A Wirelessly Powered Implantable CMOS Neural Recording Sensor Array using Pulse-based Neural Amplifier

Abstract

The most important organ in the human body is unquestionably the brain. Yet, despite its importance, it is one of the least well understood organs. One reason for this lack of understanding of the brain is the lack of data available to researchers from in vivo studies. Historically, collecting measurements from the brain has been difficult due to the high risk to the patient. Recently technology has been developed to allow electrical measurements to be taken from the brain directly, however most systems involve non-permanent sensors because of the requirement for transcranial wiring for power and data. Developments in the field of CMOS circuit design, wireless power transmission, and wireless data transmission have enabled the creation of implantable neural recording devices as a combination of these technologies. The implant designed in this paper is ~15 mm in diameter and 2 mm at its thickest point on a flexible polyamide PCB. The flexible nature of the implant allows for the implant to conform to the surface of the brain. The implant requires no transcranial orifice since it is powered wirelessly and transmits data wirelessly via Bluetooth low energy. The CMOS neural amplifier chip on the implant utilizes an enhanced form of delta modulation to remove the requirement for large ADCs to be present on the die, saving space and enabling 1024 amplifiers and electrodes to be present on the chip. The implant is capable of measuring, modulating, and wirelessly transmitting a millivolt order signal to a PC for demodulation and analysis.

Skin-Integrated Wearable Systems and Implantable Biosensors: A Comprehensive Review

“…The fabrication consisted of doped single crystal silicon nanoribbons on a silicon wafer that are transfer-printed to a thin plastic sheet. The deposition and patterning of suitable dielectric and metal layers complete the functional [131] and (c) illustration of the heart valve monitoring system, which communicates the data by wireless [132].…”

“…The wireless operation could be sustained as long as an NFC (near field communication)-enabled smartphone is in the vicinity of the implant and transmitting power through inductive coupling [132]. [131] and (c) illustration of the heart valve monitoring system, which communicates the data by wireless [132].…”

“…Additionally, it holds a system-on-chip (SOC) that operates the CMOS chip ( Figure 7 b) and sends data wirelessly via Bluetooth low energy (BLE) to a computer. The SOC contains an ARM microcontroller, which generates the required timing signals to operate the CMOS neural chip and processes and packages the data it receives to send via BLE [ 131 ].…”

“…( a ) The implantable sensor small size is achieved by the use of wireless power transfer provided by an external coil and the flexible substrate. The device transmits data via a low energy Bluetooth link to a receiving device; ( b ) Photos of the implantable neural interface: (i) the neural interface being flexed by a hand, (ii) the top side of the neural interface, (iii) the bottom side of the neural interface [ 131 ] and ( c ) illustration of the heart valve monitoring system, which communicates the data by wireless [ 132 ].…”