Tiny, Soft Robotic Spiders Could Help the Future of Surgeries

A team of Harvard and Boston researchers took inspiration from a colorful Australian spider to create spider-like soft-robotics systems.

What if spiders could help with sutures in surgeries or be deployed into dangerous and small spaces? One team of roboticists are bringing that into a reality with their innovative soft robots. 

Inspired by everyday arachnids, these soft robots only measure a few centimeters in size and contain the tools needed to succeed where rigid robots cannot. Roboticists and researchers from Harvard University's Wyss Institute for Biologically Inspired Engineering, Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and Boston University are the people behind these tiny robotic creatures.

The robotic soft spider showcases how robots on the millimeter scale with micrometer-sized features can still pack powerful and impressive performance. 

Inspiration for the robot-spider came from the millimeter-sized Australian peacock spider. The robot itself uses a single elastic material capable of body-shaping, motion, and having color.

“The smallest soft robotic systems still tend to be very simple, with usually only one degree of freedom, which means that they can only actuate one particular change in shape or type of movement,” said Sheila Russo, co-author of the study. “By developing a new hybrid technology that merges three different fabrication techniques, we created a soft robotic spider made only of silicone rubber with 18 degrees of freedom, encompassing changes in structure, motion, and color, and with tiny features in the micrometer range.”

The resarchers published the study in a recent edition of Advanced Materials.

Building a Helpful Robo-Spider

The team knew going into the project that however they created this tiny robot could influence how other small-scale soft robotics systems were created.

Robert Wood serves as a Core Faculty member and co-leader of the Bioinspired Soft Robotics program at Wyss Institute. Wood is also a professor of engineering and applied sciences with Harvard's SEAS program.

“In the realm of soft robotic devices, this new fabrication approach can pave the way toward achieving similar levels of complexity and functionality on this small scale as those exhibited by their rigid counterparts,” said Wood. "In the future, it can also help us emulate and understand structure-function relationships in small animals much better than rigid robots can."

The tiny robo-spider was known as  Microfluidic Origami for Reconfigurable Pneumatic/Hydrolic devices, or MORPH for short. In order to bring MORPH to life, teh team used a lithography technique to create 12 layers of elastic silicone to make the soft spider's body. Each layer of the body is precisely cut using a micromachining technique. The layers are then bonded together to create the 3D structure of the spider.

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Making the spider move, however, was another task. The team needed to carefully weave in microfluidic channels into the elastic silicone layers. The researchers used injection-induced self-folding and pressurized channels. With certain pressures, the individual layers of the robot will move in response, thus moving the layers above and below it.

"We can precisely control this origami-like folding process by varying the thickness and relative consistency of the silicone material adjacent to the channels across different layers or by laser-cutting at different distances from the channels. During pressurization, the channels then function as actuators that induce a permanent structural change," said first and corresponding author Tommaso Ranzani, Ph.D., who started the study as a Postdoctoral Fellow in Wood's group and now also is Assistant Professor at Boston University.

The remaining channels were then used as actuators to give color to the eyes and simulate the color patterns found on the robot's real-world counterparts.

“This first MORPH system was fabricated in a single, monolithic process that can be performed in few days and easily iterated in design optimization efforts,” said first and corresponding author Tommaso Ranzani, who started the study as a postdoctoral fellow in Wood’s group and now also is assistant professor at Boston University.

Applications of the MORPH System

The researchers hope this tiny yet effective spider could be of assistance in a variety of situations.

“The MORPH approach could open up the field of soft robotics to researchers who are more focused on medical applications where the smaller sizes and flexibility of these robots could enable an entirely new approach to endoscopy and microsurgery,” said Wyss Institute Director Donald Ingber, who is also the Judah Folkman Professor of Vascular Biology at HMS and the vascular biology program at Boston Children’s Hospital, as well as professor of bioengineering at SEAS.