The human hand is a wonder for all the things it can do and feel. Modern-day prosthetics are also marvels — for all they can do for those who have lost a hand. We’ve enhanced the capabilities of these artificial hands with an electronic glove (e-glove) system that fits onto a prosthetic hand and can detect external stimuli like temperature, humidity and pressure. The e-glove is coupled with a smartwatch to transmit this data for real-time display and feedback, providing the user with human-hand-like sensory perceptions to better navigate daily life.
This ability to detect the environment lets prosthetic hand users get feedback when they do things like shake someone’s hand, touch an object, or hold surfaces that might be hot or cold or dry or wet. We used an e-glove to grasp a baseball — monitoring the pressure on the palm area with an array of 20 pressure sensors — and found that the glove can distinguish slight pressure changes like those perceived by a human hand. Subjects asked to perform actions like touching, poking, rubbing, and shaking hands further validated the usefulness and comfort of the e-glove.
That’s a big deal: Studies show nearly 50% of people who have lost a hand get psychological assistance to help them cope with their new challenges. The e-glove combines the practicality of prosthetics with some restoration of the tactile and sensory capabilities of the human hand. The e-glove is also packaged with a unique top layer that mimics the human hand’s appearance, softness, color and textures, helping someone integrate more naturally into social contexts.
The technology breakthrough is composed of flexible, stretchable forms of sensors that collect information from the environment as well as provide a realistic hand look. The glove itself is fabricated using 3D printing for the fingers and palm sections, and screen and transfer printing to laminate multiple layers of the electronic circuit materials and devices onto a commercial glove.
We apply an epoxy glue over a glove made from nitrile, an organic compound with rubberlike qualities, and cure it in an oven. Conductive ink is screen-printed on the glove’s surface; the sensors (electrophysiological recording electrodes) are then transfer-printed onto the glove. Subsequent annealing — heating the glove, then cooling it slowly — secures the bond between the sensing elements and the conductive ink. The entire structure is coated with a silicone elastomer — also a rubberlike material — to form a thin, sealing layer over the outer surface.
The coupled smartwatch is powered by a 32-bit microprocessor for data collection; wireless transmission is enabled by Bluetooth. The e-glove wearable raises the possibility of extended capabilities beyond hand prosthetics — for example, to measure heart rate, assess fatigued muscles during or after exercise, and even to record electrical activity of heart and muscle, including electrocardiograms and electromyograms, via the human skin.
We believe the e-glove can enrich the lives of those who wear prosthetic hands, as well as lay the groundwork for a new generation of bio-integrated wearable sensors.
by Chi Hwan Lee, PhD
Assistant Professor of Biomedical and Mechanical Engineering, College of Engineering, Purdue University