2.2. Wax dipping fabrication method
To create a mould for wax dipping, a local laser cutting shop cut
an iron bar into the desired shape and size using a laser cutting
technique. The price for cutting an iron mould was about $0.35 US
per piece. An iron mould can be repeatedly used to produce numerous
pieces of PAD. In particular, based on our experience so far,
more than 1000 pieces of PAD have been fabricated from the same
iron mould without affecting the resolution. For the wax dipping
method, white Beeswax pellets were put in a beaker and heated
until they melted using a hotplate. To ensure that the temperature
was kept in the range of 120–130 ◦C, the temperature was monitored
throughout the experiment by means of an electronic contact
thermometer (IKA® ETS-D5). Whatman No.1 paper was cut into a
1.5 cm
×
2.5 cm piece and placed onto a glass slide. Then, the iron
mould was put onto the paper, and it was temporarily attached
by means of magnetic force using a permanent magnet placed on
the backside of the glass slide. Next, the assembly was dipped into
a chamber of melted wax for 1 s. After the paper was cooled to
room temperature, it was peeled off of the glass slide, and the iron
mould was removed from the paper. The wax-dipping fabrication
process for the PAD is shown in Fig. 1. Then, the hydrophobic and
hydrophilic areas of the PAD were observed under a microscope
(Fig. 2).