If we have self-healing bio robots in 2053, it started here with mouse muscle cyborgs

Light-powered droids are coming, one fraction of a millimetre at a time

Updated What do you get when you stretch mouse muscle tissue over a polymer skeleton and attach electronics capable of converting radio-frequency energy into light?

Perhaps a bit of shock when the bioelectronic bot begins to move on its own, with no attached power source.

No fewer than 21 boffins affiliated with America's University of Illinois, Northwestern University, and University of Southern California, plus the University of Technology in Dalian, China, describe this feat in an article published on Thursday in the journal Science Robotics.

The authors include: Yongdeok Kim, Yiyuan Yang, Xiaotian Zhang, Zhengwei Li, Abraham Vázquez-Guardado, Insu Park, Jiaojiao Wang, Andrew I. Efimov, Zhi Dou, Yue Wang, Junehu Park, Haiwen Luan, Xinchen Ni, Yun Seong Kim, Janice Baek, Joshua Jaehyung Park, Zhaoqian Xie, Hangbo Zhao, Mattia Gazzola, John A. Rogers, and Rashid Bashir.

Their paper, titled Remote control of muscle-driven miniature robots with battery-free wireless optoelectronics, describes the process of integrating light-sensitive biological tissue, supported by a 3D printed hydrogel scaffold, with a wireless optogenetic sensor.

A bipedal eBiobot

Behold our terrifying future ... A bipedal eBiobot. Credit: Yongdeok Kim

Optogenetics involves cells that are, or have been made, sensitive to light. In this instance, the researchers have sensitized mouse muscle to light so that the tissue will contract when illuminated.

Activating a light source like a micro-LED typically requires a wired power source like a battery. The makers of this muscular mini robot have chosen instead to transmit power wirelessly through radio-frequency emissions that can be harvested via resonant magnetic induction using an antenna coil.

The gathered energy activates onboard micro-LEDs which motivate muscle contractions that make the whole assembly move, as can be seen in this video demonstration:

Youtube Video

These resulting "eBiobots" are less formidable than one might expect when imagining a bioelectronic hybrid – a cyborg. They're more sinew-and-silicon in aspic than Terminator.

And they're slow, moving only about 0.3-0.8 millimeters per second, depending on the number of LEDs are used. Below is a video illustrating the tech:

"Centimeter-scale walking robots were computationally designed and optimized to host on-board optoelectronics with independent stimulation of multiple optogenetic skeletal muscles, achieving remote command of walking, turning, plowing, and transport functions both at individual and collective levels," the paper explains.

"This work paves the way toward a class of biohybrid machines able to combine biological actuation and sensing with on-board computing."

According to the News Bureau of the University of Illinois at Urbana-Champaign, Northwestern University professor John A. Rogers, one of the paper's co-authors, said the project "​​opens up vast opportunities in creating self-healing, learning, evolving, communicating and self-organizing engineered systems."

Rest assured the researchers are looking at medical and environmental sensing applications for this technology. ®

Updated to add

In an emailed response to questions that arrived after this story was published, two of the paper’s co-authors – Yongdeok Kim, a postdoctoral researcher at University of California, Berkeley and former graduate research assistant at University of Illinois at Urbana-Champaign, and Rashid Bashir, Dean of The Grainger College of Engineering and professor of Bioengineering at the University of Illinois at Urbana-Champaign – elaborated on the eBiobot project.

The Register: What are some of the potential applications you foresee for biohybrid machines that respond to remote signals? Are they mainly medical, for diagnostics and intervention?

Kim and Bashir: "Combining microelectronics with biohybrid machines can open up various potential applications in not only biomedical areas but also environmental monitoring, and defense. Although we only showed the remote-controlled actuation and walking of the biohybrid robot in this study, other electronic sensors or complicated circuits could be integrated with this platform, which could realize diverse applications."

The Register: As this work develops, are there adequate protocols and regulations for specifying what kind of tissue can be used and in what way?

Kim and Bashir: "This is a very good question. We answer this in multiple ways.

"First of all we always get institutional approvals for the use of the mouse cells that we use for this work. The devices can certainly use other types of cells and tissue, such as human or from stem cells. But broadly speaking, yes our team (Bashir and others) have also been working with many colleagues on the ethical considerations around this kind of work.

"We have developed ethical guidelines for developing such multi cellular engineered living systems. For example see, 'Multi-cellular engineered living systems: building a community around responsible research on emergence' (Biofabrication, 2019).

"This is by far not definitive work and we need to further develop the guidelines and policies to ensure that the development of living systems and machines is performed for the benefit of humanity and the environment. It should be noted that integrating other types of tissues in this platform would be very interesting and synergistic. Especially, integrating neurons into this system would have great potential.

"We can imagine an autonomous walking biohybrid robot with an innervated system between motor neurons and skeletal muscles and closed-loop control with microelectronics. Also, the communication between neurons and microelectronics could have potential use in cybernetic communication between biological and artificial intelligence."

The Register: What are the most immediate challenges to commercializing such work? Eg, biomedical advances, electronic miniaturization and materials, regulatory?

Kim and Bashir: "We believe that commercial applications are still in the future. These devices are the building blocks for more advanced machines that use the power of biology. Currently, the operation of eBiobot is limited to inside a glucose-rich fluid and at 37 degrees due to the use of mammalian cells.

"However, future use of insect or amphibian cells could allow for expanding the operating temperature range including room temperature. Also, combining epithelial tissues or vascularization enable the biohybrid robot to move in a dry condition outside of the dish."

The Register: Is there a need to be cautious in how such work is done and discussed out of concern that the general public may misperceive the integration of biological and electronic systems?

Kim and Bashir: "Yes for sure. We need to ensure that any such systems are used for the benefit of human health or improve environmental sustainability. For example, the design rules or understanding of developing such systems can help with developing devices for prosthetic applications."

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