Nanoskiving

Nanoskiving is the name given to the process of Ultramicrotomy when it is applied towards the fabrication of structures (i.e., edge lithography) rather than sectioning samples for electron microscopy.1-5 There are x basic steps; 1) evaporate or spin-cast a thin film on to an epoxy substrate, 2) rough-cut (or pattern in step 1) lines of the desired width, 3) embed the substrate/film in an epoxy matrix, and 4) use an Ultramicrotome to cut thin sections perpendicular to the plane of the flim.  The resulting sections will contain wires (of the material that the film was made from) that are as wide as 1 mm where the depth is controlled by the thickness of the film and the height by the Ultramicrotome (~50 nm to 1 µm).  This process is summarized in Figure 1.

Figure 1.

Nanoskiving is compatible with almost any material, but brittle materials generally provide the greatest challenge.  The technique is, however, perfectly suited for soft materials such as conjugated polymers.5 We were not only able to make wires from organic materials this way, but by spin-casting alternating layers of MEH-PPV and BLL (an electron-donating and electron-withdrawing polymer respectively), rolling the resulting film, and then nanoskiving we produced an organic solar cell with perfectly ordered, interdigitated heterojunctions.6 Figures 2 shows the cartoon schematic of the process and Figure 3 shows SEM images of the resulting structures.  While the efficiency of these devices was not very high, the devices are completely un-optimized.  Nonetheless this represents not only a new method for producing heterojunction organic solar cells, but the best of our knowledge the first true ordered, interdigitated heterojunction structure.

 

Figure 2Figure 3

Here is a closeup video of the microtome in action:

 

 

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1) Xu, Q.; Gates, B. D.; Whitesides, G. M. J. Am. Chem. Soc. 2004, 126, 1332-1333.

2) Xu, Q.; Bao, J.; Capasso, F.; Whitesides, G. M. Angew. Chem., Int. Ed. 2006, 45, 3631-3635.

3) Xu, Q.; Perez-Castillejos, R.; Li, Z.; Whitesides, G. M. Nano Lett. 2006, 6, 2163-2165.

4) Xu, Q.; Bao, J.; Rioux, R. M.; Perez-Castillejos, R.; Capasso, F.; Whitesides, G. M. Nano Lett. 2007, 7, 2800.

5) Lipomi, D.J.; Chiechi, R.C.; Dickey, M.D.; Whitesides, G.M. Nano Let., 2008, 8, 2100.

6) Lipomi, D.J.; Chiechi, R.C.; Reus, W.F..; Whitesides, G.M. Adv. Func. Mater., 2008, 18, 3469.

 

 

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