Doing some research on cyclonic dust collection. These systems have been in use in industry, apparently for some time now. I won't comment on just how Dyson may have done anything unique in this regard, but I did find an interesting web site that explains a lot about cyclonic dust collection. Specifically, it's by a woodworker hobbyist who found that the commercial hobbyist cyclonic dust collection system he was using was basically worthless, capturing only a small percentage of the wood dust and leaving the rest to clog the fine filters in short order. So he set about to design his own, and has published all the of information he's gathered on the subject. His efforts, according to his web site, have led to a system that is effective at removing 95% of the fine dust, with relatively little left to be handled by the fine filters.
Some of this may be applicable to fans of cyclonic vacuum cleaners. The most interesting part is his discovery that a ratio of cyclone length to width of about 1.6 to 1 is nearly as effective as the ideal ratio of 3 to 1.