Self-Powered Artificial Synapse Gives Smart Devices Human-Like Color Vision Without Batteries

Self-Powered Artificial Synapse Enables Human-Like Color Vision in Smart Devices

A research team at Tokyo University of Science (TUS) has developed a solar-powered artificial synapse capable of distinguishing colors with precision comparable to the human eye — all without relying on batteries or external power sources.

Modern devices like drones, smartphones, and autonomous vehicles continuously process large volumes of visual data. These systems typically capture up to 60 frames per second, converting light into electrical signals and storing images. This process demands substantial energy and memory resources. In contrast, the human visual system filters sensory input to transmit only essential information, resulting in significant energy savings. Replicating this efficient filtering in machines has been a key focus for researchers aiming to create low-power, intelligent vision systems.

Overcoming the Challenge of Color Recognition

Color detection remains a major hurdle for artificial vision systems. Most existing technologies struggle to differentiate colors with human-like accuracy and require additional power, which limits their use in battery-operated devices.

The TUS team, led by Associate Professor Takashi Ikuno, tackled this problem by engineering a self-powered artificial synapse. This device functions like a brain cell that transmits signals but draws its energy directly from light through integrated dye-sensitized solar cells. It does not need any external power source.

How the Device Works

The artificial synapse incorporates two types of dye-sensitized solar cells, each coated with different light-sensitive dyes, D131 and SQ2. These dyes respond to distinct wavelengths within the visible spectrum. When exposed to specific colors, the device generates unique electrical signals: blue light induces a positive voltage, while red light produces a negative voltage.

This bipolar response allows the synapse to discriminate between colors differing by as little as 10 nanometers — matching the sensitivity of the human eye. Additionally, the device can perform basic logical operations like AND, OR, and XOR within a single unit, eliminating the need for multiple components.

Performance and Applications

In experimental trials, the synapse identified 18 different motion-color combinations with 82% accuracy, demonstrating its potential for complex visual processing.

• Autonomous Vehicles: Improved color recognition with low power consumption can enhance traffic signal detection even under challenging lighting or weather conditions.
• Healthcare Wearables: Devices monitoring vital signs such as blood oxygen levels could become more efficient by using this compact, low-power synapse.
• Smartphones and AR/VR: Cameras and headsets could benefit from precise color and motion detection while conserving battery life.
• Security and Smart Homes: Systems reliant on visual cues can become more responsive and energy-efficient.

Dr. Ikuno emphasizes that this technology moves closer to creating low-power machine vision systems with color discrimination capabilities akin to human perception.

The Science Behind the Innovation

The synapse’s dual solar cells produce voltages with opposite polarities depending on the incoming light wavelength, ranging from 450 to 750 nanometers. Blue light peaks near +0.48 volts, while red light drops to around -0.18 volts. Intermediate colors generate signals reflecting the competitive interaction between the two dyes, resulting in a nonlinear response similar to biological systems.

The team also employed reservoir computing, a machine learning approach where the device itself processes most of the data, reducing the training load on traditional AI models. This enables efficient recognition of color-coded motions using a simple output network, cutting down on energy and computational demand.

Advancements Over Previous Technologies

Previous attempts at color-sensitive artificial synapses relied on organic semiconductors or materials like molybdenum disulfide and black phosphorus. These devices struggled with fluctuating light intensities and required external voltage, increasing power consumption. Moreover, they only detected large wavelength differences, limiting their practical use.

By leveraging dye-sensitized solar cells, the TUS team achieved stable, high-voltage responses capable of detecting subtle color variations without external power. The synapse simultaneously senses, filters, learns, and processes visual information in a manner that closely resembles human neural function.

This breakthrough offers a promising step toward intelligent machines that perceive and interpret their environment efficiently, paving the way for smarter, energy-conscious devices across various sectors.

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