Wireless Stimulation of Motor Cortex Through a Collagen Dura Substitute Using an Ultra-Thin Implant Fabricated on Parylene/PDMS

Abstract

We present the design, fabrication, and in vivo testing of an ultra-thin (100 μ m) wireless and battery-free implant for stimulation of the brain’s cortex. The implant is fabricated on a flexible and transparent parylene/PDMS substrate, and it is miniaturized to dimensions of 15.6 × 6.6 mm 2 . The frequency and pulse width of the monophasic voltage pulses are determined through On-Off keying (OOK) modulation of a wireless transmission at 2.45 GHz. Furthermore, the implant triggered a motor response in vivo when tested in 6 rodents. Limb response was observed by wireless stimulation of the brain’s motor cortex through an FDA-approved collagen dura substitute that was placed on the dura in the craniotomy site, with no direct contact between the implant’s electrodes and the brain’s cortical surface. Therefore, the wireless stimulation method reported herein enables the concept of an e-dura substitute, where wireless electronics can be integrated onto a conventional dura substitute to augment its therapeutic function and administer any desired stimulation protocol without the need for post-surgical intervention for battery replacement or reprogramming stimulation parameters.

A Wireless Battery-Free Implant With Optical Telemetry for In Vivo Cortical Stimulation

“…These results show that it is possible to monitor the onset of stimulation while the device is placed under the skin for future chronic studies. Before this study, we performed in vivo tests on six animals [ 7 ] using one implant with a similar structure, and we did not observe delamination or loss of consistency in output voltage.…”

“…Therefore, there is a need to develop wireless, thin, and flexible implants to avoid these complications. Wireless implants rely on antennas [ 7 ] or coils [ 8 ] to supply power to the implant. Electrical stimulation is delivered via monophasic or biphasic voltage pulses [ 9 ], [ 10 ], using active electronics, such as microcontrollers, to determine the stimulation parameters [ 11 ], [ 12 ], or custom integrated circuitry [ 8 ].…”