Dense high aspect ratio nanostructures for cell chip applications - Fabrication, replication, and cell interactions

Culturing human cells on the surface of a microchip brings living cells in direct contact with artificial microstructured surfaces. This work focuses on the effect of high aspect ratio nanostructures – dense nanoneedle arrays – on the mechanical response and proliferation of fibroblasts. We present a fabrication process for micropatterned chips that feature areas with hierarchical high aspect ratio nanostructures directly adjacent to flat chip areas. The chip was pre-patterned by conventional lithography. We have fabricated “black silicon” arrays of densely packed, sharp, vertical nano-needles for high aspect ratio structures by cryogenic reactive ion etching in an SF6/O2 plasma. An essential requirement for many real-life applications is to make such complex high aspect ratio 3D nanostructures available in larger areas. We have successfully demonstrated the 3D replication of black silicon by a UV- nanoimprint lithography process. This study provides insight into the extent to which such nanoneedle arrays influence the growth of human fibroblasts. We have investigated microstructured samples featuring a combination of (i) smooth surfaces and (ii) nanoneedle surfaces for the mechanical behavior and proliferation of fibroblasts. Our results show that the bonding viability and proliferation of the fibroblast on the high aspect ratio nano-needle surfaces differ significantly from flat surfaces. The nanoneedles only provide a minimum area for cell attachment compared to the neighboring flat, unstructured chip areas.