Microfluidic devices have found extensive applications in mechanical, biomedical, chemical, and materials research. However, the high initial cost, low resolution, inferior feature fidelity, poor repeatability, rough surface finish, and long turn-around time of traditional prototyping methods limit their wider adoption. In this study, a strategic approach to a deterministic fabrication process based on in-situ image analysis and intermittent flow control called image-guided in-situ maskless lithography (IGIs-ML), has been proposed to overcome these challenges. By using dynamic image analysis and integrated flow control, IGIs-ML provides superior repeatability and fidelity of densely packed features across a large area and multiple devices. This general and robust approach enables the fabrication of a wide variety of microfluidic devices and resolves critical proximity effect and size limitations in rapid prototyping. The affordability and reliability of IGIs-ML make it a powerful tool for exploring the design space beyond the capabilities of traditional rapid prototyping.

Microfluidic devices have been widely used in mechanical, biomedical, chemical, and materials research. As a result, it is becoming increasingly important to have a cheap, fast, and reliable method for rapid microfabrication. However, prototyping of microfluidic devices typically suffers from the high initial cost, low resolution, rough surface finish, and long turn-around time. Here we present a strategic approach to closed-loop control of deterministic fabrication process based on in-situ image analysis called image-guided in-situ maskless lithography (IGIs-ML). Using the closed-loop control along with flush-flow functionality and leveraging the swelling behavior of the photocurable polymer, we demonstrate the fabrication of sub-micron high aspect ratio channels (800 nm width and >10 µm height) close to the light diffraction limit. This outperforms any reported rapid prototyping platforms which can typically reach tens of µm in channel width. Such dimensional capability is even comparable to some of the most advanced fabrication methods currently available. Dynamic image analysis simultaneously provides superior repeatability of densely packed patterns across a large area and multiple devices. A general and robust approach is established to fabricate a wide variety of microfluidic devices. This resolves the critical over-curing issues and size limitations in rapid prototyping of microfluidic devices, enabling affordable and reliable exploration of design space beyond the resolution of traditional photolithography.