3.1 Experimental results from lithographical techniques
In order to regulate cell shape and subsequently the cytoskeleton, adhesive islands consisting of ECM-proteins and of different geometric shapes were generated. For this approach, geometric shapes of different sizes were designed and written on a photomask during a photolithography process and subsequently transferred onto a silicon master (Fig. 6 A). The silicon master was used for casting PDMS stamps, which in turn were used for substrate patterning either by µCP (Fig. 6 B) or by stencil patterning (Fig. 6 B) through the fabrication of stencils.
The microstructures are shown in Figure 7. By way of illustration, the micropatterns are shown as they are observed on stencils. Two types of micropatterns were designed: bowtie (Fig. 7 A) and single (Fig. 7 B) patterns. Each pattern was designed in four different sizes allowing an average cell spreading area of 1600 µm², 1100 µm², 900 µm² and 700 µm². The distance between the patterns amounted to approx. 150 µm in order to prevent cells from bridging the gap between the patterns.
Most patterns were well molded and the holes spanned the entire stencil. However, some patterns (Fig. 7 *), especially those composed of thin lines, showed an insufficient or no through holes, which cause malformed or no micropatterns during stencil patterning.