<p>A mixture of beads from a combinatorial library is held in suspension either by inducing circulating flow of a liquid in a tapered vessel by rising air bubbles or by floating the beads at the interface between two immiscible liquids. Beads are selected individually from the suspension by drawing liquid into the tip of a needle having a circular opening smaller than the diameter of a bead. After a bead is captured on the tip of a needle, excess beads are jarred loose or washed away by flow of a solvent through a sheath surrounding the needle, and the needle is moved by a robotic manipulator to a well into which the bead is released.</p>
