Colloidal logic-gate circuits can process environmental signals and autonomously perform tasks

TL;DR

Colloidal enzymes-coated particles are shown to form self-assembled logical circuits that process environmental chemical signals via enzymatic reaction networks implemented as OR, AND, and XOR gates. The circuits output usable signals such as $\Phi(t)$ or $P_2$ concentrations to drive autonomous responses, including targeted suppression of invasive species through substrate-driven chemotaxis and gate cascades. The study provides a computational framework for designing chemical logic networks on active colloids, with demonstrated scenarios for single and multiple invaders and feedback that maintains non-equilibrium operation. This work offers design principles for environmental sensing and autonomous task execution by micromotor systems, with potential applications in targeted therapy and biosensing.

Abstract

Cooperative collective dynamics is a principal determinant of the ability of synthetic micromotors to perform specific functions. However, realizing controllable and predictable collective behavior in complex physiological environments remains a significant challenge. Here, we show that collections of enzyme-coated colloids can be designed as various chemical logic gates, which subsequently can be organized into functional logic circuits. These circuits take environmental information as input signals and process it to produce output chemical species needed to achieve specific goals. The chemical computation performed by the circuit endows the active colloidal system with the ability to sense its surroundings and autonomously coordinate its collective motion. The results of simulations of several examples are presented, where self-assembled colloidal circuits can identify invasive threats by their signals, produce and deliver chemicals to the targets to suppress their activity. The results of this work can aid in the design of experimental chemical logic circuits through micromotor self-assembly that autonomously respond to environmental cues to execute specific tasks.

Figures (9)

• Figure 1: Schematic depiction of the operation of the OR-AND-XOR logic circuit constructed using four enzymes, AChE, ChO, MP-11, and GDH. Details of its operation are given in the text.
• Figure 2: The OR-AND-XOR colloidal logic-gate circuit. The circuit uses three linked colloids with coats constructed from four different enzymes as described in the text. The figure shows the reactions that underlie the OR, AND, and XOR colloidal gates. The gated colloids reside in a reactive chemical medium.
• Figure 3: Temporal evolution of species concentration ratios $CR_\alpha$ in the system for two (ABCD) inputs. (a) Input (0110) results in output signal "1". (b) Input (1111) results in output signal "0". The concentration ratio $CR_\alpha = N_\alpha(t)/N_0$, where $N_\alpha(t)$ is the number of particles of species $\alpha$ at time $t$ ($\alpha = A, B, D, F_1, F_2, P_1, P_2, S$) and $N_0$ is the total particle number in the system.
• Figure 4: The XOR gate constructed from two AND gates.
• Figure 5: (a) Bar presentation of the outputs of the OR-AND-XOR circuit. Each bar corresponds to a specific input and its corresponding output signal, $\Phi(t)$. The horizontal dashed line at $\Phi(t)=0.5$ denotes the threshold between high and low $\Phi$, specifying the values of the output signals as "0" and "1" respectively. (b) Truth table for the the circuit.