Translational opportunities and challenges of invasive electrodes for neural interfaces.

Invasive brain-machine interfaces can restore motor, sensory and cognitive functions. However, their clinical adoption has been hindered by the surgical risk of implantation and by suboptimal long-term reliability. In this Review, we highlight the opportunities and challenges of invasive technology for clinically relevant electrophysiology. Specifically, we discuss the characteristics of neural probes that are most likely to facilitate the clinical translation of invasive neural interfaces, describe the neural signals that can be acquired or produced by intracranial electrodes, the abiotic and biotic factors that contribute to their failure, and emerging neural-interface architectures.

Piezoelectric-based optical modulator for miniaturized wireless medical implants.

Optical links for medical implants have recently been explored as an attractive option primarily because it provides a route to ultrasmall wireless implant systems. Existing devices for optical communication either are not CMOS compatible, require large bias voltages to operate, or consume substantial amounts of power. Here, we present a high-Q CMOS-compatible electro-optic modulator that enables establishing an optical data uplink to implants. The modulator acts as a pF-scale capacitor, requires no bias voltage, and operates at CMOS voltages of down to 0.5V. We believe this technology would provide a path towards the realization of millimeter (mm)- and sub-mm scale wireless implants for use in bio-sensing applications.

Optical voltage sensor based on a piezoelectric thin film for grid applications.

Continuous monitoring of voltages ranging from tens to hundreds of kV over environmental conditions, such as temperature, is of great interest in power grid applications. This is typically done via instrument transformers. These transformers, although accurate and robust to environmental conditions, are bulky and expensive, limiting their use in microgrids and distributed sensing applications. Here, we present a millimeter-sized optical voltage sensor based on piezoelectric aluminum nitride (AlN) thin film for continuous measurements of AC voltages <350kVrms (via capacitive division) that avoids the drawbacks of existing voltage-sensing transformers. This sensor operated with 110µW incident optical power from a low-cost LED achieved a resolution of 170mVrms in a 5kHz bandwidth, 0.04% second harmonic distortion, and a gain deviation of +/-0.2% over the temperature range of ~20-60°C. The sensor has a breakdown voltage of 100V, and its lifetime can meet or exceed that of instrument transformers when operated at voltages <70kVrms with capacitive division. We believe that our sensor has the potential to reduce the cost of grid monitoring, providing a path towards more distributed sensing and control of the grid.