Active deformation enhances target scanning in crowded two-dimensional self-propelled particle simulations.

Self-propelled particles (SPPs) model diverse transport phenomena, including T-cell motility within crowded lymph nodes. Efficient scanning of antigen-presenting cells (APCs) by T cells remains poorly understood under dense conditions. Here we simulate a two-dimensional system of radius-oscillating SPPs with random propulsion directions and short-range interactions to mimic T-cell scanning of a low-mobility APC. We find that scanning rate peaks at an optimal oscillation frequency and intermediate area fraction, with maximal efficiency in the processive limit of motion. This optimum arises from local inflow dynamics near the target and coincides with a percolation transition in the particle contact network. Active deformation enhances scanning efficiency compared to nonoscillating particles, especially at higher densities. These findings suggest that mechanical interactions and active shape changes facilitate effective target exploration in crowded environments, providing insights relevant to cellular transport and active matter systems.