We have imagined for a long time that microrobots will be able one day to monitor or repair our biological systems -- but with limited success (check A robot that travels through the body for example). Now, South Korean scientists have built robots small enough to roam the human body and powered by living heart muscle. These hybrid cell microrobots move like crabs, with their 3 short front legs (400 micrometers long) and their 3 longer back legs (1,200 micrometers long). According to one of the researchers, 'these crab-like robots could be used inside the body to clear blocked tubes or arteries.'
According to Chemical Science, Sukho Park of the Nano/Micro System Laboratory at the Seoul National University and his colleagues "made the robot by growing heart muscle tissue from a rat onto tiny robotic skeletons made from polydimethylsiloxane (PDMS)."
You can see above how the scientists prepared their microrobot: (a) Single heart cells isolated from neonatal rat heart. (b) PDMS structure prepared for culture of cardiomyocytes on its surface. (c) Primary cardiomyocytes on the culture dish containing the PDMS structure. (d) Culture of cardiomyocytes. (e) Transfer of PDMS structure into a new culture dish to observe movement. (f) Schematic image to observe vertical movement. (g) Microscopic image of vertical view. (h) Schematic image to observe lateral movement. (i) Microscopic image of lateral movement. (Credit: Sukho Park and his colleagues)
For more information, this research work is available online through another publication of the Royal Society of Chemistry, Cambridge, UK, Lab on a Chip, where it appeared on August 10, 2007 under the name "Establishment of a fabrication method for a long-term actuated hybrid cell robot."
Here is the abstract. "We developed a novel method to fabricate a crab-like microrobot that can actuate for a long period in a physiological condition. The microrobot backbone was built with a biocompatible and elastic material -- polydimethylsiloxane (PDMS) -- by using a specially designed 3D molding aligner, and consisted of three strips of PDMS connected across a body. Cardiomyocytes were then plated on the grooved top surface of the backbone, resulting in a high concentration of pulsating cells. These key techniques enabled the microrobot to walk continuously for over ten days. The performance of our crab-like microrobot was measured at an average velocity of 100 ìm s–1, and the estimated total distance it travelled was 50 m over a one-week period."
And here are some of the conclusions you'll find if you read the full paper from which the above illustration was extracted. "By growing rat muscle tissue onto a polymer backbone, the movement of a cell-powered microrobot was demonstrated for the first time. The most significant results from this study are as follows. (1) Our microrobot was a self-assembled hybrid consisting of biotic muscle cells and a PDMS backbone -- a well-known biocompatible material. (2) The surface of the PDMS backbone was engineered with a 3D grooved pattern that led to high-order cell concentrations and enabled a high generative force from the muscle cells. (3) The PDMS was easily fabricated by using a micromolding procedure thus allowing for high throughput and mass-production of cell-powered microrobots. (4) This is the first report describing the results of long-term monitoring of primary cultured cardiomyocytes on microrobots.
What would be these hybrid cell microrobots usefule for? "A potential application for the microrobot developed in this study may be to work for certain periods of time within small lumens or vessels or ducts, perhaps to remove various types of blockages which have accumulated in the ducts when the degradable elaborated microrobot is finally aimed to the blockages. By injecting or inserting into the ducts, the microrobot will survive and actively engage in beating movement along the length of the duct and some types of dissolving agent could be contained in the microrobot to clear the blockages."
Finally, if you want to see how these crab-like microrobots move, don't miss this short movie (37 seconds).
Sources: Sarah Corcoran, Chemical Science, UK, August 31, 2007; and various websites
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