Devin Carroll stepped outside of his apartment in the late summer and picked up a few sticks that he thought would work for his robot as the leaves were beginning to crisp and curl from the heat. He stripped the three sticks of their bark and made them about half an inch thick and the length of an adult hand. He then tied them with twine to StickBot, a modular robot made up of circuitry, actuators, a microcontroller, and a motor driver.
StickBot is now propelled across the table at Penn’s General Robotics, Automation, Sensing & Perception (GRASP) Lab by four AA batteries, a tangle of wires, and blinking lights. Carroll is a Ph.D. candidate in the School of Engineering and Applied Sciences.
Carroll demonstrates how StickBot can go from using the sticks as arms to utilizing them as legs by controlling it with an app he created. In “grasper mode,” the sticks move with their free end to hold a cup upright while being hinged to a controller plate on one side.
Carroll demonstrates how StickBot can go from using the sticks as arms to utilizing them as legs by controlling it with an app he created. In “grasper mode,” the sticks move with their free end to hold a cup upright while being hinged to a controller plate on one side.
StickBot is an idea, an adaptable system that can be set up in various ways, not a fixed, unique innovation. StickBot is a modular robot, meaning that parts can be added, changed, or removed as needed.
Mark Yim, Carroll’s advisor, has been at Penn for 17 years and is the current director of the GRASP Lab. The high versatility of modular robots presents a lot of potential for the technology to evolve, Yim says. One iteration of this is self-configuring robots. “People are really good at adapting to different environments: When it gets cold, you put a coat on. And robots can do that as well. But if robots could also change their shape, do different things … it gives you more possibilities.”
In addition to a robot made from sticks, Carroll has also built a robot made from ice. With a rectangular body and two large wheels, the robot looks like a cross between a monster truck and a Cushman cart. It’s called, of course, IceBot.
The Guinness Book of World Records accepted IceBot in 2020 as the first robot made entirely of ice (save its motor driver and actuators, which Carroll embedded into carved holes). Carroll envisions a future in which this technology, perhaps in the form of a self-configuring robot, will be utilized to conduct missions in Antarctica or on an icy moon. It is currently a means for him to improve his theories on modular robots.
“The lesson from IceBot, according to Carroll, is to never be afraid to do anything insane.” “It might actually work.”
Carroll continued his innovative experimentation with StickBot. This time, he concentrated on keeping expenses down and developing a straightforward system that could handle a variety of jobs.
StickBot is a robotic system designed to give users a great deal of versatility at a very low cost, and Carroll explains that we achieve this by utilizing the modularity of found materials. “We may construct truss constructions in a variety of configurations using a large collection of tree branches or sticks. By doing this, we can create everything you can think of, including robots that can crawl or grab objects. The idea of StickBot is to be able to change things and make it very affordable.”
Carroll estimates that StickBot’s total build cost is under a hundred dollars for a simple model, although larger systems may cost more. While some components (like the actuators and motor driver) are integral to the robot’s function, others can be swapped out depending on the task being performed and the materials at hand. (Carroll is exploring the use of hot glue and duct tape in lieu of string.) The robot should be able to be constructed from things people might have on hand, he says.
The reduce, reuse, and recycle ethos has been with Carroll since he was young. Carroll grew up on a farm in rural Massachusetts. He was a member of 4-H; he raised sheep. “Everything we did was intended to be renewable,” Carroll says. “Building things like barns or sheds, we would try and reuse as much material as possible.”
Later, Carroll went to the University of Massachusetts Amherst for mechanical engineering and did a summer Research Experience for Undergraduates (REU) program at Harvard, where he built his first robot. “I was a sophomore in engineering school, had no clue what I wanted to do,” Carroll says. “I had been working that winter at Harvard Forest, just doing maintenance for them. A researcher came up to me and said, “You’re a mechanical engineer, right?” Can you build this robot for me?”
Carroll built the robot, “essentially a box with a bunch of sensors,” he says, and designed a tram runway in the tree canopy, three scaffolding-heights high. Powered by a solar-charging battery, the robot was designed to traverse an area to help ecologists determine how quickly the forest would regrow following a clearcut.
It was an influential experience for a young engineer. “There I was, surrounded by ecology and trees and all of those researchers and scientists. People there were very focused on how we can affect the world around us in a positive manner and create a renewable resource so we’re not just using something up, we’re actually giving back.”
accessible and inexpensive
A StickBot-style robot could be used in therapy or prosthetic rehabilitation settings in the worldwide health care industry. Carroll argues that while expensive medical procedures are fine and beneficial, are they always within reach of the average person? How simple is it to fix that high-tech equipment if it malfunctions?
Carroll claims that if a robot like StickBot could be used in a situation like that, “many more people’s lives may be affected.” StickBot is a very straightforward modular robot, making repairs and component replacements simpler.
“By providing people with the ability to use materials around them, we do two things,” Carroll says. “One, we cut the cost of materials, which are marked up. Two, we can reduce the complexity without reducing the operational function.”
It’s definitely a timely idea for global health, says Michelle J. Johnson, associate professor of physical medicine and rehabilitation in Penn’s Perelman School of Medicine. Johnson, who is director of the rehab robotics lab (A GRASP Lab), also does research in Botswana. “One of the big issues is affordability,” she says. There is a need to support clinicians in lower resourced settings, but how do we do that?”
The concept of affordable robots that leverage material that is local and plentiful is compelling, Johnson says, because when materials and electronics have to be imported, costs can increase rapidly.
Health clinics might make future investments in a modular robot’s capability and customize it as well. According to Johnson, “you might only be able to purchase one module today, but tomorrow you might be able to afford the second, and now you have a system you can utilize in a variety of ways.” You can add to it as you go.
The StickBot system has potential to be used as a social, therapy, prosthetic, or assistive robot, Johnson says. In Botswana, some of Johnson’s patients have HIV, which can trigger strokes. A therapeutic robot like StickBot could be used to support an immediate functional need or help patients to perform a physical therapy exercise, she says.
The functional application of ideas is important to Carroll. He wants everyone to have access to interesting design that has the potential to improve lives.
“Have you seen “Big Hero 6′?” Carroll asks. He thinks the Disney movie should be required viewing, at least for those interested in robotics. In it, the hero attends an engineering presentation for students and holds up his invention—something that looks like a tiny iron filing, smaller than a pinky finger. The audience is not impressed. Then, the hero shows what thousands of these little doohickeys can do. The modular robots link together and break apart again, effortlessly building scaffolding, and creating an upside-down moving walkway. The possibilities are only limited by the hero’s imagination.
“Having the flexibility to do more things means that you can help more people,” Carroll says. “And if you can make it inexpensive, that’s even better.”
