Imagine an iPad or Kindle for the blind, with an inflatable braille that changes shape under the user’s touch. A Cornell-led collaboration created a crucial element for such technology: a haptic network of densely packaged actuators that reveal silicone membrane “dots” when triggered by combustion.
The team’s article, “Valveless Microliter Combustion for Dense Arrays of Powerful Flexible Actuators,” was published Sept. 28 in the Proceedings of the National Academy of Sciences. The main author is doctoral student Ronald Heisser.
One of the biggest hurdles in designing a dynamic braille display for electronics is figuring out how to apply the force needed for each point. Previous attempts have typically involved motors, hydraulic systems, or captive pumps, all of which are bulky, complex, and expensive, according to Rob Shepherd, associate professor of mechanical and aerospace engineering at the College of Engineering and lead author of the article.
“Having something that can shape shift in a way that you can feel, like real objects, doesn’t exist right now. There’s this trade-off between having small actuators, and size, weight, and cost. It’s so difficult, ”Shepherd said. “Everyone has tried electromechanical systems. So we said, well, what if we don’t do it at all and use combustion. Small volumes of gas can create powerful outputs.
The Cornell team collaborated with researchers at the Technion-Israel Institute of Technology to design a system, composed primarily of molded silicone and traces of microfluidic liquid metal, in which liquid metal electrodes cause a spark to ignite a microscopic volume of premixed methane and oxygen. In their network design, this fuel flows through a series of independent channels, each leading to a 3 millimeter wide actuator. The rapid combustion forces a thin silicone membrane at each site to swell several millimeters. A magnetic locking system gives these points their persistent shape and the whole system can be reset with just a push.
Because there is no need for electromechanical valves, actuators can be clustered more densely, resulting in a smaller and potentially portable system that still manages to produce large displacements at high force in less time. a millisecond. And since elastomeric fluidic actuators cool quickly and so little fuel is needed, a commercial version could be used safely.
The technology is also scalable and conformable, and the researchers predict that it could be incorporated into a range of applications, such as flexible robots and portable virtual reality equipment that simulate artificial touch. The biocompatible components could also be used for surgical tools that manipulate tissue or open blocked passageways in medical patients.
The current system consists of nine elastomeric fluidic actuators, but researchers hope to expand that and eventually create a full electronic touch display.
“For the past 30 years or more, people have tried to pack actuators into a network very tightly together,” Heisser said. “Touch, in a way, is more intimate to us than sight. The technology has real potential. I think our work shows that there are more ways to think about this. Chemical actuation is really not something to ignore.
Co-authors include Elizabeth Fisher, associate professor of mechanical and aerospace engineering; Perrine Pepiot, associate professor of mechanical and aerospace engineering; Sadaf Sobhani, assistant professor of mechanical and aerospace engineering; doctoral students Cameron Aubin and Nicholas Kincaid; postdoctoral researcher Hyeon Seok An; and researchers from the Technion-Israel Institute of Technology.
The research was supported by the National Science Foundation, the Air Force Office of Scientific Research, and the Sloan Foundation.
The team had many of its components manufactured by the professional machine shop of the Atomic and Solids Physics Laboratory (LASSP).