New robotic finger feels and works like real thing

Inspired by both nature and biology, scientists have designed a novel robotic finger that looks, feels and works like the real thing and could be adapted for use in a prosthetic hand.

Most robotic parts used to today are rigid, have a limited range of motion and don't really look lifelike.

Researchers developed and tested the new robotic finger using shape memory alloy (SMA), a 3D Computer-aided design (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, assistant professor at the Florida Atlantic University (FAU).

"Because of its light weight, dexterity and strength, our robotic design offers tremendous advantages over traditional mechanisms, and could ultimately be adapted for use as a prosthetic device, such as on a prosthetic hand," said Engeberg.

Engeberg and his team used a resistive heating process called "Joule" heating that involves the passage of electric currents through a conductor that releases heat.

Using a 3D CAD model of a human finger, they were able to create a solid model of the finger.

With a 3D printer, they created the inner and outer molds that housed a flexor and extensor actuator and a position sensor.

They used SMA plates and a multi-stage casting process to assemble the finger. An electrical chassis was designed to allow 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.

This new technology used both a heating and then a cooling process to operate the robotic finger. As the actuator cooled, the material relaxed 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.

"Because SMAs require a heating process and cooling process, there are challenges with this technology such as the lengthy amount of time it takes for them to cool and return to their natural shape, even with forced air convection," said Engeberg.

"To overcome this challenge, we explored the idea of using this technology for underwater robotics, because it would naturally provide a rapidly cooling environment," said Engeberg.

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. The research was published in the journal Bioinspiration & Biomimetics.