Method of forming a mold and molding a micro-device

Abstract

A method of forming a device including a plurality of micron or sub-micron sized features is provided. A master having a surface contour defining a plurality of features is provided. The surface contour of the master is coated with at least one layer of material to form a shell. The master is removed from the shell to form a negative image of the surface contour in the shell. The negative image in the shell is filled with material, for example, polycarbonate, polyacrylic, or polystyrene, to form a device having features substantially the same as the master. The negative image may be filled using injection molding, compression molding, embossing or any other compatible technique.

1 . A method of forming a mold for a micro-device including an array of microfeatures, comprising: 
 providing a master having a surface contour which includes skin penetration features; wherein said surface contour of said master is formed by micro-machining;    covering the surface contour with a layer of material;    removing the master from the layer of material to form a negative image of the master in the layer of material wherein the negative image is fillable by a flowable process;    filling the negative image fluidically with a flowable material to form a device having substantially the same features as the master;    solidifying said flowable material; and    separating said device from said negative image.    
     
     
         2 . The method of  claim 1 , further comprising, coating the master with a release film, before the covering of the surface contour, to facilitate removal of the master.  
     
     
         3 . The method of  claim 1 , further comprising, etching to remove the master.  
     
     
         4 . The method of  claim 3 , wherein the etchant is hydroxide.  
     
     
         5 . The method of  claim 1 , wherein the layer of material is a metal.  
     
     
         6 . The method of  claim 1 , wherein the layer of material is nickel.  
     
     
         7 . The method of  claim 1 , wherein the master is sacrificed during its removal.  
     
     
         8 . The method of  claim 1 , wherein the negative image has at least one structural feature of about 5 microns to about 250 microns in one dimension.  
     
     
         9 . The method of  claim 1 , wherein the negative image defines recesses having a depth from its surface of about 5 microns to about 250 microns.  
     
     
         10 . The method of  claim 9 , wherein the recesses are arranged in an array of uniformly spaced rows and columns to provide a density of about 1 to about 100 of the recess per mm2.  
     
     
         11 . The method of  claim 1 , wherein the master is formed from silicon.  
     
     
         12 . The method of  claim 1 , further comprising: 
 individually forming portions of the master from silicon; and    connecting the portions into a complete master.    
     
     
         13 . The method of  claim 1 , wherein the layer of material is formed via sintering.  
     
     
         14 . The method of  claim 1 , wherein the layer of material has a thickness of about 0.01-0.2 inches.  
     
     
         15 . A method of forming a device including a plurality of micron or sub-micron sized features, the method comprising: 
 providing a master having a surface contour defining skin penetration features;    coating the surface contour of the master with at least one layer of sinterable material;    sintering said sinterable material;    removing the master from the layer of material to form a negative image of the surface contour in the layer of material;    forming a mold insert from the negative image;    filling the negative image fluidically with a flowable material to form a device having substantially the same features as the master; and    separating said device formed from said flowable material from the negative image.    
     
     
         16 . The method of  claim 15 , wherein the filling step further comprises filling by injection molding.  
     
     
         17 . The method of  claim 16 , wherein the injection molding is done at a vacuum.  
     
     
         18 . The method of  claim 15 , further comprising drilling holes in the features of the device to form hollow micro-needles.  
     
     
         19 . The method of  claim 15 , wherein the layer of material is at least 0.07 inches thick.  
     
     
         20 . The method of  claim 15 , wherein the layer of material is about 0.01 to about 0.2 inches thick.  
     
     
         21 . The method of  claim 15 , further comprising, coating the master with a release film, before the covering of the surface contour, to facilitate removal of the master.  
     
     
         22 . The method of  claim 15 , further comprising, etching to remove the master.  
     
     
         23 . The method of  claim 15 , wherein the layer of material is a metal.  
     
     
         24 . The method of  claim 15 , wherein the layer of material is nickel.  
     
     
         25 . The method of  claim 16 , further comprising removing residual air during the injection molding.  
     
     
         26 . The method of  claim 15 , further comprising forming vents in the mold insert.  
     
     
         27 . The method of  claim 15 , wherein the negative image is filled with a polymer.  
     
     
         28 . The method of  claim 15 , wherein the negative image is filled with one of polyethylene, polypropylene, acrylic, cyclic olefinic copolymers, polyamide, polystyrenes, polyester and polycarbonate.  
     
     
         29 . The method of  claim 18 , wherein the drilling is performed via lasers.  
     
     
         30 . The method of  claim 15 , wherein the master is formed by micromachining.  
     
     
         31 . The method of  claim 15 , wherein the filling step further comprises: 
 filling the negative image with a flowable powdered metallic material; and    sintering the powdered metallic material to form the micro-device.    
     
     
         32 . The method of  claim 15 , wherein the master is formed from silicon.  
     
     
         33 . The method of  claim 32 , further comprising: 
 individually forming portions of the master from silicon; and    connecting the portions into a complete master.