This bracelet, a cuff with spiky transducers, has 24 speakers that emit ultrasonic signals when the wearer turns it on. Ben Zhao and Heather Zheng, both computer science professors at the University of Chicago, along with the help of assistant prof Pedro Lopes, designed this bracelet of silence that will jam an Echo or Alexa or any other microphones in the vicinity from listening in on the wearers conversations.

(Petra Ford/The New York Times)