Imagine a tiny machine so small it could travel along a single strand of DNA — the long, coiled molecule that holds the instructions for life. That's exactly what scientists at UNSW Sydney have built, and they're calling it Tumbleweed.
Researchers there have created the world's first artificial protein motor that can walk along DNA in controlled, reversible steps. Think of it like a microscopic inchworm with three feet, each one grabbing onto specific spots on a DNA track before letting go and taking another step. Each step measures just 16 nanometers — so small that thousands of them would fit across the width of a human hair.
The team, led by Professor Paul Curmi, published their work in the journal Nature Nanotechnology. Curmi says this moment marks the end of a 20-year research journey for scientists around the world. "We've demonstrated that we can engineer entirely new behaviors into proteins by assembling existing biological components in new ways," he said.
Natural molecular motors already exist inside our cells. Kinesin, dynein, and myosin are proteins that carry cargo, power muscle movement, and keep our bodies running. But building an artificial version from scratch has always been a major goal in science because it teaches researchers how these natural machines work — and how they might be redesigned for new tasks.
What's special about Tumbleweed is that its individual parts don't move on their own. Only when assembled together do they produce a walking machine. The researchers control when it steps and which direction it travels by changing the chemical signals in its environment. Flip the signals one way, and Tumbleweed walks forward. Flip them another way, and it reverses course.
Right now, Tumbleweed can walk about 100 nanometers before it stops, and it moves at roughly 1 nanometer per second. The team is working to make it go farther and faster. Eventually, they hope to design versions that walk on their own, without needing scientists to send external commands.
Looking ahead, this research could help build tiny machines for computing that are more energy-efficient and sustainable than today's technology. The researchers cite physicist Richard Feynman, who once said: "What I cannot create, I do not understand." By building Tumbleweed, the team says they're finally beginning to grasp how nature's smallest motors work — and how humans might one day build their own.