Transfer printing enhanced by new laser-driven shape memory effect

 

A unique transfer printing approach detailed in Assistant Professor Seok Kim’s paper, “Laser-Driven Shape Memory Effect for Transfer Printing Combining Parallelism with Individual Object Control,” was published last week in the journal Advanced Materials Technologies. His graduate student Jeffrey Eisenhaure is first author on the paper.

 

“Transfer printing, a method using polymeric stamps to transfer micro-objects, has been demonstrated either as a parallel process with high throughput, or as a low throughput process allowing individual manipulation of micro-objects—but not both simultaneously,” Kim said. “So it has been challenging to claim that transfer printing-based microassembly is a highly flexible and scalable, manufacturing process.”

 

To address this challenge, Kim and Eisenhaure presented a unique transfer printing approach which enables arbitrary pattern transfer from an array of micro-objects via localized control of adhesion. The technique relies on thermally induced shape change of shape memory polymer (SMP) stamp arrays with carbon black-composite shape memory polymer (CBSMP) microstructuring. 

 

In this process, heat is first delivered globally by a resistive heater, facilitating parallel micro-object pickup, then locally by laser illumination absorbed within the CBSMP during printing. This enables precise and selective micro-object release with packing density limited only by the spot size of the accompanying laser system. 

 

“In such a way, the transfer printing approach shown in our work combines parallelism with individual object control to elevate transfer printing-based microassembly toward not only highly scalable but also very flexible manufacturing processes,” Kim said. 

 

This work, along with Kim’s “micro-LEGO” manufacturing techniques, serves as a foundation to make transfer printing-based assembly one of the common micro-manufacturing methods, enabling microsystems with higher performance or new functionalities, with relevance not only to microelectromechanical systems (MEMS) but also to electronics, photonics, and other areas. 

 

Kim is a leading scientist in advanced transfer printing and transfer printing-based microassembly. His work on multiple-material assembly, called “micro-LEGO,” was recently published by Scientific Reports. He joined the MechSE department as an assistant professor in 2011. He earned a bachelor’s degree in mechanical engineering in 2000 from Pohang University of Science and Technology (South Korea), a master’s degree in mechanical and aerospace engineering in 2005 from UCLA, and a PhD in mechanical engineering in 2009 from Carnegie Mellon University.

 

Eisenhaure received his bachelor’s degree in chemical engineering in 2007 from the University of Massachusetts Amherst.