Patterned Stress Relief Layer for Non-Flat Device Thermoforming
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Solution Overview
Problem
Existing thermoforming methods for fabricating non-flat devices, such as smart contact lenses, induce stress profiles that can hamper the integrity of circuits and structures, leading to issues like buckling and wrinkle formation due to tensile or compressive stresses, particularly affecting components like antennas near the edges.
Innovation Solution
A method involving a patterned stress relief layer of thermo-formable material is mechanically attached to the flat device before deformation, designed to reduce local stress by distributing compressive stress evenly and preventing wrinkle formation, allowing the device to maintain a shape-retaining non-flat structure without damaging the circuit during thermoforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fully clamped condition is used during thermoforming, then the structure maintains stability during deformation, but tensile stress causes buckling of the material near the outer edges
Solution Approach 1:
The patent introduces a patterned stress relief layer with a grid-like structure that segments the continuous material into discrete regions. This segmentation allows localized deformation and stress relief at the grid intersections while maintaining overall structural stability during thermoforming, preventing both buckling and wrinkle formation
Solution Approach 2:
The stress relief layer is applied selectively to specific regions where stress concentration occurs during thermoforming. The patterned structure provides different mechanical properties in different locations, with higher flexibility in high-stress areas and maintained rigidity in low-stress areas, optimizing both stability and material integrity
2Stress or pressure
If a free-standing condition is used during thermoforming, then compressive stress is reduced, but buckling occurs mainly near the outer edges
Solution Approach 1:
The patterned stress relief layer creates a segmented structure that prevents continuous buckling propagation. The grid pattern divides the material into discrete cells that can deform independently, localizing any buckling behavior and preventing it from spreading across the entire structure, thereby maintaining material integrity
3Adaptability or versatility
If an antenna is positioned near the edges of the contact lens, then wireless communication capability is enabled, but wrinkles or folding damage occur in the material supporting the antenna
Solution Approach 1:
The stress relief layer is strategically positioned and patterned to provide enhanced stress relief specifically in the regions where antennas are located near the edges. This localized quality improvement protects the antenna-supporting material from wrinkle and fold damage while maintaining the antenna's wireless communication functionality
Solution Approach 2:
The stress relief layer is applied beforehand to the regions that will experience high stress during thermoforming, particularly near the edges where antennas are positioned. This pre-applied cushioning layer prevents wrinkle and fold formation that would otherwise damage the antenna and its supporting material during the deformation process
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 method effectively reduces stress levels below the tensile strength of materials, preventing buckling and wrinkle formation, ensuring the non-flat device maintains mechanical robustness and flexibility, even after thermoforming, with improved stress distribution during use.
Implementation Method 1
heating the structure to a temperature above the glass transition temperature of the thermoplastic material
Implementation Method 2
The thermoplastic material in which the device is embedded may for example be a polyethylene terephthalate (PET) or a thermoplastic polyurethane (TPU)... heating the structure to a temperature above the glass transition temperature
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
In a first aspect, the present disclosure relates to a method for designing a pattern of a stress relief layer for a flat device to be transformed into a shape-retaining non-flat device by deformation of the flat device. The flat device (and thus also the non-flat device) may comprise at least two components and at least one electrical interconnection between two components. In a second aspect, the present disclosure is related to a method of manufacturing a shape-retaining non-flat device by deformation of a flat device, wherein the flat device is attached to a patterned stress relief layer designed in accordance with the first aspect of the present disclosure. In preferred embodiments, the stress relief layer is a thermoplastic layer or a layer comprising a thermoplastic material and deformation of the flat device comprises deformation by a thermoforming process, after attachment of the flat device to the stress relief layer.