Active targeting in a random porous medium by chemical swarm robots with secondary chemical signaling

The multibody dynamics of a system of chemical swarm robots in a porous environment is investigated. The chemical swarm robots are modeled as Brownian particles capable of delivering an encapsulated chemical payload toward a given target location and releasing it in response to an external stimulus. The presence of chemical signals (chemo-attractant) in the system plays a crucial role in coordinating the collective movement of the particles via chemotaxis. For a number of applications, such as distributed chemical processing and targeted drug delivery, the understanding of factors that govern the collective behavior of the particles, especially their ability to localize a given target, is of immense importance. A hybrid modeling methodology based on the combination of the Brownian dynamics method and diffusion problem coupled through the chemotaxis phenomena is used to analyze the impact of a varying signaling threshold and the strength of chemotaxis on the ability of the chemical robots to fulfill their target localization mission. The results demonstrate that the selected performance criteria (the localization half time and the success rate) can be improved when an appropriate signaling process is chosen. Furthermore, for an optimum target localization strategy, the topological complexity of the porous environment needs to be reflected.

Figure 1

Progress of a typical target localization mission of Brownian particles (indicated by dots) in a porous medium. The contaminant source is indicated by a cross and the contaminant concentration by the light gray (cyan) gradient ($c^{*}=0.3$). The concentration of the chemical signals is indicated by the dark gray (magenta) gradient.

Figure 2

The target localization time distribution and the success rate (a) without and (b) with chemical signaling ($c^{*}=0.3$).

Figure 3

(a), (d), (g) Dependence of the target localization half time and (b), (e), (h) the success rate of the particles that reached the target, for observation times $t=15$, 20, and 50 h on the signaling threshold $c^{*}$ in porous media, with (c), (f), (i) varying level of geometrical complexity.

Figure 4

Effect of the chemotaxis force prefactor. (a) The displayed values correspond to a set of simulations performed in a porous medium with $\varepsilon =0.7$ and $\tau =2.2$ with $c^{*}=0.5$. (b) The success rates were recorded for observation times $t=15$, 25, and 50 h.