The concept of a living machine might make you imagine a walking, talking humanoid. However, a research team from Tufts University, Massachusetts, has created microscopic machines that more closely resemble a tardigrade – a tiny living organism – than the Terminator.
Called ‘Xenobots’, these spongy cloud-like living robots consist of biological stitchings of different types of cells collected from the surface of a developing frog embryo. One of the reasons that frog cells were used in this study was due to a natural energy source that allows them to survive around ten days in a water solution during the experiment.
The cells collected from the frog embryos were developing stem cells, which have the potential to diversify into many other types of cells. By scraping cells at particular locations on the embryos’ surface or exposing them to different chemical or genetic treatments in the laboratory, researchers were able to determine what types of cells they became. In the case of the Xenobots, passive skin and cardiac muscle cells were required.
In its infancy as a scientific concept these living machines were not designed to carry out complex or stimulus tasks, but rather to simply survive and move. It’s the cardiac muscle cells that give the Xenobots their ability to move through contraction and relaxation in the same way they facilitate
One of the challenges of making a living machine lies in knowing how to arrange each of the cellular building blocks. However, collaborating with the University of Vermont, researchers ran an evolutionary algorithm through a supercomputer, which then generates different configurations of these cells to produce the optimal Xenobot based on a desired set of attributes. For example, one of the most robust forms tested out by the research team was one commonly seen in nature: a leg at the front and at the back with contacting cardiac muscle cells in between. As the cardiac muscles contract, they pull the legs together and then release them. This makes the Xenobot move in a way reminiscent of how a caterpillar or worm might crawl along a branch.