(5bu) Molecular Handles: Nanoscale Chemical Engineering with Optoelectronic Tweezers

The design and fabrication of future nanoscale devices for applications in biotechnology, communications, information processing, and energy conversion will require massive parallelism, low cost, as well as the ability to address a range of both inorganic and organic nanostructures with many different sizes, shapes, and chemistries. In addition to massive parallelism, an ideal fabrication platform will also have the ability to address single structures at molecular length scales. Employing chemical engineering fundamentals such as momentum, heat, and mass transfer will be crucial in realizing future nanoscale design goals. For instance, due to the extremely low Reynolds numbers at sub-micron dimensions, the forces employed in solution-phase processing must overcome viscous drag while withstanding significant randomizing effects from Brownian mass transfer.

Optoelectronic tweezers (OET) have emerged in recent years [1] as a low-cost, massively parallel means for the optical assembly of both inorganic and biological building blocks using 100,000x less optical power than conventional laser tweezers [2]. Recent work with OET [3] has demonstrated that the separation of semiconducting and metallic nanowires is possible based on the large intrinsic differences in conductivity and dielectric constant between silicon and silver nanowires. A similar approach can be extended to multi-walled carbon nanotubes (CNTs) [4] and fluorescently-labeled single-walled CNTs, promising a flexible new approach to nanoscale separations with far-reaching implications for future engineering with near-molecular scale materials.

Furthermore, heat transfer and temperature distributions are significant constraints in addressing biological nanostructures. Current work with the ellipsoidal pathogenic bacterium 'Y. pestis' (bubonic plague) requires a thorough understanding of heat generation and transfer within the OET device. Thermal measurements with a thermographic infrared camera correlate well with finite-element simulations of heat transfer in OET chambers, suggesting that OET is a powerful new platform for future chemical engineering with inorganic and biological nanostructures.

[1] Chiou, P.Y. et al., Nature (2005)

[2] Pauzauskie, P.J. et al. Nature Materials (2006); Nakayama, Y.*; Pauzauskie, P.J.*; et al., Nature (2007)

[3] Jamshidi, A.*; Pauzauskie, P.J.*; et al., Nature Photonics (2008)

[4] Pauzauskie, P.J.*; Jamshidi, A.*; et al., Applied Physics Letters (in press, 2009)

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