Composite Pillar Structures for Adhesion to Rough Surfaces
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Solution Overview
Problem
Existing technologies have limited success in implementing fibrillar adhesive systems on rough and soft surfaces, such as skin, due to challenges in achieving strong adhesion while maintaining mechanical stability and avoiding issues like Eulerian buckling and agglomeration.
Innovation Solution
A structured surface with projections having a stem and an end face, where the stem comprises areas with different moduli of elasticity, and a phase interface with curvature, allowing for improved adhesion by shifting stress from the edge to the center, thus enhancing mechanical stability and adaptability to rough surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fibrils with high aspect ratios are used, then adhesion forces are improved through better elastic energy dissipation, but mechanical stability deteriorates due to increased susceptibility to Eulerian buckling and agglomeration
Solution Approach 1:
The projection is divided into two areas with different moduli of elasticity: a first area (end face) with lower modulus for flexibility and adhesion, and a second area (stem) with higher modulus for mechanical stability. This local differentiation resolves the contradiction by assigning different functional properties to different regions of the same structure.
Solution Approach 2:
The projection combines two materials with different elastic properties in a composite structure. The first material (lower modulus) provides flexibility and conformability to rough surfaces, while the second material (higher modulus) provides structural rigidity and resistance to buckling, thus resolving the mechanical stability issue.
2Strength
If the end face area is increased to improve adhesion to rough surfaces, then adhesion forces are improved, but structural stability deteriorates due to increased tendency for collapse
Solution Approach 1:
The end face (first area) is designed with lower modulus of elasticity to maximize flexibility and conformability to rough surfaces, while the stem (second area) has higher modulus to maintain structural stability. This local quality differentiation allows the end face to be larger without compromising overall structural integrity.
Solution Approach 2:
The composite structure combines a soft, flexible material in the end face region with a stiffer material in the stem region. This material composite allows the projection to have a larger end face area for better adhesion while the stiffer stem prevents collapse, resolving the stability issue.
3Ease of manufacture
If unstructured surfaces are used, then manufacturing is simpler, but adhesion to rough substrates deteriorates due to inability to conform to surface irregularities
Solution Approach 1:
The surface is segmented into multiple projections distributed across the substrate. Each projection is an independent composite structure that can conform to local surface irregularities. This segmentation allows the surface to adapt to rough substrates while maintaining manufacturing feasibility through standardized projection fabrication.
Solution Approach 2:
The modulus of elasticity parameter is changed spatially within each projection, with the end face having lower modulus than the stem. This parameter change enables the projection to conform to rough surfaces while maintaining structural integrity, improving adhesion without requiring complex unstructured geometries.
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
The solution significantly increases adhesion forces on rough and soft surfaces, reducing the tendency for the projections to collapse, and allows for better conformity to surface irregularities, achieving adhesion previously only possible with mushroom structures which are difficult to produce and maintain stability.
Implementation Method 1
the stem comprises at least two areas with different moduli of elasticity in the longitudinal direction
Implementation Method 2
fibrils with high aspect ratios dissipate the elastic energy better during detachment
Implementation Method 3
adhesion forces can be significantly increased again by selecting the geometry of the interface, in particular in the case of curved interfaces
Implementation Method 4
Fibrillated structures increase the elastic flexibility in the contact area, allowing these rough substrates to conform better than unstructured surfaces of the same material
Data Source
Figure 1~2
Figure 3a~3c
Figure 4
AI summary
The invention relates to composite pillar structures, particularly for adhesion to soft and rough surfaces. The composite pillar structures comprise, in the longitudinal direction, at least one region with a lower modulus of elasticity and at least one region with a higher modulus of elasticity, the region that has the lower modulus of elasticity preferably comprising the end face, and these two regions adjoining one another.