Jamie Palk, a new tenure-track Assistant Professor who came to the EPFL from Harvard in January, is working on a new, highly unconventional robot. Some might even call her robot downright strange: it’s a flat square that can “self-morph” (i.e., bend and fold itself into three-dimensional shape), a sort of “robotic origami.” It is part of an emerging, fast-moving field: soft robotics.
Professor Paik’s current robotics project takes the unusual form of a soft, flexible 5cm-by-5cm square. It is only 1/2mm thick, and features “stretchable” copper electronic circuitry. The project, called “Programmable Matter,” was originally developed at Harvard. Professor Paik’s robot can be programmed to “self-morph” into various three-dimensional structures, much like an origami sheet, in a matter of seconds. “My robot’s shape is unconventional, to be sure,” says Paik. “My previous robots tended to be anthropomorphic, with human-like structures that are round, rigid and heavy. Soft robots like my ‘robotic origami’ concept, pushes the boundaries of conventional shapes.”
A mathematics proof of concept
Professor Paik’s current project got its start during a post-doc at Harvard’s Microrobotics Lab. “The well-known mathematician Erik Demaine had proven that it was possible to build any three-dimensional structure out of a flat surface composed of triangles. He already got virtual simulation data, but he wanted a concrete physical representation of his concept.”
Thermally activated programmable sheet
Creating these functional programmable robotic origami sheets had its engineering challenges, and necessitated novel fabrication methods to assemble and integrate the body materials and design and fit in the actuators and the electronics –all in a very small space! In fact, due to the extreme space constraints of the origami sheets, the motors Professor Paik had used on her previous robot projects in Paris (cf. “Brief Bio”, below) wouldn’t work. Another way to move the robot had to be found: shape memory alloy (SMA) torsional actuators. SMA actuators are thermally activated to resume its “memorized” shape. They work on a principle of crystal shape change. When the transition temperature (for the origami actuators, 60degC) is reached, the squished (twinned) crystals becomes unsquished (detwinned) shape. This change in crystal shapes produces the "memorized" form. "What is unique is that I can produce new memories in the SMA material by special special annealing process," says Paik. SMAs are often used in medical devices, where their super-elasticity character is used in catheters. Super-bendy SMA wires can go through irregularly shaped veins without plastically deforming itself.” In Paik’s work, it’s the “memory” of the SMA rather than its elasticity that allows the robot to move.
The robotic origamis look like a little square sheet covered in magnets. Each sheet weighs 5 grams and is composed of fiberglass tiles joined by polyurethane elastomer flexures. Inside the thin sheets is copper electronic circuitry. The circuits are stretchable, to maintain electrical conductivity even when the tile bends. “Once it has been carefully programmed, the origami sheet can self-morph into a small table, or a little house, or even an airplane…the possibilities are infinite,” says Paik.
Developing the complex origami fabrication process was a challenge for Paik, who had worked on a larger scale previously. “At Seoul National University, working for Samsung Electronics, I had designed the arm and hand for an anthropomorphic robot that was the size of person. That had already seemed like scale-wise a great challenge to me, since the actuators, motors and other components were all quite small compared with the scales we normally see in manufacturing,” recounts Paik. “Then I went to the Université Pierre et Marie Curie in Paris and began to work on smaller scales, like that of the JAiMY, a 5mm motorized laparoscopic surgery instrument that’s about to be launched commercially. But even the JAiMY seems big and bulky compared to the scales we worked on at the Harvard Microrobotics Laboratory: at Harvard, we measured in micrometers (1/1000 of a millimeter). I was used to machining metals like steel and aluminum, but had to start using unconventional fabrication techniques that involved polymers and micro-lasers.”
What the future holds for origami sheet soft robotics
Professor Paik now wants to push the robotic origami concept even farther. “For the moment, my origami is a proof of conception and almost seems artistic. The robot was shown at the “Talk to Me” exhibition in New York late last year, for example. But now I want to make it into a practical device, by adding sensors, among other things. It could then become a multi-functional measuring device for both medical and other applications.” Another future project is to design a robot that could be programmed and reprogrammed after it is built, which would make it multi-functional. “I currently pre-program each robot when it’s built. If I want a different program, I have to build a new robot.” Yet another goal is “to build the same type of origami sheet robots on a larger scale.” These are the challenges that will face Professor Paik in her new Reconfigurable Robotics Lab, for which she is currently recruiting her team. It will be made up of two PhD students and one post-doc. “I’m also looking for electrical engineers, micro-engineers and mechanical engineers. It’s going to be a multidisciplinary group where it is important to be hands-on on building moving, reconfiguring and evolving robots that is not limited to virtual data simulations on their PCs.”