AsianScientist (Aug. 8, 2019) – In a study published in Scientific Reports, researchers describe a valve on a microchip powered by earthworm cells. Unlike electrically controlled valves, this valve powered by living cells does not require an external power source like batteries, say the researchers from the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan.
For several decades, researchers have been trying to combine microelectromechanical systems (MEMS) with living material. Bio-MEMS have many applications, ranging from improved drug delivery and optical and electrochemical sensors to organs-on-chips. Researchers from RIKEN BDR and Tokyo Denki University have previously developed a bio-MEMS micropump, and in this study have extended their findings to a proof-of-concept muscle-driven valve.
In mechanics, an actuator is the part of a machine that controls a mechanism by making it move, such as the opening and closing of a valve. Actuators require a power source and a control signal, which are typically electric current or some kind of fluid pressure. The main advantage for using muscles as actuators in bio-MEM systems is that they can be powered the same way as they are in living bodies: chemically. For muscles, the signal for contraction is the molecule acetylcholine and the energy source is adenosine triphosphate (ATP).
“Not only can our bio-MEMS work without an external power source, but unlike other chemically driven valves that are controlled by acids, our muscle-driven valve runs on molecules that are naturally abundant in living organisms,” said study first author Dr. Yo Tanaka from RIKEN BDR. “This makes it bio-friendly and especially suited for medical applications in which the use of electricity is difficult or not advised.”
The team initially determined that a small 1 cm × 3 cm sheet of earthworm muscle could produce an average contractile force of about 1.5 milli-newtons over a two-minute period when stimulated by a very small amount of acetylcholine. Using this data, they built a microfluid channel and valve on a 2 cm × 2 cm microchip that could be controlled by the contraction or relaxation of earthworm muscle.
To test the system, they used a microscope to monitor fluorescently labeled microparticles in liquid as it flowed through the microchannel. When acetylcholine was applied, the muscle contacted. The resulting force was transduced to a bar that was pushed down to close the valve, which successfully stopped the flow of liquid. When the acetylcholine was washed away, the muscle relaxed, the valve re-opened, and the fluid flowed again.
“Now that we have shown that on-chip muscle-driven valves are possible, we can work on improvements that will make it practical,” said Tanaka. “One option is to use cultured muscle cells. This might enable mass-production, better control and flexibility in terms of shape. However, we will have to account for the reduction in the amount of force that can be produced this way compared with real muscle sheets.”
The article can be found at: Tanaka et al. (2019) A Valve Powered by Earthworm Muscle With Both Electrical and 100% Chemical Control.
Source: RIKEN; Photo: Pixabay.
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