System Bits: Feb. 5

Rubbery material for stretchable electronics
Researchers at the University of Houston came up with a rubbery semiconducting material that they say could find applications in stretchable electronics, such as human-machine interfaces, implantable bioelectronics, and robotic skins.

Cunjiang Yu, Bill D. Cook Assistant Professor of mechanical engineering at the University of Houston and corresponding author on the paper, led a team of five researchers, who published their work in the Science Advances journal.

“We report fully rubbery integrated electronics from a rubbery semiconductor with a high effective mobility…obtained by introducing metallic carbon nanotubes into a rubbery semiconductor with organic semiconductor nanofibrils percolated,” the researchers wrote. “This enhancement in carrier mobility is enabled by providing fast paths and, therefore, a shortened carrier transport distance.”

This research could resolve the low carrier mobility of previous attempts at stretchable electronics, the team notes, while also alleviating the complex fabrication requirements previously needed. The team added minute amounts of metallic carbon nanotubes to the rubbery semiconductor of polydimethylsiloxane composite (P3HT) to speed up the carrier transport across the semiconductor. Professor Yu said the team will next focus on increasing the carrier mobility and creating more complex hierarchy and high-level integrated digital circuits for microchips, biomedical devices, and other applications.

Advances in 3D printing
The University of California at Berkeley has come up with a 3D printer that uses light to turn gooey liquids into small, solid objects. The research team has nicknamed the printer as the “replicator,” after the “Star Trek” device which could materialize any object on demand.

“I think this is a route to being able to mass-customize objects even more, whether they are prosthetics or running shoes,” said Hayden Taylor, assistant professor of mechanical engineering at UC Berkeley and senior author of a paper describing the printer, which is detailed in the journal Science. “The fact that you could take a metallic component or something from another manufacturing process and add on customizable geometry, I think that may change the way products are designed,” he added.

Rather than making things on a layer-by-layer basis, as most 3D printers do, the Berkeley machine employs a viscous liquid that forms a solid when it is exposed to a certain threshold of light. Carefully crafted patterns of light shining on a rotating cylinder of liquid produces solid objects in desired shapes all at once.

“Basically, you’ve got an off-the-shelf video projector, which I literally brought in from home, and then you plug it into a laptop and use it to project a series of computed images, while a motor turns a cylinder that has a 3D printing resin in it,” Taylor said. “Obviously there are a lot of subtleties to it — how you formulate the resin, and, above all, how you compute the images that are going to be projected, but the barrier to creating a very simple version of this tool is not that high.”

Meanwhile, at the University of Pennsylvania’s School of Engineering and Applied Science, researchers created smart structures with “embodied logic” using multi-material 3D printers. The study was led by Jordan Raney, assistant professor in Penn Engineering’s Department of Mechanical Engineering and Applied Mechanics, and Yijie Jiang, a postdoctoral researcher in his lab. Lucia Korpas, a graduate student in Raney’s lab, also contributed to the study.

“Bistability is determined by geometry, whereas responsiveness comes out of the material’s chemical properties,” Raney says. “Our approach uses multi-material 3D printing to bridge across these separate fields so that we can harness material responsiveness to change our structures’ geometric parameters in just the right ways.”

The researchers created an artificial Venus flytrap, which closes when a weight is inside the device and the actuator is exposed to a solvent.

“That could be useful for applications in microfluidics,” Raney says. “Rather than using a solid-state sensor and microprocessor that are constantly reading what’s flowing into a microfluidic chip, we could, for example, design a gate that shuts automatically if it detects a certain contaminant.”

Robot could help people with dementia
Washington State University scientists developed the Robot Activity Support System (RAS), which ties in with sensors in a WSU smart home to determine the location of residents, what they are doing, and whether they require assistance with daily activities. The robot may be helpful in keeping tabs on elderly adults with dementia and other limitations to have an independent life in their homes.

“RAS combines the convenience of a mobile robot with the activity detection technology of a WSU smart home to provide assistance in the moment, as the need for help is detected,” says Bryan Minor, a postdoctoral researcher in the WSU School of Electrical Engineering and Computer Science. Minor works in the lab of Diane Cook, Regents professor of electrical engineering and computer science and director of the WSU Center for Advanced Studies in Adaptive Systems.

“Upwards of 90% of older adults prefer to age in place as opposed to moving into a nursing home,” Cook said. “We want to make it so that instead of bringing in a caregiver or sending these people to a nursing home, we can use technology to help them live independently on their own.”

The scientists published a study in the journal Cognitive Systems Research on how RAS could make life easier for older adults living independently.