# Is there any material available whose strength changes with an input stimulus, say current or magnetic field etc?

Is there any material available whose strength can be controlled by varying an input stimulus like current flowing through the material or magnetic field without actually deteriorating the material itself? We know with temperature material strength changes but that is not a stable solution as the material itself degrades for appreciable change in strength.

• Is the strength mean its elasticity? Sep 20, 2022 at 4:16

There are polymeres, that change size or shape when stimulated by an electric field They are called Electroactive Polymers. Those materials are used (among others) to create artificial muscles.

Depending on what you want to achieve, they might be the right solution. Another solution could be to use a bag of iron powder and an electro magnet. If there is no magnetic field, the powder in the bag is loose and the system has low strenght. If a magnetic field of sufficient strength is applied, the powder starts to clump together and form a realtively stiff shape.

It's a fairly low tec solution but depending on the use case might be just waht's needed.

A magnetic powder clutch uses a variant of this principle. They were among other places used in IBM tape drives and Curious Marc has a wonderful video where he repairs such a clutch for a tape drive in a museam.

• I am looking for something that has the same strength as steel under unstimulated conditions and goes to higher strength (maybe equalling the strength of steel of a larger cross-section) under the application of the stimulus.
– rkn
Sep 20, 2022 at 11:49
• @rkn please put that information into your question. Be as specific as possible in your questions so others don't waste time trying to answer something you're not interested in. Sep 20, 2022 at 13:24
• Thanks for the suggestion.
– rkn
Sep 21, 2022 at 14:35

Electromagnetic locks might be a solution.

If strength means elasticity, I am going out on a long shot here: EuRu$$_2$$P$$_2$$ and EuPd$$_2$$Si$$_2$$ under go a valence transition at some combination of pressure and temperature, for EuRu$$_2$$P$$_2$$ (https://doi.org/10.1016/j.jallcom.2021.158753) ,this is in the GPa range. This valence transition is in turn accompanied by a change in the a)magnetic order b) elastic constants https://pubs.acs.org/doi/abs/10.1021/acs.cgd.2c00475 so at least near the phase transitions you can definitely influence the elastic constants of these two materials using magnetic fields. In fact EuRu$$_2$$P$$_2$$ may even exhibit critical elasticity! (https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.025703) to read up on critical elasticity