Over the past decade, researchers in the biomedical field have been requesting for a minimally-invasive tool capable of interfacing with hundreds of neurons anywhere in the CNS. A technology that can precisely modulate brain activity of the entire brain can potentially: (1) revolutionize our understanding of the brain by studying the correlations between neural networks from different regions of the brain and the mechanisms of cognitive functions; (2) treat mental health illnesses and brain disorders that affect distributed locations throughout the CNS (e.g., Alzheimer’s, epilepsy, mood disorder, OCD); and (3) cover a larger area in the sensorimotor cortex of amputees to more accurately control robotic prosthetic limbs or better evoke a sense of touch.
Non-invasive approaches such as magnetic and ultrasonic stimulation, are very promising for future systems, but currently lack the specificity needed to minimize side effects. Therefore, it is evident that electrical stimulation still has an important role to play in today’s clinical and research neuroscience as direct stimulation at the level of small ensembles of neurons or even individual neurons can be achieved using microelectrodes. Unfortunately, current state-of-the-art implantable technologies that rely on intracortical or depth electrodes are either limited in the number of sites and spatial extent coverable or become too invasive when multiple electrodes are implanted.
To overcome these limitations, a major goal of my research is to develop the next generation of chronic brain stimulation devices, which are basically minimally-invasive floating beads. In the context of my work, the term “floating” means that the single-channel device is wirelessly powered and can be injected anywhere in the brain. Some beads are wirelessly powered using an ultra-compact acoustically actuated magnetoelectric antenna and some are powered using an on-chip coil. The beads are considered to be a minimally-invasive technology for 3 main reasons: (1) the miniaturized devices are smaller than 0.009 mm3, making it the smallest wirelessly powered stimulator; (2) the beads are injectable using a minimally invasive surgical approach; (3) the beads are wirelessly powered using a transmitter coil which sits on top of the scalp.