Lab-on-a-chip (LOC) devices have been developed to minimise
the scale of laboratory tests. These LOC devices only need a small
volume of the reagents and samples, therefore providing portable
and disposable diagnostic devices [1,2]. However, the fabrication
processes of LOC devices are quite complicated, as demonstrated
by the need for mechanical components, such as pumps or valves,
to control the flow of the solution within the microfluidic device.
Currently, paper tests or strip tests are widely used in clinical
laboratories for diagnosing various diseases. The strip tests are
utilised in several areas of healthcare, such as screening tests,
self-monitoring by patients, treatment monitoring or preventive
medicine. Recently, Whitesides’s group has developed microfluidic
paper-based analytical devices (PADs) [3], also known as a
lab-on-paper technology. The concept of a PAD is to perform an
experiment on a small piece of paper. Unlike the conventional strip