Rubber Digital-Logic Technology To Create Soft Robot

Researchers at Harvard University have built a soft robot with no rigid parts thanks to their invention of a rubber digital logic gate, which operates the robot.

Scientists have already invented soft robots as safer and more agile counterparts to robots with rigid parts. However, even robots made of soft materials usually have some hard electronic parts included to operate the robot and control its functionality.

Until now, that is, thanks to researchers at Harvard University, who have invented a soft rubber computer that can acts as the digital logic of a robotic device that also uses no electricity.

A new soft robot gripper using no electronics and only soft parts is shown here holding a screwdriver. The robot was invented by researchers at Harvard University. (Image source: Daniel Preston / Harvard University)

A Computer Using Rubber and Air

A team from Harvard’s Wyss Institute for Biologically Inspired Engineering—which is at the forefront of robotics research—developed the computer using just rubber and air, said Daniel Preston, a postdoctoral researcher who worked under the direction of Wyss Professor George Whitesides, also of Harvard’s Department of Chemistry and Chemical Biology.

“We’re emulating the thought process of an electronic computer using only soft materials and pneumatic signals, replacing electronics with pressurized air,” Preston explained.

Computer used digital logic gates—electronic circuits that receive messages (inputs) and determine reactions (outputs) based on their programming—to make decisions. To create their rubber digital logic gate, researchers considered how human biology works, particularly the literal “knee-jerk” reactions of the nervous system.

Preston’s soft computer mimics this system using silicone tubing and pressurized air, he said. He achieved the minimum type of logic gates required for complex operations—that is, “not,” “and,” and “or”—by programming the soft valves to react to different air pressures.

For example, if the “not” logic gate input is high pressure, the output is low pressure. Using these three logic gates, then, Preston said, “you could replicate any behavior found on any electronic computer.”

Demonstrating Soft Robots

Soft robots have come a long way in the last decade or so, with Wyss and other researchers demonstrating various soft gripper robots made from silicone-based materials that already are being used in assembly lines. If robots are made from soft materials they can be used for more delicate industrial tasks—such as moving fruits and vegetables or glass bottles that could break if dropped.

They are also safer in industrial settings, like automobile factories, where massive robotic machines can severely injure or even kill someone if he or she gets in the way. This was painfully evidenced by a story out of factory in Hunan, China, recently in which a robot malfunctioned and impaled a worker with 10 metal spikes.

But if a soft robot bumps into a human, Preston said, “you wouldn’t have to worry about injury or a catastrophic failure” because they don’t have rigid parts and can only exert so much force.

Most soft robots until now, however, have relied on some type of hardware to achieve their functionality, such as metal valves that open and close channels of air to operate the rubbery grippers and arms, and a computer that gives those valves commands. The robot developed by the Harvard team is a departure from this, researchers said.

Non-Rigid Parts

The invention also doesn’t use electronics, replacing them with the air-based pneumatic system. Soft robots currently exist that operate without electronics, but normally they use microfluidic circuits for this purpose. These type of logic circuits have some limitations, however, in that often they use hard materials like glass or hard plastics, and are designed in such a way that they slow the robot’s motion.

The robots designed by Preston’s team, in contrast, can move much more quickly and without the need for any rigid parts. Moreover, soft robotics without electronics can venture to places where robots using electronics would struggle. This includes locations with high radiation—such as a place where a nuclear malfunction has occurred—in space, or inside MRI machines.  Researchers published a paper on their work in the journal PNAS.

The team’s robot also has another unique characteristic in that it can be made to appear invisible based on its use and the soft material used to fabricate it, Preston said. For example, if he chooses a material that camouflages in water, the robot would appear transparent when submerged.

In the future, Preston and his colleagues hope to create autonomous robots that are invisible to the naked eye or even can evade sonar detection. “It’s just a matter of choosing the right materials,” he said.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

 

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