http://bhlnasxdqyyqhuak6m4nuqhwwrpphec2we3mhdjofvw5lrrm65doa3yd.onion/robowaifu/res/24152.html
So tentatively it looks very easy to 3D print with normal 3D printers after making into filament.
They then dipped in a refractive index polymer,
"...A low refractive index coating material (THV 220, n = 1.36; Dyneon, Germany) was later applied by dip coating the fibers in 5 wt% acetone solution (23°C).