Oct 12, 2015 | By Benedict

Researchers from Florida Atlantic University have given a whole new meaning to the term ‘finger print’, after they unveiled their new 3D-printed robotic finger. The bionic digit, made from shape memory alloy (SMA), looks and moves almost like a real human finger.

Professor Erik Engeberg, from the Department of Ocean and Mechanical Engineering at Florida Atlantic University, led a team of researchers to develop the bio-inspired robotic finger, using SMA, a 3D CAD model of a human finger, a 3D printer, and a unique thermal training technique. Engeberg's BioRobotics Laboratory at FAU is principally devoted to research into robotics and prosthetics, controller design, bioinspiration and biomemetics.

“We have been able to thermomechanically train our robotic finger to mimic the motions of a human finger like flexion and extension,” explained Engeberg. “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.”

To create the most lifelike model possible, the team sourced a 3D CAD model of a human finger online, from which they were able to 3D print a solid model, comprised of inner and outer molds. After the molds were printed, a flexor actuator, extensor actuator, and position sensor were placed inside them. The actuators hold the secret to the bionic finger’s realistic motion: The extensor actuator straightens out when heated, whilst the flexor actuator takes a curved shape when heated, realistically imitating muscle movement.

SMA plates and a multi-stage casting process were used to construct the remainder of the finger, before an electrical chassis was incorporated into the structure to allow electric currents to flow through the actuators. Engeberg and co employed a resistive heating process called Joule heating, in which electric currents run through a heat-emitting conductor. The robotic finger straightens when its extensor actuator is heated, and bends when its flexor actuator is heated. “Thus, alternately heating and cooling the flexor and extensor actuators caused the finger to flex and extend,” the researchers explained.

“Because [SMAs] require a heating 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,” added Engeberg. Because of this, the team are initially deploying this technology in underwater robotics, since temperates drop more rapidly underwater than in other settings. In order to reap the rewards of an underwater environment, open thermal insulators were placed at the tip of the 3D-printed finger, which facilitated internal water flow. This helped to cool the actuators as the finger moved back and forth. Engeberg reported an improved operational speed when tested underwater. A less restrictive cooling device will need to be implemented before the finger can be considered for use as a prosthetic. The research paper, authored by Engeberg, Savas Dilibal, Morteza Vatani, Jae-Won Choi and John Lavery, which documents the team’s findings, can be found over at IOP Science.

Posted in 3D Printing Applications

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