Researchers at East Lansing’s Michigan State University have developed a potential solution to improve power sources in emerging wearable tech using crumpled carbon nanotube forests, or CNT forests. The solution could have applications in stretchable energy electronic systems, implantable biomedical devices, and smart packaging systems.
Changyong Cao, director of MSU’s Soft Machines and Electronics Laboratory, led a team of scientists in creating highly stretchable supercapacitors for powering wearable electronics. The newly developed supercapacitor has exhibited solid performance and stability even when stretched 800 percent of its original size for thousands of stretching/relaxing cycles.
“The key to success is the innovative approach of crumpling vertically aligned CNT arrays, or CNT forests,” says Cao, who is also an assistant professor at MSU’s School of Packaging. “Instead of having a flat thin film strictly constrained during fabrication, our design enables the three-dimensionally interconnected CNT forest to maintain good electrical conductivity, making it much more efficient, reliable, and robust.”
While most people know wearable tech in its most basic form as smart watches that connect to smartphones, both of which require batteries, Cao’s invention can lead to the creation of patches of smart skin for burn victims that monitor healing and power themselves.
In medicine, stretchable/wearable technology, the team is developing a system that is capable of handling extreme contortions and can conform to complicated, uneven surfaces. The inventions could later be incorporated into biological tissues and organs to detect disease, monitor improvement, and communicate with medical practitioners.
Cao is the first to use crumpled standing CNTs for stretchable energy storage applications, which grow like trees with their canopies tangled on wafers. The forest is 10-30 micrometers high and forms stretchable patterns once transferred and crumpled. The 3-D interconnected CNT forest has a larger surface area and can be modified with nanoparticles or adapted to other designs. The CNT-forest electrodes have to be charged.
“It’s more robust; it’s truly a design breakthrough,” says Cao. “Even when it’s stretched up to 300 percent along each direction, it still conducts efficiently. Other designs lose efficiency, can usually be stretched in only one direction, or malfunction completely when they are stretched at much lower levels.”
Cao’s crumpled nano-forests outperformed the majority of other CNT-based supercapacitors in their ability to collect and store energy.
Metal oxide nanoparticles can be integrated into the crumpled CNTs easily to improve its efficiency. Cao adds that this new approach should spark the advancement of self-powered stretchable electronic systems.
The research was funded in part by the U.S. Department of Agriculture and the National Science Foundation.
The team published their results in the Advanced Energy Materials journal.