Given one had a metamaterial of a given type, containing some limited types of elements... if one were to use just one isotope of a given element (assuming it had more than one) in the construction of the metamaterial, would the properties of the metamaterial differ substantially?
If so-- what attributes of the isotope are contributing most to this? Nuclear spin? Momentum? Subtle changes in the electronic configuration?
An isotope is determined by the number of neutrons. Ultimately a change in neutrons wont contribute much except a change in mass. Chemical properties are primarily determined by number of electrons which are determined by the number of protons. So different isotopes of the same element are going to behave almost identically because they'll still have the same number of electrons.
Mass of the nucleus does cause a slight change though. One example is protium vs deuterium. With protium a water molecule behaves normally. With deuterium a water molecule is heavier. In the body this changes the density of fluids. In the inner ear this could make you experience dizziness. In cells changing the fluid density can have more severe consequences.
With larger atoms the light change in mass has less of an impact due to the percent change being less.
I would like to add to the answer by Bigjoemonger that isotopes of stable nuclei may be radioactive as seen in this chart.
Take carbon, as an example, which is in all organic matter. It has two stable and one decaying in 20 minutes with a β+. Its electronic composition changes and it is a Boron isotope which will replace it in the lattice of your material. This is stable but the chemical composition is no longer appropriate for organic matter ,and there will be radiation damage from the e+.
Take iron, as another example.There are three stable ones, 56Fe, 57Fe and 58Fe, and two unstable. You could choose between the three stable ones and there would be only the effects described in the other answer.
In general in the substitutions you want check carefully the isotope stability content, a radioactive one will 1) introduce radiation damage and danger 2) after decay the nucleus will be a different one with different electromagnetic properties and the chemical bonds will be broken.
Helium-4 becomes superfluid at the temperature of about 2K, helium-3 is superfluid at temperatures that are three orders of magnitude less, as nuclei of helium-4 and helium-3 are bosons and fermions, respectively.
