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To solve the challenge of powering and communication in a brain implant with low end-end energy loss, we present Bi-Phasic Quasi-static Brain Communication (BP-QBC), achieving < 60dB worst-case channel loss, and ~41X lower power w.r.t. traditional Galvanic body channel communication (G-BCC) at a carrier frequency of 1MHz (~6X lower power than G-BCC at 10MHz) by blocking DC current paths through the brain tissue. An additional 16X improvement in net energy-efficiency (pJ/b) is achieved through compressive sensing (CS), allowing a scalable (6kbps-10Mbps) duty-cycled uplink (UL) from the implant to an external wearable, while reducing the active power consumption to 0.52μW at 10Mbps, i.e. within the range of harvested body-coupled power in the downlink (DL), with externally applied electric currents < 1/5th of ICNIRP safety limits. BP-QBC eliminates the need for sub-cranial interrogators, utilizing quasi-static electrical signals for end-to-end BCC, avoiding transduction losses.
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Biphasic quasistatic brain communication for energy-efficient wireless neural implants
Wearable devices typically use electromagnetic fields for wireless information exchange. For implanted devices, electromagnetic signals suffer from a high amount of absorption in tissue, and alternative modes of transmission (ultrasound, optical and magneto-electric) cause large transduction losses due to energy conversion. To mitigate this challenge, we report biphasic quasistatic brain communication for wireless neural implants. The approach is based on electro-quasistatic signalling that avoids transduction losses and leads to an end-to-end channel loss of only around 60 dB at a distance of 55 mm. It utilizes dipole-coupling-based signal transfer through the brain tissue via differential excitation in the transmitter (implant) and differential signal pickup at the receiver (external hub). It also employs a series capacitor before the signal electrode to block d.c. current flow through the tissue and maintain ion balance. Since the electrical signal transfer through the brain is electro-quasistatic up to the several tens of megahertz, it provides a scalable (up to 10 Mbps), low-loss and energy-efficient uplink from the implant to an external wearable. The transmit power consumption is only 0.52 μW at 1 Mbps (with 1% duty cycling)—within the range of possible energy harvesting in the downlink from a wearable hub to an implant.
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- Award ID(s):
- 1944602
- PAR ID:
- 10541377
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Nature Electronics
- Volume:
- 6
- Issue:
- 9
- ISSN:
- 2520-1131
- Page Range / eLocation ID:
- 703 to 716
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41928-023-01000-3
