Engineers at Brown University have developed a wireless, broadband fully implantable brain sensor that is rechargeable, and has performed well in animal models for more than a year.
The team worked closely with neurosurgeons to implant the device in three pigs and three rhesus macaque monkeys. It can, they say, relay real-time broadband signals from up to 100 neurons in freely moving subjects.
"This has features that are somewhat akin to a cell phone, except the conversation that is being sent out is the brain talking wirelessly," says professor of engineering Arto Nurmikko.
In the device, a small chip of electrodes implanted on the cortex sends signals through uniquely designed electrical connections into the device's laser-welded, hermetically sealed titanium 'can' a couple of inches long. This houses an entire signal processing system: a lithium ion battery, ultralow-power integrated circuits for signal processing and conversion, wireless radio and infrared transmitters, and a copper coil for recharging.
"What makes the achievement discussed in this paper unique is how it integrated many individual innovations into a complete system with potential for neuroscientific gain greater than the sum of its parts," says David Borton, formerly of Brown.
"Most importantly, we show the first fully implanted microsystem operated wirelessly for more than 12 months in large animal models -- a milestone for potential [human] clinical translation."
The device transmits data at 24 Mbps via 3.2 and 3.8 Ghz microwave frequencies to an external receiver. After a two-hour charge, delivered wirelessly through the scalp via induction, it can operate for more than six hours.
"The device uses less than 100 milliwatts of power, a key figure of merit," says Nurmikko.
The new wireless device isn't approved for use in humans, and hasn't been tried in clinical trials of brain-computer interfaces. It has, however, been designed with that in mind as a long-term goal.
The team's working on the ability to handle even larger amounts of neural data transmission, reducing its size and improving other aspects of the device's safety and reliability so that it can someday be considered for clinical application in people with movement disabilities.