Structures for lossless ion manipulations (SLIM) are a form of ion optics to which various radio frequency and dc electric potentials can be applied and used to enable a broad range of ion manipulations, such as separations based upon ion mobility spectrometry, reactions (unimolecular, ion-molecule, and ion-ion), and storage (i.e. ion trapping).  SLIM was developed by Richard D. Smith and coworkers at Pacific Northwest National Laboratory (PNNL) and are generally fabricated from arrays of electrodes on evenly spaced planar surfaces. In 2017, Erin S. Baker, Sandilya Garimella, Yehia Ibrahim, Richard D. Smith and Ian Webb from the Interactive Omics Group of PNNL received the R&D 100 Award for the development of SLIM.
In SLIM, ions move in the space between the two surfaces, in directions controlled using electric fields, and also moved between different of multi-level SLIM, as can be constructed from a stack of printed circuit boards (PCBs). The lossless nature of SLIM is derived from the use of rf electric fields, and particularly the pseudo potential derived from the inhomogeneous electric fields resulting from rf of appropriate frequency applied to multiple adjacent electrodes, and that serves to prevent ions from closely approaching the electrodes and surface where loss would conventionally be expected.  SLIM are generally used in conjunction with mass spectrometry for analytical applications.