Tiny flying machines have the ability to survey anything from indoors to buildings that have collapsed. Now researchers are mimicking nature's small flyers - and developing robotic bats that offer increased manoeuvrability and performance.

Small flyers, or micro-aerial vehicles (MAVs), have garnered a great deal of interest due to their potential applications where manoeuvrability in tight spaces is necessary, said Gheorghe Bunget of North Carolina State University (NCSU) researcher. 

"Due to the availability of small sensors, MAVs can be used for detection missions of biological, chemical and nuclear agents," said Bunget. 

But, because of their size, devices using a traditional fixed-wing or rotary-wing design have low manoeuvrability and aerodynamic efficiency. 

So Bunget and his adviser Stefan Seelecke looked to nature. "We are trying to mimic nature as closely as possible," Seelecke said, "because it is very efficient. And, at the MAV scale, nature tells us that flapping flight - like that of the bat - is the most effective." 

The researchers have done extensive analysis of bats' skeletal and muscular systems before developing a "robo-bat" skeleton using rapid prototyping technologies.

The fully assembled skeleton rests easily in the palm of your hand and, at less than six grams, feels as light as a feather. The researchers are currently completing fabrication and assembly of the joints, muscular system and wing membrane for the robo-bat, which should allow it to fly with the same efficient flapping motion used by real bats. 

"The key concept here is the use of smart materials," Seelecke said. "We are using a shape-memory metal alloy that is super-elastic for the joints. The material provides a full range of motion, but will always return to its original position - a function performed by many tiny bones, cartilage and tendons in real bats."

Bunget will present the study at the American Society of Mechanical Engineers Conference in California in September.