Hi Sarah,

The stifness of your gel will largely depend on the crosslink density and the type of polymer you are starting with. I’m unsure if you’re asking how to model/predict the values or just how to practically measure them in the lab?

Hi Adrian Gestos ,

Thank you for your answer. I am using photopolymerizable PEG Acrylategel surrounded by PDMS stencil.. I do not have access to AFM or other modalities at the moment to measure it practically, so I would rather simulate it. I was wondering what parameter should I consider besides Young modulus.

Best,

Hi Sarah, that is an interesting challenge. I haven't done any predictive modelling of gel mechanical properties. I'm not sure it is possible based on pure fundamentals. Is your gel a commercial product? If it is the vendor should be able to give you a specification. For example, at amount of crosslinker = x and amount of UV time =y, modulus will be = z.

The first thing to ask when looking at mechanical properties is what are you using the information for? Do you want to know how much you can stretch the material before it breaks? Do you want to know the modulus so you can determine its interaction with other soft materials such as living cells?

In the world of mehcanical properties I am most familiar with stress strain curves which will give you parameters such as:

• Youngs modulus
• Yield stress/strain (the point at which irreversible or plastic deformation begins)
• Stress/strain at break (the point at which the material breaks)
• Toughness (The total work required to break the polymer or area under a stress strain curve)

I've also done a bit of AFM indentation modulus testing but as you say you don't have access to this technique.

Maybe you could try a Buchholz Indentation Tester. You should be able to pick one up for a reasonable price. It will be a somewhat qualitative test but you will be able to say one gel is different to another. However, I'm not sure if this tester will be gentle enough to work with gels but there may be other cheap indentation devices that will do the same thing on a soft gel.

Hi Adrian Gestos ,

Thank you so much for your informative answer. Yes indeed it a commercial product. Actually I would like to know the this property because I am working with living cells and would like to compare the mechanical properties of what I have with what I see in the literature. I will try to access to the mentioned technique.

Thank you again.

Best,

Sarah