Root-Inspired, Template-Constrained Additive Printing for Fabricating Highly Robust Conformal Electronics

Academic Background

With the rapid development of emerging application scenarios such as smart robotics, smart skins, and integrated sensing systems, the application of conformal electronic devices on freeform surfaces has become crucial. However, existing conformal electronic devices are prone to tearing, breaking, or cracking under mechanical or thermal influences, limiting their application reliability. To address this issue, researchers drew inspiration from the mechanical mechanisms of tree root systems and proposed a Template-Constrained Additive (TCA) printing technology for manufacturing highly robust conformal electronic devices.

Paper Source

The paper was co-authored by Guifang Liu, Xiangming Li, Yangfan Qiu, and others, affiliated with the Micro and Nano Technology Research Center and the Frontier Institute of Science and Technology at Xi’an Jiaotong University. The paper was published in 2024 in the journal Microsystems & Nanoengineering, titled “Root-inspired, template-confined additive printing for fabricating high-robust conformal electronics.”

Research Process

1. Design of TCA Printing Technology

TCA printing technology enhances the mechanical robustness of circuits by infiltrating adhesive into functional materials, allowing them to maintain electrical performance under external damaging factors such as scratching, abrasion, folding, and high temperatures. The technology uses flexible templates to define circuit shapes and strengthens circuits through adhesive penetration. The specific process includes: - Material Filling: Functional materials are filled into flexible templates to form pre-fabricated circuit patterns. - Adhesive Filling: Ultraviolet (UV) adhesive is filled into the template, penetrating the functional materials and curing under UV light. - Template Transfer: An elastic bionic stamp is used to transfer the template to a three-dimensional substrate, forming conformal contact. - Template Removal: The template is removed, and the functionalized pattern is transferred to the substrate surface.

2. Experimental Validation

Researchers validated the robustness and high resolution of TCA printing technology through a series of experiments, including: - Mechanical Robustness Testing: Tests such as scratching, folding, and high temperatures demonstrated the stability of TCA-printed circuits under extreme conditions. - Resolution Testing: Using templates fabricated by photolithography, TCA printing achieved resolutions of up to 300 nanometers and enabled self-aligned printing of multi-layer materials. - Multi-Material Adaptability Testing: TCA printing technology is suitable for various materials, such as silver nanoparticles (AgNPs), multi-walled carbon nanotubes (MWCNTs), and polyvinylidene fluoride (PVDF).

Main Results

1. Mechanical Robustness

TCA-printed circuits exhibited excellent stability in scratching, folding, and high-temperature tests. For example, circuits maintained their electrical performance at temperatures as high as 350°C. In contrast, traditionally printed circuits were prone to failure under high temperatures and mechanical damage.

2. High-Resolution Printing

Leveraging the confinement effect of templates, TCA printing technology achieved resolutions of up to 300 nanometers and allowed precise control over circuit linewidth and spacing. By adjusting the solid content of the ink or the depth of the template, the thickness of the circuits could also be controlled.

3. Multi-Material Printing

TCA printing technology enabled self-aligned printing of multi-layer materials, successfully printing multi-layer circuits composed of materials such as MWCNTs, AgNPs, and PVDF-TrFE.

4. Application Demonstrations

Researchers demonstrated the application of TCA printing technology in conformal temperature/humidity sensing systems and ultra-thin energy storage systems. For example, a conformal temperature/humidity sensing system printed on the surface of a ceramic vase accurately sensed environmental changes and maintained stable operation under extreme conditions.

Conclusion

TCA printing technology successfully achieved the fabrication of highly robust and high-resolution conformal electronic devices through adhesive infiltration and template confinement. The technology is suitable for various materials and substrates of any shape, demonstrating broad application potential in fields such as smart devices, robotics, and aerospace.

Research Highlights

1. High Robustness: TCA-printed circuits exhibited excellent mechanical and electrical stability under extreme conditions.
2. High Resolution: Leveraging the confinement effect of templates, resolutions of up to 300 nanometers were achieved.
3. Multi-Material Adaptability: Suitable for various materials and enabled self-aligned printing of multi-layer materials.
4. Broad Applications: Demonstrated successful applications in conformal temperature/humidity sensing systems and ultra-thin energy storage systems.

Research Significance

TCA printing technology provides a simple, effective, and reliable method for manufacturing conformal electronic devices, addressing the limitations of existing technologies in terms of mechanical robustness and resolution. The technology holds significant application value in fields such as smart devices, robotics, and aerospace, driving further advancements in conformal electronics.