Wireless Neuromodulation at Submillimeter Precision via a Microwave Split-Ring Resonator

Microwaves, with wavelengths on the order of millimeters, have centimeter-scale penetration depth and have been shown to reversibly inhibit neuronal activity. Yet, microwaves alone do not provide sufficient spatial precision to modulate target neurons without affecting surrounding tissues. Here, we report an implantable split-ring resonator (SRR) that generates a localized and enhanced microwave field at the gap site with submillimeter spatial precision. The SRR breaks the microwave diffraction limit and greatly enhances the efficiency of microwave inhibition. With the SRR, microwaves at dosages below the safe exposure limit are shown to inhibit neurons within 1 mm from the gap site. Application of the microwave SRR to suppress seizures in an in vivo model of epilepsy is demonstrated.