It is an ion optical device comprised on electrodes patterned on planar surfaces. Specifically, it consists of two parallel stacked circuit board (looks a bit like a sandwich) each having an array of DC guard electrodes and an array of central rung electrodes having a DC with superimposed RF similar to a conventional multipole.
Ion dynamics are similar to a multipole. Static DC guard voltage confine the ions laterally and the dynamic RF/DC voltages of the rung electrodes create a pseudo potential with a low energy region close to the central axis of the fly path to maintain the ions close to the center.
Performance wise, the linear SLIM system at a static pressure of 5-6mbar exhibits ion mobility resolution of 55 FWHM and is capable of doing tandem IMS. Since IMS resolution in drifttube ion mobility for a given ion pulse length and ion charge depends on length of drift tube, longer SLIM devices may provide higher IMS resolution.