Semipermeable ultrathin polymer membranes

Abstract

A semipermeable ultrathin polymer membrane comprises a substantially optically transparent polymer film having a surface area to thickness ratio of at least 1,000,000:1, and an array of precisely spatially ordered pores of a user-selected diameter defined therethrough. Such membranes can be fabricated by providing a mold having a patterned array of nanoholes femtosecond laser ablated in a surface thereof; applying a first polymer solution onto the mold surface so that the first polymer solution infiltrates the nanoholes; allowing the first polymer solution to dry and form a replica of the mold having a plurality of freestanding nanoneedles extending from a surface of the replica; removing the replica from the mold; coating the replica surface with a second polymer solution; drying the second polymer solution to form a porous polymer film; and dissolving the replica in a solvent to release the film from the replica as a semipermeable ultrathin polymer membrane.

What is claimed is: 
     
         1 . A semipermeable ultrathin polymer membrane, comprising an optically transparent polymer film having a surface area to thickness ratio of at least 1,000,000:1, and a plurality of ordered pores defined therethrough, each pore of said plurality having a preselected diameter of less than 2 μm. 
     
     
         2 . The membrane of  claim 1 , wherein said film includes a first surface, a second surface opposite the first surface, the first and second surfaces defining a thickness therebetween, the thickness being less than about one micron. 
     
     
         3 . A method of fabricating a semipermeable polymer membrane, comprising:
 providing a mold having a patterned array of nanoholes femtosecond laser ablated in a surface of said mold;   applying a first polymer solution onto said mold surface whereby said first polymer solution infiltrates said nanoholes;   drying said first polymer solution to form a negative replica of said mold, said replica having a first surface, a second surface opposite the first surface, and a plurality of freestanding nanoneedles extending a nanoneedle height from said first surface;   removing said replica from said mold;   coating said first replica surface with a second polymer solution, whereby said first replica surface is covered with a layer of said second polymer solution having a thickness less than said nanoneedle height such that said nanoneedles extend through said layer;   drying said second polymer solution to form a porous polymer film; and   dissolving said replica in a solvent to release said film from said replica.   
     
     
         4 . The method of  claim 3 , wherein said coating comprises spin-coating assisted deposition. 
     
     
         5 . The method of  claim 3 , wherein said porous polymer film includes a plurality of pores extending completely therethough, each pore of said plurality defined by a different nanoneedle of said plurality of nanoneedles. 
     
     
         6 . The method of  claim 3 , wherein said porous polymer film has a surface area to thickness ratio of at least 1,000,000:1. 
     
     
         7 . The method of  claim 6 , wherein said porous polymer film has a thickness of less than 1 μm. 
     
     
         8 . The method of  claim 3 , further comprising mounting said second replica surface to a backing member prior to removing said replica from said mold. 
     
     
         9 . The method of  claim 3 , further comprising aligning said film to a microfluidic layer prior to dissolving said replica. 
     
     
         10 . The method of  claim 3 , wherein said dissolving comprises adhering a first surface of said film to a first microfluidic layer having an apical chamber defined therein. 
     
     
         11 . The method of  claim 10 , further comprising adhering a second surface of said film opposite said first film surface to a second microfluidic layer having a basal chamber defined therein to form a multi-chambered microfluidic device wherein said apical and basal chambers are in fluid communication through said film. 
     
     
         12 . The method of  claim 11 , further comprising oxygen-plasma treating said device to render an exposed surface thereof hydrophilic. 
     
     
         13 . The method of  claim 3 , further comprising coating said mold with a release agent prior to applying said first polymer solution onto said mold surface. 
     
     
         14 . The method of  claim 3 , wherein said mold is formed from a transparent material. 
     
     
         15 . The method of  claim 3 , wherein said first polymer solution is polyvinyl alcohol. 
     
     
         16 . The method of  claim 3 , wherein said second polymer solution is a biocompatible polymer. 
     
     
         17 . The method of  claim 3 , wherein said second polymer solution is poly(L-lactic acid). 
     
     
         18 . A microfluidic device for studying cell biology in vitro, comprising:
 a first microfluidic layer having an upper surface, a lower surface, an apical chamber defined in said lower surface, and an aperture extending from said upper surface to said apical chamber, said aperture in fluid communication with said apical chamber;   a second microfluidic layer having an upper surface, a lower surface, and at least one basal chamber defined in said upper surface; and   an optically transparent, biocompatible polymer nanofilm having an upper surface, a lower surface, a surface area to thickness ratio of at least 1,000,000:1, and an ordered array of micrometric pores defined through said film;   wherein the upper surface of said film contacts the lower surface of said first microfluidic layer, the lower surface of said film contacts the upper surface of said second microfluidic layer, and said apical chamber is in fluid communication with said basal chamber through said pores.