Mexican jumping beans, which are actually hollow seeds containing moth larva, seem to bounce and roll around in a totally random manner as the larva move around inside, but researchers at the Georgia Institute of Technology have found that it's not random at all, and their behavior is now being used to program robots to roll in a controlled way. This discovery could ultimately be used to create solar-powered micro-robotic sensors that could be used in a host of applications.
Mexican jumping beans move because the larva inside try to escape heat and find cooler areas. The larva move the seed pods by using silk threads to attach themselves inside and then walking up one side, which causes rolling, or by rapidly striking with one side of its body, which causes jumping. It has also been found that the frequency of these movements increases as outside temperature rises.
This new study was able to determine the frequency of each type of movement -- rolling, jumping or flipping -- by building a 12-lane race track for the beans with an electric heating blanket under one end. The blanket was set to different settings to make a range of temperature gradients from one end to the other.
Phys.org reports, "Out of 550 movements, the beans jumped 85% of the time, rolled 14% of the time, and flipped 1% of the time. They noticed that this “jump-and-roll” motion closely resembles the “run-and-tumble” motion of bacteria and other organisms. Previous research has shown that this type of trajectory is optimal for locating randomly distributed targets, and the engineers hope to investigate the strategy further in the context of the jumping beans."
The researchers then created an algorithm of jumping bean behavior to control a wheeled robot based on three rules: roll or tumble randomly to the left or right, go in the direction of the lowest sensed temperature and stop when the preferred temperature is reached.
“Mexican jumping beans have many interesting abilities that are useful for robotics,” said David Hu, one of the lead researchers. “They move within an armored shell yet still are able to sense their surroundings. Although nearly spherical, they have a notch that enables them to move uphill and across small obstacles. Finally, they implement a very simple algorithm for sensing of their surroundings that is effective for enabling them to find shadows and hide in them. All these abilities might be implemented in a much smaller robot.”
The researchers see this rolling behavior being useful in designing micro-robotics with low power needs like solar-powered "jumping bean" sensors. The sensors could be programmed to detect changes in not just temperature, but chemicals or light gradients, which could be used in a variety different sensing or surveillance applications.