Phototaxis of mobile excitable lattices

A two-dimensional lattices, cells of which excite depending on exact numbers of their excited neighbors, exhibit rich patterns of space-time behavior: from chaotic activity to traveling waves to swarms of self-localized excitations. What happens if we supply each cell of a lattice with its own cilium, which beats in a direction determined by local dynamic of excitation around the cell, and make edge cells of the lattice excite light sensitively? Do lattices move toward a source of light? What types of lattice motility are observed? What classes of local excitation functions can we define from trajectories of lattice movement? We answer the questions by means of computer experiments. We demonstrate that a set of local excitation rules can be classified into four groups depending on how often the lattices hit light target and how they move toward the light source. Each class of the functions is studied in respect to lattice activity levels, inhomogeneity and sensitivity of excitation rules, and efficiency of lattice motion.