Facile Fabrication of Polymeric Microfluidic Channel Based on Fibrous Mold Base Using Near-Field Electrospinning

Microfluidic channels underpin lab-on-a-chip and analysis systems, yet their fabrication still often relies on cleanroom-intensive, photomask-based processes that limit rapid prototyping and user accessibility. Here, we present a facile fabrication strategy that uses near-field electrospinning (NFES) of polyethylene oxide (PEO) fibers as a sacrificial mold base, followed by polydimethylsiloxane (PDMS) replication and simple glass-PDMS assembly, to realize closed, capillary-driven microchannels without conventional master molds. NFES enables direct writing of straight fiber and reservoir-dot patterns on substrates, and systematic control of the applied electric field tunes fiber widths in the tens-of-micrometers range, yielding semi-elliptical channel cross-sections that are faithfully transferred into PDMS. The fiber width was controlled to approximately 34-100 μm by adjusting the voltage of the NFES to 1.4-1.9 kV. Theoretical calculations and numerical analysis showed that as the channel width decreased, the curvature of the liquid interface and the capillary driving pressure increased, leading to an increase in the flow velocity and capillary filling. Through the study, it was learned that the channel shape is a key design variable for the non-powered flow control. Experiments with aqueous solutions confirm spontaneous, pump-free capillary transport in the fabricated devices and demonstrate enhanced acceleration and reversal of flow by light-induced modulation. Therefore, the proposed NFES-based fibrous mold-based approach thus offers a simple, affordable, and facile route to microfluidic channels supporting flow control, making it well suited for rapid prototyping and iterative optimization of capillary microfluidic platforms for biosensing, sample delivery, and lab-on-a-chip applications.