Microfluidics, the manipulation of fluids at the microscale, has vast potential in biology, chemistry, and medicine. 3D printing offers an attractive fabrication method for microfluidic devices, enabling rapid prototyping and reducing costs associated with traditional methods like lithography and PDMS bonding. However, designing 3D-printed microfluidic devices, especially multi-layer ones, remains a complex task demanding expertise in fluid mechanics, 3D modeling, and 3D printing. Existing design tools often lack specialized features for 3D-printed microfluidics. This research addresses this gap by introducing Flui3d, a platform aiming to democratize access to 3D-printed microfluidics by providing an intuitive, web-based design environment that streamlines the design process and incorporates features to ensure successful fabrication on consumer-grade 3D printers. The platform's user-friendly interface and automated design-for-manufacturing capabilities are intended to lower the barrier to entry for researchers and engineers, while also enabling rapid prototyping and iteration. The importance of this study lies in its potential to accelerate microfluidic research and development by making the design and fabrication of these devices more accessible and efficient.

The literature highlights the challenges associated with designing and fabricating microfluidic devices, particularly those intended for 3D printing. Traditional methods are often expensive, time-consuming, and require specialized cleanroom facilities. While 3D printing offers a promising alternative, limitations such as light penetration depth in SLA printing and the need for specialized knowledge in CAD software present significant hurdles. Existing Electronic Design Automation (EDA) tools, such as Cloud Columba, 3DµF, Micado, and Fluigi, primarily cater to 2D microfluidics and are not suitable for 3D-printed devices. These tools lack crucial features like automated compensation for light penetration and streamlined multilayer design capabilities. The current research aims to overcome these limitations by providing an open-source platform explicitly designed for 3D-printed microfluidics, thereby addressing the need for a more accessible and user-friendly design environment.

Flui3d is an open-source, web-based application with a WYSIWYG (What You See Is What You Get) interface, eliminating the need for software installation. Its user interface features a design canvas, a task toolbar, a design toolbar, an information and status control tool, and a layer control. The design workflow begins by specifying device dimensions and default properties. Users add layers, select components from a parameterized library (chambers, chambers with pillars, serpentine channels, Tesla valves, droplet generators, channel width/height transitions), place them on the canvas, create inter-layer connections (vias), draw channels, and round corners. A Design Rule Check (DRC) function verifies design compliance. The DFM function automatically compensates for light penetration during SLA printing using two models: local compensation (dynamically adjusting feature height based on layer depth and user-specified parameters) and global compensation (adding a blank height after each layer). Designs can be exported as STL files for 3D printing or SVG files for other fabrication methods. The authors demonstrate Flui3d's efficiency by replicating seven microfluidic devices from the literature, comparing its design complexity to other CAD tools (Shapr3D, AutoCAD, Inventor, SolidWorks), and fabricating the designs using a consumer-grade DLP 3D printer (Anycubic Photon D2) with different resins. The local compensation model uses the Beer-Lambert law to calculate compensation, adjusting parameters based on user input (minimum/maximum compensation at specified heights). Global compensation adds extra space between layers to prevent unintended curing. A reference design is provided to help users optimize compensation settings for their specific printer and resin.

Flui3d significantly simplifies the design process for 3D-printed microfluidic devices compared to traditional CAD software. The platform's parameterized component library and intuitive interface reduce the design complexity by orders of magnitude, enabling users to create complex multi-layer devices in a fraction of the time required by conventional methods. The integrated DFM function effectively addresses the challenges posed by light penetration in SLA 3D printing, enabling the successful fabrication of small and multi-layer microfluidic devices using readily available consumer-grade 3D printers. The authors successfully replicated seven microfluidic devices from the literature using Flui3d, demonstrating its versatility and accuracy. The comparison of design complexities reveals that Flui3d requires significantly fewer actions compared to traditional CAD tools, highlighting its efficiency. The successful fabrication of miniaturized versions of some designs illustrates the effectiveness of the DFM function in optimizing designs for manufacturability. The use of different resins and 3D printers further validates the platform's adaptability. The open-source nature of Flui3d promotes collaboration and community expansion of the component library, further enhancing its utility and scope.

The findings demonstrate that Flui3d effectively addresses a critical need in the field of microfluidics by providing a user-friendly, open-source platform for designing and fabricating 3D-printed microfluidic devices. The platform's ease of use and advanced features, such as the integrated DFM function, significantly lower the barrier to entry for researchers and engineers with varying levels of expertise. This accessibility is crucial for accelerating the development and adoption of microfluidic technologies across diverse scientific disciplines. The significant reduction in design complexity compared to traditional CAD tools promises to streamline research workflows and enable rapid prototyping. The successful replication of complex designs from the literature underscores the platform's accuracy and reliability. The open-source nature of Flui3d fosters community engagement, potentially leading to the development of new components and functionalities over time. The platform's success in miniaturizing existing designs highlights the potential for creating more compact and efficient microfluidic systems. Future research could focus on expanding the component library, refining the DFM algorithms, and integrating advanced simulation capabilities.

Flui3d represents a significant advancement in microfluidic design automation. Its user-friendly interface, comprehensive component library, and integrated DFM function make 3D-printed microfluidics more accessible to a broader range of users. The platform's open-source nature promotes collaborative development and expansion of its capabilities. Future work should focus on expanding the component library, integrating advanced simulation tools, and refining the DFM algorithms for even greater precision and adaptability to diverse 3D printing technologies and resins.

While Flui3d offers a significant improvement in microfluidic design, some limitations exist. The current component library, though useful, is not exhaustive. The DFM function relies on approximations based on user input, potentially affecting the accuracy of compensation. The DRC function, while useful, could benefit from a more extensive set of design rules to accommodate a wider range of applications and printing technologies. Future development should address these limitations to enhance the platform's robustness and versatility.