Neurotechnology... but where's the brain?

Hey all, it’s been awhile since my last blog post but I’m back! For this week’s blog post, I want to focus on some interesting research I came across. While this research was actually initially released last year in Science, and while it may not be traditional BCI, I still think it is a very fascinating and relevant piece of neurotechnology research. This shows how neurotechnology can be applied to other sensory aspects of the nervous system and incorporate the brain without directly targeting it.

Last June, Dr. Zhenan Bao (pictured to the right), a Professor of Chemical Engineering and Material Science and Engineering at Stanford University, was able to create artificial skin. Yeah, you heard me right. Artificial skin! Of course, we are nowhere near developing a fully capable stretch of artificial skin that can perform all of the same functions that typical human skin does; however, Dr. Bao is getting closer and closer to that goal with her developments. This research project has been over a decade’s worth of efforts,

and they are finally beginning to come to fruition in the form of a flexible electronic fabric capable of acting as a rudimentary version of human skin. In this article, I will break down how the invention works as well as its future directions and implications.

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Function:

Dr. Bao’s artificial skin that she developed last summer is able to perform two of the basic sensory functions of skin: detecting pressure and carrying out a basic reflex (in this case, her group was able to replicate the knee jerk reflex). The reflex response she included in her artificial skin is able to, like an actual biological reflex, receive and transmit incoming sensory impulses to the correct synapses and thus produce two outputs, one that causes the knee to immediately move and one that is sent to the brain as a sensory-information signal. The

response time of her circuitry is actually in the millisecond range, so it is highly effective and responsive. The basic idea of her artificial skin is that it is able to generate its own pseudo “action potentials” and transmit these sensory impulses to other components of the nervous system such as the brain. While this sounds simplified, as you will see in the next section of this article, the complex structure of her device allows for these complex functions to be accomplished, and this isn’t even half of all of the amazing capabilities our skin can accomplish. On top of that, Dr. Bao’s work is not just a concept. She tested her work and the results are amazing: for example, using her sensors on a cockroach, she was able to impart a reflex on the cockroach’s leg, causing the leg to move with more or less force based on the amount of pressure imparted on the sensor. In addition, she tested the touch-sensing components of her device by (1) rolling a cylinder in different directions along the artificial skin, which was able to distinguish the direction of movement and (2) using the artificial skin to read Braille.

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Structure:

We know in biology that structure imparts function, and that could not be more true even for Dr. Bao’s artificial skin. The artificial skin models the internal structure present in the dermal and epidermal layers of the skin in order to provide complexity.

In addition, the artificial skin requires three technical components to allow proper functioning:

• A touch sensor in the top layer of the artificial skin for detecting pressure and touch sensation

• Flexible electronic neurons to conduct impulses from the top layer to the bottom layer of the artificial skin

• An artificial synaptic transistor that functions similarly to human synapses in that it can relay signals and be able to store information

As mentioned, the artificial skin is comprised of two layers. The top layer primarily functions as a sensor that can actually detect pressure. It is embedded with billions of carbon nanotubes, which are a type of nanomaterial composed of carbon hexagonal lattices joined in a way that forms a hollow cylinder. As pressure is applied to this layer, the nanotubes are forced to come closer together, which allows the nanotubes to generate and conduct electricity to the bottom

layer (carbon nanotubes are actually great electrical conductors!). Therefore, you can imagine that if no pressure is applied, no electrical impulses are sent. Following this same principle, the increasing amount of pressure you apply, the increasing extent to which you force the carbon nanotubes together, and the increasing amount of short electrical pulses sent to the bottom layer. This thus allows the artificial skin to distinguish between light touch and a firm grip. The bottom layer of the artificial skin essentially functions as a signal transporter, converting the incoming signal from the top layer into a biochemical stimulus that can be used and interpreted by other neurons throughout the body. In basic terms, Dr. Bao’s group engineering their own layer of neurons and also used their artificial synaptic transistor to translate the pressure signals from the top layer into electrical signals that can be sent from the bottom layer to activate other neurons and transmit sensory information throughout the nervous system.

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Implications and Future Directions:

While Dr. Bao was able to replicate pressure sensation and, to some extent, reflexes, her future goals include replicating many of the other sensory functions of skin, such as sensing pain, detecting temperature, and feeling texture. However, it will take some time before she is able to actually incorporate these functions into her flexible circuitry of artificial skin. Something that I personally would love to see her pursue and accomplish would be the ability to replicate the skin’s self-healing abilities. On the other hand, though, one of her other future goals that could be perceived as exciting, but to me is honestly a bit frightening, is to use the artificial skin to provide robots with more neural feedback from their environment and to improve their sensory capabilities. While I do believe Dr. Bao’s artificial skin has huge implications for prosthetics and other people who have impacted tactile sensation, enabling robots with the abilities we derive from skin is a bit of an ethical concern in my eyes as society continues to artificially create its own artificial intelligence that becomes more and more sentient and human-like.

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Check out Dr. Bao's lab for yourself:

https://baogroup.stanford.edu/

References:

https://neurosciencenews.com/artificial-nerve-robot-prosthetics-9213/

https://baogroup.stanford.edu/index.php/research-highlights/361-stanford-engineers-create-artificial-skin-that-can-send-pressure-sensation-to-brain-cell

https://robotics.sciencemag.org/content/3/24/eaau6914.full?ijkey=agtkM3Ph4MAGg&keytype=ref&siteid=robotics

https://en.wikipedia.org/wiki/Carbon_nanotube