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Miniaturization of the neuromodulation system is important for non-invasive or sub-invasive optogenetic application. This work presents an optimized wireless power transfer (WPT) system integrated with an on-chip rectification circuitry and an off-chip stimulation circuitry for optogenetic stimulation of freely moving rodents. The proposed WPT system is built using parallel transmitter (TX) coils on printed circuit board (PCB) and wire-wound based receiver (RX) coil followed by a seven-stage voltage doubler and a low dropout regulator (LDO) circuit designed in 180 nm standard Complementary Metal Oxide Semiconductor (CMOS) process. A pulse stimulation is used to stimulate the neurons which is generated using a commercially available off-the-shelf (COTS) components based oscillator circuit. The intensity of the stimulation is controlled by using a COTS based LED driver circuit which controls the current through the μ LED. The total dimension of the RX coil is 8 mm × 3.4 mm. The maximum power transfer efficiency (PTE) of the proposed WPT system is ∼ 35% and the power conversion efficiency (PCE) of the rectifier is 52%. The proposed system with reconfigurable stimulation frequency is suitable for exciting different brain areas for long-term health monitoring. 

For the treatment of chronic neuropathic diseases, long-term behavior study of the patient is very important. The behavior study is performed using neural stimulation and simultaneously recording the response from the neural cells. Headstage-based neuromodulation device has become one of the popular methods for neural stimulation in recent times. In this work, a wirelessly powered system is presented that provides constant power to a headstage based optogenetic stimulator, which includes a receiver (RX) coil, a rectifier, and an mm-sized light-emitting-diode (LED). A multi-layered transmitter (TX) coil is designed to provide uniform power transmission over the 20.7 cm × 14 cm mouse behavioral cage area. A maximum of ~49% efficiency is achieved using the proposed system at 3 cm distance through the air media at 13.56 MHz operating frequency. The proposed system uses less number of headstage resonators on the 3-D printed light-weight headstage which is able to achieve higher efficiency compared to the other state-of-the-art.