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Scientists at Japan's Biosystems Dynamics Research Center (RDR), RIKEN, have developed the world's first live cell-powered electronic valve. The muscle tissue of the earthworm allowed high contractile force that could be maintained for a few minutes. Unlike the electrically operated valves, they did not require any external power source such as batteries.
For several decades, researchers have been trying to combine microelectromechanical systems (MEMS) with living material. Bio-MEMS have many applications, ranging from improved delivery of drugs to optical and electrochemical sensors, to organs on chips. The research team of RIKEN BDR and the University of Tokyo Denki has developed a bio-MEMS based on real muscles, which could prove useful in surgical implants. Building on their on-chip micro-pump design, the new study constitutes the proof of concept of an on-chip muscular-controlled valve.
In mechanics, an actuator is the part of a machine that controls a mechanism by moving it, such as opening and closing a valve. The actuators require a power source and a control signal, which are usually electric current or some kind of fluid pressure. The main benefit of using muscles as actuators in bio-MEM systems is that they can be powered in the same way as in living bodies: chemically. For muscles, the contraction signal is the molecule of acetylcholine – which is delivered by neurons – and the source of energy is adenosine triphosphate (ATP) – which exists at the same time. inside the muscle cells.
"Not only can our bio-MEMS operate without an external source of energy, but unlike other acid-controlled chemical control valves, our muscular-controlled valve works on naturally abundant molecules in living organisms," says first author, Yo Tanaka. RIKEN BDR. "This makes it bio-friendly and particularly suitable for medical applications in which the use of electricity is difficult or discouraged."
The team initially determined that a small sheet of 1 cm × 3 cm worm muscle could produce an average contractile force of about 1.5 milli-Newton over a 2 minute period when stimulated by a very small amount of acetylcholine. Using these data, they construct a microfluidic canal and valve on a 2 cm × 2 cm microchip that can be controlled by the contraction / relaxation of the worm muscle.
To test the system, they used a microscope to monitor fluorescently labeled microparticles in a liquid as they passed through the microchannel. When acetylcholine was applied, the muscle was in contact. The resulting force was converted into a bar that was pushed down to close the valve, which successfully stopped the flow of liquid. When acetylcholine was washed away, the muscle was loosened, the valve reopened and the fluid ebbed.
"Now that we have shown that it is possible to use muscle valves on the chip, we can work on improvements that will make this practical," Tanaka says. "One option is to use muscle cells in culture, which could lead to mass production, better control and flexibility in terms of shape, but we will have to take into account the reduction in the amount of force that can be produced from this. way compared to real muscle sheets. "
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Material provided by RIKEN. Note: Content can be changed for style and length.
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