The world's smallest remote-controlled walking robot is born!

2024-01-23

Recently, an international team of engineers led by Northwestern University in the United States created and showcased the smallest remote-controlled walking robot in history. The magic of this submillimeter robot lies in its ability to walk, bend, twist, turn, and jump through laser remote control.

The team stated that this "micro robot" can expand the functionality and performance of small systems, making them closer to real-world applications, such as repairing or assembling small structures or machines, or serving as a surgical assistant to clear blocked arteries to prevent internal bleeding or eliminate cancer tumors.

Unlike existing miniaturized robot manufacturing methods, the team's submillimeter robot design method does not require complex hardware, power, or connection to remote control devices. The team's new method was inspired by the 3D images in the stereoscopic book. The research team used shape memory alloy on the crab robot, heated it from different angles with a laser, stimulated its shape to change, and generated energy to move it - the direction of the laser determines the direction of the robot's movement.

In order to create robots like crab claws, engineers first transfer and print the nickel titanium joint and polyimide (PI) skeleton of the supporting structure of the robot onto a stretched silicone elastomer substrate. Next, they release the tension on the substrate, causing the silicon wafer to shrink, causing the flat nickel titanium/pi design to bend and pop out, forming a small crab like 3D shape. These micro robots are only half a millimeter wide and can be controlled by external scanning lasers.

Engineers used scanning lasers to repeatedly heat and cool the nickel titanium joints of crabs, causing them to expand and contract (controlling the amplitude, speed, and direction of motion), thus initiating the movement of micro robots. In subsequent durability tests, Rogers and his colleagues found that nickel titanium alloy joints can undergo over 100000 continuous heating cooling transitions under 520 nanometer scanning laser without losing stability.

When the laser is irradiated on the robot, its joints will expand due to heating. When the laser stops emitting light, their joints will contract as they cool down. This causes it to move quickly like a crab, and its speed and direction depend on the frequency and angle of light.

In the concept validation demonstration, engineers demonstrated that they can control the direction of the walking robot crab by scanning the direction and angle of the laser. For example, when scanning the leg joints from left to right with a laser, the micro robot runs from right to left. Due to the small size of the micro robot, the heating and cooling of the joints occur quickly, allowing the robotic crab to move at a relatively fast speed of half a body length per second. The experiment showed that the average speed of the robot at a laser scanning frequency of 0.1 Hz was 0.017 mm/s, and the average speed increased to 0.49 mm/s at a frequency of 10 Hz.

This study also suggests that robots can be restored to their original two-dimensional shape and modified to fit different purposes. They created more complex movements such as jumping, turning, twisting, and bending through different 3D geometric shapes (mimicking geometers, crickets, and beetles) and laser scanning modes (heating and cooling crab joints separately).

Engineers have demonstrated the potential use of micro robots as wireless environmental sensors. They equipped the robot with reflective mirrors, which trigger the robot's action when the material in the environment changes color due to humidity or ultraviolet radiation.

In addition to this type of robot, the engineering team also used the same materials and manufacturing methods to create micro robots similar to circular and double layered spirals. Rogers said, "With these assembly technologies and material concepts, we can build walking robots of almost any size or 3D shape."

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