Trapping Molecules on a Chip

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Science  26 Jun 2009:
Vol. 324, Issue 5935, pp. 1699-1702
DOI: 10.1126/science.1175975

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CO on a Chip

Microfluidics technology has facilitated remarkable miniaturization of chemical synthesis platforms; through electrically gated solution flow and mixing, molecular reactions can be carried out on chips several centimeters across. When it comes to more fundamental dynamics studies, though, which involve probing gas-phase molecules in specific quantum mechanical states, the experiments still tend to require much larger interaction areas. Meek et al. (p. 1699) take a step toward miniaturization in this latter regime by demonstrating the isolation of a cold gas-phase beam of CO molecules just above a microelectrode-decorated chip. The technique relies on rapidly modulated electric fields that trap and then slow down the incoming molecules through dipole interactions. Once brought to a stop, the molecules can be held on the chip for a discrete period and then released to a detector.


Magnetic trapping of atoms on chips has recently become straightforward, but analogous trapping of molecules has proved to be challenging. We demonstrated trapping of carbon monoxide molecules above a chip using direct loading from a supersonic beam. Upon arrival above the chip, the molecules are confined in tubular electric field traps ~20 micrometers in diameter, centered 25 micrometers above the chip, that move with the molecular beam at a velocity of several hundred meters per second. An array of these miniaturized moving traps is brought to a standstill over a distance of only a few centimeters. After a certain holding time, the molecules are accelerated off the chip again for detection. This loading and detection methodology is applicable to a wide variety of polar molecules, enabling the creation of a gas-phase molecular laboratory on a chip.

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