Anodic aluminum oxide (AAO) membranes, having finely ordered arrays of nano-holes, are used to emboss polymethyl methacrylate (PMMA) on a hot plate. This controls the aspect ratio of the resulting nano-pillars and it serves as a master for further molding steps. The PMMA master is coated by a silane release layer and replicated using polydimethylsiloxane (PDMS). Utilizing this PDMS negative mold, different materials can be molded to create a replica of the nano-pillar arrays. Demonstrated in the scanning electron microscope images above, the fidelity of the replica structure is mostly preserved from the master.

Accessible

Non-collapsing PMMA nano-pillars permit visible light from the back, as shown in the photo with a SFU logo underneath a transparent PMMA sample. This sample is prepared by one embossing process which takes only 1.5 hours. Equipment for preparing the sample is easily found in a regular lab environment and the cost of preparing such arrays of nano-pillars is greatly reduced by the molding process.

Applications

As an example of a potential application, polymeric nano-pillars are prepared as bio-inspired dry adhesives and studied for their adhesion properties. By choosing a high surface energy material, the epoxy nano-pillars adhesive is able to produce three times more adhesion force than the original PMMA nano-pillars adhesive. Uniformity of the array of replicated nano-pillars and their surface chemistry can be observed from the force map acquired by a scanning probe microscopy technique.

More information about the research can be found in the journal Nanotechnology 25 285303.

Further reading

Study compares light trapping in hexagonal and square nano arrays (June 2012)
Roll-to-roll nanoimprinting to change nanolithography landscape (Nov 2012)
Nanoimprint lithography: anisotropic remastering reduces feature size (June 2012)