ith el ial ▁( H LE ) ▁cells ▁cult ured ▁for ▁four ▁hours ▁on ▁the ▁surface ▁modified ▁por ous ▁sil icon . ▁C ells ▁were ▁then ▁st ained ▁with ▁vital ▁d ye ▁F DA ▁and ▁observed ▁under ▁flu ores c ence ▁micro sc opy . ▁The ▁research ▁concluded ▁that ▁" am ino ▁sil an isation ▁and ▁co ating ▁the ▁p Si ▁surface ▁with ▁col lagen ▁en hanced ▁cell ▁attachment ▁and ▁spread ing ". ▁ ▁Classification ▁of ▁por ous ▁sil icon ▁ ▁Por os ity ▁Por os ity ▁is ▁defined ▁as ▁the ▁fraction ▁of ▁void ▁within ▁the ▁p Si ▁layer ▁and ▁can ▁be ▁determined ▁easily ▁by ▁weight ▁measurement . ▁During ▁formation ▁of ▁por ous ▁sil icon ▁layer ▁through ▁an od ization , ▁the ▁por os ity ▁of ▁a ▁wa fer ▁can ▁be ▁increased ▁through ▁increasing ▁current ▁density , ▁decre asing ▁H F ▁concentration ▁and ▁th icker ▁sil icon ▁layer . ▁The ▁por os ity ▁of ▁por ous ▁sil icon ▁may ▁range ▁from ▁ 4 % ▁for ▁mac rop orous ▁layers ▁to ▁ 9 5 % ▁for ▁mes op orous ▁layers . ▁A ▁study ▁by ▁Can ham ▁in ▁ 1 9 9 5 ▁found ▁that ▁" a ▁ 1   µ m ▁thick ▁layer ▁of ▁high ▁por os ity ▁sil icon ▁completely ▁dissol ved ▁within ▁a ▁day ▁of ▁in - v it ro ▁expos ure ▁to ▁a ▁sim ulated ▁body ▁fluid ". ▁It ▁was ▁also ▁found ▁that ▁a ▁sil icon ▁wa fer ▁with ▁medium ▁to ▁low ▁por os ity ▁displayed ▁more ▁stability . ▁Hence ,