercial projector) within seconds. Various arbitrary nanoparticle patterns and arrays (including a 10 × 10 array covering a 0.025 mm2 area) are demonstrated using this capability. One application of NanoPen is presented through the creation of surface-enhanced Raman spectroscopy hot-spots by patterning gold nanoparticles of 90 nm diameter with enhancement factors exceeding 10^7 and picomolar concentration sensitivities.

The NanoPen could provide a quick, convenient way of laying down patterns of nanoparticles — from wires to circuits — for making electronic devices, medical diagnostic tests, and other applications.

7 pages of supporting info on the nanopen.

Patterning of Multi-wall Carbon Nanotubes
The NanoPen patterning process of multi-walled carbon nanotubes (MWCNTs) is seen below. It is important to note that during the patterning process, the CNTs are oriented vertically due to the torque experienced by 1-dimensional nanostructures in the electrical fields. However, after the patterning process is completed and the AC voltage is removed, the 1-dimensional structures fall on the surface with random orientations which increases the effective linewidth of the patterned structures. One potential way to achieve better orientation of these structures would be to use a lateral field optoelectronic tweezer (LOET) device.

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