A finite-cluster phase in λ-DNA-coated colloids
We studied the aggregation of 1 Âµm colloids bridged by DNA with 32 Âµm contour length. We mixed two species of particles with grafted double-stranded ?-DNA displaying short, complementary single-stranded overhangs as free binding-ends. Confocal microscopy showed the formation of stable, size-limited clusters in which the two species of particles were at touching contact. Simulations suggest that the observed close contact and the limitation to grow both result from entropic exclusion of the bridging DNA from the space between nearby particle surfaces.