Structural Transformation by Electrodeposition on Patterned Substrates (STEPS) - A New Versatile Nanofabrication Method
Original Entry: Peter Foster, AP 225, Fall 2011 In Progress...
Authors: Philseok Kim, Alexander K Epstein, Mughees Khan, Lauren D. Zarzar, Darren J. Lipomi, George M. Whitesides, and Joanna Aizenberg
Publication:Kim et al. Structural Transformation by Electrodeposition on Patterned Substrates (STEPS): A New Versatile Nanofabrication Method. Nano Lett
The main idea in this paper is to present a method to make a versatile array of high aspect ratio (HAR) structures from a single template. A common way to make periodic arrays of these structures is to use deep reactive ion etching to make a master model of your array out of silicon. PDMS can then be used to make a mold of the master and then another array can be made using the PDMS mold. The problem with the approach is that generally one has to make a new master if they want to change some property of the array. This paper presents an approach where a variety of structures can be made from the same master.
The method is called Structural Transformation by Electrodeposition on Patterned Substrates (STEPS). The general idea is that gold can be deposited on the HAR array to serve as an electrode. The array is immersed in a solution containing a conductive polymer (sodium dodecylbenzenesulfonate (NaDBS)-doped polypyrrole in this case). When a voltage is applied between the solution and the deposited gold, the conductive polymer will deposit on the array. Depending on how the gold is deposited on the array and how long the voltage is applied for, one can create many different structures.
Figure 1 shows the three main ways this technique is used. STEPS I (at the top of the figure) uses sputter coating to coat the structures in gold. This leads to a uniform covering of the entire surface. When a voltage is applied, the polymer uniformly coats the surface, increasing the cylinder's radius uniformly. STEPS II (in the middle of figure 1) uses electron beam evaporation for the gold coating, with the gold coming from a direction parallel to the long axis of the cylinder (i.e. from above).
Kim et al. Structural Transformation by Electrodeposition on Patterned Substrates (STEPS): A New Versatile Nanofabrication Method. Nano Lett