Flexible, high-performance transistors pave the way for mini medical sensors and implants
Scientists at Columbia University have developed flexible, functional, waterproof transistors. These could find use in building miniaturized medical sensors, brain-machine interfaces, or long-term implants.
Silicon-basedtransistors don't mix well with liquids, because their metalliccomponents can get short-circuited or corroded in a matter of seconds.Unfortunately, waterproofing makes electronic devices bulky andrigid. For devices that must be flexible and waterproof at the sametime – such as medical sensors – plastic organic electronicsare a promising solution for the future but, for the time being, theirperformance lags far behind that of their silicon cousins.
A teamof researchers led by Dion Knodagholy, Jennifer Gelinas and GeorgeSpyropoulos has now developed what promises to be the best of bothworlds: a flexible, water-resistant transistor which is also fastenough to allow for high-performance applications like real-time medical monitoring or implantable brain-machine interfaces.
Amongthe essential components of a transistor are a "source" fromwhich electric charge carriers originate, a "drain" whichrepresents the charges' end-point, and a "channel" connecting thetwo. The main innovation here is the unique design of thetransistor's channel.
"We've made a transistor thatcan communicate using ions, the body's charge carriers, at speedsfast enough to perform complex computations required forneurophysiology, the study of the nervous system function," saysKhodagholy. "Our transistor's channel is made out of fullybiocompatible materials and can interact with both ions andelectrons, making communication with neural signals of the body moreefficient."
Thechannel is made from electrically-conductive polymers. As ions travelthrough it, supplemental ions embedded in the channel itself interactwith them, effectively shortening the distance that they need totravel on their way to the transistor's drain. According to theresearchers, this trick improved the transistor's performance by anorder of magnitude compared to similar ionic devices of the samesize.
Theresearchers demonstrated the utility of their technology forelectroencephalography (EEG), recording human brain waves from thesurface of the scalp. Thanks to the improved size and performance,the contact size of the sensors could be reduced by five orders ofmagnitude, with the entire device easily fitting between hairfollicles and resulting in a much more comfortable experience for thepatient.
In termsof bio-monitoring, other uses could include the recording of heart,muscle, and eye movement. Closed-loop devices, such as those used totreat some forms of refractory epilepsy, are also among the possiblefuture applications.
A paperdetailing the study was published in the journal Science Advances. More details about the technology are available in the video below.