Transfer printing of vertical-type microscale light-emitting diode array onto flexible substrate using biomimetic...

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Microscale vertical-type light-emitting diodes (μ-VLEDs) are crucial for advanced display and lighting applications.
• Efficient and reliable transfer printing methods are needed for fabricating μ-VLED-based devices, especially on flexible substrates.

Purpose of the Study:

• To develop a novel transfer printing technique for GaN-based μ-VLEDs.
• To enhance adhesion and repeatability in the transfer printing process using biomimetic stamps.
• To evaluate the performance and stability of μ-VLEDs fabricated on flexible substrates.

Main Methods:

• Insertion of an oxide-based functional layer to facilitate chip separation during UV laser pulse transfer printing.
• Fabrication of polydimethylsiloxane (PDMS)-based biomimetic stamps mimicking gecko lizard cilia for improved adhesion.
• Testing of stamp adhesion force and repeatability over 100,000 cycles.
• Fabrication of a flexible 10x10 μ-VLED array on a polyimide substrate and assessment of its performance under bending conditions.

Main Results:

• The biomimetic stamp achieved an adhesion force 12 times greater than a flat stamp (25.6 N/cm²).
• High adhesion force (≥10 N/cm²) was maintained after 100,000 repeated adhesion tests.
• The flexible μ-VLED prototype array exhibited less than 1% strain effect on forward voltage and output power during bending tests.

Conclusions:

• The developed transfer printing method using functional layers and biomimetic stamps is highly effective for GaN-based μ-VLEDs.
• The biomimetic stamp design provides superior adhesion and long-term repeatability, crucial for microfabrication.
• The demonstrated stability of μ-VLEDs on flexible substrates paves the way for practical applications in flexible electronics.