CNC-lithography: Computer-controlled multidirectional light-motion-synchronized lithography for 3-D microfabrication

This paper presents a computer-controlled multidirectional UV-LED (ultraviolet light-emitting diode) lithography system for three-dimensional (3-D) microfabrication, introducing the concept of CNC-lithography. The system comprises a switchable, movable UV-LED array as a light source and a motorized tilt-rotational sample holder, in which each system element is computer-controlled. This approach enables a relatively small size and overall portability of the system. The proposed system has two unique features; (1) the movable LED array improves the uniform UV light distribution over the substrate area; and (2) the switchable function of the LEDs is synchronized with the movement of the tilt-rotational sample holder, enabling the creation of 3-D patterns of substantial complexity. Unlike layer-by-layer additive approaches such as stereolithography, the CNC-lithography system can form fine shapes with no layering artifacts in a batch-compatible manner, at the expense of true arbitrariness of formable shape. When compared to conventional inclined lithography, CNC-lithography greatly increases ease of fabrication by eliminating multiple manual exposure steps and also enables the fabrication of new 3-D structures that would have been challenging to implement previously. Demonstration lithographic shapes, including a micro-`pipe,´ a micro-`hi,´ a micro-`Calla lily,´ and a micro-`cyborg´, are fabricated to illustrate the range of the process.