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This paper presents modeling and optimization of the steering range of a microstrip planar phased array antenna to steer the unidirectional near-field focused beam towards a certain direction. This antenna can be implemented in headstage-based neural stimulation system and wireless recording system for optogenetic neuromodulation applications. The proposed phased-array antenna consists of sixteen elements that are designed to provide a uniform power transmission over the 27 cm×23 cm×16 cm rat behavioral cage area. The proposed transmitter (TX) antenna implements a near-field-based wireless power transmission system operating at 2.4 GHz frequency. The phased array antenna steers the beam from -30° to 60° in the elevation plane by feeding the individual elements with different phases using four 4-bit phase shifters. A design analysis of the beam-steering approach of the phased array antenna is presented and the corresponding simulation and measurement results are included in this paper. 

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. 

This paper demonstrates a commercial off-the-shelf components (COTS)-based miniaturized wireless optogenetic headstage with simultaneous optical stimulation and electro-physiological recording capability for freely moving rodents. The proposed headstage contains 32 recording channels. The optical stimulation system is a battery-powered neural stimulator, comprised of a low dropout regulator (LDO), an oscillator, and a µLED. The electrophysiological signal recording system includes an intracortical neural probe made of a GaN-on-silicon substrate, an array of neural amplifiers with an integrated analog-to-digital converter (ADC), a transceiver integrated circuit, and a ceramic antenna. The integrated MUX with the ADC allows sampling of the amplified voltage at a sampling rate of 4000 kSamples/s. By placing the headstage on the head of a rodent and recording the neural signals from the Ventral Tegmental area of the brain, the system is experimentally validated in in-vivo. Experimental result shows that the proposed headstage can trigger neuron activity while collecting and detecting single-cell microvolt amplitude activity from multiple channels. 

This work presents a miniaturized wireless power transfer (WPT) system integrated with a neuromodulation headstage for duty-cycled optical stimulation of freely moving rodents. The proposed WPT system is built using the commercially available off-the-shelf components (COTS) for the optogenetic neuromodulation system consisting of a bridge rectifier, a DC-DC converter, an oscillator circuit, an LED driver, and a μLED. The total power consumption of the stimulation system is 14 mW which is provided using the WPT method. The WPT system includes a novel transmitter (TX) coil implemented on a printed circuit board (PCB), and a solenoid receiver (RX) coil wrapped around a customized 3-D printed headstage. The proposed TX coil is designed in such a way that the magnetic field all across the TX coil is sufficient to provide the required power to the optical stimulation system that is worn as a headstage by the freely moving rat. The headstage device's dimension is 18.75 mm × 21.95 mm, weighing 4.75 g. The ratio of the weight of the headstage and rat is 4.75:300. The proposed system is able to achieve a maximum overall efficiency of ∼63% at 5 cm separation between the TX and RX coils, where the maximum power transfer efficiency (PTE) of the WPT system is ∼88% and the power conversion efficiency (PCE) of the rectifier is 71.6%. The proposed system with reconfigurable stimulation frequency is suitable for exciting different brain areas for long-term health monitoring. 

To avoid interruption of experiment and risk of infection, wireless power transfer (WPT) techniques have been used to eliminate the bulky wires and batteries attached to the animals in rodent electrophysiological applications for long-term in-vivo electrophysiological recordings. Headstage-based neuromodulation device has become one of the most popular methods for neural stimulation in recent times. In this work, a wireless power transfer system is designed which provides a constant power to a headstage based optogenetic stimulator. The proposed research is composed of two parts: i) a unidirectional 28 cm × 21 cm phased array transmitter antenna, and ii) an electrically small bi-directional 2.4 cm × 2.4 cm receiver antenna. A phased array transmitter antenna is designed to provide a uniform power transmission over the 27 cm × 23 cm × 16 cm rat behavioral cage area. The proposed WPT scheme utilizes a near-field power transmission scheme at 2.4 GHz frequency. Simulation results show that the transmitter antenna achieves a -24 dB and receiver antenna achieves a −27 dB return loss (S 11 ) at the resonating frequency. The proposed WPT system shows a maximum of 24.5% power transfer efficiency (PTE) when the receiver is in the center position and is 10 cm distance apart from the transmitter, which is much higher compared to the other state-of-the-art works. The transmitter antenna steers beam from −21° to 27° in ϕ axis and −108° to 74° in θ axis which covers the maximum 6.27 cm 2 area of the cage. The preliminary simulation results of the proposed WPT module show a better prospect for future optogenetics based applications.