Novel 3D nanofabrication techniques enable miniaturized robots

In the 1980s when micro-electro-mechanical systems (MEMS) were first created, computer engineers were excited by the idea that these new devices that combine electrical and mechanical components at the microscale could be used to build miniature robots.

The idea of shrinking robotic mechanisms to such tiny sizes was particularly exciting given the potential to achieve exceptional performance in metrics such as speed and precision by leveraging a robot’s smaller size and mass. But making robots at smaller scales is easier said than done due to limitations in microscale 3D manufacturing.

Nearly 50 years later, Ph.D. students Steven Man and Sukjun Kim, working with Mechanical Engineering Professor Sarah Bergbreiter, have developed a 3D printing process to build tiny Delta robots called microDeltas. Delta robots at larger scales (typically two to four feet in height) are used for picking, placing, and sorting tasks in manufacturing, packaging, and electronics assembly. The much smaller microDeltas have the potential for real-world applications in micromanipulation, micro assembly, minimally invasive surgeries, and wearable haptic devices.

The findings are published in the journal Science Robotics.

Previous methods for making robotic mechanisms at these smaller sizes required manual assembly and folding of microfabricated components.

Bergbreiter’s team developed a 3D printing process for microrobotics that uses two-photon polymerization, an advanced nanofabrication technique in which a focused laser solidifies photosensitive material with extremely high precision. Then a thin metal layer is deposited that enables electrical functionality for the complex 3D geometries and actuators without folding or manual assembly.

The microDelta robots, which are 1.4 mm and 0.7 mm in height, are the smallest and fastest Delta robots ever demonstrated. By building microDelta robots at different sizes, the researchers were able to test those predictions that scientists made almost 50 years ago. As expected, shrinking the robot improved precision to less than a micrometer, increased speed by operating at frequencies over 1 kHz, and delivered enough power to launch a grain of salt—a projectile that is 7.4% the mass of the entire robot.

Bergbreiter said that Man quickly pushed through eight iterations of the design of the microDelta robots. This fast turnaround is due to the 3D design and printing of these robots in contrast to previous approaches that might take weeks or months to design and fabricate.

“I love how quickly Steven and Sukjun quickly pushed through eight iterations of these designs, and moving forward, students can more easily continue that work, which will result in future improvements.”

Using the model developed in this work, students can further improve desired metrics such as bandwidth, accuracy, and workspace by changing the robot’s design parameters, creating large arrays of microDeltas, or even adding further improvements like sensing for closed-loop operation.

Robotic Institute faculty members Zeynep Temel and Oliver Kroemer are already using arrays of larger scale Delta robots for complex manipulation. Because the microDelta robots are so small, densely packed arrays of multiple microDelta robots could enable entirely new robot capabilities at small scales for rich haptic feedback or previously infeasible micromanipulation tasks.

“Eliminating the need for assembly has huge benefits in terms of rapid fabrication and design iteration,” said Bergbreiter. “At large scales, researchers can assemble robots from motors and mechanisms that you can buy off-the-shelf. We don’t have that luxury at these small scales where both making and connecting tiny pieces together is hard. That’s where this new fabrication process is incredibly beneficial.”