| The ability to control both cell placement and chemical gradients within micropatterned three-dimensional (3D) scaffolds is important for tissue engineering. Several layer-by-layer microfabrication techniques such as direct-write printing, molding and sequential photolithographic patterning have been adapted to culture cells within 3D blocks of hydrogels and in microfluidic chips. However, patterning cell populations into curved, anatomically relevant 3D geometries still remains a considerable challenge, especially at small-length scales. In this dissertation, we characterize three methods that we have developed to culture cells in 3D. Our strategy involves the wafer-scale assembly of initially planar templates that are engineered to self-fold into intricate "bio-origami" 3D geometries.;We first introduce the concept of self-folding bio-origami by engineering curved, nanometer-scale-thick bilayer films of chromium and gold. Lift-off metallization was used to pattern the thermally evaporated bilayers and upon release from the underlying wafer, intrinsic stresses within the films drove the self-folding process. Fibroblasts were cultured on these 3D micropatterned scaffolds and conventional imaging techniques such as fluorescence and scanning electron microscopy could be readily performed.;We then develop a differential photocrosslinking method to achieve reversible self-folding of single-layered polymeric films of SU-8. These films could be integrated with other materials, and the incorporation of microfluidic channels enabled the self-folding of curved and flexible microfluidic devices. Moreover, the inclusion of lithographically defined pores in the device walls enabled localized delivery of biochemicals to externally cultured cells in 3D.;Lastly, we develop a facile method to self-fold cell-laden hydrogel bilayers for long-term 3D cell culture in curved and micropatterned geometries. The difference in molecular weights of the constituent hydrogel layers resulted in differential swelling of the bilayers in aqueous solutions such as cell culture media. Photoencapsulation of cells within the hydrogel layers prior to swelling enabled the engineering of multilayered hydrogel co-cultures.;A significant highlight of our methodology is that it harnesses the many strengths of conventional two-dimensional lithographic patterning, yet enables the wafer-scale self-folding of intricate, curved 3D geometries including cylinders, helices, polyhedra and corrugated sheets. We envision that bio-origami may ultimately provide a low-cost route to building 3D heterogeneous cell cultures with precisely engineered microenvironments. |
