Dual Curvature Micro-Truss Fabrication via Index-Matched Photopolymerization
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Solution Overview
Problem
Existing methods for forming micro-truss structures into curved shapes are expensive and/or destructive, as they require converting flat sheets of materials like honeycomb or foam into complex shapes for applications such as automobile dashboards or aircraft wings.
Innovation Solution
A method involving a transparent mold with an index-matched material and fluid, illuminated with collimated light through a photomask, allowing for the formation of micro-truss structures in arbitrary shapes without the need for initial flat sheet conversion, using self-propagating polymer waveguides to create truss elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If flat sheets of honeycomb or foam are converted into curved shapes using existing methods, then the desired curved geometry is achieved, but the process becomes expensive and destructive
Solution Approach 1:
Instead of converting flat sheets into curved shapes through expensive and destructive processes, the invention inverts the approach by directly fabricating micro-truss structures in their final curved geometry using photopolymerization. The mold defines the desired curved shape from the beginning, and light propagates through the curved mold walls to form the micro-truss structure directly in that shape, eliminating the need for subsequent forming operations.
Solution Approach 2:
The invention replaces mechanical forming processes with optical methods. By using photopolymerization initiated by light propagation through index-matched transparent mold walls, the micro-truss structure is formed chemically and optically rather than mechanically. This substitution eliminates the need for expensive mechanical forming equipment and destructive shaping operations.
2Shape
If collimated light is projected through a curved mold wall, then micro-truss structures can be formed in arbitrary shapes, but light refraction at the interface may distort the beam paths
Solution Approach 1:
The invention applies index-matching to create optical homogeneity across the mold interface. The transparent mold wall material is selected to have the same refractive index as the photomonomer resin, eliminating refraction at the interface. This allows collimated light to propagate through the curved mold wall without distortion, maintaining precise beam paths even in arbitrary curved geometries.
3Manufacturing precision
If the mold material is index-matched with the photomonomer resin, then light propagates without refraction, but the mold material selection becomes more restricted
Solution Approach 1:
The invention uses composite material strategies to achieve index-matched transparent mold walls. Options include using transparent plastics with appropriate refractive indices, glass materials, or transparent composites such as long-fiber reinforced plastics where the fiber orientation and matrix composition are selected to achieve the desired optical properties. This allows maintaining optical precision while having some flexibility in material selection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the cost-effective and non-destructive fabrication of micro-truss structures with complex geometries, such as dual curvature shapes, by forming micro-truss structures directly within a mold, improving structural support and impact protection in various applications.
Implementation Method 1
illuminated, from outside the fluid, through a photomask, with collimated light... forming self-propagating polymer waveguides that create micro-truss elements
Implementation Method 2
The material for the transparent portion of the mold is selected to be a material that is index of refraction matched with the photomonomer resin... The collimated light travels through the photomask forming beams of light that enter the transparent fluid, propagate into the mold
Data Source
AI summary
A method and/or system for forming a micro-truss structure in an essentially arbitrary shape. A mold that has a transparent portion, and having an interior volume in the desired shape, is filled with photomonomer resin. The material for the transparent portion of the mold is selected to be a material that is index-matched to the photomonomer resin. The filled mold, placed into a bath of transparent fluid index-matched to the transparent portion of the mold, and illuminated, from outside the fluid, through a photomask, with collimated light. The collimated light travels through the photomask forming beams of light that enter the transparent fluid, propagate into the mold, and form a micro-truss structure in the shape of the interior volume of the mold. The micro-truss structure may then be removed from the mold, or part or all of the mold may be left adhered to the micro-truss structure, forming covering face sheets.