July 22, 2024

Flex Tech

Innovation in Every Curve

New Printing Method Paves the Way for Flexible Electronics

A team of researchers at the Institute for Basic Science (IBS) in South Korea has developed a novel dry transfer printing method for flexible electronic devices. This breakthrough enables the transfer of high-quality electronic materials without causing damage. The study detailing this innovation has been published in the journal Nature Materials.

Concept of damage-free dry transfer printing using stress engineering. a, b) Schematic illustrations describing the formation of a single (a) and bilayer (b) structured Pt thin films. c) Stress distribution in the bilayer film and further stress enhancement through mechanical bending. Image Credit: Institute for Basic Science

This method, spearheaded by Prof. KIM Dae-Hyeong and Dr. LEE Sangkyu from the IBS Center for Nanoparticle Research, along with Prof. KIM Jihoon from Pusan University, represents a significant advancement in the field by allowing for the transfer of high-quality electronic materials without damage.

Typically, high-quality electronic materials require synthesis and processing at high temperatures to develop the necessary crystalline structures and electrical properties. However, these elevated temperatures make it difficult to directly process these materials on flexible or stretchable substrates.

To build flexible or stretchable devices, the electronics must be “transfer printed” from solid to soft substrates. Existing transfer printing technologies face issues such as the use of toxic chemicals and potential mechanical damage during the transfer process.

To tackle these challenges, various methods like laser or thermal processes and water-based delamination have been developed. However, these approaches often necessitate costly equipment, involve extra post-processing steps, or are restricted to specific environments. Additionally, conventional transfer printing poses difficulties when used with high-quality electronic materials that need high-temperature treatment to form crystalline structures.

To address these challenges, the research team developed a damage-free dry transfer printing method that controls stress within thin films. This innovative technique allows metal and oxide thin films, which are processed at high temperatures, to be transferred to flexible substrates without incurring any damage.

By adjusting sputtering parameters, the team was able to control the type and magnitude of stress within the thin film. They created bilayer structures with varying stress levels to maximize the stress gradient and applied additional tensile stress through external bending deformation. This process maximizes the strain energy release rate, enabling reliable delamination by exceeding the interfacial strength between the thin film and the substrate.

Our transfer method avoids toxic substances, minimizes device damage, and eliminates the need for post-processing, resulting in shorter transfer times. It can transfer large areas as well as micro-scale patterns, making it highly versatile.

Dr. Yoonsu Shin, Study Co-First Author, Institute for Basic Science

The team demonstrated that greater stress gradients within thin films result in larger bending moments, causing the films to curl and transform from a two-dimensional (2D) thin film into a three-dimensional (3D) structure. The configuration of these 3D structures can be adjusted by the pattern of the adhesive layer during transfer printing, allowing for the design and fabrication of desired structures to meet various requirements.

One of the corresponding authors, Dr. Sangkyu Lee, emphasized, “The key to this research is the development of a damage-free dry transfer printing technique by controlling only material properties, unlike previous studies. We plan to further research the fabrication of diverse 3D devices, leveraging the technology to transform 2D thin films into 3D structures, beyond the simple 2D flexible battery devices demonstrated in the paper.”

Transfer printing technology has applications across fields such as flexible electronics, optoelectronics, bioelectronics, and energy devices. Our method offers significant advantages for producing high-density 2D and 3D functional thin film structures without damage, greatly benefiting the development of new high-performance electronic devices.

Dae-Hyeong Kim, Professor, Institute for Basic Science

Journal Reference:

Shin, Y., et al. (2024) Damage-free dry transfer method using stress engineering for high-performance two- and three-dimensional electronics. Nature Materials. doi.org/10.1038/s41563-024-01931-y