The goal of substrate topography is to direct the cells to grow in a certain pattern

and direction. Cells tend to align along a groove and move along this surface. Studies

have shown that moderately porous materials improve cellular adhesion, which is

possibly due to mechanical stability along with increased surface area for adhesion.[22-24]

Endothelial cells (ECs) also have been shown to align along the direction of fluid flow.[25-

27] In addition flow has been demonstrated to play a role in altering the mechanical

properties of ECs. When subjected to a shear stress of 2 Pa over 24 hours, the endothelial

cells gradually increased their stiffness as measured by the atomic force microscope.[26]

 The methods of producing the precise surface morphologies vary depending on

the size of the pattern and the material on which the pattern is being replicated. The

smallest patterns are produced with direct write laser lithography[28] and AFM

lithography while those on the 2-10 um scale are produced with UV photolithography,

followed by reactive ion etching to control the slope of the walls.12' 29-32] The most

common method used in these experiments for producing features is to first

lithographically produce the pattern on a silicon wafer, then replicate that pattern by

embossing or spin casting onto the substrate.[33]

 The grooves and ridges formed on these substrates have shown significant control

over growth directions of cells. Current discussion focuses on the mechanisms behind

the alignment of these cells to the surface topography. Von Recum and van Kooten

question whether or not the actual geometries of the features are the defining factor, or

the fact that there is a change in surface free energy due to edges and disruptions in the

planar surface.[34] den Braber et al. concluded that parameters such as surface free energy

and wettability influence fibroblast growth and proliferation on microtextured surfaces,