Brain-inspired learning in action: This schematic illustrates how the flexible plastic chip developed at IIT Bombay mimics the way neurons communicate in the human brain. Just like Neuron 1 sends a signal to Neuron 2 via a synapse, the chip processes external stimuli, like light or heat, and produces a long-lasting response, shown here as a postsynaptic signal. This neuromorphic behavior enables the chip to learn and adapt over time, just like our brain does.
Written by Sirsendu Ghosh, PhD Student at Department of Physics, Indian Institute of Technology Bombay
Consider a chip that is small and flexible, one that can ‘sense’ light and warmth. More importantly, it “learns from them”, just like your brain learns from touch or sight. The new device uses a neuron-like approach, where it adapts to stimuli through learning and changes with experiences over time. The device is created using a unique soft plastic material that not only conducts electricity but also ‘mesmerizes’ in how it was stimulated. It remembers and without aid of conscious intent, forgets gradually, akin to human memory.
One of the most remarkable milestones in humanity’s achievements is: how we acquire knowledge resources, process data through information systems, while efficiently multi-tasking. Nowadays, scientists targets these sets of abilities to replicate this behavior into electronic machines; they could think for themselves which would classify them as Neuromorphic Devices.
The recent invention [1] from IIT Bombay scientists- Mr. Sirsendu Ghosh, Dr. Gaurav Shukla, and Prof. Pramod Kumar, is one of the simplest and most exciting examples of this kind. It’s a two-terminal electronic device, made from a material called PBTTT‑C14, which belongs to a class of carbon-based compounds known as organic semiconductors. The way this gadget learns is what distinguishes it from other brain-like chips.
It reacts to light and temperature in addition to electrical signals. The electrical current of the device changes when light is shone on it and applied heat; more significantly, the effect is long-lasting. The longer the gadget “remembers,” the more frequently you shine the light. The memory gradually disappears when the heat or light is removed. This is similar to a brain cell’s short-term memory. This chip’s response is strengthened by repeated light pulses, much like how listening to a song repeatedly helps you remember it. However, like your brain, it eventually let go of unnecessary information. This natural, brain-like response to light and heat opens up a world of possibilities because light and temperature are all around us. No extra wires or computers needed.
In the reported study, an organic photonic synaptic device was fabricated using PBTTT-C14 as the photoactive layer on an ITO-coated PET substrate. The device was constructed in a vertical architecture with Au contact on top. The fabrication involved standard spin coating and annealing steps to ensure good film quality and interface contact. For measurements, the device was exposed to a broad spectrum of UV to IR light pulses while recording the output current using a source-measure unit.
The device exhibited synaptic plasticity behaviors, such as short-term memory, paired-pulse facilitation, excitatory to inhibitory post synaptic signal, etc. The device also able to perform the logic operations like “AND”, “OR”. Notably, the device could show its potential for neuromorphic and multispectral sensing applications.
Although this research may seem abstract, there are actual potential uses for it: more intelligent robots with compassionate reactions and the ability to sense warmth, sensors for the environment that collect information from sunlight or regular weather patterns, wearable technology that adapts to the light or temperature of your skin, brain-inspired computing systems that are flexible, soft, and low power.
One day, the devices might be printed on pliable materials like textiles or plastic films because the material is flexible and organic. This implies that your skin patch or clothing may eventually think, just a little bit, and adjust to your surroundings. The machines in our world are getting smarter. However, true intelligence involves feeling, learning, and adapting in addition to calculations. This tiny plastic chip, designed at IIT Bombay, brings us a step closer to that dream. Instead of just following instructions, the devices of tomorrow might learn with us and even from us.
Reference
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