preventing adhesion forces able to withstand the shear forces during motion.[114' 115] By

using low surface energy silicones, coatings are foul releasing rather than antifouling.

Singer and others in this field have realized the importance of the mechanical properties

in determining the ability of a cell to adhere and remain adhered to a surface.[5] He

simulated barnacle pull-off tests by epoxying a stud onto a silicone surface, and

determined the critical force to pull it off with respect to the material's thickness and

elastic modulus. The result was for lower modulus materials (E* = 3 MPa) and thicker

coatings (up to 4 mm), the force needed to detach was less than for higher modulus (23

MPa) and thinner (0.08 mm) coatings. Gatenholm's group examined the use of

microtextured surfaces in the marine biofouling environment by imparting 50-100 [im

deep and wide features through use of a wire mesh as a mold. They found that barnacle

adhesion on the macro scale decreased on textured surfaces compared to smooth. Many

of these same principles of concern in biofouling can be used in biomedical applications

to improve the biocompatibility of polymeric surfaces in the body.

Surface Energy

 Due to its hydrophobic nature, silicone experiences rather high amounts of protein

adsorption and poor spreading of cells.[92] Thus, to improve cell adhesion to a silicone

surface, the chemistry of that surface is usually modified. Unmodified silicone is

hydrophobic with advancing contact angles around 110-120. The difference between

the advancing and receding contact angle is known as hysteresis, and gives some

understanding of a surface's ability to remodel itself as well as the surface roughness. As

the silicone is exposed to water, hydrophilic areas of the siloxane backbone migrate to the

surface, masking the hydrophobic methyl groups.[701 This provides a more hydrophilic

surface and a lower contact angle while receding. This rearrangement of the silicone