Fibrillar Microstructure and Processes for the Production Thereof

Abstract

This invention relates to a fibrillar microstructure and processes for the manufacture thereof. These processes involve micromachining and molding, and can prepare sub-micron dimensioned fibrillar microstructures of any shape from polymeric as well as other materials.

1 . A process for making a fibrillar microstructure, comprising
 (a) applying a first layer of photoresist material to a substrate wherein the layer has a pre-selected thickness;   (b) removing material from the first layer at a plurality of locations to create at each location a channel through the first layer wherein each channel has a pre-selected cross-sectional shape and size, and wherein the substrate is exposed at the location of each channel;   (c) creating in the substrate at each location a corresponding channel having a pre-selected depth and having the same cross-sectional shape and size of the channel in the first layer at that location;   (d) removing the remainder of the first layer of photoresist material from the substrate;   (e) applying a second layer of photoresist material on the substrate and in the channels of the substrate wherein the second layer has a pre-selected thickness;   (f) removing material from the second layer at a plurality of locations to create at each location a channel through the second layer wherein each channel has a pre-selected cross-sectional shape and size, and wherein a plurality of channels in the substrate are exposed at the location of each channel in the second layer;   (g) removing from each channel in the substrate exposed by a channel in the second layer the photoresist material of the second layer;   (h) applying a flowable microstructure material to the second layer of photoresist material to fill the exposed channels of the substrate and of the second photoresist layer and to create a layer of flowable material on the second photoresist layer;   (i) hardening the flowable microstructure material to form a fibrillar microstructure; and   (j) separating the fibrillar microstructure from the channels of the second layer and the substrate.   
     
     
         2 . A process according to  claim 1  wherein a channel is created in a layer of photoresist material having a cross-sectional shape that is selected from the group consisting of circular, elliptical and polygonal; and a channel is created in the substrate having a different cross-sectional shape that is selected from the group consisting of circular, elliptical and polygonal. 
     
     
         3 . A process according to  claim 1  wherein a channel having a circular cross-sectional shape is created in the second layer of photoresist material; and a channel having a cross-sectional shape selected from triangular and diamond is created in the substrate. 
     
     
         4 . A process according to  claim 1  wherein the pre-selected thickness of the second photoresist layer is in the range of about 10 to about 150 microns. 
     
     
         5 . A process according to  claim 1  wherein the cross-sectional size of the channels created in the second photoresist layer is in the range of about 2 to about 10 microns. 
     
     
         6 . A process according to  claim 1  wherein the depth of the channels in the substrate is in the range of about 0.5 to about 15 microns. 
     
     
         7 . A process according to  claim 1  wherein the cross-sectional size of the channels created in the substrate is in the range of about 0.1 to about 1 microns. 
     
     
         8 . A process according to  claim 1  wherein the channels created in the second photoresist layer are spaced to give fibrils secured to a foundation of the fibrillar microstructure an areal density in the range of about 3 to about 30 percent. 
     
     
         9 . A process according to  claim 1  wherein the flowable microstructure material is selected from the group consisting of polyamide, poly(ether/amide), polyester, poly(ether/ester), polypropylene, polyacrylate, polystyrene, polyethylene, polypropylene, polydimethyl siloxane and polyvinylidine chloride. 
     
     
         10 . A process for making a fibrillar microstructure, comprising
 (a) applying a first layer of photoresist material to a substrate wherein the layer has a pre-selected thickness;   (b) removing material from the first layer at a plurality of locations to create at each location a channel through the first layer wherein each channel has a pre-selected cross-sectional shape and size, and wherein the substrate is exposed at the location of each channel;   (c) creating in the substrate at each location a corresponding channel having a pre-selected depth and having the same cross-sectional shape and size of the channel in the first layer at that location;   (d) applying a second layer of photoresist material on the first layer and in the channels of the first layer and in the channels of the substrate wherein the second layer has a pre-selected thickness;   (e) removing material from the second layer at a plurality of locations to create at each location a channel through the second layer wherein each channel has a pre-selected cross-sectional shape and size, and wherein a plurality of channels in the first layer are exposed at the location of each channel in the second layer;   (f) removing from each channel in the first layer exposed by a channel in the second layer, and removing from each corresponding channel in the substrate, the photoresist material of the second layer;   (g) applying a flowable microstructure material to the second layer of photoresist material to fill the exposed channels in the second layer, the first layer and the substrate and to create a layer of flowable material on the second photoresist layer;   (h) hardening the flowable microstructure material to form a fibrillar microstructure; and   (i) separating the fibrillar microstructure from the channels of the first and second layers and the substrate.   
     
     
         11 . A process according to  claim 10  wherein a channel is created in a layer of photoresist material having a cross-sectional shape that is selected from the group consisting of circular, elliptical and polygonal; and
 a channel is created in the substrate having a different cross-sectional shape that is selected from the group consisting of circular, elliptical and polygonal.   
     
     
         12 . A process according to  claim 10  wherein a channel having a circular cross-sectional shape is created in the second layer of photoresist material; and a channel having a cross-sectional shape selected from triangular and diamond is created in the substrate. 
     
     
         13 . A process according to  claim 10  wherein the pre-selected thickness of the second photoresist layer is in the range of about 10 to about 150 microns. 
     
     
         14 . A process according to  claim 10  wherein the cross-sectional size of the channels created in the second photoresist layer is in the range of about 2 to about 10 microns. 
     
     
         15 . A process according to  claim 10  wherein the depth of the channels in the substrate added to the pre-selected thickness of the first photoresist layer is in the range of about 0.5 to about 15 microns. 
     
     
         16 . A process according to  claim 10  wherein the cross-sectional size of the channels created in the first photoresist layer, and the corresponding channels in the substrate, is in the range of about 0.1 to about 1 microns. 
     
     
         17 . A process according to  claim 10  wherein the channels created in the second photoresist layer are spaced to give fibrils secured to a foundation of the fibrillar microstructure an areal density in the range of about 3 to about 30 percent. 
     
     
         18 . A process according to  claim 10  wherein the flowable microstructure material is selected from the group consisting of polyamide, poly(ether/amide), polyester, poly(ether/ester), polypropylene, polyacrylate, polystyrene, polyethylene, polypropylene, polydimethyl siloxane and polyvinylidine chloride. 
     
     
         19 . A process for making a fibrillar microstructure, comprising
 (a) applying a layer of photoresist material to a surface of a substrate wherein the layer has a pre-selected thickness;   (b) removing material from the photoresist layer at a plurality of locations to create at each location a channel through the layer wherein each channel has a pre-selected cross-sectional shape and size, and wherein the substrate is exposed at the location of each channel;   (c) creating in the substrate at each location a corresponding channel having a pre-selected depth and
 having in a portion of the substrate channel proximal to the surface the same cross-sectional shape and size of the channel in the photoresist layer at that location, and 
 having in a portion of the substrate channel distal from the surface a different cross-sectional shape and size than the channel in the photoresist layer at that location; 
   (d) filling the channels in the substrate with a flowable microstructure material;   (e) hardening the flowable microstructure material to form a fibrillar microstructure; and   (f) separating the fibrillar microstructure from the channels of the substrate.   
     
     
         20 . A process according to  claim 19  wherein the length of the portion of the substrate channel that is proximal to the surface of the substrate, and that has the same cross-sectional shape and size of the corresponding channel in the photoresist layer at that location, is more than about 90% of the length of the channel; and the length of the portion of the substrate channel that is distal from the surface of the substrate, and that has a different cross-sectional shape and size than the corresponding channel in the photoresist layer at that location, is less than about 10% of the length of the channel. 
     
     
         21 . A process according to  claim 19  wherein one or more channels is created having a cross-sectional shape that is selected from the group consisting of circular, elliptical and polygonal; and one or more channels is created having a different cross-sectional shape that is selected from the group consisting of circular, elliptical and polygonal. 
     
     
         22 . A process according to  claim 19  further comprising a step of removing the photoresist before filling the channels. 
     
     
         23 . A process according to  claim 22  wherein the pre-selected depth of the channels created is in the range of about 10 to about 150 microns. 
     
     
         24 . A process according to  claim 19  wherein the cross-sectional size of the channels created is in the range of about 2 to about 10 microns. 
     
     
         25 . A process according to  claim 19  wherein the channels created are spaced to give fibrils secured to a foundation of the fibrillar microstructure an areal density in the range of about 3 to about 30 percent. 
     
     
         26 . A process according to  claim 19  wherein the flowable microstructure material is selected from the group consisting of polyamide, poly(ether/amide), polyester, poly(ether/ester), polypropylene, polyacrylate, polystyrene, polyethylene, polypropylene, polydimethyl siloxane and polyvinylidine chloride. 
     
     
         27 . A process according to  claim 19  wherein the flowable microstructure material is hardened by the removal of a solvent.