Method For the Fabrication of High Surface Area Ratio and High Aspect Ratio Surfaces on Substrates

Abstract

This invention provides a method for the fabrication of surfaces of high surface area ratio on polymeric/plastic materials, and their application in the control of the wetting properties of surfaces, of the transport of liquids on such fabricated surfaces, or of the separation of liquids in microchannels of said surfaces. The fabrication of surfaces of high surface area ratio comprises the following steps: (a) selection of a polymer/plastic layer which contains two or more components differing in their plasma etching behaviour (b) exposure of said polymer/plastic layer to an etching plasma to provide selective removal of one polymer component versus a second plasma-resistant component so as to result in a randomly rough columnar-like surface. In addition, exposure of the said surface to an oxidizing plasma or to a fluorocarbon. depositing plasma renders the surface fully hydrophilic or en super-hydrophobic, respectively.

1 . A method for the fabrication of randomly rough columnar-like surfaces of high surface area ratio on substrates, comprising the following steps: (a) selection of a material comprising two or more components which differ with respect to their etching behavior and (b) exposure of said layer to an etching plasma under conditions appropriate to provide selective removal of one component of the material versus a second plasma-resistant component. 
   
   
       2 . A method for the fabrication of randomly rough columnar-like surfaces of high surface area ratio on polymer/plastic substrates, characterized in that it comprises the following steps: (a) selection of a polymer/plastic material comprising two or more components which differ with respect to their etching behavior and (b) exposure of said polymer/plastic layer to an etching plasma under conditions appropriate to provide selective removal of one polymer component versus a second plasma-resistant component. 
   
   
       3 . A method according to  claim 2 , wherein the polymer/plastic material is selected from organic-inorganic polymers. 
   
   
       4 . A method according to  claim 3 , wherein the polymer/plastic material is a Siloxane (PDMS). 
   
   
       5 . A method according to  claim 2 , wherein the polymer/plastic material is selected from organic polymers which comprise in their volume and/or on their surface, components with different plasma etching behavior, and/or additives and/or impurities. 
   
   
       6 . A method according to  claim 5 , wherein the polymer/plastic material is a Plexiglass (also known as PMMA, with the chemical poly-methyl-methacrylate). 
   
   
       7 . A method according to  claim 1 , further comprising the step of plasma or spin coating deposition of a hydrophobic layer on top of said randomly-rough columnar-like surfaces, so as to render the surface super-hydrophobic. 
   
   
       8 . The method of  claim 7 , for the fabrication of surfaces exhibiting very low friction against droplet motion resulting in use of said surfaces for the control of the transport of droplets using electric fields. 
   
   
       9 . The method of  claim 7 , for the fabrication of surfaces serving as interior surfaces of micro-channels of microfluidic devices. 
   
   
       10 . A method according to  claim 1 , further comprising the step of exposure of said surfaces to an oxidizing plasma so as to render the surfaces highly hydrophilic. 
   
   
       11 . The method of  claim 10 , for the fabrication of surfaces serving as interior surfaces of micro-channels of open tubular liquid chromatography or electrochromatography or capillary electrophoresis microdevices for separation purposes. 
   
   
       12 . A method according to  claim 7  wherein the optical transparency is preserved and the cut-off wavelength is tuned, by controlling the height and aspect ratio of the randomly rough columnar-like surface.