Accidental Breakthrough Makes Web-Slinging Silk A Reality

KATHLEEN DAVIS: We’re all familiar with Spider-Man, the red-suited hero who swings through New York. In the original comic book, our hero, the young Peter Parker, invents a device that lets him shoot webs of spider silk from his wrists. Now, more than 60 years after that fictional invention, scientists have made their own version of liquid silk that solidifies and can pick up objects. Joining me to talk about this is my guest, Dr. Marco Lo Presti, biomedical engineer in the Tufts University silk lab based in Medford, Massachusetts. Welcome to Science Friday.

MARCO LO PRESTI: Hello, everyone.

KATHLEEN DAVIS: So tell me a little bit about the silk lab that you work in.

MARCO LO PRESTI: There is a lot of things going on in silk lab. There are a lot of researchers studying on sensors, on solar cells, on hybrid biological microprocessor. And there’s me that I work mainly on adhesives.

The name silk lab, of course, we are focusing the creation of most of the material we are creating here out of silk protein, silk fibroin protein, which is the protein extracted from a Bombyx mori cocoon. For my specific field, the adhesive, the protein is very appealing because it is well-known for its stiffness. It’s a very stiff protein with high mechanical properties and also, on the chemical point of view, is like a detergent, acts like a soap. So it can wet easily any kind of material.

And if you think about, a material that is very strong and has nice wettability is an amazing starting point for creating an adhesive. I created together with all my colleagues here in silk lab different formulation of adhesive, mimicking muscle, mimicking many different natural organism. And why not?

Also mimicking some superheroes inspired by– some superheroes who created this formulation which is indeed inspired by Spider-Man. It is the very first example of a solution, a liquid solution that undergoing to transition, creating a fiber that can attach on a distant object. And so you can remotely capture a distant object with this material.

KATHLEEN DAVIS: Help me imagine this. So I’m assuming you’re not shooting this out of your hands like Spider-Man does. But how are you actually making this happen?

MARCO LO PRESTI: So this started with a bit of serendipity. This started while trying– of developing underwater adhesive. Washing the vials with acetone, we’re noticing this transition into a web-like material. And again, inspired by pop culture, we started thinking about adding a bit of engineering on this chemistry and creating a material just also to find it out if it was possible to create such kind of material because so far, the only application of this was done through CGI but nothing physical.

And so with a lot of engineering, there is a lot of processing of the solution and a lot of chemistry to make this transition happen with the right timing to have the transition, maintaining of course, the fiber sticky. The transition from liquid to solid, it’s something like when your superglue cures. When it cures, it’s not adhesive anymore.

KATHLEEN DAVIS: Just a quick note, this is Science Friday from WNYC Studios. If you’re just joining us, I’m talking about real life Spider-Man science with my guest, Marco Lo Presti. So what is the component that is making it have those unique properties? What is being combined with the silk?

MARCO LO PRESTI: The components to make this happen is a molecule which is very popular in the chemistry of underwater adhesive. The molecule is dopamine. It’s very popular because the chemistry is mimicking the one of muscles. There is also something about muscles in this process.

Even if the molecule is the same, the process is very, very different because in muscles, dopamine polymerizes into a polymer to ensure crosslinking into the material. In our case, dopamine is helping washing away the water from the silk fibroin solution and accelerating its transition into fiber, similar to what the silkworm does for spinning the cocoon but with the addition of some adhesive properties.

KATHLEEN DAVIS: And is this the same dopamine that is going on in our brains and that makes us feel good?

MARCO LO PRESTI: It’s the same dopamine, exactly the same neurotransmitter that we use to feel happy, indeed. And in a natural system, usually natural system use every time same chemistry or similar molecules. You will be surprised that this same molecule that you can find in muscle for creating underwater adhesive is also chemically the base for creating melanins, which add colors to our hair or our skin.

KATHLEEN DAVIS: Wow, that is so fascinating. So tell me. How much weight can this silk solution actually hold once it’s solidified?

MARCO LO PRESTI: So, after improvement of how the silk transition into a fiber, we managed to reach two megapascal of tensile strength, where two megapascal means that a fiber with a diameter of 1 millimeter can potentially pull up to 160 grams. The maximum weight that we managed to lift was 5 grams up to a 15 centimeter of distance.

KATHLEEN DAVIS: So, give me a couple real world examples of items that you’ve actually been able to pick up.

MARCO LO PRESTI: So, using a needle and creating a single fiber, we lifted some different objects. The weight was every time around between 5 grams and 10 grams. We tried different situations, different environments.

We tried, for example, small plastic vials floating on the water. So even if a material has a wet surface, can be recovered. We tried some stainless steel nuts partially buried into a sand bath, and the solution can infiltrate, can percolate into the sand, creating a hole. And you can lift all the steel nuts with the sand.

We tried also with a glass vial of 10 milliliter, a very smooth surface. And also, that’s very easy. I would say that the solution can lift heavier object when the material is absorbing, and it’s porous because it allows the solution to be firstly absorbed, rooting into the material, and so increasing the surface area where it forms connection to the material.

KATHLEEN DAVIS: So this seems like a really fun thing to play with in the lab, but are there future applications that you see this for?

MARCO LO PRESTI: Are there future applications? So far, I would say the material is not ready for an application. Usually in the academic world, a publication also useful to share your findings with the other scientific community. And someone can think, hey, this technology might be very, very useful to solve this specific problem. We can address specific problem.

KATHLEEN DAVIS: Thank you so much for your time. It was great speaking to you about all this.

MARCO LO PRESTI: Thank you, Kathleen.

KATHLEEN DAVIS: Dr. Marco Lo Presti, biomedical engineer in the Tufts University Silk Lab based in Medford, Massachusetts. And if you want to see videos of this technology, you can do so on our website sciencefriday.com/silkscience.

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