Brain-machine interface (BMI) is a link between a brain and a device that enables signals from the brain to direct some external activity in the body. But these devices can cause infections through the opening in the skull.
To overcome this problem, researchers from the Toyohashi University of Technology have developed a tiny wireless device for monitoring brain activity. They have developed a wafer-level packaging technique to integrate a silicon large-scale integration (LSI) chip in a very thin film of a thickness 10 μm.
‘A low-invasive flexible device developed based on a flip-chip bonding helps in monitoring brain activity.’
The fabricated device is of size 27 mm × 5 mm, and 97% of the device area is composed of a flexible film as the silicon chip has a small area. Therefore, it has sufficient flexibility to fit the shape of the brain surface.
Kenji Okabe, first author, said, "We have investigated how to integrate flexible antenna and high-performance circuits and tried this fabrication method with process conditions obtained through experiments."
The technique is based on a flip-chip bonding. The researchers have fabricated a wireless power transmission (WPT) device including a flexible antenna and rectifier chip by using the proposed method.The WPT device can supply electricity to other circuits included in the neural interface.
Assistant Professor Ippei Akita, who is leading the project, said, "Using flexible device technology is a good solution to implement bio-compatible passive devices such as antennas or sensor electrodes. On the other hand, silicon-based integrated circuit technology, which has long history, is suitable for ultra-low-power systems with many functionalities. So, we believe that combining these technologies is essential to establish such minimum invasive implantable devices."
Researchers are trying to integrate more functions such as amplifiers, analog-to-digital converters, signal processors, and radio frequency circuits to an LSI chip. They conclude that this study may contribute to the development of safer BMI systems.