Periodic Reporting for period 1 - SonoNeuroS (Wireless UltraSound Powered Diamond based Neural Stimulators)
Reporting period: 2023-01-11 to 2025-01-10
This project aims to develop wireless, battery-free, ultrasound-based stimulators using Piezoelectric Micro-machined Ultrasonic Transducer (p-MUT) technology by combining p-MUT and microelectrode arrays. A key focus is on developing wireless neural stimulators and to assess their efficiency using the mouse retinal explant model.
Electrical stimulation of the nervous system including retinal neurons, the brain and spinal cord, has significant potential for both scientific research and therapeutic use. A core challenge in chronic applications is the power supply of the implant. For instance, the battery of Deep Brain Stimulators must be changed every 4 to 5 years for standard implant, inducing skin sacring and patient discomfort. Wireless systems using near-field power transfer could circumvent the issues with rechargeable batteries extending the replacement period to 15 years. Wireless and battery stimulators offers a transformative advantage over traditional battery-powered and wired microelectrode systems for implantable medical devices. In this context ultrasound-based wireless solutions provide a safer, less invasive, and more flexible alternative for powering implants.
Our study was performed in collaboration with ESIEE Paris and CEA Grenoble, by the combining two different technologies pMUTs and microelectrodes array to provide neural stimulator, which is proof of concept to provide electrical stimulation pulses for future application of neural stimulator in Retinal ganglion cells. In the SonoNeuroS project, a micrometers-sized piezoelectric micromachined ultrasound transducer (pMUT) connected to microelectrodes for a wireless implantable neural stimulator that addresses these limitations, by investigates the feasibility to use micromachined ultrasound transducer pMUT array, resonating at 110-140 kHz, as a wireless neural stimulator. Electrical current flow between microelectrodes with varying impedance, connected to the pMUT terminals in a phosphate-buffered saline (PBS) solution, was measured to evaluate its performance. Preliminary results demonstrate that the pMUT is capable of delivering pulsed current with amplitudes up to 10 µA in PBS. These findings establish a critical step in advancing the design of a wireless neural stimulation device, with the potential for optimized current delivery across different microelectrode arrays. The results indicate that the pMUT-microelectrode combination holds substantial promise for efficient electrical stimulation. The proposed solution could enable the entire micro-implanted system to be integrated into a single device, advancing the development of a wireless implantable neural stimulator with improved biocompatibility, integration, and miniaturization. However, results are not perfectly aligned that was proposed in the project.
Electrical stimulation of the nervous system including retinal neurons, the brain and spinal cord, has significant potential for both scientific research and therapeutic use. A core challenge in chronic applications is the power supply of the implant. For instance, the battery of Deep Brain Stimulators must be changed every 4 to 5 years for standard implant, inducing skin sacring and patient discomfort. Wireless systems using near-field power transfer could circumvent the issues with rechargeable batteries extending the replacement period to 15 years. Wireless and battery stimulators offers a transformative advantage over traditional battery-powered and wired microelectrode systems for implantable medical devices. In this context ultrasound-based wireless solutions provide a safer, less invasive, and more flexible alternative for powering implants.
Our study was performed in collaboration with ESIEE Paris and CEA Grenoble, by the combining two different technologies pMUTs and microelectrodes array to provide neural stimulator, which is proof of concept to provide electrical stimulation pulses for future application of neural stimulator in Retinal ganglion cells. In the SonoNeuroS project, a micrometers-sized piezoelectric micromachined ultrasound transducer (pMUT) connected to microelectrodes for a wireless implantable neural stimulator that addresses these limitations, by investigates the feasibility to use micromachined ultrasound transducer pMUT array, resonating at 110-140 kHz, as a wireless neural stimulator. Electrical current flow between microelectrodes with varying impedance, connected to the pMUT terminals in a phosphate-buffered saline (PBS) solution, was measured to evaluate its performance. Preliminary results demonstrate that the pMUT is capable of delivering pulsed current with amplitudes up to 10 µA in PBS. These findings establish a critical step in advancing the design of a wireless neural stimulation device, with the potential for optimized current delivery across different microelectrode arrays. The results indicate that the pMUT-microelectrode combination holds substantial promise for efficient electrical stimulation. The proposed solution could enable the entire micro-implanted system to be integrated into a single device, advancing the development of a wireless implantable neural stimulator with improved biocompatibility, integration, and miniaturization. However, results are not perfectly aligned that was proposed in the project.
Microelectrode Characterization for Neural Stimulation
Three types of microelectrode arrays were connected to the p-MUT array to investigate their ability to conduct neural stimulation in PBS:
• Diamond coated PEDOT:PSS electrodes
• Gold coated PEDOT:PSS electrodes on diamond
• Pure gold electrodes
All three electrodes were tested under the same experimental conditions, including:
• Cyclic voltammetry
• Electrochemical impedance spectroscopy (three-electrode configuration in PBS)
• System electrical impedance response (two-electrode configuration)
• Current vs. frequency response
Experiments were conducted in a PBS-filled tank, simulating biological conditions. Results showed that the gold electrode had the lowest impedance (~10 kΩ), resulting in the highest current output, while diamond-pdot-pss electrodes exhibited higher impedance and lower current at frequencies above 100 kHz.
Three types of microelectrode arrays were connected to the p-MUT array to investigate their ability to conduct neural stimulation in PBS:
• Diamond coated PEDOT:PSS electrodes
• Gold coated PEDOT:PSS electrodes on diamond
• Pure gold electrodes
All three electrodes were tested under the same experimental conditions, including:
• Cyclic voltammetry
• Electrochemical impedance spectroscopy (three-electrode configuration in PBS)
• System electrical impedance response (two-electrode configuration)
• Current vs. frequency response
Experiments were conducted in a PBS-filled tank, simulating biological conditions. Results showed that the gold electrode had the lowest impedance (~10 kΩ), resulting in the highest current output, while diamond-pdot-pss electrodes exhibited higher impedance and lower current at frequencies above 100 kHz.
Wireless electrical stimulation was assessed using a diamond-pdot-pss electrode as the working electrode, with current recordings taken at different frequencies. The system exhibited a slight frequency shift when the electrode was in place, as reflected in the impedance and current plots. For comparison, gold-pdot-pss and gold electrodes were also characterized. A single microelectrode acted as the current source in PBS, while other electrode served as to acquire current and voltage. Among the tested electrodes, the diamond micro-electrodes show higher impedance and lower electrical current and the gold pdot-pss micro-electrode and (10 kΩ impedance) demonstrated the highest current output. The frequency-swept current responses for various electrodes were analyzed, revealing distinct impedance and current characteristics across different electrode types