Engineers have designed a tiny, low-weight and cordless robot that can act independently and with ultra-high precision in all directions in some of the most extreme conditions. The robot, which the designers call "Holonomic Beetle 3" (or HB-3)—as they were inspired by the movements and anatomy of the rhinoceros beetle—combines the use of piezoelectric actuators with autonomous technology to enable micro-scale manipulation tasks that were previously out of reach for robots.
HB-3 addresses a growing need across various industries—including laboratory automation, medical procedures, and scientific research—for precise manipulation at multiple scales, from nanomaterial and cell manipulation up to to chip component assembly, where human presence is limited or impossible. This is particularly necessary in vacuum, clean, draft, and biohazard safety chambers.
A paper describing the robot's design and capabilities was published in the journal Advanced Intelligent Systems on January 26.
In recent years, autonomous (cordless) robots have been put to practical use in a range of industrial sectors, disaster sites, medical fields and extreme environments or confined spaces where human access is not feasible. Meanwhile, miniaturization of internal electronic components for all manner of devices has also proceeded apace, including the development of microbatteries and micro-supercapacitors that are only a few microns thick. However, the conventional positioning devices have remained stubbornly bulky and heavy compared with those tiny parts, so there was much room for improvement with respect to energy and space efficiency. Even if the driving circuits and batteries had become tiny, their range and operational freedom was still highly restricted.
To address these issues, various precision actuators—a robot's "muscles," basically, that convert energy (electrical, hydraulic, or pneumatic) into motion—have been developed to improve these positioning devices. Piezoelectric actuators in particular have shown great promise. Piezoelectric materials such as the quartz in quartz watches or synthetic ceramics such as PZT (lead zirconate titanate) generate an electric charge when subjected to mechanical stress (essentially a push or a squeeze). They also perform the reverse: deforming when an electric field is applied. This piezoelectric property permits ultra-fine movements by expanding or contracting in response to very precisely defined electrical signals, often at the nanometer scale.
However, while many miniature robots and grippers have been developed, until now there have been no mobile micromanipulators that integrate piezoelectric actuation technologies while also being autonomous and untethered, and adapted to real-world applications.
At the heart of HB-3's design is its compact, lightweight structure—just 515 grams and measuring only 10 cubic centimetres in size. An integrated driving circuit using a single-board computer eliminates the issues that had been caused by power-supply cables in the team's prior research. HB-3 is also equipped with an internal camera and performs tasks using machine learning algorithms that allow it to adjust its movements in real-time, a feature not found in previous micromanipulators.
In rigorous testing, the HB-3 demonstrated impressive performance across a variety of tasks in confined, isolated environments using different tools, such as precise tweezers for picking and placing a chip part or an injector for applicating a miniscule droplet, while enjoying an average positioning accuracy of just 0.08 mm along the x-axis and 0.16 mm along the y-axis, with 87 percent of tasks deemed successful. The tools can be converted into measurement probes, soldering irons, screwdrivers, and other precision instruments flexibly on demand and at many different scales from the meter down to the nanometer.
"We've been able to push the boundaries of miniaturization to create a truly autonomous, untethered device that can operate in tight, hazardous spaces," said Ohmi Fuchiwaki, associate professor with the Faculty of Engineering, at YOKOHAMA National University and one of the engineers behind the tiny machine. "The HB-3 can not only handle complex tasks but also do so with unmatched precision."
Nevertheless, the team still wants to fine-tune their little beetle. They feel that HB-3's processing speed, dependent on a Raspberry Pi CPU, could be improved, and the time that it takes for the robot to detect objects could be reduced, perhaps by offloading object detection to an external high-performance computer. Moving forward, the researchers also aim to improve its speed and precision, and explore integration of internal side-view and top-view cameras to improve z-axis positioning accuracy.
