Implantable electronic devices provide precise recording or modulation of neurological activity. They promise to be platforms for new treatments and tools for scientific discovery. Two of the key challenges in realizing implantable systems at the millimeter scale are powering and communications. Miniaturizing these devices using wireless technologies would allow the electronics to be delivered into the body using minimally invasive methods such as through a catheter or a hypodermic needle.

Power delivery for miniature implants deep within the human body cannot be done safely with inductive coupling at low frequencies. To develop new high frequency power transfer systems through tissue, new instruments are needed. A method for characterizing power receiving microstructures using an optical link is discussed. Midfield powering is introduced which uses a patterned metal plate to transform evanescent waves to propagating waves upon interaction with tissue. A spatially adaptive system is developed that can deliver power through 10 cm of tissue mimicking phantom solution. Next, a pacemaker the size of a grain of rice is developed and powered to pace from the epicardium of a rabbit and the endocardium of a pig.

A custom integrated circuit is introduced which contains the main building blocks for efficient power harvesting in tissue and transmission from an implant to outside the body. A pulsed-RF transmitter is designed to harvest energy and transmit RF pulses to an external coupler.

Next, wireless technologies are applied to scientific tools for neuroscience experiments in small animals. The challenge of power delivery for neurological experimentation with small animals is that ideally, the animal should be freely moving without any visible sign of an implant. A new approach of wireless powering is introduced for this application which requires no electronics to automatically focus electromagnetic waves to the location of a mouse. A wirelessly powered optogenetic stimulation device is developed that is fully internalized into the animal. Optical stimulation is performed in both the central and peripheral nervous system of untethered, freely moving mice.