Bottom-up nanotechnology to be speeded by nanoliter-on-a-chip reactors

Great news in the August 2006 issue of Nano Today in an opinion piece by two UCLA researchers, Guodong Sui and Hsian-Rong Tseng, titled “Reactions in hand: Digitally controlled microreactors are providing chemists with a new playground for discovery.”

First, some background. As an MIT undergrad in chemistry, I tried to make reactions work in the lab. Even procedures that were specifically designed for newbies, presumably tested repeatedly over the years, often did not work for many of us. Molecules are not like bits — software engineers are able to order the 1’s and 0’s in whatever order they wish. The final software product may not do what they want, but it’s not because the 1’s and 0’s refuse to be in the order the designer wishes them to be. Not so with molecular designs: not only may the final product not perform as desired, but persuading the atoms to connect up to match a given design can be frustratingly difficult. Repeatability is essential in figuring out what is going on and how to improve the process.

To make things worse, every time a reaction was run in those days, relatively large amounts of chemicals were needed, often nasty organic solvents and toxic reactants. The environmental costs were significant. Today, this problem translates into higher disposal costs, reducing funds available for direct research.

Sui and Tseng tell us that things are changing for the better, and this can only be good for bottom-up, molecularly-precise nanotechnology:

In the past two decades, significant efforts have been made to create microreactors in which tedious chemical operations can be carried out with reduced chemical consumption, greater precision, increased speed, and improved fidelity and efficiency compared with conventional approaches. The advent of microfluidic technology makes such microreactors achievable, especially now that soft lithography techniques have become available. The simplest configuration of microreactor is based on a network of microchannels. In general, the sizes of the microchannels are in the micrometer range, which enables the handling of nanoliter quantities of reaction volumes. Reagents and solvents are introduced into the microreactors by syringes through tubing connections. In these cases, reactions can be accomplished with great efficiency because of the short diffusion paths and high surface-to-volume ratios in the micrometer-scale environment…

With these functional modules in hand, it is now feasible to handle complicated chemical processes in a microreactor in an automated fashion…

Most chemical processes fall into either sequential or parallel reactions. The two types of microreactor described confirm that many reactions can be designed to occur in sequence and parallel on single chips. In addition to the intrinsic advantages of microfluidics, integrated microreactors provide a new playing field for chemists to test and carry out reactions beyond conventional bench-top settings.

In addition, it is important to note that, from concept to working chip, each microreactor takes less than three working days to construct because of the use of soft lithography.

Click through to the original article to see impressive photos of the microreactors. Kudos to the team involved, from UCLA, Caltech, Stanford, Siemens Biomarker Solutions, and Fluidigm! And thanks to Cordelia Sealy of Nano Today for publishing the piece. —Christine

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