UCLA researchers have built a two-legged humanoid robot whose brain is an ordinary Android smartphone, with the rest of the hardware estimated at about $400, not counting the phone.
The machine, called PhoneBot, comes from the university's Robotics and Mechanisms Laboratory, known as RoMeLa. It can walk, follow a person and get back on its feet after falling face down.
The team wants humanoid robotics to be affordable for classrooms and labs on tight budgets. Some small research models run several thousand dollars, and more capable systems cost far more.
PhoneBot stands about 19 inches tall and weighs roughly four pounds with the phone attached. Its 13 motorized joints include six in each leg and one that rotates the upper body, so the camera can turn toward someone while the feet stay planted.
The phone handles sensing and computing. An Android app draws on its motion sensors for balance, the camera identifies and tracks people, and an AI-driven walking controller decides how the robot moves.
Those commands travel over Wi-Fi to a small computer inside the robot, which drives the motors. With no wired link between phone and body, one handset can be traded for another without rewiring.
The walking system was trained in computer simulations before it was tested on the physical robot. Researchers also devised a way to make it use both legs more evenly.
Older phones still qualify
The project did not require a flagship device. Core functions were tested on four Android phones: a 2017 Honor 9, a Samsung Galaxy A16 5G and two Motorola Moto G models from 2024 and 2025. The three prepaid phones cost roughly $50 to $90 apiece at the time of testing.
All four managed movement control and camera-based recognition. The Honor 9, however, could not run one mapping feature because the Google services it needs were unavailable on that device in the United States.
Limits and next steps
PhoneBot has no arms, so it cannot carry or pick up objects. It was trained only on flat ground, leaving stairs and uneven surfaces as open problems, and its conversational feature still leans on a separate laptop to process speech and produce AI replies while the phone records and plays audio.
UCLA describes PhoneBot as an open-source research platform and has posted hardware designs and assembly resources at phonebot.dev for noncommercial use under a Creative Commons license. The site does not clearly offer a download of the full Android app and trained walking software.
Builders may also need a 3D printer and assembly tools, and shipping and other expenses could push costs above the $400 estimate.
The team's next goals include handling rougher terrain, adding lightweight arms and running more conversational AI on the phone itself to cut reliance on an outside computer.
