Your old Android phone could become a walking robot

Got an old Android phone collecting dust in a drawer? You might want to hang on to it. Researchers at UCLA have figured out how to turn an aging smartphone into the brain of a small walking robot. It's called PhoneBot, and it can walk on two legs, follow people and even get back up after falling face down.

The most surprising part? The researchers estimate the robot's hardware costs about $400, excluding the phone. So, that forgotten smartphone could have a pretty interesting second life. Here's how the researchers pulled it off and what it would take to build one yourself.

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PhoneBot comes from UCLA's Robotics and Mechanisms Laboratory, also known as RoMeLa. The team built a miniature humanoid robot that stands about 19 inches tall and weighs roughly four pounds, including the smartphone attached to its body.

Instead of developing an expensive custom computer, researchers used technology already inside an Android phone. The robot has 13 motorized joints, with six in each leg and another that lets its upper body rotate. That extra movement allows the smartphone's camera to turn toward someone while the robot's feet stay planted.

The researchers goal is to make humanoid robotics more affordable for schools and research teams that cannot spend thousands of dollars on specialized machines.

Think about everything your smartphone already does. It can recognize objects through its camera and detect movement using built-in sensors. It also has enough processing power to run sophisticated software. PhoneBot puts those capabilities to work. An Android app uses the phone's motion sensors to help the robot maintain its balance. Meanwhile, the camera helps it recognize and track people. The phone also runs an artificial intelligence-powered walking controller that tells the robot how to move. Those instructions travel over Wi-Fi to a small computer inside the robot, which communicates with the motors. The smartphone has no physical electrical connection to the robot's hardware. That design makes it easier to swap phones without rewiring the machine. Researchers trained PhoneBot's walking system in computer simulations before testing it on the actual robot. They also developed a way to improve how evenly it uses both legs. As a result, PhoneBot can walk on flat surfaces and stand up from a face-down position. For something powered largely by an old smartphone, that's quite an accomplishment.

Here's something I found especially interesting. UCLA didn't need the latest expensive smartphone to make PhoneBot work. In fact, the researchers successfully tested its core functions on four different Android devices, including an Honor 9 released back in 2017. The other models included a Samsung Galaxy A16 5G and two Motorola Moto G phones from 2024 and 2025.

Researchers purchased the three prepaid models for roughly $50 to $90 each. Those were the prices reported during testing, rather than guaranteed prices today. All four phones handled the essential functions, including movement control and camera-based recognitio