The phrase "solid substrate" refers to a stable and firm surface or material on which other substances or organisms can grow or attach. It can be used in various contexts, such as in science, technology, or even gardening. Full definition
The plants grow around the lab in soil - filled flowerpots, on solid substrate in petri dishes, and on pieces of paper immersed in nutritional broth inside test tubes on racks. (discovermagazine.com)
A RAPTOR ™ plant always starts with liquid storage tanks or solid substrate storage boxes, tanks, bunkers or silos. (cstwastewater.com)
They started with a conductive solid substrate, which they topped with droplets of an electrically conductive liquid. (sciencemag.org)