Search

This letter presents an ultrasonically powered dual-wavelength optogenetic device that targets simultaneous excitation and inhibition of neural activities, or in a broader sense, optical stimulation in two distinct wavelengths for targeting different populations of neurons. This can be applied to a variety of neurological disorders. The device features a load regulator circuit that shares the available power budget between two LEDs in a power-efficient and controlled way suppressing the need for adaptive matching and overvoltage protection circuits. Furthermore, the regulator circuit is capable of detecting power burst availability on the device and generating a control signal, accordingly. For 5.25 -mW acoustic power at the device's surface, the rectified voltage, and the total current load of the system are regulated to 2.79 V and 600A , respectively. The maximum chip and device efficiencies of 92.5% and 31.8% are measured, respectively. The total die area in 180- nm CMOS technology nose and the estimated system volume are 0.16/2 and 0.572/3 , respectively.

This paper presents a novel micro-scale ultrasonically powered optogenetic microstimulator with the vision of treating Parkinson's Disease. This system features a power-efficient active rectifier benefiting from a novel powering approach for its comparators. The main basis of the idea is to lower the Rail-to-Rail supply voltage of the comparators, thereby lowering their propagation delays. This technique improves the power conversion efficiency of the active rectifiers in two ways. First by decreasing the propagation delay of the comparators, and second by reusing the consumed power by the active diodes. The proposed system including the active rectifier, a novel double-pass regulator, a current reference, and a burst detection circuit is designed, simulated and fabricated in TSMC $\text{0.18}\, \mu$ m CMOS technology with a total silicon area of $\text{0.09}\,\text{mm}^2$ . Based on the experimental results, the proposed active rectifier exhibits a voltage conversion ratio of $\text{92.22}-\text{93.57}$ % for input voltages of around 3 V, and a power conversion efficiency of up to $\text{94.51}$ % for a load of $\text{2.84}\,\text{mW}$ and over the frequency range of $\text{1}-\text{7}\,\text{MHz}$ . A proof-of-concept system including the fabricated chip, a $\text{560} \times \text{560} \times \text{490} \,\mu\text{m}^3$ -sized lead zirconate titanate (PZT-4) piezoelectric receiver, and a custom-designed $\text{280} \times \text{180} \times \text{100} \,\mu\text{m}^3$ blue $\mu$ LED is designed and measured in a Water tank. For an acoustic intensity of $\text{28.8}\,\text{mW} \slash \text{mm}^2$ , the available electrical power at the crystal terminals, the output DC power, and the output light intensity were measured equal to $\text{2.454}\,\text{mW}$ , $\text{2.276}\,\text{mW}$ , and $\text{9.29}\,\text{mW} \slash \text{mm}^2$ , respectively. The quiescent current of the chip in absence of power bursts is measured equal to $\text{8.4} \,\mu$ A.

One of the main challenges of the current ultrasonic transducers for powering brain implants is the complexity of focusing ultrasonic waves in various axial and lateral directions. The available transducers usually use electrically controlled phased array for beamforming the ultrasonic waves, which increases the complexity of the system even further. In this article, we propose a straightforward solution for selective powering of brain implants to remove the complexity of conventional phased arrays. Our approach features a Sectored-Multiring Ultrasonic Transducer (S-MRUT) on a single piezoelectric sheet, specifically designed for powering implantable devices for optogenetics in freely moving animals. The proposed unidirectional S-MRUT is capable of focusing the ultrasonic waves on brain implants located at different depths and regions of the brain. The S-MRUT is designed based on Fresnel Zone Plate (FZP) theory, simulated in COMSOL, and fabricated with the microfabrication process. The acoustic profile of the seven different configurations of the S-MRUT was measured using a hydrophone with the total number of 7436 grid points. The measurements show the ability of the proposed S-MRUT to sweep the focus point of the acoustic waves in the axial direction in depths of 1 – 3 mm, which is suitable for powering implants in the striatum of the mouse. Furthermore, the proposed S-MRUT demonstrates a steering area with an average radius of 0.862 mm and 0.678 mm in experiments and simulations, respectively. The S-MRUT is designed with the size of ${3.8}\times {3.8}\times {0.5}$ mm3 and the weight of ${0.054}{gr}$ , showing that it is compact and light enough to be worn by a mouse. Finally, the S-MRUT was tested in our measurement setup, where it successfully transfers sufficient power to a 2.8-mm3 optogentic stimulator to turn on a micro-LED on the stimulator.

In this paper, a power-efficient and high-resolution ultrasonically powered and controlled optogenetic stimulator system is proposed. The proposed system benefits from a novel fully analog Time to Current Converter (TCC) for driving aµLED for optogenetics according to time-encoded data over ultrasonic waves. The whole system including a high-efficiency active rectifier, a double-pass regulator, a burst detector, an overvoltage regulator, a reference generator and the novel TCC are designed, analyzed and simulated in transistor level in standard TSMC 0.18 µm CMOS technology in conjunction with a lumped-element model for the piezoelectric receiver. For an LED current of 1 mA, a chip efficiency of 94 % is achieved according to the simulation results. The rectified voltage at the output of the active rectifier is equal to 2.85 V for a 1 mA load and is limited to 3.02 V by the overvoltage regulator, for loads of less than 905 µA. The proposed TCC demands only 0.2 V overhead voltage and specifically designed to converts the time duration between 5−55 µs to a current of 0−1000 µA linearlyand according to the application requirements.

In this research, a single-aligned nanofiber of pure TiO2 and gold nanoparticle (GNP)-TiO2 were fabricated using a novel electro-spinning procedure equipped with secondary electrostatic fields on highly sharp triangular and rectangular electrodes provided for gas sensing applications. The sol used for spinning nanofiber consisted of titanium tetraisopropoxide (C12H28O4Ti), acetic acid (CH3COOH), ethanol (C2H5OH), polyvinylpyrrolidone (PVP), and gold nanoparticle solution. FE-SEM, TEM, and XRD were used to characterize the single nanofiber. In triangular electrodes, the electrostatic voltage for aligning single nanofiber between electrodes depends on the angle tip of the electrode, which was around 1.4–2.1, 2–2.9, and 3.2–4.1 kV for 30°, 45°, and 60°, respectively. However, by changing the shape of the electrodes to rectangular samples and by increasing distance between electrodes from 100 to 200 μm, electro-spinning applied voltage decreased. Response of pure TiO2 single nanofiber sensor was measured for ...

We present the fabrication, characterization, and demonstration of high-efficiency ultrasound-powered micro- light emitting diodes (μLED) for use in optogenetic applications. InGaN based blue-emitting LED material wafers grown on a patterned sapphire substrate (PSS) were used to assist in the out-scattering of the light. The turn-on voltage of the LEDs is around 2.5 volts and the electrical ideality factor is 1.2 confirming high radiative recombination efficiency. A power density of more than 50 mW/mm2 was obtained from a 130 x 300 μm2 LED with a mesa of 100 μm diameter at 3 mA which is much more than is required to excite channelrhodopsin transfected neural cells. A high external quantum efficiency (EQE) of 33% is obtained at 3 mA measured in an integrating sphere. The peak wavelength of the μLED was measured at 483 nm at different current densities. The μLEDs are integrated directly onto a rectifier and Piezoelectric Transducer (PZT) harvester to realise a highly efficient ultrasound-powered light delivery unit capable to generate mWs of optical power. The concept was validated by powering the integrated device with ultrasound.

This paper presents a novel approach to improve the performance of Piezoelectric Energy Harvesters (PEHs) applicable to a variety of applications, e.g. biomedical implants. This is brought by stacking a magnet over the piezoelectric material, i.e. a piezo-magnet stack. Using the proposed piezo-magnet stack, an improvement in the generated power on the piezoelectric receiver from ultrasonic waves is observed. This is attributed to the interaction of amplified force induced by the magnetic material and the manipulation of the polarization of the piezoelectric material making the receiver more sensitive to mechanical waves. Experimental results show an output power of up to 3.27mW when equipping a 1mm^3 Lead Zirconate Titanate (PZT4) cube as piezoelectric material with the same-size cubic Neodymium (NdFeB) magnet, which is 18\% higher compared to the piezoelectric cube without the magnet. The PZT showed 13\% frequency shift of the resonance frequency to a higher frequency, when it is stacked with the magnet.

This paper presents a novel overvoltage protection technique for ultrasonically powered microsystems. The proposed idea benefits from voltage-current characteristics of the piezoelectric harvesters, and limits the amplitude of the harvested signal by regulating the current consumption of the system. For this purpose, a low-area low-power overvoltage regulator is proposed, analyzed and simulated in transistor level in standard TSMC 0.18μm CMOS technology occupying a silicon area of 285μm2. Furthermore, to avoid unnecessary power consumption of the overvoltage regulator, it is proposed to take advantage of an ultrasonic burst detection block to deactivate the regulator in the absence of ultrasonic waves. According to our simulation results, the quiescent power consumption of the proposed circuit in the presence and absence of ultrasonic waves are 37 and 3μW respectively, and the minimum phase margin of the negative feedback loop is 68 degree.

This paper proposes a novel system for ultrasonically-power optogenetic microstimulator. In this system, a novel powering approach for the comparators is proposed that improves the power conversion efficiency of the rectifier. This is done by lowering the Rail-to-Rail supply voltage of the comparators and consequently their propagation delay. This technique enhances the power conversion efficiency of the active rectifiers in two ways: a. decreasing thepropagation delay of the comparators; and b. enabling reuse of consumed power by the comparators and drivers of power transistors. The proposed system including the active rectifier, a novel double-pass regulator, a current reference, and a burst detection circuit is simulated in TSMC 0.18-µm CMOS technology and occupies an area of 0.09 mm2. The proposed active rectifier connected to a load of 3 kΩ, generates an output voltage of up to 3 V out of an input AC signal with the amplitude of 3.2V and the frequency range of 1-14 MHz. In the same frequency range and with the same load, it exhibits a voltage conversion ratio of 92.25-93.75% and power conversion efficiency of up to 95%. The double-pass regulator is proposed for seeking both power efficiency and over-voltage protection in this specific design.