Most robots, no matter their size, are typically built in a series of complex manufacturing steps that integrate the limbs, electronic and active components. The process results in heavier weights, bulkier volumes and reduced force output compared to robots that could be built using this new method. Now, a team of engineers has developed a new design strategy and 3D printing technique to build robots in one single step. The methodology could lead to new designs for biomedical robots, such as self-steering endoscopes or tiny swimming robots, which can emit ultrasounds and navigate themselves near blood vessels to deliver drug doses at specific target sites inside the body.

In a study, the engineers at UCLA (Los Angeles, CA, USA) outlined the advance, along with the construction and demonstration of an assortment of tiny robots that walk, maneuver and jump. The breakthrough enabled the entire mechanical and electronic systems needed to operate a robot to be manufactured all at once by a new type of 3D printing process for engineered active materials with multiple functions (also known as metamaterials). Once 3D printed, a “meta-bot” will be capable of propulsion, movement, sensing and decision-making. The printed metamaterials consist of an internal network of sensory, moving and structural elements and can move by themselves following programmed commands. With the internal network of moving and sensing already in place, the only external component needed is a small battery to power the robot.

The team demonstrated the integration with an on-board battery and controller for the fully autonomous operation of the 3D printed robots - each at the size of a finger nail. The key in the all-in-one method is the design and printing of piezoelectric metamaterials - a class of intricate lattice materials that can change shape and move in response to an electric field or create electrical charge as a result of physical forces. The use of active materials that can translate electricity to motions is not new. However, these materials generally have limits in their range of motion and distance of travel. They also need to be connected to gearbox-like transmission systems in order to achieve desired motions.

By contrast, the UCLA-developed robotic materials - each the size of a penny - are composed of intricate piezoelectric and structural elements that are designed to bend, flex, twist, rotate, expand or contract at high speeds. The team also presented a methodology to design these robotic materials so users could make their own models and print the materials into a robot directly. Using the technique, the team built and demonstrated three “meta-bots” with different capabilities. One robot can navigate around S-shaped corners and randomly placed obstacles, another can escape in response to a contact impact, while the third robot could walk over rough terrain and even make small jumps.

“We envision that this design and printing methodology of smart robotic materials will help realize a class of autonomous materials that could replace the current complex assembly process for making a robot,” said the study’s principal investigator Xiaoyu (Rayne) Zheng, an associate professor of civil and environmental engineering, and of mechanical and aerospace engineering at the UCLA Samueli School of Engineering. “With complex motions, multiple modes of sensing and programmable decision-making abilities all tightly integrated, it’s similar to a biological system with the nerves, bones and tendons working in tandem to execute controlled motions.”

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