▁U V ▁cur ing , ▁to ▁produce ▁o ph th al mic ▁correct ive ▁l enses . ▁No ▁support ▁structures ▁are ▁required ▁in ▁this ▁case , ▁as ▁o ph th al mic ▁l enses ▁do ▁not ▁need ▁over hang s . ▁Lux excel , ▁a ▁Dutch ▁company , ▁has ▁commercial ized ▁this ▁technology ▁and ▁printing ▁platform . ▁▁▁ ▁Ult ra - small ▁features ▁can ▁be ▁made ▁with ▁the ▁ 3 D ▁micro - fab ric ation ▁technique ▁used ▁in ▁multi ph ot on ▁phot opol ym er isation . ▁This ▁approach ▁uses ▁a ▁focused ▁las er ▁to ▁trace ▁the ▁desired ▁ 3 D ▁object ▁into ▁a ▁block ▁of ▁gel . ▁Due ▁to ▁the ▁non linear ▁nature ▁of ▁photo ▁exc itation , ▁the ▁gel ▁is ▁c ured ▁to ▁a ▁solid ▁only ▁in ▁the ▁places ▁where ▁the ▁las er ▁was ▁focused ▁while ▁the ▁remaining ▁gel ▁is ▁then ▁was hed ▁away . ▁Fe ature ▁sizes ▁of ▁under ▁ 1 0 0   nm ▁are ▁easily ▁produced , ▁as ▁well ▁as ▁complex ▁structures ▁with ▁moving ▁and ▁inter locked ▁parts . ▁ ▁Yet ▁another ▁approach ▁uses ▁a ▁synth etic ▁res in ▁that ▁is ▁solid ified ▁using ▁LED s . ▁ ▁In ▁M ask - image - pro jection - based ▁s tere ol ith ography , ▁a ▁ 3 D ▁digital ▁model ▁is ▁s lic ed ▁by ▁a ▁set ▁of ▁horizontal ▁plan es . ▁Each ▁slice ▁is ▁converted ▁into ▁a ▁two - dimensional ▁mask ▁image . ▁The ▁mask ▁image ▁is ▁then ▁project ed ▁onto ▁a ▁phot oc urable