 In this study, a new method called image-guided in situ mask lithography, IGML, was developed to address the limitations of traditional rapid prototyping techniques. IGML uses dynamic image analysis and integrated flow control to provide superior repeatability and fidelity of densely packed features across a large area and multiple devices. This method allows for the fabrication of a wide variety of microfluidic devices and resolves critical proximity effects and size limitations in rapid prototyping. As such, IGML is a powerful tool for exploring the design space beyond the capabilities of traditional rapid prototyping. This article was offered by Ritalpaw, UNGEL, Declan Costa, and others.