Humans use their fingers for some of their most delicate communication. Typing on a keyboard or phone, conversing through sign language, or performing on a guitar or piano require finely-tuned movement and coordination between multiple digits. But many of the technologies intended to control or augment these activities have struggled to recreate the precise gestures and motions they require.
A new solution from the University of Chicago’s Human Computer Integration Laboratory, directed by Asst. Prof. Pedro Lopes, solves this problem with a combination of electrical muscle stimulation (EMS) and mechanical brakes. DextrEMS, a haptic device invented and developed by Lopes’ students in the Department of Computer Science: Romain Nith, Shan-Yuan Teng, Pengyu Li, and Yujie Tao, fits unobtrusively on a user’s hand. As EMS electrodes on the forearm move fingers to their desired position, ratchet brakes at the finger joints lock them in the target gesture and restrict unwanted movement from other fingers.
The work was presented last week at the 2021 ACM Symposium on User Interface Software and Technology (UIST), one of the top human-computer interaction conferences.
“DextrEMS is a means to actuate human fingers through a computer,” said Nith, a second-year Ph.D. student. “It’s the same idea as a traditional exoskeleton, where we are providing force feedback to the fingers, but we wanted to tackle it through the perspective of miniaturizing everything. By combining EMS and brakes, we can actually create movements that weren’t possible before and users can move fingers independently.”
EMS works by affixing electrodes to the user’s skin, then sending small, painless electrical signals that cause muscles to contract. For controlling the fingers, EMS electrodes are commonly placed on the wrist and forearm, where the finger muscles originate. But because of this distance and the close proximity of muscles for different fingers, it’s hard to control digits independently. Even natural motion, controlled by the brain, struggles to move a single finger without also moving its neighbors (try it!).