External Article: Mimicking Sensory Nerves using Organic Electronics

Background

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[1]. 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[2].

Fig 1. Cranial nerve and its functioning[2]

 

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[3]

 

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[4].

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…

 

Research Work

An afferent nerve brings a sensation of touch, pain, or temperature variation to the Central Nervous System(CNS) and Brain[4][5]. 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[5]

 

An ion gel–gated organic thin film transistor is able to achieve higher-capacitance[4][6][7]. 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[6].

 

Fig 4.An example of ion-gel gated SWNT-based FET fabrication[7]

 

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 [4][10]

 

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[4][10]

 

Owing to this, the system has potential in domains like neurorobotics and neuroprosthetics.

Article

1. http://science.sciencemag.org/content/360/6392/998
2. http://www.sciencedaily.com/releases/2018/05/180531142942.htm
3. Kim Y et .al,”A bioinspired flexible organic artificial afferent nerve”, Vol. 360, Issue 6392, pp. 998-1003, Science, Jun 2018

If you want to share your opinion kindly do so in the comments section or email me at u2d2tech@gmail.com.

 

References

1. https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0022678/
2. https://www.britannica.com/science/cranial-nerve

3. J. Green and J. Elisseeff, “Mimicking biological functionality with polymers for biomedical applications”, Nature Vol. 540, Pages 386–394, 2016

4. http://science.sciencemag.org/content/360/6392/966.full
5. https://en.wikipedia.org/wiki/Afferent_nerve_fiber
6. J. Cho et.al.,”High‐Capacitance Ion Gel Gate Dielectrics with Faster Polarization Response Times for Organic Thin Film Transistors”, Advanced Materials 20(4), 686 – 690, 2008

7. H. Byeon et.al., “Ultralow voltage operation of biologically assembled all carbon nanotube nanomesh transistors with ion–gel gate dielectrics”, Scientific Reports, Volume 7, Article number: 5981 (2017)

8. https://www.eurekalert.org/pub_releases/2018-05/snu-foe053018.php

9. https://medicalxpress-com.cdn.ampproject.org/c/s/medicalxpress.com/news/2018-06-flexible-electronics-mimic-biological-mechanosensory.amp

10. Kim Y et .al,”A bioinspired flexible organic artificial afferent nerve”, Vol. 360, Issue 6392, pp. 998-1003, Science, Jun 2018

11. https://www.electrochem.org/redcat-blog/tag/prosthesis/