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NEWS AND EVENTS

Article published in Science Translational Medicine

Closed-loop neuromodulation of spinal sensorimotor circuits controls refined locomotion after comple...

14-16 November 2012 International Conference on Neurorehabilitation

NEUWalk scientists Prof. Courtine and Prof. Micera participate in the conference.

Results published in Science and Nature Magazine

Rats with spinal cord injuries and severe paralysis are now walking thanks to researchers from NEUWa...

A Wireless Controlled Multi-Channel Stimulator Implant

Stimulator implant connected to electrode leads and inductive coil receiver

An implant system for epidural stimulation provides up to three parallel stimulation channels with the flexibility of selecting one of six stimulation sites within each channel. Stimulation intensity and frequency on each site can be controlled in real time via a radio link from a remote programming device.

 

The implant consists of a multi-electrode array (24 electrodes), a stimulator and an inductive coil receiver. The stimulator comprises three custom stimulator chips, each having versatile stimulation management that provides fine-tuning of pulsatile stimulation on any of six stimulation sites. Two extra electrodes are provided for each stimulator chip as return paths for the stimuli. A crosstalk reduction mechanism enables simultaneous stimulation by the three stimulator chips with minimum cross-coupling.  

Implant control is wirelessly provided through an inductive link. The inductive link provides bidirectional communication between the implant and the external (wearable) transmitter. The same inductive link supplies power to the implant. All the components of the stimulator implant are mounted on a ceramic (96% alumina) substrate (36 mm x 38 mm) with thick-film printed gold and platinum-gold tracks and hermetically sealed in a ceramic package. The stimulator and inductive coil receiver are encapsulated in silicone rubber.

Interior of implant

A two-layer communication protocol is established between a remote host computer and the implant with a wearable transmitter as a relay. Stimulation is programmed on the host computer, where the configuration parameters are sent to the transmitter via a 900 MHz radio link. The transmitter then modulates the wireless power link using frequency-shift keying to forward the data to the implant to facilitate neural modulation.

 

Contact: Prof. Andreas Demosthenous, Department of Electronic & Electrical Engineering, University College London (UCL), email: a.demosthenous(at)ucl.ac.uk

 

Silicone Based Laser Patterned Platinum-Iridium Active Arrays

Three IC electrode active array with leads
IC bonded to the PtIr tracks

A silicone-based active electrode array containing small epidural integrated circuits (ICs) has been developed for rats to provide independent access to twelve sites on the spinal cord. The array, which is laser-patterned, uses three strong platinum-iridium (PtIr) tracks to power the ICs, to receive stimulation-related data and distribute the electrical current to the targeted sites.

Three small (1.7 mm² each) and thin (100 µm) ICs work together as a system to provide versatile stimulation protocols which allow independent access to twelve sites in monopolar, bipolar or even multipolar mode. The ICs are located inside the rat’s spinal canal and dissipate a maximum of 114 µW mean power during a full biphasic stimulation cycle.


The ICs reduce the number of wires needed for independent control of the electrodes from twelve to three, resulting in a much narrower implant and wider, stronger tracks which minimise the possibility of failure due to fractures.
The flexible implant is made of laser-patterned platinum-iridium foil, which is sandwiched between two layers of silicone rubber. The ICs are bonded to the PtIr tracks by electrical rivet bonding and are also encapsulated with silicone.

 

Contact: Prof. Andreas Demosthenous, Department of Electronic & Electrical Engineering, University College London (UCL), email: a.demosthenous(at)ucl.ac.uk