Hydrogels; goo of the future?

Sammy Nimour
Nov 1 · 6 min read

Everyone always wonders what the future will look like. Most depictions usually involve lots of technology and/or killer robots. But what if I told you that was not the case?

What if the future was transparent, springy and came in the shape of a blob? That's right, I believe that the future will arrive sooner than expected, and will take the shape of hydrogels.

Yup, this is what the future looks like ^

So, what are hydrogels?

To put it simply, hydrogels are… gels! A mixed state of matter that exhibits properties of both solids and liquids. They are elastic, but also resilient and capable of maintaining a shape that isn't dependant on a container.

Hydrogels are made of hydrophilic polymers with many polar groups in their structure (which I will refer to as side chains throughout this article) which cross link to form a net-like structure. Water gets into the spaces in between the polymer crosslinks, and is held there due to adhesion. The polymers have a property that allows them to stretch , however due to the side chains having like charges, they are prevented from getting too close to each other and thus return to their original shape.

This gives hydrogels most of their properties such as resilience and elasticity, reason why they are classified as smart materials.

Visual representation of a hydrogels’ structure. The blue lines represent the polymer chains and the orange orange balls represent water molecules.

Properties of Hydrogels

The structure and properties of hydrogels are dependant on factors such as the polarity of the side chains. External stimuli such as pH and temperature are capable of changing these properties. In order to edit the structure of a hydrogel, it not only needs exposure to a stimulus but the exposure needs to be constant. Otherwise, the material will just revert to its original shape as soon as the stimulus is removed. This means that we would need a way to secure the stimulus and ensure that the hydrogel is consistently exposed to it.

Illustration of solute and hydrogel

This is where we focus less on the gel, and more on the hydro. After all, water is a solvent capable of dissolving most polar substances. Water can dissolve either an acid or alkali thus changing the polarity of the polymer chains. This weakens the forces of repulsion between the polymers causing the overall hydrogel structure to form a different shape.

Another property that makes hydrogels useful is that they have self-regenerative properties. This means that if any damage is done to the inside structure of the gel, the bonds will get attracted to each other and repair the overall structure. This means that unless the bonds are ripped appart on a molecular scale, any damage will likely mend itself making these materials last a very long time.

Finally, just as water can be trapped by attraction to the fibers of the hydrogels, it can also be removed from the hydrogel. This is done by having the polymers lose their hydrophilic properties (which can be done by changing the pH), which is the only thing holding the water in place. The water then leaves the gel, leaving behind the dehydrated net of a gel.

This process is useful when delivering drugs to parts of the body. Being composed of just water and polymers allow hydrogels to enter the body without seeming invasive and deliver drugs such as insulin dissolved in the water.

That’s cool… now what?

Those are the properties of hydrogels but how can they be used in real life?

As mentioned, hydrogels can change their structure based on certain conditions such as pH, temperature and electrical flow. What makes hydrogels so useful in the body specifically is that most body parts have their own unique environment (composed of the aforementioned conditions) in which hydrogels can be deployed and achieve a certain function. One function is drug delivery, where hydrogels can allow drugs to enter a targeted body part.

An example of hydrogels being deployed into a tumor

Gels can also be used as a structure to help tissue regenerate. Think of it like a wall helping a vine grow. The wall provides support and allows vines to take on their desired shape.

Hydrogels achieve a similar purpose but with one key difference, they help cells grow faster. A team of researchers at Johns Hopkins School of Medicine conducted an experiment where chunks of tissue were cut from mice and replaced with hydrogels. Macrophages appeared and began infiltrating the gel and sending out signals that encouraged the body to create new cells and blood vessels inside the gel! This caused the tissue to regenerate at a noticeably faster rate than usual.

The hydrogels are incubators that also help structure cells, but we haven’t even gotten to the best part yet. They can decompose! After achieving its purpose, the hydrogel can naturally decompose over time (a property determined by whether or not the polymers are organic materials) leaving no residue in the body. This property (amongst others) makes it more useful than nanobots or other methods when it comes to uses in the human body.

Speaking of the human body…

Hydrogel is also used in the making of prosthetics. As mentioned, hydrogels are responsive to stimuli in addition to their ability to regenerate which make them durable, two aspects that are desirable features for most prosthetics. They are also bioinert (do not disturb the nearby biologic tissues), lightweight and flexible. This makes them perfect for use in an emerging field called haptic technology.

Haptic technology relies on trying to stimulate senses by tricking a body part into ‘believing something’ that doesn't exist. An example would be using gloves in a virtual setting to trick your brain into thinking you’re holding an object.

A new part of haptic technology is called haptic feedback, which involves trying to replicate nerves and the ability to feel with prosthetics. So far the field seems promising, however a major roadblock is finding a material that is durable, non invasive, and responds to electrical signals.

Sounds familiar?

Hydrogels are being used for certain parts of these haptic prosthetics due to their properties. The functional properties include them being malleable, resilient and easy to integrate within the prosthetic skeleton. However, their aesthetic properties are what really seal the deal. Due do their composition, hydrogels behave like skin. They respond to heat and moisture, wrinkle over time and also feel like human skin.

Researchers explaining and demonstrating haptic prosthetics

TL;DR/ Takeaways:

Remember how at the beginning of the article I said that the future would come in the shape of hydrogels? Well, that wasn't a metaphor.

Hydrogels are the future.

With everything they can do, why wouldn't they be.

Hydrogels will be used in the following fields:

  • Drug delivery
  • Regenerative medicine
  • Organ development
  • Prosthetics
  • Haptic technology

I firmly believe that in the next 10 years, the world will know about hydrogels. The uses for hydrogels are simply incredible, and once you realise that we’ve just begun scratching the surface you can only wonder how much there is left to discover.

That’s all from me, what do you think? Share your thoughts on this topic and article! If you have any feedback or questions you can contact me on my e-mail: snimour139@gmail.com

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