There is provided system and a separation substrate device for use with an NLM separator in separating and/or detecting at least one target analyte in a sample, the substrate comprising a micromagnet array of a plurality of micromagnets, the micromagnet array comprising a first capture region, a second focussing region, and, a third detection region, the focussing region comprising a converging and/or diverging micromagnet array region. Also provided is a method for separating and detecting at least one target analyte in a sample. The method including: contacting a plurality of magnetic beads with a sample, the magnetic beads functionalized for binding with one or more target analytes in a sample to form aggregates; providing the sample including magnetic beads and aggregates to a separating substrate comprising a micromagnet array of a plurality of micromagnets; transporting the magnetic beads and aggregates relative to the micromagnet array to provide separation and enable detection of the magnetic beads an
