Researchers develop fully implantable wireless brain sensor

The device, which could help people with severe paralysis control devices with their thoughts, contains a pill sized chip of electrodes implanted on the cortex which sends signals through electrical connections into a laser welded, hermetically sealed titanium 'can'. The can measures 2.2 x 1.65in and is 0.35in thick. It houses an entire signal processing system: a lithium ion battery, ultra low power ics designed for signal processing and conversion, wireless radio and infrared transmitters, and a copper coil for recharging. All the wireless and charging signals pass through an electromagnetically transparent sapphire window. The device, which uses less than 100milliwatts of power, transmits data at 24Mb/s via 3.2 and 3.8Ghz 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. Ming Yin, a Brown postdoctoral scholar and electrical engineer, said one of the major challenges that the team overcame in building the device was optimising its performance given the requirements that the implant be small, low power and leak proof. "We tried to make the best tradeoff between the critical specifications of the device, such as power consumption, noise performance, wireless bandwidth and operational range," he said. "Another major challenge we encountered was to integrate and assemble all the electronics into a miniaturised package that provides long term hermeticity and biocompatibility, as well as transparency to the wireless data, power, and on-off switch signals." 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 its safety and reliability so that it can one day be considered for clinical application in people with movement disabilities.