Abstract: In one example in accordance with the present disclosure, a fluid manipulation system is described. The fluid manipulation system includes a microfluidic channel through which fluid is to flow. The fluid includes biomolecules to be separated. The fluid manipulation system also includes at least one array of biomolecule-capturing pillars disposed within the microfluidic channel to capture biomolecules from the fluid. Barriers rise from a surface of the microfluidic channel. The barriers span a width of the microfluidic channel orthogonal to a flow of the fluid to induce vortices in the fluid flow.