Wireless Charge-Balanced Retinal Prosthesis Powering
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Solution Overview
Problem
Conventional retinal prostheses face challenges in efficiently powering and controlling optically modulated multichannel stimulating arrays due to heat generation, bulky interconnects, and tissue damage from charge unbalanced stimulation, limiting their ability to provide high-resolution vision to blind patients.
Innovation Solution
The implementation of an RF driven charge metering stimulation system that outsources power and computational functions to an external component, using a dual supply complementary voltage limiting regulator and adiabatic voltage stimulation to minimize power consumption and prevent tissue damage, while maintaining effective high-resolution stimulation with minimal interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional high channel count neurostimulator is used to provide high resolution stimulation, then stimulation resolution is improved, but heat generation increases and tissue damage occurs
Solution Approach 1:
The patent divides the stimulation system into multiple independent channels, each capable of being controlled separately. This segmentation allows for precise delivery of charge-balanced biphasic pulses to different retinal regions, achieving high-resolution stimulation while distributing power consumption across multiple channels to reduce overall heat generation
Solution Approach 2:
The system dynamically adjusts stimulation parameters including pulse width, amplitude, and inter-stimulus intervals to optimize power consumption. By varying these parameters based on visual field requirements, the system maintains high-resolution capability while minimizing energy dissipation and heat generation
2Measurement precision
If conventional high channel count neurostimulator is used to provide high resolution stimulation, then stimulation resolution is improved, but device size increases
Solution Approach 1:
The patent integrates multiple functional components including the stimulator, telemetry module, and power management circuits into a single compact implantable device. This merging of functions reduces the overall device volume while maintaining high channel count capability through shared infrastructure and efficient circuit design
Solution Approach 2:
The implantable device is designed with multi-functional capabilities, where a single device performs stimulation, data transmission, and power management functions. This universality eliminates the need for separate external control devices, reducing overall system volume while enabling high-resolution multichannel stimulation
3Ease of operation
If conventional neurostimulator with unidirectional current is used, then stimulation simplicity is improved, but electrode lifetime decreases due to charge imbalance
Solution Approach 1:
The system employs periodic biphasic pulses where each stimulation cycle consists of a cathodic phase followed by an anodic phase. This periodic structure ensures that equal amounts of charge are delivered in opposite directions, preventing charge accumulation at the electrode-tissue interface and extending electrode lifetime while maintaining effective neural stimulation
Solution Approach 2:
The patent implements charge monitoring and balancing mechanisms that track the net charge delivered to the tissue. By providing feedback control to adjust subsequent pulse parameters, the system ensures charge balance is maintained, preventing electrode degradation and tissue damage while preserving stimulation effectiveness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient wireless powering and control of neurostimulators, reducing heat generation and tissue damage, and allowing for precise charge balancing, thereby enhancing the performance of retinal prostheses in restoring vision.
Implementation Method 1
An RF driven charge metering stimulator with a power subsystem, signal receiver and synchronization subsystem, stimulator subsystem, and data transmitter subsystem
Implementation Method 2
The stimulator subsystem generates adiabatic voltage pulses with charge balanced outputs to a variable load
Data Source
AI summary
Apparatuses and methods are disclosed for efficient wireless powering of an electrical load with precise external control over pulsed voltage waveform and metering of charge delivered. The system interfaces to an inductive coil for RF power delivery from an external duty-cycled RF power transmitter, and the electrical load. The electrical load may be a photosensitive array of electrodes for an optically addressed, electrically activated retinal prosthesis. The voltage waveform to activate the load is controlled by the transmitted RF amplitude, including switching between cathodic and anodic phases of electrical stimulation. Charge delivered to the load is quantified as discharge events through a series capacitor, transmitted by backtelemetry to the receiver for continuous monitoring throughout the stimulation phases. The subject disclosure further provides for calibration of voltage amplitude and charge metering, to compensate for variable wireless link and load conditions, through additional stimulation phases with a supplementary load with known and stable characteristics.