A Diesel Particulate Filter (DPF) from the future.   

    General Motors is developing  a new type of DPF that is said to remove soot (particulate matter PM) while improving fuel consumption tenfold versus today's DPFs.

Traditional DPFs  have no way of cleaning themselves when they are full of soot. This being the case the engine squirts precious fuel down the exhaust pipe creating high heat (at least 1,112 degrees) needed to incinerate the particulate. Manufactures call this process regeneration. Too bad it has such a degenerate effect on mpg.

Back to the new technology. Instead of sending fuel down the pipe the new DPF has its own heat source. The source is concentrated only at the beginning of the DPF. The tail pipe is said to keep cool. There are over 40 patents in process so details are tough to get. Michigan Technological University and HRL Laboratories in Malibu, CA helped in this project.