TY - JOUR AB - In this Letter, we explore experimentally the phase behavior of a dense active suspension of self-propelled colloids. In addition to a solidlike and gaslike phase observed for high and low densities, a novel cluster phase is reported at intermediate densities. This takes the form of a stationary assembly of dense aggregates—resulting from a permanent dynamical merging and separation of active colloids—whose average size grows with activity as a linear function of the self-propelling velocity. While different possible scenarios can be considered to account for these observations—such as a generic velocity weakening instability recently put forward—we show that the experimental results are reproduced mathematically by a chemotactic aggregation mechanism, originally introduced to account for bacterial aggregation and accounting here for diffusiophoretic chemical interaction between colloidal swimmers. AU - Theurkauff, I. AU - Cottin-Bizonne, C. AU - Palacci, Jérémie A AU - Ybert, C. AU - Bocquet, L. ID - 9014 IS - 26 JF - Physical Review Letters SN - 00319007 TI - Dynamic clustering in active colloidal suspensions with chemical signaling VL - 108 ER -