Fully 3D-printed semiconductor-free devices

https://news.mit.edu/2024/mit-team-takes-major-step-toward-fully-3d-printed-active-electronics-1015

"1 step few hundred µm extrusion printed resettable fuses from inexpensive biodegradables, for basic control operations like regulating electric motor. speed... passed large electric current into polymer filament doped with copper nanoparticles exhibits huge resistance spike,  returning to original level after current stopped, enabling operation as switch... intersecting conductive regions enable resistance regulation controlling voltage fed into switch turning motor on/ off, >4K cycles... fabication uses less energy, waste"