Developing 3-D electronics with pre-distorted pattern generation and thermoforming

Overview of the fabrication method of 3DE based on predistorted pattern generation and thermoforming process (referred to as PGT3DE) featuring high customizability, conformability, and stretchability. (A) Basic mechanism of the PGT3DE. 3DE can be fabricated using thermoforming simulation and the predistorted pattern generation method. (B) Schematic cross-sectional illustration of fabricated 3DE based on PGT3DE. (C and D) Designed 3D circuit model (C) and fabricated 3DE (D) [(i) top view and (ii and iii) bird’s eye view without the 3D mold (ii) and with the 3D mold (iii)]. (E) 3D conformal property of the thermoformed SEBS film with a microscope image of thermoformed SEBS film (i) and 3D mold (ii). (F) Electrical stability under various deformations; the 3DE is robust under stretching (ii), twisting (iii), and folding (iv) deformations without electrical disconnection. (G) Ear-shaped 3DE. The LEDs in the 3DE are well lit because of the successful electrical interconnection. Photo credit: Jungrak Choi, Korea Advanced Institute of Science and Technology (KAIST). Credit: Science Advances, 10.1126/sciadv.abj0694

Three-dimensional electronics (3-DE) is attracting much interest due to the increasing demands for seamless integration on curved surfaces. Nevertheless, it is challenging to develop 3-DE with high customizable conformity and stretchability. In a new report now published in Science Advances, Jungrak Choi and a research team in mechanical engineering, materials science and science and technology in South Korea presented a method to form three-dimensional electronics based on predistorted pattern generation and thermoforming. Using thermoplastic elastomer and liquid-metal-based conductive electrodes, they accomplished high thermoformability and stretchability during device fabrication and function. The new technology can facilitate a wide range of functionalities in wearable technologies.

Developing 3-DE

Three-dimensional electronics have high customizability, 3D conformability and stretchability to form state-of-the-art stretchable electronics in response to the increasing demands to form curvilinear surfaces for wearable sensors. The process to directly develop 3-DE with high customizability, 3D conformability and stretchability on any complicated surface are in high demand. Among the many development methods, thermoforming is a manufacturing technique that uses thermoplastic deformation of a plastic film onto a 3D shaped mold with the advantages of low fabrication cost, large area scalability and quick prototyping. In this work, Choi et al. developed a method for 3-DE based on pre-distorted pattern generation and thermoforming abbreviated as PGT3DE with a thermoplastic elastomer and liquid metal-based conductive electrode. During the 3-DE fabrication process, the team applied a highly stretchable thermoplastic elastomer-based substrate such as styrene-ethylene-butylene-styrene (SEBS) and a stretchable conductive electrode such as eutectic gallium-indium-based liquid metal mixed with copper microparticles.

Electrical and mechanical stability test of the 3DE under stretching, twisting, and folding deformations. Credit: Science Advances, 10.1126/sciadv.abj0694

Experimental overview

As proof of concept, the scientists designed a 3D circuit model and lit three LEDs on the 3D surface and noted its stretchability for flexible deformations, without electrical disconnection during the process. They also developed complicated shapes including an ear-shaped 3-DE. The team followed two key steps to form 3-DE based on the pre-distorted pattern generation and thermoforming (PGT3DE)

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