Whatever happened to the Dust Sail?

I haven't seen any news on the "dust sail" concept for quite a while.
Has research on the subject been shelved? Supposedly, ionized
particles could be effectively linked to a rotating magnetic field
(generated by a spacecraft) to form a "dust disk", and somehow there
would be a transfer of thrust from this "dust disk" solar sail back to
the magnetic field and then to the craft. There was some speculation
that such a disk could be added to an M2P2 spacecraft. Any news?