Original Article: Akiyama et al. Lab on a Chip 2013
The Gist of It
Biological materials (such as our bodies) have many desirable qualities that engineers have been unable to copy in synthetic (man-made) materials. For example, when you work out, you get stronger. When you fall and hurt yourself, you heal. But what if we could make machines that adapted to their surroundings in the same way? This is exactly what Akiyama and colleagues investigated. Because muscle is more flexible, self-repairing, and energy efficient than synthetic alternatives, they decided to use muscle dissected from an insect to make a moving machine. Muscle contracts inside the body when it receives a trigger from the nervous system. The authors of this study replicated this trigger by stimulating the dissected muscle with short pulses of electricity. They then wrapped the muscle around a pair of tweezers and showed that they could make the tweezers close every time the muscle contracted in response to the electrical pulse. The insect-powered tweezers were able to work in air and at room temperature, demonstrating that a muscle-powered machine could function in a real-world environment. Now maybe you have no use for insect-powered tweezers (and I don’t blame you; who does?), but that doesn’t make this study any less impactful! It serves as a proof-of-concept that biological tissue can be used to power a synthetic machine. This sets the stage for a whole host of moving, walking, gripping, swimming machines that could be useful in our daily lives. And, like other biological systems, these machines may be able to do things like exercise to get stronger and heal when they’re damaged. Personally, I can’t wait for the day that becomes a reality!
Electrically stimulated contraction of insect muscle controls the opening and closing of a tweezer.
The Nitty Gritty
Akiyama et al. dissected insect dorsal vessels (DV) from final stage larvae of Thysanoplusia intermixta (i.e. inchworms). The muscle tissue was preserved in cell culture medium supplemented with fetal bovine serum, penicillin, and streptomycin. Microtweezers fabricated via photolithography were sterilized, and the DV tissue was placed around the tweezers and embedded in notches to ensure stable tethering. Light microscopy was used to track the tweezers’ deformation in response to electrically stimulated contraction of the muscle. Knowing the dimensions and material properties of the microtweezers, the authors were able to calculate the force produced by the muscle that resulted in the measured deformation. Calculations were verified via finite element analysis simulations. The authors used a paraffin coating on top of the culture medium reservoir to prevent medium evaporation, ensuring stable operation of the devices in air for up to five days.