Polycaprolactone solution–based ink for designing microfluidic channels on paper via 3D printing platform for biosensing application

Abstract

This work reports a novel fabrication technique for development of channels on paper-based microfluidic devices using the syringe module of a 3D printing syringebased system. In this study, printing using polycaprolactone (PCL)-based ink (Mw 70 000-90 000) was employed for the generation of functional hydrophobic barriers on Whatman qualitative filter paper grade 1 (approximate thickness of 180 μm and pore diameter of 11 μm), which would effectively channelize fluid flow to multiple assay zones dedicated for different analyte detection on a microfluidic paper-based analytical device (μPAD). The standardization studies reveal that a functional hydrophilic channel for sample conduction fabricated using the reported technique can be as narrow as 460.7 ± 20 μm and a functional hydrophobic barrier can be of any width with a lower limit of about 982.2 ± 142.75 μm when a minimum number of two layers of the ink is extruded onto paper. A comparison with the hydrodynamic model established for writing with ink is used to explain the width of the line printed by this system. A fluid flow analysis through a single channel system was also carried out to establish its conformity with the Washburn model, which governs the fluid flow in two-dimensional μPAD. The presented fabrication technique proves to be a robust strategy that effectively taps the advantages of this 3D printing technique in the production of μPADs with enhanced speed and reproducibility. K E Y W O R D S 3D printing, fluid flow, hydrophilic channel, hydrophobic barrier, microfluidic paper-based analytical device, polycaprolactone