The human body is made-up of nerves which are a bundle of fibers that send/receive messages from the brain to the body and vice versa. These messages are generated owing to the chemical and electrical changes in the cells belonging to the nerves.
The following figure shows the Cranial nerve and its functioning.
Fig 1. Cranial nerve and its functioning
Researchers over the years have been trying to study the human body and develop functionalities in accordance with it. As the understanding improves, biomaterials are being engineered which have chemical, biological and physical characteristics for use inside the body.
Fig 2. Mimicking natural functionality using biomaterials
In line with this, in a collaborative work between Stanford University(USA), Seoul National University (S.Korea), Kyung Hee University(S.Korea) and Nankai University(China), researchers have emulated a sensory(afferent) nerve.
The “neuromorphic” sensory system was designed using a flexible organic electronic circuit which comprised of pressure sensors, a ring oscillator, and an ion gel–gated transistor.
This artificial mechanoreceptor was used to control an insect’s disabled leg and distinguish the braille characters.
Let us delve further into the topic for a better understanding…
An afferent nerve brings a sensation of touch, pain, or temperature variation to the Central Nervous System(CNS) and Brain. It conveys the impulse which can be used by the Central Nervous System(CNS) for an organism to perceive its ambient and self.
Fig 3. Afferent Nerve
An ion gel–gated organic thin film transistor is able to achieve higher-capacitance. This due to low deep-trapping of holes and quick/short-range motion of cations & anions near the interface and slow ionic diffusion over a longer distance.
Fig 4.An example of ion-gel gated SWNT-based FET fabrication
In this work, a biomimetic structure can detect movement of an object and combine simultaneous pressure inputs for distinguishing braille characters.
The emulated artificial afferent nerve collects pressure information (1-80kPa) from the pressure sensors and actuates(0-100Hz) it using ring oscillators. It integrates this further using multiple ring oscillators with a synaptic transistor.
The following figure describes the control methodology for the movement using a connection between the artificial afferent nerve and biological motor (efferent) nerve
Fig A. -> An insect and an artificial mechanosensory nerve used in this experiment
Fig B. -> An artificial nerve was connected to biological motor nerve to make a hybrid reflex arc for controlling the movements of the detached insect leg
Fig C. -> The experimental set-up used to measure the force of the movements of the disabled insect leg
Fig 5. The control methodology achieved by combining an artificial & natural nerve in an insect leg 
The following figure describes how the artificial afferent nerve has been achieved to sense and actuate to the pressure applied while doing the Braille reading
Fig J. -> An artificial mechanosensory nerve with 2×3 pressure sensor array. Ring oscillators and synaptic transistors are connected to the sensors for processing information
Fig K. -> The output of the artificial nerve when the braille character “E” was pressed
Fig L. -> The performance of artificial nerves with & without synaptic transistors. The synaptic transistors help our system to distinguish braille characters clearly
Fig 6. The layout and output of the artificial mechanosensory nerve
Owing to this, the system has potential in domains like neurorobotics and neuroprosthetics.
- Kim Y et .al,”A bioinspired flexible organic artificial afferent nerve”, Vol. 360, Issue 6392, pp. 998-1003, Science, Jun 2018
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