Guo Research Group

We have significantly advanced the nanoimprint technology and the scope of its application in recent years. We have developed a reverse-nanoimprint technique and demonstrated 3D polymer nanostructure fabrication (JVST. B. 20, 2872), and nanopatterning with lower temperature and pressure, which can be applied to flexible substrate (JVST. B. 20, 2881, 2002). We also demonstrated a new polymer inking method that is especially useful for polymer materials such as conductive polymers and biomaterials (JVST. B. 21, 2749, 2003). We have explored a new technique by uniquely combining the nanoimprint and photolithography methods to create various size and density patterns in a single step (Microelectron. Eng. 71, 288, 2004), which solved the defect generation problems in conventional nanoimprinting and can be further extended to simplify the process by eliminating the dry etching step (Microelectron. Eng. 71, 277, 2004). We have developed a new spin-on UV-curable liquid resist that allows nanoimprint to be done at room temperature with very high throughput using a conventional contact exposure tool (EIPBN’2004 and Adv. Mater. 17, 1419, 2005). Recently we demonstrated a very fast thermal curing resist based on modified PDMS (Adv. Mater, 2007), and exploited copolymer system as useful resists for nanoimprint applications (Adv. Funct. Mater, 2007). We applied nanoimprinting to OLED device fabrication, and have achieved very high resolution pixels (JVST. B. 20, 2877, 2002). We have also exploited molecular self-assembly in imprinted template for photonic applications (JVST. B. 2736, 2001). To increase the throughput of this technology to a new level, we have recently developed and demonstrated continuous Roll-to-Roll Nanoimprint on flexible substrate with a printing speed of ~1 m/min (JVST. B. 2007, and Adv. Mater. 2008).

 

One of our current efforts is to broaden the scope of this technology to beyond nanopatterning, and has applied it to creating nanostructures in a number of functional polymers. This include applying nanoimprinting to fabricate photonic nanostructures in non-linear optical polymers (J. Modern Optics. 49, 663, 2002), patterning conductive polymer as electrodes for organic electronics (Appl. Phys. Lett. 88, 63513, 2006), patterning conjugated polymers for enhanced organic solar cell efficiency (Appl. Phys. Lett. 88, 123113, 2007), direct nanoimpriting Nafion® proton exchange membrane for improved micro-fuel cell efficiency (J. Power Sources, 2007),  and exploring a number of sensor and bio-applications  (see sections on Organic Electronics & Photonics, and Nano-Biotechnology).

 

Work in this area has shown that nanoimprint can enable parallel nanoscale processing capability with simple equipment set-up and much flexibility. New techniques and material development should aid the adaptation of this technique in semiconductor microelectronics. Applications exploited in the area of photonics and nano-biotechnology will significantly push the envelope of this technology (read a Review Article)

        

 

 

 

 

                (a)                                                (b)                                                (c)

(a) SEM micrograph of 700 nm period grating in polycarbonate reverse-imprinted on topographies. (b) A three-layer polymer nanostructure created by repeating the reverse-imprint process three times. (c) 700 nm period grating in PMMA over a 10-cm area reverse -imprinted onto flexible PVC thin film, showing strong and uniform light diffraction across the whole printed area.

 

Nanoimprint Technology

 

The ability to replicate patterns from micro- to nanoscale is of crucial importance to the advance of micro- and nanotechnologies and the study of nano-sciences. Nanoimprint is an emerging lithographic technology that promises high-throughput patterning of nanostructures. Based on the mechanical embossing principle, nanoimprint technique can achieve pattern resolutions beyond the limitations set by the light diffractions or beam scatterings in other conventional techniques (read a review article).