Biohybrid crawlers can be controlled using optogenetic techniques

The body movements performed by humans and other animals are known to be supported by several intricate biological and neural mechanisms. While roboticists have been trying to develop systems that emulate these mechanisms for decades, the processes driving these systems’ motions remain very different.

Researchers at University of Illinois at Urbana-Champaign, Northwestern University and other institutes recently developed new biohybrid robots that combine living cells from mice with 3D printed hydrogel structures with wireless optoelectronics.

These robots, presented in a paper published in Science Robotics, have neuromuscular junctions where the neurons can be controlled using optogenetic techniques, emulating the neural mechanisms that support human movements.

“This paper is an important next step in our work on biohybrid robotics spanning over the past 15 years,” Dr. Rashid Bashir, senior author of the paper and Professor of bioengineering and also the Dean of the Grainger College of Engineering at University of Illinois at Urbana-Champaign, told Tech Xplore.

“We demonstrated the important milestone of using neurons to control the muscles and hence the movement of these crawling biohybrid robots.”

In humans, the voluntary movement of specific body parts is controlled by the brain. Specifically, neurons are known to control muscles, generating a force that prompts actuation and movement.

Dr. Bashir and his colleagues have been trying to reproduce this crucial physiological process in miniature bio-hybrid robots.

“Another goal of our study was to show that we could optically stimulate and train the neural tissue, using on-board wireless microLEDs developed by Prof. John Rogers group at Northwestern University, to change the speed of movement of the biohybrid robots,” said Bashir.

The biohybrid robots developed by the researchers are based on a polymer scaffold that can be easily fabricated using 3D printing technology. This scaffold was carefully designed using advanced modeling and simulation methods from Prof. Yonggang Hwang’s group at Northwestern University.

The team then enhanced the polymer-based scaffold by growing biological muscle tissues around it using biohybrid tissue engineering methods.

Essentially, they differentiated stem cells from mice into motor neurons and seeded them onto the 3D printed structures, which had muscle tissues also differentiated and grown using nutrient-rich mediums to prompt their proliferation and the formation of the neuromuscular junction.

“The living muscles contract upon a stimulus (electrical, optical, or from a neuron) and if the scaffold is designed appropriately, then the robots move in a specific direction,” explained Bashir.

“The broad interest and reasons for developing these living machines is to learn the design rules for biohybrid machines and living cells and potentially utilize the advantages such as biodegradability, low energy consumption, learning and emergent properties.”

The recent study by Bashir and his colleagues could soon inspire other roboticists and geneticists to create similar bio-hybrid robotic systems. In the future, these systems could prove useful for the study of motor processes, for the completion of various tasks in biological environments or for regenerative medicine applications.

“Our work could open a pathway to the creation of biological machines with neural tissues that can learn, adapt and respond to stimuli,” added Bashir.

“We would now like to continue our work to design in higher order functionalities, such as learning, memory, and decision-making upon external stimuli. We plan to design more complex forms of movement such as bidirectional movement and movements over obstacles.”

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