The material necessary be nontoxic.
It must be viscous at liquid states.
I prefer an electrically conductive material and Non-newtonian.
The reason why i wanted a material that is liquid at room temperature but ductile at its solid state is because i wanted to produce a very small pipe filled with that liquid. Is it possible for a wire-material to electroplate it with aluminum or other metal below its melting point? so that when it is heated to room temperature, i have a pipe filled with viscous liquid?
Galinstan is a nontoxic alternative for Mercury in thermometers. These are generally not compatible with aluminum, but you'll need to do some research to see what metals they are compatible with. I would not attempt any electroplating - simply get tubes of compatible metals of the correct size and fill. You have limited choices for metals or alloys that are liquid at RT.