Ir adv c5255

Patterns of the hydrophobic channels with a toner (black features) on a filter paper (white background) were drawn using computer-aided design (CAD) software (Adobe Illustrator, Adobe Inc., California, USA). The patterns were printed once on the Whatman filter paper (Grade 1, United Scientific Equipment, Singapore) using the Canon multifunction laser printer (IR ADV-C5255; Canon, Tokyo, Japan) set to the default parameters in monochrome for printing. After printing, the filter papers were heated on a hotplate (Thermo Scientific, Massachusetts, USA) at 200 °C for 60 min. The toner reflowed and spread through the thickness of the paper. The patterned paper was removed from the hotplate and allowed to cool at room temperature. Cross-sectional images of the filter paper were taken using Leica M125 stereomicroscope (Leica Microsystems, Wetzlar, Germany) and Basler acA2040 CMOS sensor (Basler AG, Ahrensburg, Germany) under 5.0× magnification.

Colorimetric data from the images were scanned with the Canon multifunction laser printer (IR ADV-C5255; Canon, Tokyo, Japan). The reagents in 96-well paper plates were heated with VWR natural convection oven model VWRU414005-115 (VWR, Singapore) for the glucose assay. Tetrabromophenol blue (TBPB), Benedict's solution and d-glucose (Sigma Aldrich, Singapore, Singapore), bicinchoninic acid kit (Thermo Scientific, Singapore, Singapore) and bovine serum albumin (BSA) (Goldbio, Singapore, Singapore) were of analytical grade and used as purchased. Glucose and BSA solutions were prepared using 18.2 MΩ cm ultrapure water (Milli-Q, Millipore, Billerica, MA, USA).