C3PO and R2D2 are not the robots we are looking for. In the movie Star Wars, the two work side by side with their human companions, giving them information and physical assistance as needed. In reality, says Robert F. Shepherd, Mechanical and Aerospace Engineering, the robots that will work beside us in the future may look more like the softer, safer Baymax from the Disney animated movie Big Hero 6.
Shepherd is working on creating soft robots, using newly invented materials in all sorts of robotic applications. To begin with, the Shepherd Lab robots are made of rubber foam that is soft and bendable and can change shape dramatically. “We work on liquid-phase processing of robots,” Shepherd says. “We start with liquids, and then using 3-D printing or injection molding, we process them into solid robots, usually made of rubber. These rubbers can do things like sense touch, emit light, and move.” Since they are soft, the machines made from these rubbers would be much safer to work alongside humans in future applications. “You can imagine if a piece of rubber hit you, it wouldn’t hurt as much as an iron rod,” Shepherd says.
Creating Touch and Other Sensory Attributes for Robots
The materials Shepherd makes have a variety of sensory abilities. “If you want a robot, you need to have some sort of sensory feedback,” he says. “So we’ve started working on touch sensors that we can put in these soft machines. One of these is a stretchable capacitor made of rubber that feels just like skin. When you press it, you’re sending an electrical signal. The capacitance changes, and that’s our touch signal.”
These same stretchable capacitors can emit light as well, when particles inside them are exposed to an electric field. “We’ve made light-emitting displays that can stretch to 700 percent of their original size,” Shepherd says. “You can start with a little dot and turn it into a big interface because of that ability to stretch.” Known as vanishing interfaces, this type of technology could be applied to a variety of uses, from robotic displays to mobile phone screens. One of Shepherd’s graduate students and lab members, Bryan N. Peele ’13, has received funding through Cornell’s new commercialization fellowship program to explore the commercialization potential of the Shepherd Lab’s vanishing interfaces.
Shepherd’s robots can also sense light and use that ability to assist in locomotion. Their actuators, which control their ability to move, actually have LEDs that shine light through them and the amount of light detected on the other side is used to sense their motion. When the actuator bends, as in the bending of a limb, more light is lost on the way out of the actuator, and the robot knows its limb is bent.
More Awesome Abilities—Self-Healing, Shape-Changing
In its quest to find new and better materials for robots, the Organic Robotics Lab, as Shepherd calls it, has turned its attention to a class of materials known as bicontinuous metal elastomer composites. “We take the foams that make the motion in our robots and fill them with other materials like metals,” Shepherd explains. “We put in a metal alloy that’s solid and stiff at room temperature, but melts at 60 degrees Celsius. Then we heat it a little so it melts, and we stretch it and move it into different shapes before we freeze it again.”
The researchers have poked holes in the new material and watched it heal itself, and they have created objects that can turn into other objects. “We can take a box shape and turn it into a sphere and have the sphere roll,” Shepherd says. These beginnings could ultimately result in a robot with bicontinuous skin that would allow it to adapt its locomotion to its environment, morphing between different shapes. “Depending what surface the robot is moving around on, you might want a sphere or you might want legs,” says Shepherd, “or you might want the option of wheels or legs. This would be a way to go between two states.”
“If you had limited mobility, you could wear our soft robots to help you move around. If you had an exoskeleton made out of them, it would be like wearing a wet suit, soft and flexible.”
Robotic Materials for Medical Devices
In addition to his robotics work, Shepherd is researching the use of his foams for medical devices. In one project, he collaborates with James K. Min, Radiology, Weill Cornell Medicine, to create a new kind of heart-assist device—a foam heart pump. Unlike biological hearts, which work by contracting muscles that squeeze blood through the heart and into the arteries, the foam heart pump expands. “We pattern the material so there are extensible materials on the outside of the foam,” Shepherd explains. “When we pressurize the foam, it expands inward and compresses what would be the blood. We’re getting the same function as a biological heart but using a different mechanism.”
Shepherd and Min will be testing the foam hearts in the near future. If all goes well, their invention may revolutionize heart-assist devices. “It’s a long route to something useful, but this has potential,” Shepherd says. “Current heart-assist devices have to be implanted in the heart, which is not optimal. Our foam heart would be placed beside the biological heart. Having something that’s not invasive like that would be wonderful.”
In another quest for a medical application of his robotic materials, Shepherd is involved with a study that tests the use of his special sensory rubber for an orthotic glove that could be worn by stroke victims with limited hand mobility. Working with Ross A. Knepper, Computer Science, and Andy Ruina, Mechanical and Aerospace Engineering, Shepherd and his fellow researchers have found that the amount of energy needed to lift objects is reduced when wearing the glove.
The orthotic glove is just the tip of Shepherd’s vision for the possible rehabilitation uses of his creations. “If you had limited mobility, you could wear our soft robots to help you move around,” he says. “If you had an exoskeleton made out of them, it would be like wearing a wet suit, soft and flexible. If the power were turned off to the exoskeleton, it wouldn’t restrict your movement the way a metal exoskeleton does.”
Ultimately Shepherd’s many projects are the products of the interface between chemistry and mechanical engineering. “This is a very creative space to be in,” he says. “I can use new materials to make objects that I can actually see and touch. I want to develop new science and new technology, but also I want to show the potential of this area. It’s an exciting field to be in right now.”