Tom Duke
Teaching
Miscellaneous
Sorting biomolecules: The efficient separation of macromolecules is a key component of many analytical and preparative techniques in biology. Nanotechnology promises to transform separations science by permitting the construction of miniature devices that have numerous advantages over traditional methods like gel electrophoresis; these include rapidity, reproducibility, ready automation, and the ability to handle very small samples.
Arrays for pulsed-field electrophoresis: DNA molecules confined in a quasi-2-dimensional lattice of pillars move with much greater regularity than they do in a gel. This simple dynamical behaviour can be exploited to provide ultra-fast separation using pulsed fields. Employing a hexagonal array of posts, and switching the field through 120 degrees, molecules can be made to backtrack along their path before they move off in the new field direction. We have demonstrated fractionation of 100 kilobase DNA in less than 10 seconds -- three orders of magnitude faster than existing methods.
Microfabricated sieve for continuous sorting: An entirely different approach makes use of rectified diffusion of molecules flowing in an asymmetric environment. We have designed a molecular sieve which permits the continuous sorting of a mixture of molecules that is injected in a fine stream. The device consists of a periodic array of oblong obstacles, which deflect the molecules so that each species follows a different trajectory, oblique to the flow. Since different types of molecule are carried to distinct locations, this technique is well-suited to integration with subsequent analytical steps, and could therefore be a useful component of lab-on-a-chip devices.
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