A robot without electronic, completely soft, dragonfly-like material can shower over water and deal with environmental conditions such as pH, temperature, or the presence of oil.
The proof-of-principle display could be a preview of more advanced, autonomous, long-term environmental sensations for monitoring a wide range of potentially problematic signs.
The soft robot is described in the magazine Advanced advanced systems.
Soft robots are a growing trend in the industry because of their flexibility. Soft parts can handle delicate objects such as biological nappies that could damage metal or ceramic parts. Soft bodies can help robots navigate or push into tight spaces where tight frames would get a grip.
The expanding field was on the mind of Shyni Varghese, professor of biochemical engineering, mechanical engineering and materials science, and orthopedic surgery at Duke University, when motivation struck.
“I received an email from Shyni from the airport saying that she had an idea for a soft robot that uses a self-healing hydrogel created by his group in the past to respond and move automatically , ”Said Vardhman Kumar, a PhD student in Varghese’s Laboratory and the paper’s first author. “But that was the standard of the email, and I never heard from her again for days. So that kind of idea sat in limbo for a while until I had enough time to go after it, and Shyni said to go for it. ”
In 2012, Varghese and her lab created a self-healing hydrogel that treats changes in pH in seconds. Whether the hydrogel is a crack or two adjacent pieces “painted” by it, a change in acidity causes the hydrogel to form new bonds, which are completely reversible upon return. the pH to its initial levels.
Varghese’s written idea was to find a way to use this hydrogel on a soft robot that could travel over water and identify places where the pH changes. Along with a few other tricks to mark changes around it, she realized that her lab could design such a robot as a kind of independent environmental consciousness.
With the help of Ung Hyun Ko, also a graduate of Varghese’s lab, Kumar began designing a soft robot based on a fly. After several flights, the pair settled on a dragonfly-shaped shape engineered with a network of internal microcosms that allow it to be controlled by air pressure.
They formed the body – about 2.25 inches long with 1.4-inch wingspan – by pouring silicon into an aluminum mold and baking it. The team used soft lithography to create inner channels and connected them with flexible silicon tubing.
DraBot was born.
“It was difficult to get DraBot to handle air pressure controls over long distances using just self-actuators without any electronics,” says Ko. “That was definitely the most challenging part. ”
DraBot works by controlling the pressure of the air entering its wings. Microchannels carry the air into the front wings, where it escapes through a series of marked holes directly into the rear wings. If both rear wings are down, the airflow is closed, and DraBot is not going anywhere. But if both wings are up, DraBot will go ahead.
To add a control element, the team designed balloon actuators under each of the rear wings near DraBot’s body. When inflated, the balloons cause the wings to bend upwards. By changing which wings are up or down, the researchers tell DraBot where to go.
“We were happy when we were able to control DraBot, but it’s based on living things,” Kumar said. “And living things don’t just move around on their own, they accept their environment.”
That’s where self-healing hydrogel comes in handy. By painting one set of wings with the hydrogel, the researchers were able to make DraBot respond to changes in the pH of the surrounding water. If the water becomes acidic, one side front wing connects to the rear wing. Instead of traveling in a straight line as requested, the imbalance causes the robot to spin in a circle. As soon as the pH returns to normal, the hydrogel “heals,” the wings cool separately, and DraBot once again fully responds to commands.
To strengthen the environmental awareness, the researchers also placed the sponges under the wings and lined the wings with temperature-sensitive materials. When DraBot sprays over water with oil floating on the surface, the sponges suck up and change color to a corresponding oil color. And when the water gets too warm, DraBot’s wings change from red to yellow.
The researchers believe that such measurements could play an important role in future environmental robotics. Response to pH can detect freshwater acidification, which is an environmental problem that affects several geologically sensitive regions. The ability to capture oil makes long-distance skimming robots a unique candidate for early detection of oil spills. Color change due to temperature may help to see signs of high tide and swelling of coral reefs, leading to a decline in aquatic population.
The team also sees many ways in which they could improve their assertion. Wireless cameras or state-of-the-art sensors could enhance DraBot’s capabilities. And creating some sort of on-board stimulator would help similar bots break free from their tubing.
“Instead of using air pressure to control the wings, I could think of using some kind of synthetic biology that generates energy,” says Varghese. “That’s a completely different area than I work, so we need to have a conversation with some colleagues to see what’s possible. But that’s part of the fun of working on an interdisciplinary project like this. ”
The researchers did most of this work at Duke University’s Shared Materials and Instrumentation (SMIF) facility, a core resource supported by the National Science Foundation as part of the National Coordinated Nanotechnology (NNCI) Infrastructure .
Source: Duke University