The hybrid “eBiobots” are the first to combine soft materials, living muscles and microelectronics, said researchers from the University of Illinois Urbana-Champaign, Northwestern University and collaborating institutions. They described their centimeter-scale biological machines in the journal Science Robotics.
“The integration of microelectronics enables the merging of the biological world and the world of electronics, both with many advantages of their own, to produce these electronic biobots and machines that could be useful for many medical, sensing and environmental applications in the future,” the study said. co-leader Rashid Bashir, Illinois professor of bioengineering and dean of the Grainger College of Engineering.
3D-printed polymer skeleton
Bashir’s group pioneered the development of biobots, small biological robots powered by mouse muscle tissue grown on a soft 3D-printed polymer skeleton. They demonstrated walking biobots in 2012 and light-activated biobots in 2016. Light activation has given researchers some control, but practical applications have been limited by the question of how to deliver light pulses to biobots outside of a laboratory environment.
The answer to that question came from Northwestern University professor John A. Rogers, a pioneer in flexible bioelectronics whose team helped integrate tiny wireless microelectronics and battery-free micro-LEDs. This allowed the scientists to remotely control the eBiobots.
Rogers, professor of materials science and engineering, biomedical engineering and neurological surgery at Northwestern University and director of the Querrey Simpson Institute for Bioelectronics says “This unusual combination of technology and biology opens up enormous possibilities in creating self-healing, learning, evolving, communicating and self-organizing engineered systems. We feel this is very fertile ground for future research with specific potential applications in biomedicine and environmental monitoring”.
eBiobots use a receiver coil to harvest power
To give the biobots the freedom of movement needed for practical applications, the researchers decided to remove bulky batteries and tethering wires. The eBiobots use a receiver coil to harvest power and provide a regulated output voltage to power the micro-LEDs, said co-first author Zhengwei Li, an assistant professor of biomedical engineering at the University of Houston.
Researchers can send a wireless signal to the eBiobots, which prompts the LEDs to pulse. LEDs stimulate the light-sensitive muscle to contract and move the polymer legs to make the machines “walk”. The micro-LEDs are so targeted that they can activate specific parts of the muscles so that the eBiobot turns in the desired direction.
The researchers used computational modeling to optimize the eBiobot design and component integration for robustness, speed and maneuverability. Illinois mechanical sciences and engineering professor Mattia Gazzola led the simulation and design of the eBiobots. The iterative design and additive 3D printing of the scaffold enabled rapid cycle times of experiments and improved performance, said Gazzola and co-author Xiaotian Zhang, a postdoctoral researcher in the Gazzola lab.
The design allows for the possible future integration of other microelectronics, such as chemical and biological sensors or 3D-printed parts of the scaffold for functions such as pushing or transporting things the biobots encounter, said co-author Youngdeok Kim, who completed the work as a graduate student at Illinois.
Integrating electronic sensors or biological neurons would allow eBiobots to sense and respond to toxins in the environment, biomarkers for disease and other possibilities, the researchers said.
