A mm-Sized Wireless Implantable Device for Electrical Stimulation of Peripheral Nerves

Abstract

A wireless electrical stimulation implant for peripheral nerves, achieving >10× improvement over state of the art in the depth/volume figure of merit, is presented. The fully integrated implant measures just 2 mm × 3 mm × 6.5 mm (39 mm, 78 mg), and operates at a large depth of 10.5 cm in a tissue phantom. The implant is powered using ultrasound and includes a miniaturized piezoelectric receiver (piezo), an IC designed in 180 nm HV BCD process, an off-chip energy storage capacitor, and platinum stimulation electrodes. The package also includes an optional blue light-emitting diode for potential applications in optogenetic stimulation in the future. A system-level design strategy for complete operation of the implant during the charging transient of the storage capacitor, as well as a unique downlink command/data transfer protocol, is presented. The implant enables externally programmable current-controlled stimulation of peripheral nerves, with a wide range of stimulation parameters, both for electrical (22 to 5000 μA amplitude, ∼14 to 470 μs pulse-width, 0 to 60 Hz repetition rate) and optical (up to 23 mW/mm optical intensity) stimulation. Additionally, the implant achieves 15 V compliance voltage for chronic applications. Full integration of the implant components, end-to-end in vitro system characterizations, and results for the electrical stimulation of a sciatic nerve, demonstrate the feasibility and efficacy of the proposed stimulator for peripheral nerves.

Biointegrated and Wirelessly Powered Implantable Brain Devices: A Review

“…So far, some of the most common forms of wireless power system for implantable neural devices are discussed and summarized in Table II. Apart from these, there are emerging technologies which combines multiple stimulation options and optofluidic channel [146], [147], uses innovative approach to achieve an ultra-miniaturized implant [148], introduces scalable and distributed wireless neural platform [149], [150], wireless optoelectronic photometer for dynamic mapping of the brain [151], simultaneous multichannel optogenetics stimulation and multichannel electrical recording system [152]. Fig.…”

Circuit Design Considerations for Power-Efficient and Safe Implantable Electrical Neurostimulators

“…However, one common disadvantage of all WPT methods is that the links are not always reliable or constant, and the receiver side does not always behave like an ideal current or voltage source. As a result, in order to have a reliable source when a WPT method is in place, standard implantable electrical neurostimulators usually have a small energy storage unit [11]. If the local power storage unit is minimized or removed altogether, the control of the charge cannot be made by setting the duration of the stimulation pulse.…”

Developing Next-Generation Brain Sensing Technologies—A Review

“…Active CMOS arrays can also be created by thinning silicon CMOS down to thicknesses below 15 mm, rendering these devices flexible and pliable [29]. Ultra-small wireless implants generally require other energy modes for communication and telemetry at depth, including ultrasound [30]- [32], or magnetic fields [33].…”