Nanostructures such as carbon nanotubes (CNTs) have been the source of much excitement thanks to their exceptional material properties. For example, CNTs have 10-500 times the strength-to-weight ratio of steel and are extremely flexible. However, commercially viable macroscale materials incorporating such nanostructures have yet to be developed, due in large part to challenges in producing bulk quantities of CNT in forms that replicate the properties of individual CNTs. Existing methods of growing bulk CNTs produce tangled, bundled, or agglomerated nanotubes with inferior mechanical properties at unfeasible costs. Producing aligned CNTs at macroscale lengths requires close monitoring and control of growth conditions. This invention provides a method for rapid real-time feedback control of CNT growth process variables.