Scientists at Linköping University have discovered a way to make artificial muscles that run off the same power sources as real biological muscles. They have brought science one step closer to blurring the boundaries between robot and organism. Their life-like plastic muscles made of a special polymer could pave the way for implantable artificial muscles and micro-robots that can be powered like living organs. The research was published in Advanced Materials.
To be able to replace traditional actuators powered by electricity with ones that more closely mimic the body’s own natural processes, the Linköping team led by Edwin Jager, senior lecturer in Sensor and Actuator Systems in the Department of Physics, Chemistry and Biology, had to create a robotic muscle that “feeds” the same as the one it replaces. To do this, they turned to muscles made out of a “polymer actuator” made from polypyrrole.
Polypyrrole is a polymer of pyrrole that is noted for its highly electroconductive properties. It is typically used in electronic devices and sensors. What’s special about it is it alters its volume when it is subjected to an electrical current. To turn this material into an artificial muscle, the researchers formed the polymer into two layers with a thin membrane between them. The whole thing is able to bend and contract like a muscle because when a charge is developed on one side, the ions in the polymer are expelled across the membrane and the sheet shrinks. Meanwhile, the sheet on the other side absorbs the electrons and expands.
This charge can be applied from a battery but they wanted it to be as close to the real thing as possible so they figured out a way to supply the charge using just glucose and oxygen. What they did was: they integrated enzymes that burn the glucose for energy (like a biological muscle does) into this material. They realized that by doping the polymer with enzymes that enhance the reaction, the material was able to burn the glucose for energy the same as a muscle does.
Jager said:
These enzymes convert glucose and oxygen, in the same way as in the body, to produce the electrons required to power motion in an artificial muscle made from an electroactive polymer. No source of voltage is required: it’s enough simply to immerse the actuator into a solution of glucose in water.
The next phase of their research will be to both, control the reaction, and see if it can be maintained through many repeat cycles. Now that the principle has been demonstrated, their next goal is to eventually completely mimic a living muscle, as well as apply it to micro-robotics.
Jager said:
Glucose is available in all organs of the body, and it’s a useful substance to start with. But it is possible to switch to other enzymes, which would enable the actuator to be used in, for example, autonomous micro-robots for environmental monitoring in lakes. The advances we present here make it possible to power actuators with energy from substances in their natural surroundings.
