A special sleeve has been developed that gives people with prosthetic hands the dexterity of real fingers.
It enables them to unscrew a water bottle while holding a card, type on a keyboard, press buttons on a remote control or braid a child’s hair.
The soft robotic ‘armband’ is the first of its kind, conveying artificial sensations of touch.
It opens the door to limbless individuals pursuing careers as surgeons – or rock stars on keyboards or guitar.
First author Moaed Abd, a PhD student at Florida Atlantic University, said: “Examples included the proportional control of a card being pinched between the index and middle fingers at the same time the thumb and little finger were used to unscrew the lid of a water bottle.
“Another simultaneous control demonstration was with a ball that was grasped with three fingers while the little finger was simultaneously used to toggle a light switch.”
We use our hands for a wide variety of tasks, seldom thinking about how complicated with muscles and signals working together for each gesture.
Building fakes with equivalent motor function has stumped bioengineers for decades. The US team described the device as a “game changer”.
It combines haptic or touch sensation feedback with EMG (electromyogram) signals from the forearm.
Subjects grabbed and transported objects simultaneously without breaking or dropping them – even when vision of both was obstructed.
They performed as well in key performance metrics as able bodies individuals.
What is more, they rated feeling much more important than seeing. There was little visually perceptible warning before objects were broken.
Corresponding author Professor Erik Engeberg, from the same lab, said: “Our study is the first to demonstrate the feasibility of this complex simultaneous control task while integrating multiple channels of haptic feedback non-invasively.
“None of our study participants had significant prior use of EMG-controlled artificial hands, yet they were able to learn to harness this multitasking functionality after two short training sessions.”
The armband, called Shadow Hand, is fitted with soft actuators to convey a proportional sense of contact forces.
Haptic feedback occurs at three locations corresponding to the thumb, index and little finger. Air chambers correspond to ‘fingertips’.
They convey the amplitudes of the forces applied to both objects grasped by the hand. Vibratory sensors indicate if they break.
It is hoped the study in the journal Scientific Reports will be used in the future frameworks of highly complex bimanual operations.
These include those required of surgeons and guitarists. The goal is for people without arms to pursue careers and recreational pursuits currently unattainable to them.
Dr Stella Batalama, dean of the university’s College of Engineering and Computer Science, said: “Enabling refined dexterous control is a highly complex problem to solve and continues to be an active area of research.
“It necessitates not only the interpretation of human grasp control intentions, but also complementary haptic feedback of tactile sensations.
“With this innovative study, our researchers are addressing the loss of tactile sensations, which is currently a major roadblock in preventing upper limb-absent people from multitasking or using the full dexterity of their prosthetic hands.”