Mechanical interlocking with precisely controlled nano- and microscale geometries for implantable microdevices

A new method to enhance the adhesion strength between nano- or microfabricated surface and biological tissue has been demonstrated. Patterning of the surface of a silicon wafer with microfabricated geometries enhanced the strength of interface adhesion without any chemical treatment. In this study, poly-dimethylsiloxane (PDMS) was used as a surrogate for biological tissue, and the adhesion strengths between this elastomer and silicon surface were measured using the 90-degree peel test. Two different geometries, repeating square and linear patterns, were studied by varying the depth of the pattern in micro and nanoscales. As the ratio of the depth to the width of the pattern increased, the strength increased and leveled off with both geometries. With the linear pattern, the peel strength in the patterned area was 4.7 times higher than that of the plain surface when the aspect ratio was greater than 2 and the peeling edge was parallel to the patterned channels. However, unstable fracture occurred in the orthogonal direction. The highest enhancement in peel strength of square patterned surfaces was less than in the linear patterned areas, but the PDMS showed better stability under fracture in all directions