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Small Yet Powerful, Bug-Like Microdrones Are Gaining Strength

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A team at MIT can now build small drones that fly around with bug-like agility and elasticity because of a new type of artificial muscle. Kevin Chen, senior author of the paper, states that “This opens up a lot of opportunity in the future for us to transition to putting power electronics on the microrobot,”.

The new production technique gives the researchers the opportunity to produce low-voltage, power-dense, high-endurance soft actuators for an aerial microrobot. These artificial muscles greatly improve the payload of the robot, enabling it to hover for 20 seconds, which is the longest ever recorded for a robot of its size.

The rectangular microrobot weighs less than one-fourth of a penny and has four sets of wings, each driven by a soft actuator. These muscle-like actuators are made from elastomer layers situated between two very thin electrodes and then rolled into a squishy cylinder. When the energy is applied to the actuator the electrodes squeeze the elastomer and that mechanical strain is used to flap the wing. This new production technique creates artificial muscles with fewer defects, which drastically prolong the lifespan of its components and improves the robot’s performance and payload.

The more surface area the actuator has the less energy is needed, so the researchers built these between as many ultra-thin layers of elastomer and electrode as they could. They were able to produce an actuator with 20 layers, each of which is ten micrometres in thickness, about the diameter of a red blood cell. During the spin-coating process an elastomer is poured into a flat surface and rotated rapidly.

The centrifugal force pulls the film outward to make it thinner. However, air comes back into the elastomer and creates a lot of microscopic air bubbles, which become stronger as the layers get thinner. They found that if they perform a vacuuming process immediately after spin-coating, while the elastomer is still wet, it removes the air bubbles. Removing these defects increases the power output of the actuator by more than 300 per cent and substantially increases its lifespan. Currently, the team is limited to how they can make the layers because of dust in the air and a limited spin-coating speed.

They intend to work in a clean room in the future, as this will eliminate this problem and enable them to use more precise methods. Eventually, they want to reduce the actuator layer from ten micrometres to only one micrometre, which would pave the way for many applications for insect-sized robots.

Written by Berber Bijlsma