In a tiny laboratory pond, a robotic stingray flaps its fins and swims around. Roughly the width of a dime, the bot dashes distances multiple times its body size. It easily navigates around corners and swims far longer than previous flapping microbots of an identical design.
Its secret? The robot is a biohybrid mix of living, human-derived neurons and muscle cells controlled by a programmable electronic “brain.” The cells cover an artificial “skeleton” with fins and form dense connections like those who drive movement in our bodies.
Also onboard is a wireless electronic circuit with magnetic coils. The circuit controls the robot’s neurons—either amping up or damping their activity. In turn, the brain cells trigger muscle fibers. The robot can flap its fins individually or along with the pliability of a stingray or a butterfly.
Watching the robot move is mesmerizing, however the study isn’t nearly cool visuals.
Robots have long tapped into examples of movement in nature to extend their dexterity and reduce energy usage. For now, the biohybrid bots can only live and operate in a nutritious soup of chemicals. But unlike previous designs, the bots push the sector into the “brain-to-motor frontier” and could lead on to autonomous systems “able to advanced adaptive motor control and learning,” wrote study creator Su Ryon Shin at Harvard Medical School and colleagues.
The technology may very well be a boon for biomedicine. Since it’s often compatible with living bodies, “tissue-based biohybrid robotics offers additional interdisciplinary insights in human health, medicine, and fundamental research in biology,” wrote Nicole Xu on the University of Colorado Boulder, who was not involved within the research.
Nature’s Touch
Scientists have long sought to develop soft, agile, and versatile robots that may navigate different terrain while using minimal energy—a far cry from the rigid, mechanical Terminator.
Often, they give the impression of being to nature for ideas.
Because of evolution, every species on Earth has a fine-tuned system of movement tailored to its survival. Although each system differs—the brain wiring behind a butterfly flapping its wings is hardly much like that of a blue whale spreading its fins—one central concept connects all of them.
Each species needs a system that connects movement to its environment and quickly responds to stimuli. While this comes naturally to living creatures, robots often stumble when faced with unexpected challenges.
“Animals typically have a better performance—equivalent to increased energy efficiency, agility, and damage tolerance—in comparison with their robotic counterparts due to evolutionary pressures driving biological adaptations,” wrote Xu.
It’s no wonder scientists look to nature to design bioinspired robots. Two favorites are ray fishes and butterflies, each of which use little or no energy to flap their fins or wings.
Last 12 months, one team engineered a butterfly-like underwater robot with an artificial hydrogel. Using light as a controller, it could flap its wings to swim upwards. One other mostly silicone minibot swam at high speeds with a “snapping” motion, like when closing hairpins.
Each bots used entirely engineered materials and needed actuators to sense stimuli, say, light or pressure, and alter the robot’s moving components. Though successful, these can often fail.
Brain Meets Machine
Enter biohybrid robots.
These bots use biological actuators to simply convert several types of energy utilized by the body—like, for instance, routinely translating electricity or light into chemical energy.
The strategy has had successes, including ray-like robots that use muscle tissues to swim forward and switch using an external light source. Here, the light-controlled bots had a single layer of rat heart cells genetically engineered to reply to flashes of sunshine. In comparison with biobots built from purely synthetic materials, these could swim far longer.
The brand new study took this approach a step further by adding brain cells into the combo. Neurons form intricate connections with muscle cells to direct them when to flex.
The team used induced pluripotent stem cells (iPSCs) for his or her bot. Scientists make these cells by reverting skin cells right into a stem cell-like state after which nudging them to form other cell types. On this case, they grew motor neurons, the brain cells that direct muscle movement, and muscle cells similar to people who keep the center pumping. The cells linked up in a petri dish, allowing the neurons to manage muscle contractions.
Living cells in hand, the team then assembled the robot’s two most important components.
The primary of those embeds neurons and muscle cells in a thin-film scaffold fabricated from carbon nanotubes and gelatin—the most important ingredient in Jello—and shaped into the robot’s body and fins.
The opposite is an “artificial brain” that controls the bot wirelessly using magnetic stimulation to alter the electrical activity of the neurons, increasing or decreasing their activity.
Neuro-Bot
In several tests, the team showed they may control the biohybrid bot’s behavior because it navigated its pool. Using multiple frequencies, each activating neurons for either the left or right fin, they easily steered the bot in a direct line and made turns.
Depending on the input, the bot could also flap a single fin, each fins, or alternate fins. The latter increased its stamina for longer swims—a bit like alternating arms in kayaking.
The bot’s neurons and muscle cells took the team by surprise by forming a style of connection that relies on electricity alone to transmit data. Normally, these connections, called synapses, need an extra chemical messenger to bridge communications, and so they’re only one-way.
In contrast, the networks formed within the bot could transmit data in each directions faster and longer, controlling muscles as much as 150 seconds or roughly 7.5 times longer than standard chemical synapses. And in comparison with bio-inspired systems using only synthetic materials, the biohybrid bot slashed energy needs.
For now, the minibots can only survive in a nutrient-rich soup of chemicals. But they show living components will be seamlessly integrated with electronics and non-biological scaffolding. Living robots could form the subsequent generation of organoids-on-a-chip for study of diseases related to the brain and muscles or to check recent drug treatments. Using purely electrical connections, that are easier to implement than standard chemical synapses, could help scale up the production of biohybrid bots.
“The arrival of this bioelectronic neuromuscular robotic swimmer suggests a possible frontier [where we can] construct autonomous biohybrid robotic systems that may achieve adaptive motor control, sensing, and learning,” wrote the team.
