A solid-state ornithopter with no moving parts has been developed by researchers in the US, writes Nick Flaherty.

The ornithopter uses induced-strain actuators based on composite piezoelectric materials to eliminate the need for electromagnetic motors and conventional power transmission mechanisms, potentially saving weight and energy consumption, improving durability and reducing overall mechanical complexity.

Ornithopter flight is highly sensitive to weight and power consumption. Efforts to save weight include using light materials for bar-type mechanisms, onboard electronics and even custom integrated circuits. However, the weight of the motors and driving mechanisms significantly reduces the aerodynamic efficiency, power density and bandwidth of ornithopters, making them impractical for most uses.

“We apply electricity to the piezoelectric materials and they move the surface directly, without extra joints, extra linkages or motors,” said Onur Bilgen, an associate professor in the Department of Mechanical and Aerospace Engineering in the Rutgers School of Engineering. “The wing is a composite including a piezoelectric material layer and a carbon-fibre layer. Apply voltage to the piezoelectric layer, and the whole composite flexes.

“We want to achieve flapping flight without bone-like structures or muscle-like actuators, flapping in a much simpler way,” said Bilgen.

To control the ornithopter, thin Macro Fiber Composite (MFC) strips are bonded directly onto flexible wings. When an electric current is applied to the MFCs, the wings exhibit flapping, twisting and morphing movements without the need for a motor or transmission.

“The carbon fibre acts like feathers and bone, and the surface-mounted MFCs act like muscles and nerves,” said Bilgen.