Low-cost colourimetric biosensing using laser-patterned cellophane-based fluidic devices

Cellophane is an attractive low-cost substrate for environmentally sustainable fluidic devices because it is biodegradable. Here, we report a laser direct-write (LDW) method, which relies on the principle of photo-polymerisation of a light-sensitive polymer for rapid fabrication of cellophane-based fluidic devices. In this method, a photo-polymer is first deposited on a cellophane substrate in a user-defined pattern and subsequently illuminated using a 405 nm laser to photo-polymerise the pre-deposited patterns and form hydrophobic polymer structures that form the walls of open wells and enclosed flow channels. By tuning the photo-polymer deposition speeds and deposition–photo-polymerisation cycles, polymerised structures with widths of 0.5–2 mm and heights of 0.1–2 mm were reproducibly fabricated on both uncoated and polymer-coated cellophane. Enclosed flow channels with coated cellophane as both layers supported pump-driven flow at 50–250 μL min−1, while hybrid channels with an uncoated bottom layer and coated top layer enabled pump-free capillary transport. Quantitative colourimetric detection of glucose (GOx/HRP–o-dianisidine assay) and nitrite (Griess reaction) was implemented within open wells. The limit-of-detection and limit-of-quantification were 7.31/23.8 μg mL−1 and 6.57/21.9 μM across the ranges of 10–100 μg mL−1 and 5–200 μM for glucose and nitrite respectively. We also report the detection of glucose and nitrite in artificial urine samples within both open well and enclosed flow channels. This LDW-based fabrication approach provides a practical and flexible route for rapid prototyping of disposable cellophane-based fluidic devices for colourimetric sensing.