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IR sensor sheds light on ant activity

01 Feb 2007

Researchers in Cuba are using an infrared sensor to study the collective behaviour of ants and hope to apply their findings to engineering problems.

Using simple optical components to quantify the behaviour of ants could help scientists tackle problems such as traffic management say researchers at the University of Havana in Cuba. (Review of Scientific Instruments 77 126102)

"Ants show a highly nonlinear, collective behaviour that somehow produces an overall intelligence out of individual simplicity," Ernesto Altshuler from Havana's Complex Systems and Superconductivity Laboratory told optics.org. "We want to quantify and understand the process of self organization that produces this overall intelligence. Many authors believe that ant behaviour may teach us robust algorithms to be used in engineering."

Altshuler and colleagues use an infrared LED, a mirror and a phototransistor. Both the LED and the phototransistor have a peak emission/sensitivity around 850 nm.

"The LED and phototransistor are placed back-to-back and carefully aligned in an incision within the cylindrical mirror," explained researcher Claro Noda. "The result is a thin light curtain that propagates over the inner surface of the mirror from the LED to the phototransistor."

The researchers installed their infrared sensor at the entry-exit point of a bibijaguas nest, a leaf cutting ant that is endemic to Cuba. When an ant enters the nest, it steps through a ring and interrupts a light curtain which triggers a count. The key term is "activity" which is defined as the number of counts the sensor generates when ants enter or leave the nest during a given time interval.

"Very low power and low noise electronics were used for conditioning the signal and detecting changes in the infrared light," explained Noda. "We used a filter to isolate the signal shifts produced by ants from those created by environmental light changes. Power consumption per node is less than 50 mW, with 90% of that feeding the LED."

Preliminary results show that the activity of a nest is typically periodic with steady activity during night hours and almost no activity during the day. "The most interesting intervals are where this steady activity builds up and slows down," said Altshuler. "We already have a preliminary size distribution of activity bursts that can be interpreted in terms of theories involving self-organization."

The team now hopes to measure the activity of ants in a trail leading to and from the nest. "We plan to learn how perturbations travel through a queue of ants and compare the dynamics of ant traffic with that of urban or human traffic, which is a subject of very intense research nowadays."

Jacqueline Hewett is editor of Optics & Laser Europe magazine.

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