Neural Implant See U
Full technical documentation on the visual cortical prosthesis, including hardware specifications, stimulation protocols, system architecture, and implementation notes.
1. System architecture
1.1 Overview
The See U neural implant system is made of three main components that work together to capture, process, and send visual information directly to the user’s primary visual cortex.
External component
- • CMOS camera (16MP)
- • Processing unit
- • External battery (2500mAh)
- • RF transmitter
Subcutaneous component
- • RF receiver
- • Signal processor
- • Implantable battery
- • Electrode controller
Intracortical component
- • 1024-electrode array
- • Flexible substrate
- • Neural interface
- • Impedance sensors
1.2 Data flow
Image capture
The CMOS camera captures 60 FPS frames at 1920x1080. A high-sensitivity sensor (up to ISO 6400) supports low-light operation.
Preprocessing
Computer-vision algorithms apply edge detection, adaptive contrast, and noise reduction. The image is downsampled to a 32x32 map while keeping critical information.
Retinotopic mapping
Spatial image coordinates are mapped to corresponding positions in visual cortex, following natural V1 retinotopic organization.
Stimulus encoding
Electrical pulse patterns are generated with optimized parameters (amplitude, frequency, duration) for each electrode based on the corresponding pixel intensity.
RF transmission
Encoded data is sent over 13.56 MHz RF through the skin to the subcutaneous receiver, with end-to-end latency under 50 ms.
Neural stimulation
The electrode controller applies biphasic pulses to microelectrodes, driving specific neurons and eliciting phosphenes perceived by the user.
2. Hardware specifications
2.1 External unit
Camera
Processor
Power
2.2 Implantable unit
RF receiver
Signal processor
Implantable battery
Physical dimensions
3. Microelectrode array
3.1 Electrode specifications
Geometric parameters
Materials and coatings
3.2 Electrical characteristics
Stimulation
Safety
Monitoring
3.3 Biocompatibility
Tissue response
PEDOT:PSS coating reduces inflammation and glial scarring. Studies show stable impedance for over 2 years in vivo.
Mechanical flexibility
Flexible polyimide (Young’s modulus ~2.5 GPa) lowers stress on cortical tissue (~1 kPa), reducing micro-trauma from brain motion.
Sterilization
Ethylene oxide (EtO) preserves materials and electrical properties, validated to ISO 11135.
4. Signal processing
4.1 Processing pipeline
Step 1: Capture and preprocessing
- • Capture: RGB frames 1920x1080 @ 60 FPS
- • Conversion: RGB → grayscale (luminance weighting)
- • Equalization: Adaptive histogram (CLAHE) for contrast
- • Denoising: Bilateral filter preserving edges
- • Latency: <5ms
Step 2: Feature extraction
- • Edge detection: Multi-scale Sobel filter
- • Saliency: Contrast-based visual attention map
- • Segmentation: Figure–ground with adaptive threshold
- • Priority: Moving objects get higher weight
- • Latency: <8ms
Step 3: Smart downsampling
- • Target resolution: 32x32 pixels (1024 points)
- • Method: Adaptive pooling keeping critical information
- • Weighting: Central regions get more effective resolution
- • Quantization: 8 intensity levels per pixel
- • Latency: <3ms
Step 4: Retinotopic mapping
- • Transform: Cartesian → log-polar coordinates
- • Cortical magnification: Higher central density (fovea)
- • Calibration: Per-user tuning
- • Compensation: Cortical curvature distortion
- • Latency: <2ms
Step 5: Stimulus encoding
- • Mapping: Pixel intensity → pulse parameters
- • Modulation: Pulse amplitude and/or frequency
- • Timing: Synchronization of all 1024 channels
- • Optimization: Adaptive learning algorithm
- • Latency: <2ms
⚡ End-to-end pipeline latency: <20ms (from capture to stimulation)
4.2 Optimization algorithms
Adaptive learning
The system uses machine learning to tune stimulation from user feedback and performance metrics.
- • Automatic per-electrode amplitude
- • Perceptual contrast tuning
- • Impedance drift compensation
- • Personalized retinotopic map
Motion prediction
Optical flow and temporal prediction cut perceived lag and improve moving-object perception.
- • Speed and direction estimates
- • Future position extrapolation
- • Trajectory smoothing
- • Priority for moving objects
5. Communications
5.1 Data telemetry
RF specifications
Communication protocol
5.2 Link security
Encryption
AES-128 for real-time data. Per-device keys created at first pairing. Session key rotation every 24 hours.
Authentication
Mutual challenge–response between the external unit and implant, blocking replay and hijacking. Session timeout after 5 minutes idle.
Interference protection
FHSS across 50 channels, automatic collision handling, and a fallback mode for high-RF noise environments.
6. Power management
6.1 Inductive charging
Operating principle
Resonant inductive coupling at 13.56 MHz transfers power through the skin with no percutaneous connectors.
- • Transmit coil: 50 mm diameter, 10 turns
- • Receive coil: 35 mm diameter, 15 turns
- • Efficiency: 60–70% at 5 mm gap
- • Power delivered: 500 mW typical, 1 W max
- • Alignment: ±10 mm lateral tolerance
Management circuit
A dedicated PMIC governs charging and power routing to all implant subsystems.
- • Rectification: Schottky bridge
- • Regulation: Buck 3.6V → 1.8V/3.3V
- • Charging: CC/CV with automatic termination
- • Protection: Overcurrent, overvoltage, temperature
- • Monitoring: Coulomb counter for state of charge
6.2 Power optimization
Power budget split
(60mW)
(45mW)
(30mW)
(15mW)
Operating modes
Continuous 60 FPS stimulation, all subsystems on.
30 FPS, lighter processing, longer battery life.
Stimulation off; RF and monitoring on; quick wake.
Minimal: clock and charge detect only; months of life.
7. Safety and biocompatibility
7.1 Standards and certifications
Biocompatibility
- ISO 10993: Biological evaluation of medical devices
- USP Class VI: Cytotoxicity testing
- ASTM F756: Implantable materials
Electrical safety
- IEC 60601-1: Medical equipment safety
- IEC 60601-2-40: Neurostimulators
- IEEE C95.1: RF exposure limits
7.2 Safety mechanisms
Hardware protections
- • Current limit: Compliance network caps output at 200μA
- • Short-circuit detect: Automatic cut-off in <1ms
- • Temperature: Thermal shutdown at 41°C
- • Watchdog: Reset on firmware hang
- • Energy buffer: Capacitor for controlled shutdown
Software protections
- • Integrity: CRC on firmware and parameters
- • Stim limits: Validation on every change
- • Event log: Fault and anomaly history
- • Safe mode: Conservative defaults
- • OTA updates: Secure with rollback
Continuous monitoring
- • Electrode Z: Sampled every 100ms
- • Implant temp: Four distributed sensors
- • Battery: Live SOC and SOH
- • RF link: RSSI and error rate
- • Injected charge: Per-electrode integrator
7.3 Safety testing
In vitro
- • Neural cell culture
- • Cytotoxicity
- • Corrosion
- • Mechanical fatigue
- • Electrical characterization
In vivo
- • Animal models
- • Tissue response
- • Functional tests
- • Long-term follow-up
- • Histology
Clinical
- • Feasibility
- • Safety trials
- • Efficacy
- • Long-term follow-up
- • Adverse events
8. Stimulation protocols
8.1 Stimulation parameters
Waveform
Symmetric biphasic pulses: cathodic phase first, then anodic. 50 μs inter-pulse gap for capacitive discharge. <1% charge imbalance to avoid electrochemical buildup.
Cathodic (stimulating) phase
- • Amplitude: 10–200 μA (tunable)
- • Duration: 100–500 μs
- • Polarity: Negative
- • Shape: Rectangular
Anodic (recovery) phase
- • Amplitude: Matches cathodic
- • Duration: Matches cathodic
- • Polarity: Positive
- • Shape: Rectangular
Perceived intensity control
Phosphene strength is modulated in three complementary ways:
Current range 10–200 μA; approximately logarithmic with perceived brightness. Eight discrete levels for efficiency.
Pulse rate 50–300 Hz; higher rates read brighter, useful for fine control without retuning current.
100–500 μs; longer pulses inject more charge and look brighter, bounded by electrochemistry safety.
8.2 Encoding strategies
Spatial coding
Direct map from each image pixel to its array electrode, aligned with retinotopic cortical layout.
- • Resolution: 32x32 → 1024 electrodes
- • Cortical magnification: Dense center
- • Transform: Log-polar fovea model
- • Calibration: Per-user tuning
Temporal coding
Stimulation timing encodes more than intensity—motion, depth, and salience.
- • Burst: Trains for moving items
- • Sync: Relative phase across sites
- • Time patterns: Texture codes
- • Rate adaptation: Rate tracks contrast
8.3 Optimization and personalization
Initial calibration
Two to four weeks to set thresholds and safe operating points per site:
- Perception thresholds (10–50 μA typical)
- Comfort range (100–150 μA typical)
- Custom retinotopic map
- Time-domain tuning (rate, width)
- Simple pattern tests
Continuous adaptation
The system learns over time from:
- • User input: Manual brightness/contrast
- • Task success: Navigation and recognition scores
- • Z drift: Auto correction
- • Use patterns: Frequent-scene tuning
- • Neural plasticity: Long-term recalibration
Specialized modes
Pre-built profiles for common use:
High edge contrast, low motion
Motion, depth, and obstacles
Faces, objects, and shape cues
Gain and adaptive contrast