A team of neuroengineers based at Brown University, Providence, RI, has developed a fully implantable and rechargeable wireless brain sensor capable of relaying real-time broadband signals from up to 100 neurons in freely moving subjects. Several copies of the novel low-power device, described in the Journal of Neural Engineering, have been performing well in animal models for more than year, a first in the brain-computer interface field. Brain-computer interfaces could someday help people with severe paralysis control devices with their thoughts.
In the device, a pill-sized chip of electrodes implanted on the cortex sends signals through uniquely designed electrical connections into the device’s laser-welded, hermetically sealed titanium “can.” The can measures 2.2 inches (56 mm) long, 1.65 inches (42 mm) wide, and 0.35 inches (9 mm) thick. That small volume houses an entire signal processing system: a lithium ion battery, ultralow-power integrated circuits designed at Brown for signal processing and conversion, wireless radio and infrared transmitters, and a copper coil for recharging—a “brain radio.” All the wireless and charging signals pass through an electromagnetically transparent sapphire window.
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.
In the experiments described, the device is connected to one array of 100 cortical electrodes, but the new device design allows for multiple arrays to be connected, which would allow scientists to observe ensembles of neurons in multiple related areas of a brain network.
The Brown team is continuing work on advancing the device for even larger amounts of neural data transmission, reducing its size even further, 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.
