Method of making self-cleaning skin-like prosthetic polymer surfaces

Abstract

An external covering and method of making an external covering for hiding the internal endoskeleton of a mechanical (e.g., prosthetic) device that exhibits skin-like qualities is provided. The external covering generally comprises an internal bulk layer in contact with the endoskeleton of the prosthetic device and an external skin layer disposed about the internal bulk layer. The external skin layer is comprised of a polymer composite with carbon nanotubes embedded therein. The outer surface of the skin layer has multiple cone-shaped projections that provide the external skin layer with superhydrophobicity. The carbon nanotubes are preferably vertically aligned between the inner surface and outer surface of the external skin layer in order to provide the skin layer with the ability to transmit heat. Superhydrophobic powders may optionally be used as part of the polymer composite or applied as a coating to the surface of the skin layer to enhance superhydrophobicity.

1 . A method of making an external covering for use with a mechanical device that provides the external surface of the device with skin-like qualities, the method comprising the steps of:
 providing a mold having a cavity with a predetermined shape and at least one surface having a pattern selected as one from the group of a nano-funnel array, micro-funnel array, or combination thereof;   inserting a film comprised of a polymer composite with carbon nanotubes embedded therein that has a first side and a second side into the cavity of the mold; the first side of the film being in contact with the patterned surface of the mold's cavity;   applying one selected from the group of heat, vacuum, pressure, or a combination thereof to the cavity or the film to form the film into the predetermined shape and to induce the formation of superhydrophobic cone-shaped projections on the first side of the film;   cooling and removing the shaped film from the mold; and   performing one step selected from the group consisting of adhering the second side of the shaped film to a pre-shaped internal bulk layer to form the external covering and back-molding the internal bulk layer to be in contact with the second side of the film;   wherein the cone-shaped projections provide the first side of the film with superhydrophobicity, while the embedded carbon nanotubes provide the film with enhanced thermal conductivity.   
     
     
         2 . The method of  claim 1 , further comprising the step of applying a superhydrophobic powder to the first side of the film prior to the film being inserted into the mold. 
     
     
         3 . The method of  claim 1 , further comprising the step of annealing the carbon nanotubes prior to the nanotubes being embedded into the polymer composite of the film. 
     
     
         4 . The method of  claim 1 , further comprising the step of opening a gap in the mold and injecting an in-mold coating into the gap to coat the first side of the film. 
     
     
         5 . A method of making a prosthetic device having an external surface providing skin-like qualities, the method comprising the steps of:
 forming an external covering according to  claim 1 , the external covering having an external skin layer and an internal bulk layer ; and   fastening the internal bulk layer of the external covering to an internal endoskeleton.   
     
     
         6 . The method of  claim 5 , further comprising the step of applying a superhydrophobic powder to the external skin layer. 
     
     
         7 . The method of  claim 5 , further comprising the step of annealing the carbon nanotubes prior to the nanotubes being embedded into the polymer composite of the film. 
     
     
         8 . The method of  claim 1 , wherein the method further comprises the step of embedding a biosensor in the internal bulk layer proximate to the shaped film. 
     
     
         9 . The method of  claim 1 , wherein the step of inserting a film comprised of a polymer composite with carbon nanotubes therein uses a polymer composite in which the carbon nanotubes are oriented such that the composite exhibits a predetermined amount of enhancement in at least one mechanical property selected from the group consisting of Young's modulus, hardness, scratch resistance, and polymer creep. 
     
     
         10 . The method of  claim 9 , wherein the step of inserting a film comprised of a polymer composite with carbon nanotubes embedded therein uses a polymer composite in which the carbon nanotubes are vertically aligned between the first side and the second side. 
     
     
         11 . The method of  claim 9 , wherein the step of inserting a film comprised of a polymer composite with carbon nanotubes uses a polymer composite that comprises at least one selected from the group of polyimides, fluoropolymers, polyamides, polyesters, silicones, polyurethanes, epoxies, and polyacrylates.