BBC-1: Of Arteries, Patient Nutrition, and Pogonophoras

To understand what is going on in this post, take 5 minutes to read this one. It’s an introduction to the concept of Biomimicry Biweekly Challenge. Besides, you all are very brave to have read my incoherent thoughts this far. Stay strong! You can get through this!

Of birthdays, arteries, and Möbius strips

It all comes down to my husband, again. Well, to him and his bookshelf. Have you ever heard of a book “Imagining the Tenth Dimension” by Rob Bryanton? I highly recommend reading it, if you are into mind-expanding exercises.

According to Rob, as we move through the fourth dimension – time – we are very much like an ant on a Möbius strip. To us, time feels like a straight line, moving from past to the future. But as we move along the straight line, our choices are constantly branching in the fifth dimension. When we look back in time, it feels like a straight line to us moving in the fourth dimension, but that straight line is an illusion.

As you read this post, your fifth-dimensional self might now have two main branches – one would be the version of you that continues reading into the next paragraph, while another would be the one who decides to take a break and go do something else.

 Scenario 1

Hello to all those fifth-dimensional selves, who have chosen to tread onto the next paragraph! Let me introduce you to Mykola and Max.

Myk is a computer scientist, specializing in game programming. This particular choice of branch was influenced by his father, who specializes in cybernetics, by Myk’s exposure to computers and games at a very early age, and many other factors. He is also surrounded by the multitude of paths, one of which might as well lead him to become a surgeon. This has been his dream for many years. In the future – if chance, choice, and the actions of others permits – Myk will achieve his dream, regardless of how improbable it may seem at the moment.

On one of his birthdays, Myk was given a book – titled “The Human Body” – with beautiful illustrations explaining the structure, functions, and malfunctions of the machine we operate. This action, in principle, led me to my first Biomimicry Challenge.

A scan from a book that really caught my attention!

 Scenario 2

Max is an incredibly talented surgeon in Cambridge, England, specializing in throat cancer. He is also fascinated by the world of design and is constantly thinking of ways to improve medical equipment for the benefit of his patients. During one of our conversations, he mentioned a problem with administering nutrition to throat cancer patients.

Problem-based approach

Source: Cleveland Clinic

Percutaneous endoscopic gastrostomy (PEG) is a safe and effective way to provide nutrition and medications directly into the patient’s stomach. The procedure is usually done for throat cancer patients, who have just undergone a surgery.

During the procedure, a physician places an endoscope (a long, thin, flexible instrument about 1/2 inch in diameter) into the patient’s mouth. The endoscope is then advanced through an esophagus and into a stomach. The endoscope is used to ensure correct positioning of the PEG tube. The PEG tube rests in the stomach and exits through the skin of the abdomen. Some of the main problems with this design are:

  1. High level of leakage, causing infections;
  2. Possibility of dislodgment;
  3. Seeding of cancer cells into a stomach.

Of tentacles and arteries

Max asked me a question: what are the alternative ways of carrying food to the stomach, bypassing a mouth and esophagus?

This question made me think of a paragraph I read in a book – titled Incredible Biology by Igor Akimushkin – some ten years ago. Pogonophora have fascinated me ever since.

These beard worms have a complex closed circulatory system and a well-developed nervous system, but as adults, they completely lack a mouth, gut and anus. So, how do these creatures feed? Most of a pogonophoran’s nutrition is provided by symbiotic bacteria living inside the worm. But I was interested in their tentacles that absorb nutrients directly from water.

It is thought that some pogonophorans feed by extending their tentacles from the mouth of the tube to gather organic detritus and plankton. Suspended particles of food may be trapped on the pinnules, and cilia are thought to drive water from anterior to posterior through the cylinder or funnel made by the tentacles.

Definitely, worth exploring.

However, one of the important conditions that I wanted to observe was “being locally attuned” – beard worms reside in a deep sea, and are not planning to visit Ottawa any time soon. Is my body local enough? As I was leafing through Myk’s book, I noticed an illustration of an artery section with the following accompanying sentence:

An artery narrows when the heart relaxes, helping push blood onward.

Source: MedGadget

As I began to dig deeper, I found a great article titled Three-Dimensional Polymer Constructs Exhibiting a Tunable Negative Poisson’s Ratio by David Y. Fozdar and others. Here’s the excerpt:

A scaffold made out of an auxetic material would expand and contract in tandem with the strains resulting from the cyclical pressures from pulsatile blood flow. Thus, an auxetic scaffold that exhibits concurrent axial and transverse expansion (contraction) would likely better integrate with native tissues and better promote clinical tissue regeneration.

First level of biomimicry: Form

The reason for a high level of leakage – and, thus, infections – is due to a constant movement and dislodging of the tube. So, if there was a mesh around the structure that would expand, whenever it is tugged on?

The reason for seeding cancer cells into a stomach is due to the oral administering of endoscope to secure the tube internally. You simply can’t go around it, unless, there is a tube that expands as soon as it is administered through an abdomen, bypassing the esophagus altogether. What if the Ni-Ti mushroom, covered with the mesh expanded not unlike flower petals in the morning, as soon as it entered the inside of the abdomen?

As soon as it is expanded, it is secured in place through a negative Poisson’s behaviour. To take the tube out, a nurse tugs on a string that causes the Ni Ti structure to collapse and withdraws it from the abdomen.

Now, I’m curious, if the fifth dimension me were to go off and explore the beard worm anatomy, what solution would I end up with? Comments and criticism are very much welcomed, as the necropsy of what worked, and what didn’t is waiting to be written! Max, as well, would be interested in the feedback on our design.

5 thoughts on “BBC-1: Of Arteries, Patient Nutrition, and Pogonophoras

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  2. I like the way you are exploring the concepts, and presenting your thinking along the way. However, I think the challenges seem many-fold, and as you explore I think it is a good idea to continue to refine them, and keep clear about what the various challenges are. I see:

    1. How might we avoid introducing cancer cells to stomach?
    2. How might we maintain constant contact or fit of installed tube?

    Underneath each of these challenges are lot’s of biomimicry opportunities, as well as some assumptions.

    * The first thing I’m wondering is if a PEG operation can be avoided by using other sensing technology?
    * Is 3D ultrasound too expensive or not clear enough for procedure?
    * Why not place the camera on the end of the ‘mushroom’ that can then be extracted through the core of the tube?

    I might begin by looking at how does nature sense?
    – Ultrasound in whales, dolphins (we have ultrasound)
    – Electrosensing in sharks (not sure if we have a similar technology)
    – Detecting different wavelengths of electromagnetic spectrum- bees see ultrasound, it is unclear if other spectrums are detected by organisims (we have detection capabilites from x-ray & radio to terrahertz- what about using the new airport type screening with slightly different intensity?)
    – Haptic responses (touch), can you ‘feel’ when you reach the stomach?

    I like the solution you have- it is very elegant. That when it encounters the open space of the stomach it expands. I think we may need to understand the context a bit better, my understanding of anatomy is that the stomach is not tightly packed against the body wall, and that there could be a mistake of expanding the mushroom inside the body cavity rather than the stomach- thus you would still need a detection type of instrument to understand location.

    We are dealing with tissues that are flexible and compliant, thus we need a flexible and compliant solution to ‘match’ the dynamics of the tissues involved.

    I think the auxetic type structure makes a lot of sense. So that when it is stretched it is also expanded. It might make sense for the tube to be auxetic itself. But I think we are also dealing with connecting multiple tissues that are not typically tightly correlated- thus we need to be very ‘flexible’ and absorb the energy of movement.

    This has me thinking of how would nature connect two dissimilar materials?
    How would nature create compliant connections?

    I keep going back to the Mussel Byssus- That is very stretchy on one end, and stiffer on the other. The mussel matches the ‘byssus thread’ material properties to the properties of the substrate it is attaching to. The mussel byssus is engineered on the polymer level, and ideally we would do the same. But given existing technology I know about we can achieve a similar type of result by adhering to the same trick the mussel uses- a principle I like to call ‘hidden length’.

    Think of hidden length like wrinkles that enable stretching, so that the tube that connects is very very wrinkly and made out of a material that allows the wrinkles to unfold to absorb the energy of movement. Thus the placement of the mushroom, and the outer ring can keep contact with their tissues. There may be other ways to create hidden length (auxetic materials so this), as would ‘slip knots’ in a rope type of model.

    Another part of this challenge is forming a close bond with the surface of the stomach. This is where I would look to gecko feet. Not because I think you should use gecko tape or something like that, but because gecko’s have figured out how to create SUPER accommodating structures. They need their toes to really fit closely to the terrain, so that the hairs can make molecular contact.

    We don’t need to get to the molecular level, but we could learn a lot from gecko foot design to consider how to conform to surface. My initial thought it to think of the ‘mushroom’ as having a contact surface that has lot’s of levels of very very soft springs, so that at some level there is always a barrier in place.

    Ok- that is all for now- I might try to do some sketches, but maybe that is where you can help me out?

    • As always the current design solutions appear bulky and cumbersome compared to the delicate sophistication of the natural system. I feel like surface structure is something overlooked within the insertion / maintenance of an opening, etc… as well as the discussion around “accommodating structures”…

      Alena’s collapsing mushroom is a superb start, I wonder if parasitic models might be interesting… organisms that extract nutrients might be models for a flow reversal? Small insertions that grow as nutrients flow?

  3. Tim, firstly, let me thank you for such thorough comment! I would even call it an extremely detailed and informative speech 🙂 These will definitely occupy my mind for many evenings to come. I agree with you (very perceptive!) – the first challenge was not addressed by the idea of the expanding mushroom and I’m really looking forward to exploring this one.

    Regarding challenge #2: As I was researching caterpillars for my other challenge, I was quite fascinated with the structures called crochets on their prolegs. These little hooks not only allow them to hold on and grab a substrate or an object, but also has a robust withdrawal reflex. So, It can hold on to something very tightly, but also has ‘sensory hairs’ that will cause the proleg to retract for whatever reason. So, if these biodegradable crochets are placed at the base of a mushroom to hook on to the stomach wall, and then, as the nurse starts folding the device, the crochets disengage. Those that don’t, rip off the device and are later digested by the stomach acid (similarly to a caterpillar crochets – when it is ripped off the branch to quickly, the hooks tear off).

    Thank you for pointing me in the direction of mussel byssus: what an incredible mechanism! Strong and stiff at one end, and elastic at the other. I also liked this phrase in an article I’m reading about the material: “Although yield usually suggests permanent deformation in the loaded material, it is reversible in bysus during relaxation”.

    Now, I want to completely get rid of nickel-titanium wires inside the mushroom mesh, and replace them with a byssus-like material. It would provide strength at one end, elasticity at another, and would be able to repeatedly expand and contract. Well, definitely, more time for research is needed.

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