Composite Search of Active Particles in Three‐dimensional Space Based on Non‐directional Cues

Abstract We theoretically address minimal search strategies of self‐propelled particles towards hidden targets in three‐dimensional space. The particles can sense if targets are close, e. g., by detecting released signaling molecules, but they cannot deduce directional cues. We investigate composite search strategies, where particles switch between extensive outer search and intensive inner search; inner search is started when proximity of a target is detected and ends when a certain inner search time has elapsed. In the simplest strategy, active particles move ballistically during outer search, and transiently reduce their directional persistence during inner search. In a second, adaptive strategy, particles exploit a dynamic scattering effect by reducing directional persistence only outside a well‐defined target zone. These two search strategies require only minimal information processing capabilities, yet increase target encounter rates substantially. The optimal inner search time scales as power‐law with exponent −2/3 with target density, reflecting a trade‐off between exploration and exploitation.