▁e . g . ▁sil icon ▁wa fer , ▁to ▁which ▁they ▁ad here ▁after ▁printing ▁as ▁they ▁are ▁too ▁small ▁and ▁frag ile ▁to ▁be ▁manip ulated ▁post - const ruction . ▁ ▁In ▁one ▁technique , ▁ 3 D ▁nan ost ruct ures ▁can ▁be ▁printed ▁by ▁phys ically ▁moving ▁a ▁dynamic ▁st enc il ▁mask ▁during ▁the ▁material ▁de position ▁process , ▁somewhat ▁analog ous ▁to ▁the ▁extr usion ▁method ▁of ▁traditional ▁ 3 D ▁printer s . ▁ ▁Program m able - height ▁nan ost ruct ures ▁with ▁resolution s ▁as ▁small ▁as ▁ 1 0   nm ▁have ▁been ▁produced ▁in ▁this ▁fashion , ▁by ▁met all ic ▁physical ▁v apor ▁de position ▁Mechan ical pie zo - act u ator ▁controlled ▁st enc il ▁mask ▁having ▁a ▁mil led ▁nan op ore ▁in ▁a ▁sil icon ▁nit ride ▁memb rane . ▁ ▁Another ▁method ▁enh ances ▁the ▁phot opol ym er ization ▁process ▁on ▁a ▁much ▁smaller ▁scale , ▁using ▁fin ely - f oc used ▁las ers ▁controlled ▁by ▁adjust able ▁mirror s . ▁ ▁This ▁method ▁has ▁produced ▁objects ▁with ▁feature ▁resolution s ▁of ▁ 1 0 0   nm . ▁Mic ron ▁wide , ▁mill imet re ▁long ▁co pper ▁w ires ▁have ▁also ▁been ▁printed ▁using ▁las ers . ▁▁ ▁References ▁▁ ▁Further ▁reading ▁ ▁Be aum ont ▁New hall ▁( May ▁ 1 9 5 8 ) ▁" Ph otos cul pt ure ," ▁Image , ▁ 7 ▁( 5 ) ▁: