Board Thread:Questions and Answers/@comment-26082739-20181202210151/@comment-28802873-20181222063407

Problem with the Omnitrix being alien tech, we literally don't know what material that is.

It's probably alien matter, considering it can go from metallic to symbiotic to elastic to whatever form the watch is under.

For the energy, according to the wiki: "The Omnitrix is powered by a special self-renewable power supply that will long outlive Ben." I think it means whatever energy source it is, it can never die out and will always renew itself to find energy to recharge the watch