Analyte sampling in paper biosensors powered by graphite-based light absorption

In this paper we exploit graphite's thermal absorption properties to drive the process of analyte sampling in paper-based biosensors. Graphite structures can be easily patterned or drawn on paper using a standard pencil and selective heating of the patterned layers can be remotely achieved using a light source. The resulting thermal gradient manifests itself as concentration gradients across the paper substrate which then triggers the flow of analyte to the selective areas. In this paper we have validated this hypothesis using a prototype made out of a low-cost filter paper substrate and a 300mW 808nm remote infrared laser source. Compared to a control paper substrate, we show an increase in temperature by more than 70°C (from 50°C to 120°C) in areas where the graphite is patterned. As a result the proposed prototype is also shown to demonstrate a higher sample-flow rate compared to the control. We anticipate that the proposed remote triggering of sample acquisition would be useful for different variants of paper-based biosensors that need to be integrated inside the food-package.