Stretchable 3D Printed Circuits for Skin-Conformable Wearables
Solution Overview
Problem
Current methods for producing stretchable printed circuit boards (PCBs) result in thick, invasive devices that cannot conform to the skin or incorporate complex circuits, limiting their utility in wearable technology and applications requiring flexibility and stretchability.
Innovation Solution
The development of ultra-thin, multi-layer stretchable 3D circuit boards using aerosol-jet printing to create polymer-conductor-polymer layers within elastomeric substrates like PDMS, with three-dimensional solid or hollow vias, enabling thin, flexible, and stretchable interconnects that can be integrated into textiles or applied directly to the skin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If commercial flexible printed-circuit boards are embedded in PDMS to create stretchable PCBs, then the PCB becomes stretchable, but the thickness increases significantly making it unable to conform to the skin
Solution Approach 1:
The patent segments the circuit board into multiple thin flexible layers separated by elastomeric material. Each layer is thin enough to conform to skin, while the stacked arrangement provides structural integrity. This segmentation allows the PCB to maintain stretchability without increasing overall thickness, directly resolving the contradiction between adaptability and volume.
Solution Approach 2:
The patent transitions from a single thick layer to a multi-layer stacked structure, utilizing the vertical dimension to distribute thickness across multiple thin planes. This dimensional approach allows the PCB to achieve stretchability through layer stacking while maintaining ultra-thin individual layers that can conform to skin surfaces.
2Adaptability or versatility
If multiple flex PCBs are embedded in PDMS to enable complex circuits, then circuit complexity increases, but manual manipulation and alignment become relatively complex
Solution Approach 1:
The patent merges multiple fabrication steps into a single integrated process. Conductive traces, vias, and elastomeric layers are deposited and cured sequentially in one manufacturing run rather than requiring separate assembly steps. This merging eliminates complex manual manipulation and alignment, directly resolving the contradiction between circuit complexity and ease of manufacture.
Solution Approach 2:
The patent changes the manufacturing parameters from manual assembly to automated aerosol-jet printing and in-situ curing. This parameter change enables precise deposition of conductive materials and elastomeric layers with controlled thickness and pattern, achieving complex multi-layer circuits without complex manual manipulation.
3Volume of moving object
If liquid metal or conductive polymers are used as interconnects to reduce thickness, then the PCB can be made thinner, but liquid metal stains surfaces and conductive polymers have much lower electrical conductivity
Solution Approach 1:
The patent uses composite conductive materials consisting of metal particles embedded in a polymer matrix. This composite approach combines the high electrical conductivity of metal with the flexibility and processability of polymers, achieving both thin thickness and high reliability in electrical conductivity simultaneously.
Solution Approach 2:
The patent changes the material parameters by optimizing the metal particle concentration, size distribution, and polymer matrix composition. These parameter adjustments ensure the conductive composite achieves sufficient electrical conductivity for reliable circuit operation while maintaining the thin thickness required for skin conformability.
4Strength
If thicker stretchable PCBs are produced using current methods, then the PCB achieves structural integrity, but it cannot conform to the skin and requires adhesive or mechanical layers that are invasive and irritating
Solution Approach 1:
The patent uses thin elastomeric films as both the substrate and structural support material. These thin flexible films provide sufficient structural integrity for the PCB while being thin enough to conform directly to skin without requiring additional adhesive layers or mechanical supports that would cause irritation.
Solution Approach 2:
The patent segments the structural support function across multiple thin elastomeric layers interspersed between conductive layers. This segmentation distributes the structural load throughout the thickness, maintaining overall structural integrity while keeping each individual layer thin and skin-friendly.
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 allows for the creation of thin, conformable PCBs that can flex and stretch with the skin, reducing long-term skin irritation and enabling the integration of modern sensors, while maintaining high electrical conductivity and mechanical integrity.
Implementation Method 1
Interconnects are made through aerosol-jet printing (AJP) steps forming polymer-conductor-polymer (e.g., polyimide-silver-polyimide) layers
Data Source
AI summary
Disclosed herein are devices comprising stretchable 3D circuits and methods for fabricating the circuits. The fabrication process includes providing in the elastomeric polymer as a substrate and providing conductive interconnects within the substrate encased in an insulating polymer, such as polyimide, to provide a stiffness gradient between the conductive interconnects and the flexible elastomeric substrate. The circuit may be fabricated as a multilayer construction using three-dimensional pillars as vias and as external interconnects to the circuit.