Developing invisible implantable medical sensor arrays, a team of University of Wisconsin-Madison engineers has overcome a major technological hurdle in researchers’ efforts to understand the brain.
The team described its technology, which has applications in fields ranging from neuroscience to cardiac care and even contact lenses, in the Oct. 20 issue of the online journal Nature Communications.
Neural researchers study, monitor or stimulate the brain using imaging techniques in conjunction with implantable sensors that allow them to continuously capture and associate fleeting brain signals with the brain activity they can see. However, it’s difficult to see brain activity when there are sensors blocking the view.
"One of the holy grails of neural implant technology is that we’d really like to have an implant device that doesn’t interfere with any of the traditional imaging diagnostics," says Justin Williams, a professor of biomedical engineering and neurological surgery at UW-Madison. "A traditional implant looks like a square of dots, and you can’t see anything under it. We wanted to make a transparent electronic device."
The researchers chose graphene, a material gaining wider use in everything from solar cells to electronics, because of its versatility and biocompatibility. And in fact, they can make their sensors incredibly flexible and transparent because the electronic circuit elements are only 4 atoms thick — an astounding thinness made possible by graphene’s excellent conductive properties. “It’s got to be very thin and robust to survive in the body,” says Zhenqiang (Jack) Ma, a professor of electrical and computer engineering at UW-Madison. “It is soft and flexible, and a good tradeoff between transparency, strength and conductivity.”
Drawing on his expertise in developing revolutionary flexible electronics, he, Williams and their students designed and fabricated the microelectrode arrays, which — unlike existing devices — work in tandem with a range of imaging technologies. “Other implantable microdevices might be transparent at one wavelength, but not at others, or they lose their properties,” says Ma. “Our devices are transparent across a large spectrum — all the way from ultraviolet to deep infrared. We’ve even implanted them and you cannot find them in an MR scan.”