Open-source CNC workstation for paper-based diagnostic assay assembly

Paper-based diagnostics are promising for point-of-care testing, but their assembly is often manual and can introduce alignment variability. To address this, we developed a low-cost, open-source workstation that repurposes a three-axis computer numerical control (CNC) machine for automated pick-and-place assembly of paper-based assays. The system integrates an Arduino-based controller with GRBL firmware, a custom vacuum end effector, and component holders to handle delicate assay components. This design eliminates reliance on proprietary CNC controls, reducing the costs to under $900 while enabling machine-agnostic adaptability. Performance was validated across dipstick, lateral flow immunoassay, and custom duplex immunoassay formats. Linear placement accuracy averaged ∼0.5-0.6 mm (within functional tolerance for diagnostic readability), while angular deviations (1-3°) remained acceptable for sample flow. Control line intensity in CNC-assembled assays were statistically indistinguishable from hand-assembled assays, confirming preserved diagnostic performance. By lowering the barrier to automated fabrication, this workstation provides an accessible platform for academic labs, startups, and decentralized environments to prototype and scale paper-based diagnostics. The open-source hardware and design files expand opportunities for reproducible, affordable diagnostic assembly in early-stage research and development.