Shape memory polymers with nanotips help to solve micro-driven chip transfer problems

A research team at Pohang University of Science and Technology (POSPECH) has developed a new dry bonding technique that allows easy installation and separation of microscale electronic components to common household materials.

The study was recently published in the Journal of Nature Communications, and the team was led by Professor Seok Kim in collaboration with Professor Seok Kim (Postech), Professor Namjoong Kim (Gachon University), Professor Haneol Lee (Chonbuk National University), and Dr. Chang-Hee Son (University of Connecticut, Connecticut).

Micro-LEDS, the next-generation display technology, offers great benefits, including higher brightness, longer lifespan, and the ability to enable flexible, transparent displays. However, moving microred chips from target substrates with high accuracy and minimal residues was a sustained challenge. Traditional methods that rely on liquid adhesives or specialized films often result in excessively complex processes, poor consistency accuracy, and residual contamination.

Furthermore, researchers have struggled with what is called adhesion paradox. This is theoretical prediction that the surface should adhere strongly at the atomic level, in contrast to the actual difficulty of achieving strong adhesion due to surface roughness that limits the actual contact area.

The Posttech team has made good use of this paradox. Their solutions are found in the use of shape memory polymers (SMPS), which feature densely packed nanotips. At room temperature, the surface remains rough and exhibits low adhesion. When heated and pressed, the surface will become smooth – like an iron-like wrinkle – achieves a rather strong adhesion. Reheating will restore the surface to its original rough state, greatly reducing adhesion and release it easily.

This technology provides over 15 atmospheric bond strength during bonding and provides near-zero force peeling via a self-release function. The difference in bond strength between “on” and “off” states is over 1,000 times, exceeding the traditional approach by orders of magnitude. The team used a robotic system to demonstrate accurate pick-and-place for micro-driven chips, and also confirmed stable adhesion on materials such as paper and fabric.

“This innovation allows for precise operation of delicate components without the need for sticky adhesives,” says Professor Seok Kim of Postech. “It has great potential in display and semiconductor manufacturing applications and can lead to transformative changes when integrated with smart manufacturing systems across a variety of industries.”