A miniaturized and low-energy subcutaneous optical telemetry module for neurotechnology.

This study presents a proof-of-concept optical telemetry module that leverages a single light-emitting diode (LED) to transmit data at a high bit rate while consuming low power and occupying a minimal area. Our experiments showed that we could achieve 108 Mbit/s and 54 Mbit/s back telemetry data rates for tissue thicknesses of 3 mm and 8 mm, respectively. The proposed module is designed to be powered by near-field coupling and achieve bidirectional communication by low-speed downlink from near-field communication (NFC). It aims to minimize the size of the implant while providing reliable transmission that meets the requirements of high-speed wireless communication from a multi-electrode array neurotechnology implant outside the body. The power consumption of the module is 1.57 mW, including the power consumption of related circuits, resulting in an efficiency of 14.5 pJ/bit, at a tissue thickness of 3 mm and a data rate of 108 Mbit. The use of an optical lens, combined with tissue scattering effect and optimized emission angle, makes the module robust to misalignments of up to ±5 mm and ±15˚ between the implantable and external units. The LED in the implantable unit is only 0.98 x 0.98 x 0.6 mm3, and the testing module is composed of discrete components and laboratory instruments. This work aims to show how it is possible to strike a balance between a small, reliable, and high-bit-rate data uplink between a neural implant and its proximal, wirelessly connected external unit. This optical telemetry module has the potential to be integrated into a significantly miniaturized system through an application-specific integrated circuit (ASIC) and can support up to 1,000 channels of neural recordings, each sampled at 9 kSps with a 12-bit readout resolution.