Self-Folding Nanocellulose PCB via SU-8 Stress
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Solution Overview
Problem
Existing 4D printing techniques require energy to induce form changes and use materials that are not suitable for printed circuit board (PCB) manufacturing, particularly failing to produce durable and functional 3D printed circuit boards.
Innovation Solution
The development of flexible printed circuit boards that self-assemble or self-fold into 3D shapes by using a nanocellulose sheet with a stressing layer of SU-8 epoxy, where ultraviolet exposure induces strain to cause folding, enabling the creation of 4D printed circuit boards with integrated electrical circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing 4D printing techniques are used to create self-folding structures, then the structures can change form, but energy is required to induce the change and specialized materials are needed that are not suitable for PCB manufacturing
Solution Approach 1:
The patent applies self-service by enabling the PCB to automatically fold into its 3D configuration without external energy input or control systems. The pre-stressed SU-8 epoxy layer stores mechanical energy that is released upon UV curing to drive the folding action autonomously, eliminating the need for motors, actuators, or power sources that would otherwise be required to achieve movement or shape change.
Solution Approach 2:
The patent implements preliminary action by pre-stressing the SU-8 epoxy layer during the manufacturing process before the final assembly. The epoxy is applied in a stressed state and then cured in place, locking in the stress. This pre-stressing allows the structure to fold automatically when released, rather than requiring real-time control or energy input during operation.
2Shape
If complex 3D shapes are printed directly using existing 4D printing methods, then the desired geometry can be achieved, but the process requires specialized materials and high energy consumption
Solution Approach 1:
The patent applies dimensionality change by transitioning from direct 3D printing to a 2D printed circuit board with a pre-stressed epoxy layer that folds into 3D upon release. The complexity is embedded in the 2D plane through the pattern of the stressed epoxy layer and cut lines, which guide the folding process to create the final 3D configuration without requiring energy-intensive 3D printing operations.
Solution Approach 2:
The patent replaces mechanical systems with chemical and physical processes. Instead of using motors, actuators, or mechanical linkages to achieve movement and shape change, the invention uses UV light to cure the epoxy and chemical stress to drive the folding action. This substitution eliminates the need for complex mechanical systems and reduces energy consumption significantly.
3Ease of manufacture
If standard PCB manufacturing processes are used, then manufacturing simplicity is maintained, but 4D self-folding functionality cannot be achieved
Solution Approach 1:
The patent uses composite materials by combining the nanocellulose PCB substrate with the SU-8 epoxy stress layer. This composite structure allows the PCB to maintain its structural integrity while the epoxy layer provides the stress-driven folding capability. The combination of these two materials enables both manufacturing simplicity (using standard PCB processes) and 4D functionality (self-folding upon UV exposure).
Solution Approach 2:
The patent applies parameter changes by utilizing the UV curing process to transform the epoxy from a liquid or soft state to a cured solid state. This parameter change (from uncured to cured) triggers the stress release and folding action. The same UV parameter is used both to cure the epoxy and to initiate the 4D functionality, integrating the activation process into the existing manufacturing workflow.
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
This method allows for the mass production of complex self-folding electronic devices with no need for specialized materials or pre-stressed substrates, offering low-cost, high-throughput fabrication and temporal control over the folding process, suitable for applications like 3D antennas and medical equipment.
Implementation Method 1
exposing the SU-8 to ultraviolet light to cure the SU-8, wherein stress induced by the cured SU-8 is sufficient to cause folding of the nanocellulose sheet
Data Source
AI summary
Described herein are ultra-thin nanocellulose flexible electronic device on which SU-8, an epoxy material which can become highly stressed upon UV exposure, is printed on desired areas. Upon UV exposure and then release from the surface it is anchored on, the nanocellulose device will spontaneously self-mold into a desired form due to stress differences between the SU-8 and the nanocellulose sheet. The flexible electronics can be manufactured using standard printed circuit board processing techniques, including electroless metallization and soldering of surface mount components.