Fig. 8.8 (A) Diagram depicting the method for patterning paper into millimeter-sized channels:
(a) Use of photolithography to pattern SU-8 photoresist embedded into paper; (b) modification of
patterned paper for bioassays. (B) Images of patterned paper (a) After absorbing Waterman red ink
(5 mL) by capillary action. (b) After spotting the reagents. (c) Negative control for glucose (left)
and protein (right) by using an artificial urine solution (5 mL). (d) Positive assay for glucose (left)
and protein (right) by using a solution that contained 550 mm glucose and 75 mm BSA in an
artificial urine solution (5 mL). (e) Glucose and protein detection assays by using varying
concentrations of glucose and BSA [ 71 ]. (C)(a) Schematic illustration of the multistep fabrication
process. (b) 3D illustration of the resulting structure. (c) Raw fluorescence images of the paper
cross section showing the effect of lamination temperature on the penetration of wax into the
paper, resulting in control of the channel depth [ 72 ]
210 S. Solanki and C.M. Pandey