Microstructure patterns

Abstract

In one aspect, there is provided a method of creating a microstructure pattern on an exterior surface of an aircraft, boat, automobile or other vehicle is disclosed. A layer of photopolymer ( 44 ) is applied to the top coat or substrate ( 43 ) by nozzles ( 45 ). The photopolymer is selectively irradiated to activate its photoinitiator and the unirradiated polymer is removed. The irradiation can be via a mask ( 49 ) which does not come into contact with the polymer, or via a beam splitting arrangement ( 63, 64 ) or a diffraction grating ( 71 ). The pattern can be formed by either leaving the exposed photopolymer in situ, or using the exposed photopolymer to mask the substrate, etching the substrate, and then removing the exposed photopolymer. In another aspect, there is provided a method 1100 comprising the step 1102 of applying a layer of photocurable material to the exterior surface, the step 1104 of irradiating the photocurable material with radiation including a predetermined irradiation intensity profile, and the step 1106 of removing uncured photocurable material to form the microstructure pattern. The radiation initiates curing of the irradiated photocurable material, causing a curing depth profile across the layer of the photocurable material corresponding to the selected intensity profile.

1 . A method, comprising:
 initiating a process of irradiating at least a portion of a layer of photocurable material on a substrate with light for curing the photocurable material to initiate curing of the photocurable material proximate the substrate, wherein the light comprises an intensity profile with variations along at least a first dimension; and   ceasing the process of irradiating of the layer of photocurable material, to form cured photocurable material within the layer of photocurable material in a microstructure pattern, the cured photocurable material having a variable curing height profile relative to the substrate, including a variable curing height profile across microstructures in the microstructure pattern.   
     
     
         2 . The method of  claim 1 , further comprising continuing the process of irradiating at least a portion of the layer of photocurable material after the initiation and until the ceasing, whereby the microstructure pattern is formed by a single exposure of the photocurable material to the curing light. 
     
     
         3 . The method of  claim 1 , further comprising controlling, between the initiation and ceasing of the process of irradiating the layer of photocurable material, at least one of the irradiation intensity and duration to affect the variable curing height profile across microstructures in the microstructure pattern. 
     
     
         4 . The method of  claim 1 , comprising ceasing the process of irradiating the layer of phtocurable material before the photocurable material has cured the full height of the photocurable material. 
     
     
         5 . The method of  claim 1 , comprising ceasing the process of irradiating the layer of phtocurable material after the photocurable material has cured the full height of the photocurable material in one part of a microstructure in the microstructure and before the photocurable material has cured the full height of the photocurable material in another part of the same microstructure. 
     
     
         6 . The method of  claim 1 , wherein the light does not comprise substantial intensity variations along a second dimension substantially orthogonal to the first dimension, and wherein the irradiating comprising irradiating a first portion of the layer of photocurable material and translation along the second dimension to irradiate a second portion of the layer of photocurable material, different to the first portion, whereby the microstructure pattern comprises a riblet geometry with riblets extending across the first and second portions of the layer of photocurable material. 
     
     
         7 . The method of  claim 6 , further comprising maintaining a substantially constant translation speed, to provide a constant curing depth profile in the second dimension. 
     
     
         8 . The method of  claim 6 , further comprising varying a speed of the translation, to provide a non-constant curing depth profile in the second dimension. 
     
     
         9 . The method of  claim 1 , further comprising forming the intensity profile with variations along at least a first dimension passing through a mask spaced apart from the layer of photocurable material by a gap of approximately 10 to 100 centimetres. 
     
     
         10 . The method of  claim 1 , further comprising removing uncured photocurable material within the layer of photocurable material, thereby exposing at least part of the microstructure pattern.