University of Pennsylvania researchers built a sub-millimeter robot with onboard sensors, an actuator, and a microcontroller; the devices are solar-powered, can move through fluids via electric-field propulsion, and cost under a penny apiece to produce in the lab. The team led by Marc Miskin demonstrated sensing and autonomous actions at scales smaller than a grain of salt. Investigators position the platform as a potential tool for minimally invasive diagnostics and targeted biomedical interventions, though substantial translational hurdles remain, including biocompatibility, navigation in vivo, and regulatory pathways for swarms of microscopic devices.