Inspired by both nature and biology, a Florida Atlantic University scientist has built a lifelike robotic finger. The design required shape memory alloy (SMA), a three-dimensional CAD model of a human finger, a 3D printer, and a unique thermal training technique.
“We have been able to thermomechanically train our robotic finger to mimic the motions of a human finger like flexion and extension,” said Erik Engeberg, Ph.D., assistant professor in the Department of Ocean and Mechanical Engineering within the College of Engineering and Computer Science at FAU.
In the study, Engeberg and his team employed "Joule" heating - a resistive process that passes electric currents through a conductor that releases heat. Using a 3D CAD model of a human finger, the engineers were able to create a solid model of the finger.
With a 3D printer, the researchers created the inner and outer molds that housed a flexor and extensor actuator and a position sensor. The extensor actuator takes a straight shape when heated, while the flexor actuator takes a curved shape.
The FAU researchers used SMA plates and a multi-stage casting process to assemble the finger. An electrical chassis allowed electric currents to flow through each SMA actuator. Its U-shaped design directed the electric current to flow the SMAs to an electric power source at the base of the finger.
The new technology features both a heating and then a cooling process to operate the robotic finger. As the actuator is cooled, the material relaxes slightly.
Results from the study showed a more rapid flexing and extending motion of the finger as well as its ability to recover its trained shape more accurately and more completely, confirming the biomechanical basis of its trained shape.
Since the initial application of this finger will be used for undersea operations, Engeberg used thermal insulators at the fingertip, which were kept open to facilitate water flow inside the finger. As the finger flexed and extended, water flowed through the inner cavity within each insulator to cool the actuators.
