Date: 11/10/2020
Writer: Vladimir Avina, 575-646-7234, vlad23@nmsu.edu
Deep in the rainforests of Madagascar lives an endangered lemur whose unique evolution is paving the way to improve non-destructive testing on aging infrastructure and composite materials.
Ehsan Dehghan-Niri, assistant professor in the Department of Civil Engineering at New Mexico State University, is studying the aye-aye lemur. The features of an aye-aye are similar to non-destructive testing technologies used by engineers to inspect aging infrastructure including pipelines, composite materials used in the aviation industry, and bridges.
This small fuzzy primate uses its elongated middle finger to tap on tree bark, along with its large ears and superior hearing, to find food.
“The aye-aye displays a unique acoustic foraging behavior called tap-scanning or percussive foraging to locate and extract wood-boring larvae from trees,” Niri said. “There are different types of tap-scanners used to find delamination, voids or inclusions. It’s a practical and inexpensive non-destructive testing method, but it has its own limitations.”
Niri’s research aims to revolutionize tap-scanning instruments by studying the aye-aye’s distinctive anatomy. Niri is collaborating with other universities and using resources within the College of Engineering for the first stages of his research.
Access to captive aye-ayes outside Madagascar is difficult and rare. Luckily for Niri, researchers at the Duke Lemur Center (DLC) in North Carolina invited him for an up-close and personal experience. According to their website, the DLC has the world’s most diverse non-invasive research facility, home to more than 200 lemurs across 14 species.
“Two years ago, I had a chance to be inside the cage with a captive aye-aye,” Niri said, “Keep in mind they are nocturnal, so it was really dark with red lights inside the cage.”
The DLC provided Niri with CT scans of an aye-aye to study the ear’s structure, shape and role in near-field sensing. Niri 3D printed an aye-aye’s head and hand with the elongated finger.
With help from the Aggie Innovation Space (AIS), his research team used a bio-mimetic approach to mimic the tapping process with robotic arms. Using a microphone, an amplifier, the robotic arm and a tiny hammer, Niri’s team was able to create a biometric system to simulate the near-field sensing of an aye-aye.
“The results obtained with the biomimetic approach suggest that the cupped-shape conformation of the pinna (ear) can substantially enhance the near-field acoustic measurement and sensitivity of the aye-aye’s auditory system through three mechanisms,” Niri explained.
The three mechanisms Niri’s initial tests found that enhance an aye-aye’s acoustic measurement and sensitivity are: An increase in signal to noise ratio (SNR), creating a focal area and possibly a focal point to increase linear spacing of a measurement, and increasing the receiver peak frequency by changing near-field beam pattern for higher frequencies that enhance sensitivity.
The next steps of Niri’s research are to take an even closer look at the morphological features of the aye-aye like their ears and elongated fingers, as well as the biological materials they are made of.
“While the current results have evaluated the effects of the entire aye-aye pinna, the effect of individual morphological features of aye-aye pinna, head, and pinna’s material have not been considered,” Niri said. “Further work is undergoing to reveal each feature effect in developing such a unique auditory near-field sensing system.”
