Engineers with the Massachusetts Institute of Technology (MIT) have developed a noninvasive pacemaker that uses ultrasound to stimulate the heart. The group shared its early experience with the device in Nature Biomedical Engineering, highlighting its compact, wearable design. “Pacemakers are one of the most important and widely used human implants, and they have saved millions of lives,” Gengxi Lu, the study’s co-corresponding author, said in a statement.