At exactly 67 degrees Celsius, the crystal structure undergoes a phase shift that allows the free flow of electrons through the system — and it also physically deforms the metal. That physical change occurs with incredible force — as seen in the video below, a coil of vanadium dioxide can launch objects 50 times heavier than itself over a distance five times its length within 60 milliseconds.
The robo-myosin was able to undergo over a million cycles without degrading, snapping back and forth in its basic contractile cycle. Since this cycle is controlled by heat, the researchers came up with two methods of heat delivery. To cause all the units to contract as one, a tiny heating pad can be used to change the overall temperature. The better solution is passing an electrical current down the filament, since it uses less energy per contraction and allows targeted heating of individual motors.
The advantages of this model of muscle action are numerous. Think about the fact that, despite being made from relatively weak constituents like protein and fat chains, animal muscle has only now been surpassed by technology. Of course, a bulky, pneumatic Atlas muscle could outperform both this and a human in terms of raw strength, but not while remaining so light and compact, nor is it so instantaneously responsive as a system based on micro-meter movements. The actual energy costs per unit strength are unknown right now, but has the potential to be extremely efficient, relative to current solutions.
Research Paper : 10.1002/adma.201304064 : Powerful, Multifunctional Torsional Micromuscles Activated by Phase Transition
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