Multi-material microstereolithography

We have previously described the development of a microstereolithography (A mu SL) system using a Digital Micromirror Device (DMD) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365 nm for crosslinking a photoreactive polymer solution. The A mu SL system was designed with x-y resolution of approximately 2 A mu m and a vertical (z) resolution of approximately 1 A mu m (with practical build limitations on vertical resolution of approximately 30 A mu m due to limitations on controlling UV penetration in z). The developed A mu SL system is capable of producing real three-dimensional (3D) microstructures, which can be employed in applications such as microfluidics, tissue engineering, and various functional microsystems. Many benefits will potentially be derived from producing multiple material microstructures in A mu SL, and one particular application area of interest is in producing multi-material microscaffolds for tissue engineering. In the present work, a method for multi-material A mu SL fabrication was developed using a syringe pump system to add a material to a small, removable vat designed specifically for the multi-material A mu SL system. Multi-material fabrication was accomplished using a material changeover process that included manually removing the vat, draining the current material, rinsing the vat, returning the vat to the system, and finally dispensing a prescribed volume in the vat using the syringe pump. Layer thicknesses of approximately 30 A mu m were achieved using this process. To demonstrate this system, several multi-material microstructures were produced to highlight the capability of this promising technology for fabricating 3D functional, multi-material microstructures with spatial control over placement of both material and structure.