The results demonstrated that dipping the paper into the melted
wax when the temperature was lower than 120 ◦C for 1 s did not
result in good resolution, in that the hydrophobic and hydrophilic
areas were not completely separated. On the other hand, using
a melting temperature above 130 ◦C resulted in excessive wax
spreading into the paper. For the optimal dipping time experiment,
the paper was dipped into the melted wax for varying amounts of
time, from 1 to 20 s. It was determined that the optimal time for
dipping the paper in the melted wax was only 1 s (just dipped and
immediately lifted out). Dipping times longer than 1 s could not
generate the patterns on the paper because of excessive spreading
of the wax into the paper. In addition, using a high temperature
(>130 ◦C) and long dipping time (>5 s) can boil the paper, causing
it to separate from the glass slide. Therefore, the optimal melting
temperature for wax dipping was 120–130 ◦C, and the optimal dipping
time was 1 s (see supplementary data Table S-1). However, the
temperature used for wax dipping in all subsequent experiments
was at 125 ◦C