Low-cost fabrication of paper-based microfluidic devices by one-step plotting

In this technical note, we describe a facile method for one-step fabrication of paper-based microfluidic devices, by simply using commercially available permanent markers and metal templates with specific patterns. The fabrication process involves only a single step of plotting pattern in paper; it can be typically finished within 1 min. The ink marks formed in the patterned paper will act as the hydrophobic barriers to define the hydrophilic flow paths or separate test zones. Various paper devices can be created by using different templates with corresponding patterns. Transparent adhesive tape-sandwiched devices could protect their assay surfaces from potential contamination. In the proof-of-concept experiments, circular paper test zones (~3 mm diameter) were fabricated for colorimetric and quantification detection of prostate-specific antigen (PSA) as a model target, based on dot-immunogold staining assays coupled with gold enhancement amplification. Several serum specimens were additionally evaluated with this new approach and the results were compared with the commercial chemiluminescence immunoassay, validating its feasibility of practical applications. Such a one-step plotting method for paper patterning does not require any specialized equipments and skills, is quite inexpensive and rapid, and thus holds great potential to find wide applications especially in remote regions and resource-limited environments such as small laboratories and private clinics.