Imagine a soft material capable of autonomous motion, not powered by electronics, motors, or complex machinery, but instead driven entirely by fundamental chemical signaling—the kind that orchestrates the movements of the most primitive life forms. This concept, once relegated to the realm of theoretical speculation, has now emerged from the laboratory and into rigorous computational modeling at the University of Pittsburgh’s Swanson School of Engineering. Scientists there have developed an innovative synthetic system that translates chemical reactions directly into mechanical forces, bypassing the tangled networks of proteins, cells, and electrical signals common in living organisms.
In nature, the simplest creatures, such as jellyfish, lack centralized nervous systems or brains. Instead, they operate through what is termed a “nerve net”—a diffuse web of neurons communicating via chemical signals, generating spontaneous waves that propagate movement throughout the organism. These phenomena highlight the remarkable ability of biological systems to coordinate complex motions without centralized control, a principle that researchers sought to replicate artificially. By mimicking these rudimentary networks, they hope to design materials that respond and move independently, radically transforming the field of soft robotics and adaptive materials.
At the core of this breakthrough is the coupling of chemical and mechanical networks into a seamless feedback loop that generates rhythmic pulses of motion. The research, published recently in PNAS Nexus, introduces a computationally simulated structure composed of enzyme-coated microscopic beads interconnected by flexible links. These beads serve as active sites where chemical reactions oscillate in a rhythmic fashion, similar to biological repressilator circuits known for generating periodic gene expression cycles. As chemical waves ripple through this bead network, they induce fluid flows around the structure, effectively transforming chemical energy into coordinated mechanical deformation—a phenomenon termed the chemo-mechanical network (CMN).
The researchers’ model elegantly demonstrates how waves of chemical reactions, propagating spatially along the bead chain, induce corresponding mechanical oscillations that mimic biological contraction waves seen in centipedes or flatworms. This coupling of chemistry to mechanics creates directed movement without the need for external stimuli or complex electronic feedback systems. By carefully tuning the chemical parameters and network geometry, especially by arranging the beads into closed loops, the team achieved continuous, self-sustained motion. This revelation suggests pathways for soft materials capable of perpetual movement driven purely by internal chemical dynamics.
To better conceptualize this system, one might imagine an everyday Slinky toy placed on a staircase. A simple nudge propels it downward driven by gravity, converting potential energy into motion. Now, picture selective coils of this Slinky coated with specific enzymes that trigger chemical reactions spontaneously. Once initiated, these reactions send waves of chemical signaling along the coils, bending and flexing them rhythmically and autonomously. This chemically driven Slinky model exemplifies how targeted chemical excitation of material regions directs motion in a predetermined sequence, a principle underpinning the new soft material’s design.
Unlike traditional stimuli-responsive materials that react to external cues such as light, heat, or electric fields—and typically exhibit limited movement repertoires—the enzyme-coated beads in this chemo-mechanical system inherently encode a spatially sequenced chemical signaling map. This encoding allows a much broader range of complex motions controlled by the chemical environment and mechanical layout, potentially enabling the creation of soft robots or active materials with sophisticated behavior emerging from simple chemical instructions. The materials are not passive receivers but active participants in their own self-sustained dynamics.
One of the most groundbreaking aspects of this research lies in the elimination of any centralized control or electrical circuitry. The entire system operates autonomously, self-contained within its chemical reaction network. Once activated, the enzymatic reactions create fluid flows that deform the elastic linked-bead network, producing mechanical motions that in turn feedback on the chemical processes. This closed-loop chemo-mechanical interface exemplifies a new class of materials that “think” chemically rather than electronically—a paradigm shift with vast implications for the development of future soft machines.
This work also offers fresh insights into biological mechanics, suggesting mechanisms by which enzymatic chemical networks within the body’s aqueous environment interact with elastic tissues to generate coordinated motion. Humans, for instance, are composed largely of water and enzymes, and the formation of chemo-mechanical networks within our tissues may play an underappreciated role in physiological processes, from nutrient transport to cellular response to stimuli. By modeling these interactions in synthetic systems, researchers hope to gain a deeper understanding of life’s basic mechanical principles and how chemistry can orchestrate motion in soft matter.
Moreover, the potential applications of chemically-driven autonomous materials are profound, extending to fields like soft robotics, where machines must adapt flexibly to complex environments without heavy electronics or rigid components. These chemically powered materials could operate in fluidic environments—for example, inside the human body or in aquatic systems—executing tasks such as targeted therapeutics delivery or environmental sensing, all controlled by the material’s intrinsic chemistry rather than external commands.
The researchers employed computational simulations and advanced fluid-structure interaction modeling to design and understand this chemo-mechanical coupling. Their approach integrates chemical kinetics of enzymatic reactions with classical mechanics of elastic beads and hydrodynamics of the surrounding fluid, generating predictive insights into how different chemical configurations and network topologies influence motion. This comprehensive model forms a blueprint for fabricating new soft materials and robots that harness reactions, elasticity, and fluids synergistically.
From a philosophical perspective, this research embodies the elegance of emergent phenomena where simplicity begets complexity. By strategically leveraging minimal components—chemical oscillators, mechanical links, and fluid-mediated forces—the team has recapitulated intricate biological dynamics in man-made materials. The system transforms chemical fuel directly into work, coordinating its moving parts autonomously without need for neurons, batteries, or motors. This stripping down of autonomy to its chemical core redefines the boundaries between living and synthetic, opening avenues for autonomous materials that embody life-like intelligence.
Beyond the fundamental science, the cultural resonance of this discovery is compelling. It challenges our assumptions about what is required for movement and decision-making in materials, blending chemistry and physics into a unified, self-sustaining cycle. As Anna C. Balazs, lead researcher, whimsically put it, “It’s a bit like eating a cheeseburger, and then moving your arm—you add fuel, and it does the rest.” This potent metaphor captures the essence of energy transduction from chemical potential directly into motion in a system free of wires, motors, or conventional computation.
Ultimately, this pioneering work charts a course toward future adaptive materials that operate like living tissues, processing signals chemically and moving purposefully with minimal external input. These materials, born at the intersection of synthetic biology, chemistry, physics, and engineering, promise to revolutionize not only how we fabricate machines but also deepen our understanding of life’s fundamental processes, translating nature’s simplest principles into the next generation of smart, autonomous soft matter.
Subject of Research:
Not applicable
Article Title:
Chemical signaling in reaction networks generates corresponding mechanical impulses
News Publication Date:
October 16, 2023
Web References:
https://doi.org/10.1093/pnasnexus/pgaf330
https://academic.oup.com/pnasnexus/advance-article/doi/10.1093/pnasnexus/pgaf330/8287403
References:
Oleg E. Shklyaev, Anna C. Balazs, “Chemical signaling in reaction networks generates corresponding mechanical impulses,” PNAS Nexus, 2023.
Image Credits:
Credit: Oleg E. Shklyaev
Keywords:
Adaptive systems, Chemical signals, Synthetic biology, Chemical kinetics, Biomechanics, Computational chemistry
