We are entering a time where the boundaries between traditional robotics and biological systems will increasingly blur. This shift has given rise to what I think of as “living machines.”
This project focuses on cardiomyocytes, or heart cells, a small yet powerful component under the larger umbrella of biohybrid robotics. Cardiomyocytes can provide living actuation for biohybrid robots through contraction. Xenobots, which are considered the first fully synthetic biological organism evolved in silico, are composed of both cardiomyocytes and skin cells.
In silico designs (top) approximate match sculpted using real cells (bottom)
Xenobot research envisions exciting applications such as microplastic clean up and targeted drug delivery, their small size and biodegradability makes them a plausible future candidate for such tasks. However, xenobots are still considered a moonshot idea due to a lack of understanding about their emergent behavior, a lack of precise control over their movements, and a lack of a standard, scalable approach to fabricating them.
This project aims to test how we can use stimuli, specifically light pulses, to control and direct the contractions of the bots. I envision a method where a light sensitive protein, Channelrhodopsin (ChR), would be introduced to the cardiomyocytes. This could be done via lentivirus transduction, which is a common method used to introduce foreign DNA sequences into a cell via a virus. Lentivirus transduction has been used in the past to introduce genes into cardiomyocytes, which is why I chose it as an approach. However, future tests could be done via CRISPR methods, and for a variety of stimulus tests such as temperature and pH.
After this first step, it would be useful to add additional sensitivity by making the movement of the xenobots vary based on specific light intensity, which could be achieved by adding promoters to drive the expression of ChR at different intensities. I envision creating a microfluidics system to provide a controlled environment for the xenobots. Such a system could be useful in allowing for precise manipulation over light conditions and then observing the response of the xenobots.
Finally, I aim to address the broader challenge of a lack of scalability and standardization of bio-bot creation. Instead of having to manually stitch together the cells, I plan to experiment with bioprinting as a viable alternative by creating a bioink containing living cells and hydrogel.
Creating Living Machines: Cardiomyocyte Actuation for Biohybrid Robots aims to explore how we can control and develop xenobots at scale. Introducing a light sensitive protein entails plasmid design and lentivirus transduction, though CRISPR methods could also be experimented with. To observe the bots’ contraction response to varying light intensities, a microfluidics system could be fabricated for precise environment control. Work related to the future development of xenobots should include a comprehensive ethics section, taking into account the development of standard ethical frameworks to be used by researchers, methods of ensuring non-harm to surrounding environments, and developing emergency safety switches.
For centuries, people have drawn inspiration from nature to engineer better solutions. In robotics, living organisms have served as a baseline for creating safe, flexible, and autonomous designs. While we've seen tremendous progress, human-made creations still fall short of biology's ability to self-assemble, self-heal, efficiently produce energy, and eventually biodegrade.
As a result, interest has surged in the past decade to move beyond pure biomimicry and into the realm of biohybridization**. By viewing living cells not only as the building blocks of life but also as potential building blocks that we can incorporate into novel designs, we can better leverage nature's unparalleled capabilities.** As one paper beautifully writes:
“It [the field of biohybrid robotics] seeks applications beyond a mere replication of nature, but it wants to create a generation of robots that are able to fulfill tasks that neither nature nor physical robots can presently achieve.”
The wide range and possibilities of biohybrid robots, from microscopic DNA tweezers to larger bio-bots that incorporate entire multicellular organisms (source)
There exists a wide range of approaches for biological integration in this nascent field, from seeding cells onto artificial elastomer string rays as a source of actuation to, on the further end of the spectrum, using entire insects as cyborgs for rescue applications. The field promises an exciting future that stretches the imagination and begs ethical questions.
I chose to explore leveraging living cells, specifically cardiomyocytes, for their ability to contract as a source of actuation for biohybrid robots. Cardiomyocytes have been used in experiments with both micro and macro-scale robots, including the aforementioned artificial stingray.
On a micro level, recent research conducted at the Institution for Computationally Designed Organisms aimed to develop the first fully biological robot designed in silico. They call it the “xenobot.” Although still in its early stages, I’m excited about the long-term applications envisioned for bio-bots: