Slip-X-Chip: A Sliding Microfluidic Platform with Cross-Flow

In sliding microfluidic platforms ("SlipChip" [1]), two plates with microfluidic wells slide in close contact to perform multiplexed reactions in a single operation. In-plane "sliding-flow" liquid transport, however, limits the potential assay operations to 1) sample compartmentalization/metering, 2) reagent addition, 3) mixing, and 4) aliquoting. Here, we introduce a three-plate sliding microfluidics platform, "Slip-X-Chip", that additionally includes out-of-plane "cross-flow" liquid transport. Slip-X-Chip allows two additional assay operations: 5) sample concentration and 6) liquid exchange/washing, while retaining the simplicity of operation (one-step operation; no precise pipetting required; no external equipment). These additional assay operations extend the range and complexity of applications enabled by sliding microfluidics. We here demonstrate 1) splitting bead solutions in compartments with different concentrations and 2) compartmentalizing human cells from solution, followed by a viability assay. We foresee that Slip-X-Chip could be further adapted to, e.g., cell counting, cell staining, or ELISA.